The Age of Plants

The advent of agriculture in Southwest Asia about 12,000 years ago, and its subsequent independent origin in six or so additional regions of the world, marked a new relationship between humans and the land. Previously, humans had lived within nature in small nomadic bands of hunter-gatherers. But with the population increase that accompanied settled agricultural life, surroundings were increasingly man-made. Humans were shifting from environments of nature to environments of culture – from being surrounded by wild plants to being surrounded by cultivated plants and buildings.

This was a change in the human environment of evolutionary adaptation as rapid cultural change now supplanted slow biological change. Certainly, the human use of fire had altered natural landscapes, and human harvesting of animals, especially the megafauna, had altered trophic cascades – but tilling the land was a new and more directly intrusive method of land management.

These historical circumstances were dwarfed as, in the 400 years between 1550 and 1950, the global landscape underwent unprecedented change as the exponentially increasing human population became mouths for agriculture to feed.

European colonial expansion resulted in major land grabs across the world as humanity, as never before, recorded and harnessed the world’s vegetation for food, drink, clothing, timber, and ornament. Agriculture, forestry, and horticulture flourished as never before until the urbanization that they created concealed the vital role of plants in the buildings, machinery, transport systems and economic activity that they had created.

The long-term Big History analysis of the relationship between humans and plants showed how, during Natura, plants were the life-sustaining primary producers of energy at the base of the food chain for both humans and the animals that they hunted. Then, during the Neolithic Agrarian Revolution, the food source shifted from wild plants to cultivated plants.

Industria presented the conditions for a completely new human-plant relationship during a phase of rapid social complexification. This was a time when plants were increasingly concealed within the fabric of process as the products of industrialized society.

In the overall scheme of things the social significance of plants had shifted from their being the source of life-sustaining biological food energy, to their provision of fossil fuel social energy that powered the cultural increase in social complexity.

This is the long-term view of history spanning many thousand years . . . the full 315,000-year history of our species Homo sapiens. Using social organization as the yardstick for historical change we see, over time, an acceleration in social complexity, combined with increasing global interconnection and interdependence. Natura lasted about 300,000 years, Agraria about 10,000 years, and Industria around 400 years.

When we narrow the historical focus from thousands to hundreds of years, a remarkable Age of Plants comes into focus, lasting for around 400 years – from about 1550 to 1950. The impersonal factors of energy and geography are still crucial, but the consequences of increasing social organization – of culture – are now more in evidence . . . the place of plants in a world of increasing trade, urbanization, collective learning, industrial agriculture, transport, communication, and the other factors that contribute to modern society.

The Age of Plants is a period of history that coincides with what historians refer to as the Great Divergence. This was a time of heightened plant awareness as humans explored the earth’s vegetation at a global scale, incorporating plants into the fabric of an increasingly global culture and social organization. This exploration of the world flora as food, medicine, and ornament – a sharing of the Earth’s plant bounty – is now drawing to a close.

The Great Divergence

As western society expanded in space and increased in complexity, plants would feature in politics, culture, commerce, science, art, and exploration as humanity began a transition from local markets based on rural solar agriculture to urban living and a global fossil-fuel-based industrial agriculture. By 1914 ‘… most people on earth were part of a Western fossil-fuel economy tied to global markets with Europe and its colonies controlling 84% of the planet’s landmass and 100% of its oceans‘.^[1]

The Neolithic Agricultural Revolution had taken people out of wild nature into cultivated nature. The Industrial Revolution now moved people off cultivated land and into the cities creating another fundamentally different relation between plants and people – one deeply embedded, not nature, but in culture.

The Great Divergence was a period of growth, not only in human population but in social complexity and diversity. European spatial expansion across the world was also combined with faster and more closely integrated communication networks and the accelerating knowledge (information) accumulation of collective learning. The Great Divergence and Age of Plants were just a prelude to the Great Acceleration of Informatia that would follow World War II.

One way of identifying the place of plants, both in society and individual lives, is to trace the role that they played in each of these periods.

The Great Divergence was a time when the West dominated the rest of the world through a period of social, economic, and environmental globalization. The biological aspect of this globalization entailed not only the dispersal of European people and their institutions, but also their domesticated organisms, pests, pathogens, and commensals. It was also a time when plants, formerly so much a part of subsistence living, were now given pride of place in European culture at this time.

The Age of Plants was an era when the role of plants in our lives was both obvious and celebrated, before gathering urbanization, technology, manufacturing, and industrial agriculture obscured our dependence on their existence.

The following discussion examines in more detail the role of plants through this period: their place in science, economics, society, globalization, and horticulture. It also explains why these circumstances provide ample justification for the recognition of an Age of Plants, and how they have also determined the character of botanic gardens.

Britain

Imperial Britian would play a vital role in the economic botany and horticulture that was at the centre of the Age of Plants. However, in 1550 Britain was, in global terms, a culturally and economically insignificant island situated off the coast of north-west Europe, detached from Europe’s economic and cultural centre, the Mediterranean: it was one of the last European countries to experience the Renaissance humanist revival.

Over the following century or so the focus of European culture and trade shifted to western Europe as maritime trade routes were forged across the Atlantic to the New World and around the Cape of South Africa into the Indian and Pacific Oceans. It was therefore the countries and cities of coastal western Europe that flourished, first those in Spain and Portugal, then Holland, France, and Britain in a period of European colonial expansion when much of the world fell under the economic control of the West.

Change in Europe was so dramatic in this modern era that historians have used a series of overlapping historical periods to embrace its many different aspects, including: Renaissance, Scientific Revolution, Age of Discovery, Age of Revolutions, Commercial Revolution, Enlightenment, and Industrial Revolution.

By 1900 London was the world’s largest city by far. Industrialized Britain had the world’s largest navy and most extensive empire at the hub of a network of maritime entrepôts drawing East and West into a global economy. Following industrialization, per capita income and standard of living in the countries of the British Empire was markedly ‘higher’ than that of agrarian people in Asia and Africa as, from the mid-19th century, modernization opened up a lasting economic gap between industrialized nations and the rest of the world.

The vast improvement in technology, transport and communication that was part of the Great Divergence connected the peoples of the world as never before. England became the administrative centre for international plant exchange as the world’s botanical bounty was traded in an unprecedented phase of cultivated plant globalization.

But why should such an already over-labelled and protracted era warrant the additional title Age of Plants? What are the distinguishing features of this Age, what defined its beginning and end, and why is such a periodization useful?

The international exchange of economically significant plants had a profound effect on social development, penetrating deeply into the fabric of society. In simple practical terms it transformed, and made more internationally uniform, the items that people across the world encountered in their daily lives – what they ate, drank, wore, smoked, cultivated in parks, gardens and fields, and experienced in their wider surrounding landscapes.

Science

The Lyceum of ancient Athens has a compelling claim to be not only the institution where botanical science was first practiced but also the stimulus for later botanic gardens. It was the Lyceum and similar institutions like Plato’s Academy, as repositories of knowledge and establishments for learning, on which modern era European universities were modelled. Sadly, nearly two millennia would pass before plant science re-emerged from its Greek origins in the form of simple plant taxonomy and morphology . . . but still clinging to its former preoccupation with medicinal plants. This happened in the crude modern-era medicinal gardens associated with the medical faculties of early Renaissance universities in northern Italy – in Pisa, Padua, and Florence (Mueller 1871b; Morton 1981; Spencer & Cross 2017). Their emergence coincided with the publication of Nicolaus Copernicus’s De revolutionibus orbium coelestium (1543) (On the Revolutions of the Heavenly Spheres) which launched the Scientific Revolution in physics, astronomy and mathematics and culminated in the monumental work of Englishman Isaac Newton (1642-1726/27) in his Philosophiæ Naturalis Principia Mathematica (1687) (Mathematical Principles of Natural Philosophy) which demonstrated the law-like regularities of the cosmos thus revealing the secrets of matter in motion.

Modern-era plant science was, at first, the descriptive botany adopted by the first professors of botany at these universities as botanical science diverged from medicine to become an independent discipline. Here the first herbaria were assembled as collections of dried plants, and students gathered to learn botany by studying the collections of living plants in the associated physic gardens. There had been a simple continuity from the academic medicinal interests of antiquity and medieval monastic herb gardens that preceded these modern era university physic gardens.

As plant description and classification developed, so the medicinal theme incorporated more elaborate scientific classification beds or system gardens like those of the Jussieu brothers in the 18th century Jardin des Plantes in Paris.

Over time these early botanic gardens adjusted, first to the interests of their academic caretakers, then to a wider audience. Communication about plants was revolutionized by the advent of printing in the mid-15th century. Medicinal herbals printed between about 1470 and 1670, and often illustrated, encouraged plant description and communication that would later follow separate medicinal and botanical paths into either specialized medical pharmacopoeias or botanical Floras that provided descriptions of the plants growing in specific geographic regions. The advent of the printed word opened the door to a formal and universal system of plant knowledge such that by the 19th century, the initially inward-looking, and closed, academic botanic gardens had embraced wider economic and aesthetic interests as they fell under increasing public control.

Towards the 18th century Englishman John Ray (1627-1705) the ‘English Linnaeus’ took the first tentative steps towards a natural system of classification while biology was revolutionized by the 17th century use of the microscope. The microscope exposed a new scale of biological structure in the worlds of anatomy and histology while plant function was being addressed by experimentation in plant physiology, these two lines of investigation combining in the 18th century to begin elucidating the mysteries of plant metabolism – translocation, respiration, photosynthesis, and reproduction.

The success of plant science depended on the existence of a community of botanical scientists with an agreed framework of theory, principles, procedures and technical terms. Britain had taken the lead in science when it established the Royal Society in 1660. Botany would receive special attention during Joseph Banks’s 41-year presidency from 1778 to 1820. By the mid-18th century England’s political and economic pre-eminence allowed it to advance the cause of global plant science through the formation of several of the world’s most influential plant academies: Kew Gardens (1759, becoming public in 1841), the British Linnean Society (1788), and the Horticultural Society of London (1804, a Royal Charter granted in 1861).

Though Linnaeus is often associated with the system of binomial nomenclature, his genius lay in achieving the unification of botany as a distinct scientific discipline. Through the 16th and 17th centuries botanists devised a standardized botanical terminology and nomenclature so, when general agreement was reached concerning the notions of genus and species, the simple tools needed for a universal plant taxonomy were in place. Though both the French and English had persisted with a ‘natural’ system of classification, it was Swedish naturalist Carl Linnaeus (1707-1778) who eventually achieved botanical consensus with an ‘artificial’ system of plant classification and system of plant inventory that was broadly accepted across Europe. Like Darwin’s On the origin of species by means of natural selection . . . , Linnaeus’s work was directed to the general public. Historian Richard Drayton expresses this as follows ‘Far more than Ray or Tournefort, let alone Newton, Linnaeus brought the frontier of knowledge within reach of amateurs: princes might praise the achievement of the Principia to the skies, the Systema Naturae instead invited their participation. His system represented a game which allowed its initiates to name and reorder the variety of creation, and helped to make natural history, and botany in particular, more popular in the eighteenth and early 19th centuries than any other science then or since’ (Drayton 2000, p. 41).

With the introduction of new plants to Europe during the Ages of Discovery and Enlightenment botanic gardens had also followed another less academic path as they blossoming into a celebration of the economically important, beautiful and curious plant novelties that poured into Europe with colonial expansion. One sign of the desire for more diverse and ornamental plant collections had come at the beginning of the 17th century when there was a noticeable shift in the role of the botanic garden from Hortus medicus (medicinal or physic gardens like those in the city states of northern Italy, or of the Portuguese in India) to the Hortus botanicus, like Hortus Botanicus Leiden under Carolus Clusius (1526–1609), which was established in 1590. The collections at Leiden included not only economically important plants but ornamental and other plant curiosities recovered from foreign lands donated by, among others, the employees of the Dutch East India Company.

Later, as industrialization progressed, so botanic gardens took increasing account of human impact on global ecosystems such that modern botanic gardens display an eclectic blend of scientific and other plant interests. Botanic gardens which, during the 18th century, were closely and directly linked to agriculture through their association with food plants and economic botany, are still so connected – but indirectly via the environmental impacts of agriculture – weed invasions, extinctions, land degradation, the environmental impacts of nutrients and chemicals, the diversion of water for food production etc. concerns that translate into policies directed at plant conservation, sustainability, and climate change.

All this was a seemingly distinctive and desperate Western desire to possess nature both physically (in museums, cabinets, herbaria, private and public gardens, arboreta and botanic gardens) and intellectually (as a formal system of knowledge buried in publications such as herbals, plant encyclopaedias, pharmacopoeias, dictionaries, scientific journals and Floras) (Fig. 6). The global stocktake of plants, both indigenous and cultivated, has been a Western preoccupation since the commencement of the Age of Plants around the time of the Age of Discovery, gathering momentum in the 19th century with one of its most remarkable milestones being the set of Floras that catalogued the plants of the British Empire on the way to a World Flora (to be launched in 2020). But only in recent years has it been possible to propose a realistic estimate of the number of the world’s seed plants at around 350,000 species.

In the universities the emphasis was on experimentation. By the mid- to late 20th century the in-principle mysteries of plant structure and function were resolved with research moving towards the boundaries of investigable scale – molecular and global. The early genetic alteration of plants by human selection had taken a quantum leap in the 1930s with the new science of genetics and plant breeding. Then, all within an evolutionary framework, biology, on the one hand, narrowed down analytically using sophisticated technology to drill ever deeper into the structure of matter in a proliferation of subjects based around genetics and molecular biology. The structure of DNA was revealed in 1968 as a double helix and, with the deciphering of its structure (the ‘genetic code’), the door was opened to the genetic engineering and biotechnology boom of the 1980s whose momentum shows no sign of abating. On the other hand, inspired by the blossoming of ecology and environmental movement of the 1960s, there has been a broadening synthetic (holistic) awareness of the biosphere (the word ‘biosphere’ was coined in 1875, ‘ecosystem’ in 1935) as the vital interconnection between all organisms and their environments including the recent acknowledgement of the current planetary influence of humans in the ‘Anthropocene’.

During the 18th century Enlightenment, scientific interests were pushed to the fore as voyages of scientific discovery were launched as part of the humanistic and progressive application of reason and science. With geographic access to the world and a universal system of plant taxonomy in place, a global plant inventory (both wild and cultivated) was now a credible enterprise. And as cultivated plant redistribution began to accelerate so the world plant stocktake would also accelerate through the 19th century.

So, through the Age of Plants we see, within the broader Scientific Revolution, the origin of modern botanic gardens and emergence of plant science as a discipline distinct from medicine. Botany now had its own community of scientists – with an agreed, and therefore universal, theoretical framework and terminology – in a collaboration cemented through the published and printed word.

Following the first investigations into plant anatomy and physiology and the constant addition of new technologies plant science of the 19th and 20th centuries broadened into subject areas too numerous to mention here but with present-day research directed mostly at the molecular and global scales.

Economics

When Islamic forces captured Constantinople in 1453 the highly lucrative overland spice trade, especially nutmeg and cloves, fell into the hands of Arab and Indian merchants. Their high prices forced European traders to seek a direct maritime trade route to their source on the other side of the world. Encouraged by improvements in maritime technology Europeans sailors set off on an Age of Discovery that was initiated as a naval spice race to the unknown source of spices in the East Indies. Sea lanes were forged to the New World, India, China and the Far East as a network of trading hubs was established, feeding into a strengthening global economy.

Following a Western route Spaniard Columbus had encountered the Americas. Following an easterly route, the Portuguese Diaz, then da Gama forged a way via the Cape into the Indian Ocean and India, and in 1512 António de Abreu filled his hulls with mace and nutmeg in the south Moluccas and Francisco Serrão established a trading post for cloves on Ternate in the north Moluccas. Europeans had finally reached the source of the highly desired spices (Turner 2005). On a Spanish expedition lasting from 1519 to 1522 the Portuguese Ferdinand Magellan, following a westerly route, had rounded South America and crossed the Pacific Ocean to the East Indies, the expedition continuing to complete the first circumnavigation of the world, although Magellan himself was killed in the Philippines.

It was the lure of spices that had initially drawn European seafarers into the world’s oceans. In the 50 years between 1490 and 1540 navigators charted the coastal boundaries of the world’s great land masses (Australia and New Zealand were exceptions) – Africa by 1487, India (1498), West Indies and Americas (1503), Malacca and East Indies (1511), China (1516), and Japan (1542) (Morton 1981, p. 150). This established beyond doubt that the world was a sphere and, with the physical boundaries of the continents drawn, the stage was set for a future world-scale scientific inventory and economic interchange.

Following the discovery of precious metals in the Americas, an extremely profitable triangular Atlantic trade sprang up between Europe, Africa and the Americas as a slave trade based on plantation crops – notably sugar (rum), cotton, rubber and tobacco. Plantation crops were the largest privately-owned businesses of their day (Standage 2009, p. 117) producing the world’s wealthiest men who contributed much of the capital needed to modernise Western Europe and finance Britain’s looming Industrial Revolution.

In retrospect we can see a quickening of economic activity that engaged all the major economic plant groups. Not only the way spices had attracted merchants into the world’s oceans in the 16th and 17th centuries and the 18th and 19th century plantation crops that provided Europeans with the wealth to finance further social development and global expansion.

Beer and wine were the plant-based global beverages of antiquity and these were supplemented in the 18th and 19th centuries by the equally socially transformative (and now universal) plant drinks of tea from China, coffee from Arabia, and cacao from the Americas . . . all sweetened with sugar: ‘Sugar and potatoes, as much as the steam engine, underpinned the Industrial Revolution’ (Standage 2009, p. xi). Wealth from plants produced not only economic growth but a surge in the European population that needed food. This demand was met by industrial agriculture implemented on colonially appropriated arable land where mostly familiar temperate cereals were cultivated.

There was now an increasing need for timber, both for housing and world-conquering navies, and this prompted the formalisation of forestry practices. In England, for example, Medieval forests had been used primarily for hunting: only in the reign of Elizabeth I (ruled 1558-1603) was there official acknowledgement of their use for timber production (James 1981).

Botanic gardens took a leading role in these developments with Enlightenment science and society being especially preoccupied with plants of scientific and ornamental interest. Joseph Banks in his time as de facto director of London’s Royal gardens at Kew (1773 to 1820), amassed the world’s largest collections of living and dried plants, giving special attention to economic botany as Kew, which became the world-leading botanical institution at the centre of the British Empire (Fig. 4), playing a major role in the collection and distribution of pineapple, banana, cacao, coffee, quinine, rubber and tea. Botanic gardens provided not only the first plant acclimatisation and redistribution centres but also the gardener-botanist plant hunters who acted as plant prospectors and adventurers scouring the world for its botanical treasures.

Eighteenth century European interest in ornamental plants led to a rapid proliferation of commercial plant nurseries, while the important food crops were being grown in the colonies. In the early 20th century the introduction of novel plant varieties from wild populations slowed but new varieties of all groups of cultivated plants multiplied under the breeding and selection made possible by the new science of genetics.

Through the Age of Plants we see that plants were both the catalyst for, and major ingredients, of the changes leading to the global economy that defines our modern world. Early unregulated world plant trade resulted in a more equitable global distribution of the world’s plant resources, its horticultural and agricultural crops and ornamental plants as plants and plant products were progressively woven into the fabric of human industrial and technological systems.

Collectively these, and other, changes constituted a globalisation of cultivated plants on a spectacular scale.

Food & Agriculture

As the growing 18th and 19th century European population demanded more food and raw materials this was increasingly sourced from the wider world using improved transport and communication systems in the increasingly complex web of connections that linked all human activity. Food production has, throughout history, had more environmental impact than any other human activity.

As soaring populations created an increased demand for food various options were explored: putting more local land under cultivation (a limited option); improving the efficiency of agricultural practices by shifting to industrialised agriculture; increasing productivity by using crops that yielded more energy per unit area (e.g. potatoes rather than wheat); and in the 20th and 21st centuries by breeding higher-yielding crops.

Local food production was augmented by putting colonial land under cultivation. This was achieved by a series of imperial colonial land grabs in territories that included the Great Plains of the USA and parts of Canada, also land in Argentina, Uruguay, Brazil, Australia’s south-west and eastern coast, Tasmania, New Zealand, central India, parts of Africa, Asia and elsewhere – all expanding the mostly temperate agricultural landscapes that had crept over the Earth’s surface since the Neolithic Revolution.

The benefits and costs of this global exchange to its participants are complicated, but part of the equation was the export of the environmental problems of food production from Europe to its colonies. The use of natural resources on a global scale created a natural economy of global ecological debtor and creditor nations. This process has continued as developing nations struggle to survive by catering for the needs of the more affluent nations – like the palm oil plantations in Indonesia, the clearing of the Amazon for agriculture and, post 1990s, the progressive clearing of the world’s most biodiverse savannah, the Brazilian cerrado, about 35% of which is an anthropic landscape now supplying a large quantity of the world’s beef as well as animal feed, coffee, soy, eucalyptus pulp and charcoal for steel production (Castro et al. 1999).

During the post-WW II Great Acceleration in human population, challenges to food security have been addressed by the mass-production of super-farms during a Green Revolution that included controlled irrigation and application of agrochemicals, all supported by sophisticated global agribusiness and biotechnology that has included the breeding of high-yielding, sometimes genetically engineered, crop varieties.

Plant food provides the energy that is essential to life. This simple fact forces us to acknowledge that the mode of capture of this life-energy (whether from wild plants, cultivated plants, or cultivated plants managed with the assistance of the fossil energy) has had a profound influence on the development of human social organization and thence human history.^[1] The transition to industrial agriculture during the Great Divergence, made possible by the use of fossil fuels (for machinery, manufacture of fertilizers etc.) released people from the land for manufacturing and the diversification of societal pursuits. This plant-dependent social change alone, as a second Agricultural Revolution, deserves rightful recognition as a key determining factor in human history.

Across the world in about the year 1300, with the exception of small urban elites, people lived similar lives on the land, surviving by means of subsistence agriculture based on a few staple crops. Plants featured in a rich tradition of folklore and social rituals associated with agriculture and the many uses of plants as medicines, drugs and poisons, dyes, fibres, perfumes, oils, waxes and resins, timber as fuel and structural material and so on. Though Plants would be at the forefront of the rapid social change that was about to occur, to a degree that we will never see again. Up to this time ‘… almost all the necessities of life had been provided by things that grew on the land … products, directly or indirectly, of photosynthesis …’ (Standage 2009, p. 129).

The release of people from the land at a time when the population is growing demonstrates the more efficient provision of plant food-energy which can be regarded as a form of wealth. The wealth that arose during the Great Divergence as people moved off the land and into the cities occurred because the human and animal labour needed to produce food was being provided by the machinery and other efficiencies generated by fossil-fuel-based industrial agriculture.

Among the various cultivated plants staple crops have had by far the greatest environmental impact, not only by appropriation of land surface but also in the demand that agriculture makes on the earth’s resources, especially water. In the absence of efficiencies demand for resources and land correlates directly with the size of population to be fed. The area of arable land needed to feed European peoples was insufficient for the population growth generated during the European developing Industrial Revolution so large areas of land was annexed as colonial land grabs … in the Great Plains of the United States, Canada, SW Australia, Tasmania, New Zealand, also parts of Africa, Argentina, Uruguay, Brazil, central India and elsewhere. Russia would eventually harness parts of the formerly unproductive steppes. Through the Great Divergence fossil-fuel industrial agriculture created a Second Agricultural Revolution which brought the world population from 350 million in 1500 to about 1 billion in 1800 and 2 billion in 1930. Today’s international food markets have translated these earlier developments into a wider system of ecological debtor and creditor nations.

Society & Environment

As human numbers increased there was a corresponding decrease in connection with the wild environments of Natura and an increasing connection, first, with the rural landscapes of Agraria and then the city surroundings associated with the manufacture, industry and business of Industria. Human experience of the environment today is largely a consequence of these two major human activities: food production, and urbanisation.

Global ecological debtor and creditor countries in 2003

Over time the world has become more clearly divided into those that import ecological services and those countries with ecological reserves. Australia is a strong ecological creditor
National ecological footprint relative to nationally available biocapacity
Courtesy WWF Report 2006

Urbanisation

– The rise in manufacturing that occurred in the Industrial Revolution was based in cities that could provide the necessary labour and resources. Cities are not only centres of production and trade, they are also the sources of new technology and places for the exchange of ideas; they are hubs of political power. Here are estimates of populations in the world’s largest cities at particular times in history showing how they reflect historical centres of civilisation (Chandler 1987). Memphis Egypt c. 0.3 million from 3100- 2240 BCE; Xi’an China c. 0.4 million in 195 BCE; Rome 1 to 2 million in c. 150 CE; Baghdad > 1 million c. 775 CE. In 1900 London’s total of 6.5 million exceeded the second-largest city, New York, by about 2.2 million but by 1950 New York’s population of 12.5 million exceeded that of the world’s then second largest city, London, by 3.6 million. In 2015 the world’s largest cities were: Tokyo 37 million, Delhi 26 million, Shanghai 24 million reflecting the passage of economic activity to Asia.

England’s coal was conveniently located near potential industrial centres where plants (now often imported from the colonies) provided much of the raw material processed by the world’s first factories – the textile and paper mills of England’s north. Profitable factory mass-production soon spread to the continent as economies based on rural agrarian societies and local markets depending on solar (non-fossil-fuel) agriculture switched to the 19th century globally connected urban industrial model.

Colonial botanic gardens, though initially involved in all aspects of economic botany, quickly ceded their connections with food and agriculture to other government departments and organisations. But agriculture, as the human life-support system, is a crucial element in the Age of Plants as indicated by its cumulative historical influence on the global biogeochemical cycles that define our present. Botanic gardens, though advocates for the natural world, are the children of civilisation and cities and now well represented across the world.

Parks & gardens

The creative use of plants to decorate urban environments dates back into antiquity. Perhaps harking back to the sacred groves and meeting places of prehistory, the Bronze Age cities with their tree-like stone columns, the carefully designed parks and gardens that culminated perhaps in the Hanging Gardens of Babylon as one of the seven wonders of the ancient world, probably served as a conceptual inspiration for the refined gardens of the wealthy dignitaries in the Roman Empire who would set a standard for the European gardens to come. Though Western-style ornamental horticulture has its roots in the gardens of ancient Egypt, Mesopotamia, Persia, and the Mediterranean classical civilizations of Greece and Rome, it was the Roman synthesis of these traditions that was embedded in continental European culture and transferred to Britain during the approximately 350 years of occupation by Roman garrisons between around 43 CE and 410 CE. The Romans also introduced to Britain their agriculture, market gardens, orchards and vineyards.

After the collapse of Roman civilization and an interlude of Christian medieval monasteries, it was essentially the royal courts and wealthy educated elites of economically and politically powerful European countries that would set the agenda for European horticulture as it passed from Italy in the late 15th and 16th centuries to Holland during the 17th century Dutch Golden Age before political and economic power passed to 18th century Enlightenment France and Britain. In 1817 the first tropical botanic garden was established by the Dutch just north of Australia in Indonesia’s Bogor although this was just one of many European botanic garden trading hubs.

Horticulture and science in the Age of Plants have followed the progressive transfer of wealth, power, land and knowledge from royalty, nobility, the landed gentry, and the intellectual elite to the ‘lower’ orders of society. This process of increasing democratization and egalitarianism has addressed social exclusion based on race, religion, gender, property, and education, a trend that continues today. Resistance to rigid social hierarchies was especially strident in the Age of Revolutions (roughly 1774 to 1849) with opposition to absolute monarchy and demands for the devolution of political power. Egalitarian values gathered momentum from two World Wars which created greater social mobility, the female franchise, and further resistance to authoritarian control, whether that be the monolithic British Empire (which itself metamorphosed into a commonwealth of nations) to countries, schools, families, and horticulture.

Throughout history the creation of artistic pleasure gardens had entailed a costly labour force, a privilege only afforded by the rich and powerful. Garden fashions were initiated by royal courts and then passed down the social ladder: it was rulers, kings, aristocrats and the landed gentry who could afford this luxury – and these were the people and gardens that would grace the pages of books on garden history and who would determine the fads and fashions of the ‘rest’. In Britain, as the Age of Plants progressed, there was the emergence of a nouveau riche of merchant plutocrats whose wealth was gained from colonial expansion and manufacturing. These men challenged the landed gentry as politics was steadily ‘socialised’ and that process has continued. Today’s gardening has sloughed off much of the residue of social stratification, though the cult of celebrity is still strong and the desire to compete continues – whether for the prize pumpkin, or laurels at the Chelsea Flower Show (RBGV was awarded a gold medal in 2011!). Western garden fashions traditionally generated by Europe’s aristocracy are now established in the global public domain . . . today’s international TV garden documentaries, social media gardening celebrities, citizen scientists and so forth. Once the preserve of the wealthy, the latest gardening trends are now ‘everyman’.

There was one period in this transition whose legacy still lingers today. The 18th century Enlightenment was a time of heightened excitement about the plant world enjoyed, at first, by Europe’s intellectuals and social elite. James Cook, more than any other explorer, had captured the attention of European high society when botanists Joseph Banks and Daniel Solander sailed with him to the Pacific in the Endeavour, collecting plants at Botany Bay in New Holland on the other side of the globe and returning to London as plant celebrities. The plant obsession that gripped Europe at this time has been referred to as botanophilia, ‘an intensified passion for the products of the Vegetable Kingdom’ (Williams 2001). It was a plant exuberance associated with maritime trade and exploration – not only the possibility of windfall profits from yet unknown plant products, but the discovery of botanical novelties in exotic and distant lands where there were fascinating peoples, cultures, and natural wonders. Botanophilia was an Enlightenment preoccupation that reached beyond profits and utility to novelty, beauty, and the satisfaction of scientific curiosity, to a different form of greed as the European wealthy elite competed for rare ornamental plants from distant lands to decorate their gardens and conservatories in a yearning for garden novelties that has continued unabated to the present.

Botanophilia was the zenith of the Age of Plants,: it was like a grand intellectual and cultural celebration of the world’s flora – its beauty when displayed in palaces and aristocratic country estates; its culinary variety enjoyed as newly introduced condiments, spices, foods and drinks; its scientific diversity displayed in botanic gardens, museums, and herbaria, and described in new encyclopaedias, dictionaries and journals; and the utility of newly-acquired fibres, dyes, and medicines that flooded into Europe at this time. This was the European discovery, exploitation and enjoyment of the Earth’s botanical bounty on the ultimate geographic scale.

Botanophilia was a plant mania that then spread across society attracting intrepid explorers and plant hunters who published dramatic travelogues describing their adventures. Learned garden chroniclers contributed to the new garden journals as did a new generation of botanical artists. Entrepreneurial nurserymen and avid private collectors imbued botany with a new scientific and social prestige that engaged society as never before. The gathering of information on Australian plants that occurred between 1606 and Darwin’s arrival in 1836 is referred to by botanist-historian David Mabberley as a ‘Botanical Revelation’ (Mabberley 2019). The excitement generated by plant novelty and discovery at this time has never been surpassed as botanic gardens, botanists and horticultural adventurers basked in the social and political sun for a brief historical moment when plants were front and centre in colonial communication, trade, science, and economic botany.

Britain by the mid-19th century was leading a vibrant European commercial nursery network and the proliferation of public parks and botanic gardens that now extended into the provinces.
Colonial botanic gardens watched developments from a distance keeping in touch with the latest fashions through the popular garden literature. In 1902 Australia became the second western country, after New Zealand, to give women the vote, and the first country where women could stand for parliament. This was symptomatic of changes flowing through western society. The first gardening book written by a female, and for females, was Jane Loudon’s (1807-1858) Gardening for Ladies (1840). Only in 1896 did Kew accepted three female gardeners during the directorship of Thistleton-Dyer (1843-1928) much to the disgust of the ageing Joseph Hooker who said that such women were ‘not ladies in any sense of the word’ (Campbell-Culver 2001, p. 399). Following the ancient Greek aristocratic abhorrence of physical labour, passed on to the subsequent Western ruling class, the wives of socially influential men were expected to manage estates, not work on them. However, by 1917 there were more than 30 female gardeners at Kew, even before two world wars opened the doors to a female workforce. The first female gardener employed by the RBGV was Vivian Young, appointed in late 1972.

In the course of the Age of Plants, modern botanical gardens were not only created, their initial objectives were turned on their head as ‘egalitarianism’ transformed specialised university physic gardens – created for the benefit of academics and medical students and closed to the general public – into largely publicly funded and open gardens displaying to their visitors the plant kingdom in all its diversity, utility and splendour.

Globalization

Following the European circumnavigation of the globe in the 16th century there followed a remarkable period of globalisation as western European trading hubs and colonies were established around the Atlantic, Indian and Pacific Oceans, binding the world together in ever more complex ways through the integration of trade, cultures, biota, technologies and ideas. Advances in science informed technology that increased the efficiency of transport and communication systems. After 17th and 18th century European colonial expansion, the 19th century brought steamships and railways that accelerated the economic activity emanating from the Industrial Revolution in the Old World, providing the means for the Neo-Europes’ to penetrate inland from their coastal ports. For most people, though, the world was still a vast and mysterious place.

When the Apollo spacecraft, in 1972, sent back pictures of Earth as a small blue marble adrift in space, the perception of humanity in the scheme of things was changed forever. The world was no longer a secretive source of natural wonders and unlimited resources awaiting discovery and exploitation, it was more like a cleverly designed and bounded garden with an expanding vegetable patch to support the expanding buildings and household, and therefore needing sensitive and informed management.

One important, and often neglected, aspect of globalisation (loosely defined here as ‘the extension, intensification and acceleration of global interconnection and interdependence’) has been biological globalisation, the global dispersal of animals and plants, including pathogens and weeds. The cultivated plant component of this biological globalisation has converted much of the planet’s vegetation from wild nature to cultural landscape.

Wild plant distribution is usually treated as a function of natural environmental factors and this contrasts with the distribution of cultivated plants’ which, though still dependent on such factors, is largely a consequence of human geopolitical history. It is not surprising that the geographic dispersal of plants out of their native habitats gathered pace through the Age of Plants as the human population escalated from about 480 million in 1550 to 7.7 billion today. Spencer and Cross (in press) discuss the human factors that have influenced the distribution of six major categories of economically important plants that have followed their own historical paths: spices and medicinal plants; cereals (mainly the temperate cereals of western agriculture); horticultural crops such as sugar, cotton, tea and coffee, grapes, fruit, nuts and vegetables; plantation forestry; ornamental garden plants; and the unintentional but costly dispersal of weeds, invasive plants, pests and diseases.

Plant redistribution began in earnest as a ‘Columbean Exchange’ of economically useful plants between the Old and New Worlds before the Old World’s historically assembled plants of agriculture, forestry and horticulture were passed on to the European colonies – the ‘Neo-Europes’ in the Americas, Asia, Africa, the Far East, the Southern Hemisphere and beyond (Crosby 1993). There was also a homogenisation of tropical crops in an exchange between the East and West Indies as an ‘Indo-Pacific and Caribbean exchange’ which had developed out of the activities of colonial botanic gardens, mainly the Dutch at the Cape and Bogor (Indonesia), French on Mauritius, and British on St Vincent (Groves 1995, p. 475).

The increasing homogenisation of the world’s plants that followed this biological globalisation has created climate-zone-specific cultivated floras consisting mostly of cultivated crops and naturalised weeds. Cultivated plants are now key indicators of recent (Anthropocene) human impact since they are major constituents of planet-wide anthropogenic biomes, the ‘anthromes’ of Ellis & Ramankutty (2008) who claim that more than 75% of Earth’s ice-free land area can no longer be considered wild. Perhaps cultivated plants are the best adapted plants on a planet where natural populations are in decline? These vast areas of land taken up by the few species used in the monocultures of agriculture and forestry contrast with the small area occupied by the species-rich menu of ornamental plants cultivated in our parks and gardens that take up only a small proportion of urban areas of the world that cover less than 3% of the land surface (Liu & He, 2014).

The food demand that accompanied massive population growth of Europe’s fossil-fuel economies resulted in an equally substantial appropriation of arable land from their colonies as a series of colonial land grabs. Occupation usually entailed the subduing and eventual outnumbering of indigenous peoples. At the same time the early demand for timber, mostly needed to build merchant and military navies, depleted native forests prompting the creation of a new industry and science, plantation forestry.

The global plant exchange that occurred during the Age of Plants has had both benefits and costs, although at first it seemed that only good could follow: ‘In New South Wales the gardens of the settlers are filled with the plants which they cultivated in their native country. Colonization universally produces this good; and thus the intercourse of mankind may in time make the world one vast garden, in which all the blessings of a bounteous Providence shall be naturalized, as far as climate, or the science of man, can render those plants common to all, which were originally the property of the few.’ (Mudie 1829). It has taken a while for the costs to become apparent. The globally unplanned and unregulated redistribution of plants, the sharing of the world’s botanical bounty, has come at considerable detriment to the natural environment. Though there was a vigorous international exchange of plants, even after WWII, the downside of cultivated plant globalisation was surfacing as a series of environmental and social problems that included the potential for genetic piracy, the inadvertent spread of invasive weeds, and the pervasive environmental impact of agriculture, horticulture and forestry on natural systems.

One way of assessing plant redistribution is by looking at the historical record of plant numbers. In 1500 the total number of recorded plant species stood at around 1000, which was the total descriptive legacy of the ancient and medieval western world (Morton 1981, p. 145). Conrad Gessner in his De Hortis Germaniae Liber of 1561 listed over 1000 plants growing in German gardens (Stearn 1984). By 1623 the number of known and described species had increased to about 6000 and, in 1753, about 10,000 (Linnaeus’s estimate), a tribute to the botanical scholarship of the modern era. European botanic gardens competed to hold the largest collections of cultivated plants: in the 1660s Jardin du Roi (c. 4000); 1720 Hortus Botanicus Leiden (c. 5900); 1770 Chelsea Physic Garden (c. 5000). In 1788 Head Gardener Thouin of the Jardin du Roi in Paris claimed 6000 species, the most numerous in Europe confirmed in 1789 by Kew’s inventory (c. 5500). However, Kew’s total had climbed to about 11,000 by 1813 until, by the 18th and 19th centuries, the desire to accumulate had been replaced by more selective and thematic collection policies.

The phase of plant ‘discovery’, most notably that of food and ornamental plants, has now slowed down with the major prizes already seized, this being one useful marker for the transition from Industria to Informatia. Though the homogenisation of the world weed flora is likely to continue for a while, plant novelties of the future are more likely to be obtained by biotechnology – breeding and genetic engineering. Historian Blainey’s prescient remark that, at the time of Australian settlement ‘Nature was still seen as the great creator and inventor’ (Blainey 2015, p. 378, see later) draws attention to the way 20th century science has turned away from the natural world to one where the economic plant wonders, the discoveries of the future, are more likely to emanate from biotechnology than dark, mysterious and unexplored jungles.

All this arose not only from the initial ‘spice race’ but also from a Western tradition of plant prospecting on a grand scale that dated back to antiquity – as plant hunting by soldiers, merchants, governments officials, missionaries and other ecclesiastics, gardeners and botanists (employees of botanic gardens, horticultural societies, wealthy nurseries) and sometimes self-employed adventurers and biological bounty hunters. Many lives were sacrificed in the pursuit of ornamental plants, reminding us of the high price we are prepared to pay for natural wonders. It also reminds us of the need for horticultural botanists to not only find ways of satiating the public desire for plant diversions, but to also document patterns of human plant dispersal (local and global) with dates of introduction and commercialisation.
Much has been written informally on the introduction of plants to the British Isles without due recognition that with Britain, in effect, a repository for ornamental plants, this was also a major point of plant entry to the Western world and beyond (see Campbell-Culver 2004). Intrepid plant hunters are now a vanishing breed, partly because of the diminished area of unexplored land in the world, and partly because of the unfortunate environmental consequences of unregulated plant introduction. In response to the emergence of cosmopolitan temperate and tropical weed floras (both urban and rural) international biosecurity standards have now tightened, limiting the intermingling of native floras.

In the course of the Age of Plants there has been a redistribution of world vegetation that has entailed a ‘Macready explosion’ of cultivated plant biomass relative to that of wild plants along with a reconfiguration of the species composition of plants across the surface of the planet, most obviously cereals and the beverages tea, coffee, cocoa and cola and major plants of food and industry such as timbers, spices, sugar, cotton, rubber, tobacco and garden plants – our planetary stock of plants available for agriculture, horticulture and forestry. We now mostly experience nature through rural landscapes, parks and gardens which consist largely of anthropogenic (human introduced and selected) plants . . . with all the benefits and costs that this has entailed.

The end of an era?

The dawn of the Age of Plants was signalled by two key events, one scientific, the other socio-economic. First, was the origin, in the 1540s, of botany with the first plant professors in the world’s first modern-era botanic gardens at the dawn of the European Scientific Revolution. Second, was the launch of a European spice race to locate the source of the lucrative botanical holy grail of nutmeg, mace and cloves on the other side of the world. This was the first major step towards a global economy, achieved without using the plant energy or fossil fuels but, instead, the power of wind propelling sailing ships. The following 400 years of exploration, trade and economic botany reached its height with 18th century botanophilia before plants became deeply rooted in the socio-economic fabric of complex industrial societies.

But what justifies the claim that the Age of Plants is now essentially played out?

The answer to this question lies both in the closure of scientific projects that had their serious beginning at the start of the modern era, and in the onset of a new set of social, economic and environmental circumstances specific to Informatia.

There are at least three major scientific endeavours that are, in effect, heading towards completion.

First, the global plant inventory launched at the start of the modern era and gathering pace through the 18th and 19th centuries has an end in sight, marked by the accomplishment of a World Flora (http://worldfloraonline.org/). The Plant List Version 1.1 (Sept. 2013, see http://www.theplantlist.org/ ) is a working list of all known plant species of vascular plants (flowering plants, conifers, ferns and their allies) including mosses and liverworts. A recent Kew publication refers to 350,699 accepted species names in 17,020 plant genera which we assume approaches the actual number (RBG Kew 2016). Though taxonomists studying non-vascular plants and fungi will have work for many years to come, the discovery and description of vascular plants is now tapering into its final phase. The remaining vascular plant taxonomy has concentrated on tropical regions with the exact locations of vulnerable species withheld and international trade performed under CITES regulation.

Second, though technologies with the capacity to finalise plant classification have been heralded many times in the past, it does appears that full genome sequencing can now provide us with a finely resolved and lasting classification of the plant kingdom.

Third, the number of academic disciplines falling under the banner of ‘plant science’ multiplied rapidly through the 19th century and, by the mid-20th century, the in-principle problems of plant structure and function had been resolved. Plant science then, uniting with new technologies and global concerns, turned its attention to new scales of research. Under the influence of the 1960s environmental movement and ecologically based subjects (ecology itself a late starter) some research was becoming more holistic and directed at the global scale – subjects like conservation biology, environmental history, environmental science, studies of food security, the influence of plants on the global carbon and water cycles, sustainability etc. On the other hand, the cracking of the genetic code in 1968 spawned a host of new disciplines in molecular and evolutionary biology that found wide application in industrial biotechnology.

The world of gardening has also undergone major social transformation. Post 1950s populist horticulture has had to cater for the small-scale gardens of vast suburbias. Garden plants, like the major economic plants of agriculture and forestry, are now globalised (Spencer & Cross in press) giving us a seemingly infinite and shared palette of plants for our streets, parks, and gardens. The introduction to the New Royal Horticultural Society Dictionary of Gardening (1992) by historian William Stearn opens by noting the ‘ . . . enrichment of gardens by [the] ever increasing introduction of new plants’ and the manager of the world’s most comprehensive database of garden plants in England has recently declared: ‘Other countries have quickly acquired (doubtless with the help of the RHS Plant Finder) the same plants we grow here, resulting in the internationalisation of the world’s garden flora’ (Lord 2017). The plants of The European Garden Flora (Cullen, Knees & Cubey 2011) are clearly similar to those of the Horticultural Flora of South-eastern Australia (Spencer 1995-2005) and the internationally-sourced range of street trees in London (Wood 2017) is hardly distinguishable from those growing in the streets of Melbourne, Australia. Wikipedia’s List of garden plants is an international compendium of 2264 genera which is 13% of the world total. There are now garden floras of Spain (Sanchez de Lorenzo Cáceres 2000-2010), Europe (Cullen, Knees & Cubey 2011), North America (Bailey 1949, now becoming outdated), South-eastern Australia (Spencer 1995-2005), Hawaii and the tropics (Staples & Herbst 2005) which collectively amount to the foundations of a global Flora of cultivated plants.

Economically we are experiencing plants in an increasingly detached and cryptic way. World-wide the plant diet is now founded on about 15 cultivated species of which four make up the major supply: wheat, rice, corn and potatoes. Even considering today’s predilection for boutique foods, international cuisine, and the move to vegetarian and vegan diets, new plant foods – and even garden plants – are now increasingly likely to be the products of culture . . . wonders of technology, not wonders of nature. By the end of the 19th century the era of global botanical and horticultural exploration was already on the wane as plant hunting moved away from ornamental plants and back to its origins as a search for medicines and plants with undiscovered chemical properties and practical applications. The likelihood of finding new world-changing crops like wheat, tea, coffee and sugar seems remote: nature, it appears, has now yielded most of its ornamental and economic treasures. The politics of international plant collection and trade has also changed dramatically, being transacted by permission and invitation rather than persuasive plunder.

The international supply of food plants today is a consequence of large-scale industrial farming and an agribusiness that accesses stock seasonally from the world pool. The ongoing Green Revolution(s) is now dependent on sophisticated biotechnology (genetic engineering) to increase crop yield per unit area and provide the food energy needed to sustain humanity through peak human population, expected to be around 11.2 billion people as we approach 2100, before a decline in numbers occurs (DESA 2017).

Environmentally there has been a further progression in urbanisation and land appropriation as the world population moves from rural to urban surroundings. Up to the early modern period small-scale rural subsistence provided a uniform standard of living across the world with food production the major occupation for all but the social elites. Industrialisation in the Age of Plants introduced a new form of land use and lifestyle as the number of people employed in agriculture dropped dramatically in a global migration from rural to urban centres. Today about 55% of people live in cities, a figure that is expected to reach 68% by 2050 (UN Department of Economic and Social Affairs) as rural land is absorbed by peri-urbanisation (Shaw et al. 2020) and as expanding city suburbias coalesce with those of other cities to create the ‘megalopolis’. Increasingly divorced from wild nature during the Agricultural Revolution, citizens of Informatia are now becoming more and more detached from their rural roots as well. Within the ‘concrete jungle’ it is now in parks and gardens that most of us, most of the time, encounter plants and nature.

Though yet to be formally ratified, the most significant environmental signal for a new human transition is the declaration of the Anthropocene, proposed as a human-induced geological-stratigraphic period bounded by the explosion of the world’s first nuclear bomb in 1945 followed by a period of widespread nuclear testing. This time ‘has the most pronounced and globally synchronous signal’ and it is ‘ . . . from the mid-20th century that the worldwide impact of the accelerating Industrial Revolution became both global and near-synchronous’ (Zalasiewicz 2015). The ‘bomb’ is just one of the human influences that have, over this period, influenced global biogeochemical cycles. Though per capita HANPP is decreasing; in absolute terms its substantial increase in the latter half of the 20th century serves as a benchmark indicator for the Anthropocene. The International Panel on Climate Change in its 2019 Refinement to the 2006 Guidelines for National Greenhouse Gas Inventories notes that land produces about a quarter of global emissions, recommending combatting human-induced climate change with modifications to human diet and land use, and pointing out that desertification has the greatest impact on poor nations and those occupying arid regions.

It is easy to become maudlin about this transition out of the Age of Plants and into Informatia. As urbanites, most of us know the names of only a few trees, common garden and food plants, and some weeds. We have hardly noticed the passing of a rich plant mythology, folklore, and symbolism . . . the ritual and meaning that was once so much a part of our association with plants. Echoes of this past come to those living in the West through, for example, the numerous references to plants in the works of Shakespeare, the Bible, and traditional poetry, the ‘doctrine of signatures’, and ‘language of flowers’ as well as the rich plant history that was part of religious ritual such as the harvest festival, May Day, and a deep awareness of the seasonal cycles of nature. Todays ‘. . .useful flowers’ are devoid of even the 19th century ‘ . . . sentiment, morality, snobbery and controversy’ (Scourse 1983, p. 1). We have unwittingly exorcised old cultural meanings and associations, rejecting them as superstition and imaginative over-indulgence. Challenged by evidence-based science, they have fallen out of favour. We find it of little consequence that our word ‘flora’ referred originally to a Roman goddess, or that the annoying Latinised names of plants are a brilliant distillation of the history of botany, a binomial narrative taking us on a fascinating journey from antiquity to the present. Many traditional medicines, materials and natural products have been replaced by synthetics – like the hyper-real plastic plants now pervasive in offices and shopping malls. Mass production and artificial environments have won the day. Plants are no longer socially charged objects of meaning and wonder. We are not entranced or impressed, like our 19th century predecessors, by the thought of plant novelty or the countries and peoples where unfamiliar plants are found.

Nostalgia or not . . . as sources of inspiration for our creative imagination, plants are on the decline, becoming buried among all the commodities of our daily lives – the globally dispersed systems of manufacture and trade, food production and technology – so that their significance becomes obscure, difficult to assess, and therefore overlooked. Most of us neither know nor care, for example, how our vegetables and fruits are grown, where they were sourced, their genetic history, or the resources required for their cultivation and distribution (for a contrary view see Vickery 2019).

The golden years of the RBGV under 19th century directors Mueller and Guilfoyle coincided with a period when industrial Victorian England was undergoing rapid social change and the British Empire was at its height. Neo-European educated elites, like those in America, were heir to British classical liberal democratic values and Renaissance humanism. The character of Australian institutions and lifestyles, including its science, botany and horticulture, was firmly British, so understanding this social context, including that of Britain’s parks and gardens, provides insight into the significance of this time for not only Australian but world plant history.
We need to look more closely at this British legacy if we are to understand botanical developments in Australia.

The Scientific Revolution

The period encompassing the Scientific Revolution is generally taken to begin with the Copernican Revolution in 1543, gathering momentum with the inductive logic and empiricism promoted in Bacon’s Novum Organum (1620), and ending with Newton’s Principia in 1687. From ancient times mathematics, physics, and astronomy retained the status of core science subjects, even when challenged by Aristotle‘s philosophy of biology. But biology would re-emerge in the years leading up to and including the 18th century Enlightenment, having its own revolution about a century after that of the physical sciences and culminating in the taxonomic work of Carl Linnaeus (1707-1778) and the botanical world of Joseph Banks (1743-1820).

Modern plant science is dated to the appointment of professors of botany to the medical faculties of universities (the physic gardens and herbaria of the first early-modern botanic gardens) in the mid-16^th century Renaissance Italy. The term ‘botany’, referring to the scientific study of plants, was first generally accepted in the mid-17^th century, while the full-blown Linnaean taxonomy toolbox did not achieve international acceptance until the mid-18^th century (Williams 2001). At first botany was largely medicinal botany with a literature that consisted of printed herbals (c. 1470-1670) as rudimentary plant encyclopaedias listing the medicinal properties of plants. Modern plant science thus emerged out of medicine as herbals evolved, on the one hand, into medicinal pharmacopoeias and, on the other, into the descriptive botany of regional plant floras. The arrival of new plants from overseas during the Age of Discovery accentuated the need for system and order in the plant kingdom, a need that grew during the later Enlightenment voyages of scientific exploration when it was botanists and their assistant gardeners who were often given pride of place among the naturalists aboard ship who were newly acquainted with the works of Linnaeus. An international consensus methodology of biological inventory was the great achievement of the Enlightenment’s most illustrious botanist-naturalist Carl Linnaeus who was in many ways the starting point for a biological revolution that has persisted to this day through Darwin to genetics and modern biotechnology – his taxonomic foundations supplemented by the work of botanists in France and England.

Competitive plant accumulation and inventory began in earnest in the 17^th century. Estimates of the number of wild plants in the world would take some time to become realistic. The classical world had bequeathed a legacy of about 1000 species descriptions. This number increased to 4,000 in 1613 (Jean Bauhin), and 6,000 in 1623 (Gaspard Bauhin) (Morton 1981, p. 175). English botanist John Ray listed some 18,700 different kinds of plants in his three-volume Historia Plantarum (1686-1704) although in 1753 Linnaeus (a few decades before Australian settlement by Europeans) estimated that the total number of plant species in the world was unlikely to exceed 10,000 (Stearn, 1959).

But there was also the world of cultivated plants as botanic gardens competed to hold the most extensive living collections (often associated with reference herbaria of dried plants, mostly collected in the wild). Up to around 1670 when the era of herbals was drawing to a close the total number of recorded cultivated species remained at around 1000 species with few additions since the classical era. In the 1660s the Jardin du Roi claimed about 4000 species, in 1720 Leiden listed 5846 while in 1770 the Chelsea Physic garden had about 5000 until in 1789 Hortus Kewensis, a catalogue of plants grown at Kew, which included ‘… almost all the species then cultivated in England (Stearn 1961, pp. cvii-cviii) totaled 5500. But by 1813 Hortus Kewensis had swollen to 11,000 species and garden chronicler John Loudon in 1839 catalogued about 18,000 species in cultivation in Britain (check).

As plants flooded into Europe at the end of the 18^th century it was clear that Linnaeus had grossly underestimated. Between 1829 and 1933 Britain greatly extended existing plant knowledge as Kew botanists published a series of floras (effectively a stocktake of plants growing within the British empire, an Imperial Flora). These were Floras of North America, Antarctica, New Zealand, Tasmania, British West Indies, Sri Lanka (Ceylon), the Cape of South Africa, Hong Kong, Australia, and British India and the numbers of plants known to science quickly grew. Today the total number of naturally-occurring seed plant taxa in the world is estimated at about 374,000 (Royal Botanic Gardens Kew, 2016).

The microscope had opened up the discipline of plant anatomy in the 17th century and experimental botany advanced in the 18^th century as plant physiology united with anatomy to elucidate the mysteries of translocation, respiration, photosynthesis, and reproduction. From here new disciplines would diverge as, in the 19th century as more and more people became involved in the assembling of nature into collections … of living and dried plants in cabinets, museums, botanic gardens, the information housed in their associated libraries. United into a sophisticated republic of letters they formed learned societies, produced scientific and technical journals, often finely illustrated.

Commercial Revolution

Development of distance trade in Europe, which began in the Middle Ages, would develop into the international trade networks, mercantilism, and colonial expansion that preceded the Industrial Revolution. The outcome was a global economy with a sophisticated financial system of banking, insurance, and investment. Economic botany would play a major part in this complex social transition.

High on the list of socially captivating plants up to about the 18^th century were the aromatic herbs and spices, and medicinal plants. Our fascination with these plants probably dates back to their associations with gods and the spirit world. Their scarcity, religious significance, use as food additives, and association with distant paradise-like places guaranteed them high social status as luxury goods accessible only to the rich and powerful in a tradition that dates back to Bronze Age priesthoods and, before that, the shaman/medicine-men of pre-history. These aromata played a major role in Roman, and before that Greek, Egyptian and other civilizations, the use of scents and perfumes in religious observance continuing to this day.

The Age of Plants was launched when Europeans decided to by-pass the Arab and Indian merchant middlemen who controlled the lucrative trade in nutmeg and cloves sourced from a secret location in the East Indies.
The desire to control this trade resulted in a spice race that opened up maritime trade routes westward to the Americas and West Indies, and eastward to India and East Indies generating considerable wealth for the maritime countries of north-west Europe that faced the Atlantic Ocean. Western trade, formerly confined to the Mediterranean, now had unimpeded access to the world through the Atlantic, Indian, and Pacific Oceans. The resulting commerce would eventually create a global economy made famous by Spanish conquistadores plundering the gold and silver of native peoples but affecting peoples’ lives more directly through a circular Atlantic economy that involved trading in new food plants and the African slaves needed to maintain plantations of cotton, sugar, tobacco and rubber. First Spain and Portugal, then Holland, fought to control this trade.

Columbus’s voyages (1492) had opened up an Atlantic ‘Columbian Exchange’ (Crosby 2004) of plants, sometimes grown as plantation crops, and these would transform European cuisine.

Exchange of animals and plants between Europe and the Americas included not only agricultural and horticultural crops but their commensals and diseases in a fusion of Old World and New World biology now known as the ‘Columbian Exchange’(Crosby, 2004), named after Christopher Columbus. During the Great Divergence the western food palette, much of it inherited from the Roman Empire, was enhanced by the horticultural crops that were the spoils of exploration. These included not only vegetables, fruits, nuts and seeds, but food additives like sugar, beverages like tea, and coffee, but also non-food crops like tobacco, cotton, and rubber – essentially economically important plants not included in the other groups. New World food crops passing to Europe included avocado, cashew, cassava, chilli peppers, cocoa, Jerusalem artichoke, Lima bean, peanuts, pineapple, pumpkin, French and runner beans, squash, sunflower, sweet potato, and vanilla – but perhaps most notably the tomato and potato (Vaughan & Geissler, 1998). In return, Old World crops introduced to the New World (in addition to the traditional cereals) included the apple, apricot, eggplant (aubergine), cabbage, chick pea, citrus, coffee, grapes, mango, olives, onions, peaches, pears, spinach, sugarbeet, and tea. From Africa came sorghum, henna, and watermelons (Vaughan & Geissler, 1998).

Garden plants appear to have been of little economic or environmental consequence in this exchange but there were several important consequences. American trees and shrubs with spectacularly coloured autumn foliage (e.g. maples, liquidambar) would transform European and later world temperate landscapes. The development of a commercial nursery industry to feed the British hunger for garden plant novelty was also popular on the continent as a tradition and enthusiastic hobby to be passed on to the colonial Neo-Europes. Unfortunately ornamental plants occasionally jumped garden fences

Today’s seemingly inconsequential medicinal plants had initiated the establishment of the first Renaissance botanic gardens in Italian universities where plant medicine would be transformed into modern plant science: and today’s seemingly inconsequential spices initiated the global economy.

Clearly there is a close connection between economic botany, plant hunting and exploration, and Cultivated plant globalization.

Cultivated plant globalization

The human relationship to plants has passed through three major phases: as an association with wild nature and wild plants, to the cultural environment of cultivated plants and agriculture in rural environments adjacent to wild nature, to urban-industrial cities societies that have supplemented the life-sustaining energy of food plants with the additional cultural benefits made possible by the use of the concentrated plant energy present in fossil fuels to post-industrial societies.

Globally, wild natural landscapes have been progressively transformed into cultural landscapes. Though the effects of human fires in prehistory cannot be ignored, along with the use of land for agriculture during the Neolithic Revolution, the rate of land appropriation for human use has increased dramatically over the last 300 years during the Great Divergence as the world population has increased from about 480 million in 1550 to 2 billion in 1800 and 7.5 billion in 2018. Today more than half the population lives in cities and by some estimates more than half of the earth’s ice-free land comprises rangeland, pasture, crops, and human settlements.^[3] Cultivated plants now cover a significant proportion of the earth’s land surface and, as anthropogenic biomes (anthromes) they are a key global indicator of human planetary impact in the Anthropocene requiring global monitoring and integration with other ecosystems.^[2] It is the task of cultivated plant taxonomy to monitor the classification and nomenclature of the cultigens (anthropogenic plants) that constitute the bulk of these cultivated plants.

The study of the historical geography of cultivated plants (the factors that have given rise to their current distribution and species composition) is still in its infancy. The distribution of wild plants proceeds as an examination of biotic and abiotic factors. Spencer and Cross (in press) have accounted for the human factor in plant distribution by relating the historically sequential distribution of six economically important plant groups (cereals and staple crops, spices and medicinal plants, horticultural crops, timber trees, ornamental plants, and naturalised plants) to four broad and interlinked geopolitical historical periods (the Agricultural Revolution (c. 10,000-2000 BCE), Bronze Age civilizations and trading networks (c. 4000-750BCE), historic mostly land trade between East and West (c.3500 BCE-1500 CE), and the Great Divergence (c.1550-1914).

Neolithic Revolution – c. 10,000-2000 BCE

The first major phase of plant cultivation modifying plant geography is generally associated with settled communities of the Neolithic Revolution that grew and distributed cereals along fertile river valleys in the Near East, India, China, the Americas around 10,000 to 6000 BCE although plantations of banana and taro in the highlands of New Guinea are believed to date back about 10,000 years. The first gardens and functional urban spaces amenable to plant cultivation are associated with Bronze Age cities where the influence of culture had become more important than that of nature and where the scale of civilization had enabled trade, diplomacy and military conquest.

A few cultivated plants were no doubt distributed during the Neolithic Agricultural Revolution. In the Americas civilisations were, from about 5500 BP founded on maize, in Europe on wheat c. 10,500 BP in Europe and on rice in Asia c. 7500 BP.

Bronze Age Civilization c. 4000-750 BCEs

Cultivated plant dispersal gathered momentum when agrarian communities turned into urban city-states that engaged in long-distance exploration, expansion, and trade based mainly around Egypt, Mesopotamia and the Mediterranean in the West, and the Yellow and Yangtze Rivers in the East. Exchange between East and West, chiefly in luxury goods, occurred along the Silk Road, this route being especially active during the period of the Roman Empire and Han Dynasty.

Trade between East and West – c. 3500 BCE-1500 CE

A greater range of food plants, along with herbs and spices, were later dispersed along major trade routes between the ancient core civilizations of Mesopotamia, Egypt, and India, and across the steppes of Central Asia to China in the East.

The Silk Road connecting the Mediterranean with China and Japan was at its height during the great days of the Han dynasty and Roman Empire (c. 202 BCE-220 CE) when there was also a southern offshoot, the Indian Grand Trunk Road which linked to the Incense Route across Arabia and Horn of Africa. Between 1100 and 1430 China was a thriving trading nation before turning inwards, internal trade being greatly enhanced by the completion of the Ming dynasty 1700 km-long Grand Canal which linked the Yellow and Yangtze Rivers in 1415.

Perhaps it was with the Romans that plant distribution gathered momentum at a time when historical records become more accessible. Archaeological research has revealed that during the Roman occupation of Britain about 50 new (presumably) food plants (mostly Mediterranean fruits, herbs, spices, and vegetables) were introduced by the Romans to supplement the local food (Van der Veen & Hill 2008). Of these 50 species, 36 (over 70%) are now naturalised in Australia. (check)

An imprecise second phase of cultivated plant distribution occurred between about 3500 BCE and 1500 CE as a cultural diffusion between East and West which had been geographically separated by the inhospitable steppes of Central Asia. Western trading networks had united the Eastern Mediterranean with the great European rivers flowing into the North Sea including an Amber Road into the Baltic. By the time of the Egyptian New Kingdom (c. 1550-1070 BCE) ships were trading along the Nile, Red Sea, East African and Arabian coasts connecting to trade routes that extended to India and beyond (Cunliffe 2008).

Islamic Golden Age

Between the 8th and 14th centuries there was an Islamic Golden Age as Muslim forces occupied North Africa, the Iberian Peninsula, the Middle East, to the borders of India, Central Asia, and China, giving way to the Ottoman Turks between about 1300 and 1600. The Ottomans dominated much of world trade and were responsible for the distribution of several major economic crops. When Constantinople fell to the Turks in 1453 scholars and merchants fled to the trading Italian city-states of Venice, Genoa where the beginnings of a Western cultural Renaissance were stirring. During the Middle-Ages Islamic culture controlled trade through the Middle East and much of the Mediterranean region including the Iberian Peninsula, so Arab merchants were at this time the primary agents of worldwide plant exchange, several introductions to Europe arrived via Moorish Spain probably including the eggplant (aubergine), lemon (possibly Roman), lime, pomelo, rice, Seville orange (possibly Roman), and spinach (Vaughan & Geissler, 1998).

The Italian city-states were a major influence on global commerce at this time. Around the 9th century Venice was the financial centre of Europe becoming, by the 13th century, the most prosperous city in Europe, trading in silk, spices, gold, silver, and jewels.

After a period of Islamic East-West exchange that followed the decline of the Roman Empire, Western Europe entered an Age of Discovery as maritime trade moved out of the Mediterranean to establish an Atlantic economy while other trade routes reached across the Indian Ocean to the Pacific Ocean and Indonesian Archipelago. During the Enlightenment there was a major acceleration in scientific inventory and economic growth. Through the 17th to 19th centuries uncompromising colonial expansion knitted disparate trading networks into a European-led global economy that exported temperate agriculture and forestry to temperate regions of the world, merged the horticultural crops of the eastern and western tropics, and imported ornamental plants on a grand scale (Drayton, 2000; Crosby, 2004). This Western ascendancy, the Great Divergence, was injected with additional impetus as the Industrial Revolution in north-west Europe released the additional power of machinery using fossil fuels, modernizing transport and communication systems, and launching industrial agriculture.

The connecting the great ancient civilisations of East and West, and the later world religions Christianity and Islam, were a minor prelude to the monumental changes in cultivated plant geography that would occur during the relatively brief 400-year third phase, the Great Divergence (c. 1500-1914).

The Great Divergence – c.1550-1914

The period of British Empire between the defeat of Napoleon at Waterloo in 1815 and the eve of World War 1 in 1914 as a critical period for environmental, social, political, economic and environmental history as European people, institutions, technology and biota passed into Africa, India, the Americas, Asia, Australasia and elsewhere accompanied by their domesticated and other biota, but most notably their favoured cultivated plants of agriculture, forestry, and ornamental horticulture. This was the final gasp of colonial plant bounty hunters, adventurers, missionaries, entrepreneurs, and scientific explorers – a continuation of former activity but accelerated by the energy of fossil fuels, the world population over this period doubling from about 1 to 2 billion.

The acceleration of cultivated plant globalization through the Age of Plants has changed the landscape of the world, altering plant geography for all time with the spread of agriculture to new regions of the world, along with industrial-scale horticultural crops, forestry, and the diversity of species available to ornamental horticulture. So great has been the impact that we can add a sixth category to this list of plant groups as a by-product of the others – the spread of exotic plants from cultivation into native vegetation (Spencer & Cross in press). The arrival of maize and sweet potatoes in China probably accounts for some of the population increase from 140 million in 1650 to 400 million in 1850 (Standage 2010, p. 124). Maize and potatoes did the same in Europe, the latter an important ingredient of the Industrial Revolution. Effect of diseases on native peoples.

The biological globalization that occurred during the Great Divergence included both plants (Spencer & Cross in press), and animals (Kisling 1998) including pests and diseases, although It was plants in particular that were at the centre of this period of unprecedented social, economic and environmental change. By far the greatest environmental impact of The history and impact of ornamental plants has received much less attention.

Spices

Human plant distribution across the world gathered pace during the 16th century as the search for the source of nutmeg and cloves led to the establishment of European maritime trade routes. Following a western route had led eventually to the Americas and a ‘Columbian Exchange’ (named after Columbus) of socially- economically- and environmentally-transforming plants flowing between the Old and New worlds.

Sailing around the Cape of Good Hope, and across the Indian Ocean towards to the Pacific where the source of nutmeg and cloves was finally located in 1512 by the Portuguese in the Banda Islands of the Indonesian Archipelago, prompting the establishment of colonies and trading hubs throughout the tropical East Indies. The result of a hunt for luxury spices, European trading hubs and colonies were soon dotted along maritime trading routes that spanned the world.

Horticultural crops

Among the plants passing from Europe to the Americas as part of a ‘Columbian Exchange’ were: apple, apricot, banana, eggplant, cabbage, chick pea, citrus, coffee, grapes, mango, olives, onions, peaches, pears, rice, spinach, sugarbeet, tea, and wheat. From the Americas to Europe came: avocado, cashew, cassava, chili peppers, cocoa, Jerusalem artichoke, Lima bean, maize, peanuts, pineapple, pumpkin, French and runner beans, squash, sunflower, sweet potato, vanilla but most notably the tomato and potato. This was the most significant human-related plant impact on the planet since the Agricultural Revolution.

New horticultural plantation crops at the heart of this economic transition were profoundly socially-transforming, a second wave of food and material plants in addition to the cereals and pulses of the Neolithic Revolution – the plant-based beverages tea, coffee, wine, cocoa and, later, cola (Standage 2007) as well as the cotton, tobacco, rubber, and sugar plantation crops associated with the slave trade that had moved the focus of European culture and trade out of the Mediterranean into a highly lucrative circular Atlantic economy with manufactured goods passing from Europe to Africa and the Americas before returning to Europe with cotton and sugar to then repeat the cycle (Musgrave T. & W. 2000; Prance & Nesbitt 2005). Tropical plant products had been added to Europe’s temperate staples.

Modern-era crops were now passing along the new and busy world trade routes. Exchange of horticultural crops between imperial trading hubs in the East and West Indies created a pantropical food source and new exotic fruits and other plant delicacies appeared on European tables. Temperate cereals were introduced by Europeans to arable land in the Neo-Europes of North America, Australia, Tasmania, New Zealand, South America, Africa, parts of Asia and elsewhere – grown on land that had been seized in a series of colonial 18th and 19th century land grabs. In Australia it took 50 years or so to settle most of the continent’s prime agricultural land that stretched in an arc from southern Queensland through New South Wales and Victoria to South Australia. Though providing food for the rapidly expanding population, these land grabs supplanted natural ecosystems and often displaced indigenous peoples, introducing western industrial agriculture with its crop monocultures and associated commensal invasive biota.

Throughout history scarce natural products have been prized as exclusive therefore expensive luxury items available to a privileged few. This was the case for spices collected in Punt for Egyptian Pharoah Hatshepsut (1508–1458 BCE), the tulips of tulipomania in Holland whose financial bubble burst in 1637, and the spices that prompted the trans-oceanic spice race that unleashed the European Age of Discovery. During the 18th century, Europe’s social elite engaged in polite competition to acquire the world’s plant gems as they were discovered and returned from distant lands as ornamental plants were collected, exchanged, and commercialized on a grand scale across the world through an increasingly vibrant nursery industry.

Wonder & opportunity

On the one hand scientific curiosity was beginning the process of global bio-inventory by accumulating knowledge about the distribution and composition of world vegetation and, on the other, there was the desire to own and compete, both socially and economically – to hoard rare and beautiful objects in horticulture – to own and preserve nature’s precious wonder in a garden, for oneself, one’s country, and posterity. These two motives appear to have driven the distinctly western desire to amass collections of objects and knowledge – in cabinets, museums, botanic gardens and libraries. For the plant world this translated to stacks of dried plants displayed on card as herbarium specimens in herbaria, and the stockpiling of living plant collections in public and private gardens, and displays of the natural order labelled in Latin (the language of learning) in botanical gardens.

It is difficult to quantify the process of plant globalisation. The impact on land and landscape came from the distribution of relatively few different kinds of cereals and other crops. The introduction of species diversity was a consequence of the passion for novelty in ornamental horticulture. In Britain trade in ornamental plants was at first London-based, the number of commercial nurseries increasing from 5 to 15 between 1690 and 1700. By 1760 there were about 42 nurseries in London and 40 in the provinces (Harvey 1974, pp. 4-6). From this time on, the numbers of plants and commercial outlets would explode, facilitated by not only overseas exploration but by the improvement of the canal system, the building of railways, increase in worker leisure time, improved technologies like cartography and shipbuilding, wide use of the Wardian case, and so forth. In 1839 Loudon’s list of 18,000 species in cultivation in Britain would become dwarfed towards the end of the 19th century. The English Plant Finder of 2018 has 72,000 entries although Britain may have as many as 400,000 different kinds of plants (RHS 2015). Plant Finders produced in Australia (2004) and New Zealand (1997) listed 35,000 and 22,000 respectively, both based on 400 nurseries.

Whatever the motivation, the gathering of botanical novelties from around the world enthused gardeners with a vastly increased palette of ornamental possibility that inspired some of the world’s finest botanical art, and it coaxed natural scientists into a phase of unprecedented taxonomic and descriptive botany.

More important than the gathering of global plant diversity in European gardens and conservatories was the impact of changing cultivated plant geography at the planetary scale, both in terms of the land area covered and species composition. Between 1650 and 1850 the world population had doubled and this trend showed every sign of gathering pace.

Following a westward route across the Atlantic Columbus (a Genoese sugar merchant) found the West Indies and Americas, as leading to an Atlantic trade that would encompass Europe, Africa, and the New World. Following an eastern route Diaz first rounded the African cape (1488) and Da Gama extending the route across the Indian Ocean to Calicut and the spice-rich Kerala coast (1498), ?others reaching Malacca in the same year. Antonio de Abreu located the Spice Islands with their nutmeg and cloves (1512) before the Magellan expedition completed the world’s first circumnavigation (1519-1522).

The most obvious presence of cultivated plants in our world, both spatially and in terms of biomass, has occurred through the use of land for food production. The Great Divergence bequeathed us a planet with about 11% of the land surface used for crops (UNFAO, 2015) although this figure can conceal much wider human ecological influence. Human appropriation of planetary net primary production now totals about 25% (Kraussmann et al., 2013). In the current human-centred geological epoch, the Anthropocene, cultivated plants are a key indicator of human impact since they are major constituents of planetary anthropogenic biomes or ‘anthromes’ (see Ellis & Ramankutty, 2008). Though only about 5% of forests (which cover about 30% of the world’s land surface) consist of timber plantations, a far greater percentage is actively managed, enclosed, or semi-natural (World Bank, 2017).

Naturalised plants

One consequence of the blending of wild and cultivated plants has been the global expense of managing alien and invasive species (which can make their presence felt in unexpected ways).
There are now near-cosmopolitan tropical and temperate urban weed floras and, of the world’s 374,000 species about 44,000 have naturalized beyond their natural distribution (Randall, 2017). The senior author of this paper has noticed that weedy plants growing around the rails of Kew’s tube station in Richmond, London, are almost identical to those growing at Richmond Station, near the Royal Botanic Gardens in Melbourne, Australia – a quirky reminder of the human-plant alliance in globalization, and the trend towards floristic homogenization.

Apart from the agricultural cereals of the Neolithic Revolution, it is likely that the first major influx of exotic plants to Britain occurred during its occupation by Roman garrisons (c. 45-410 CE). Archaeological research has revealed that during this period about 50 new (presumably) food plants (mostly Mediterranean fruits, herbs, spices, and vegetables) were introduced by the Romans to supplement the local food (Van der Veen & Hill, 2008). Of these 50 species, 36 (over 70%) are now naturalized in Australia – another striking example of the cultural diffusion of plants around the planet and another signal that plants do not recognize the boundaries of our fields and gardens.

From the Age of Discovery into the Enlightenment

Western civilization, born out of cities trading along the fertile river valleys of the Nile, Tigris and Euphrates developed into the Mediterranean civilizations of the Phoenicians, Carthaginians, Greece and Rome. There was a fascination with the mystery of distant lands, the beauty and utility of unknown plant treasures that could be grown in gardens and fields as trophies of human endeavor drove adventurers ever outward. From ancient and classical times plants had featured among the spoils of trade, exploration and conquest. The role heroic conqueror, intrepid adventurer, and curious naturalist would continue into the 20th century in the form of the garden Plant hunter.

Claudius Ptolemy’s (c. 100-c. 170 CE) classical map of the world remained the standard navigational reference for over 1000 years until completely re-drawn during the Age of Discovery when the first circumnavigation of the globe occurred, and the coastlines of the world’s continents were charted. Awareness of this finite world prompted the first steps towards the documentation of the earth’s biota that included printed regional floras of wild plants as an advance on the old herbals. One major exemplary contribution was the completion of what was, in effect, a flora of the British Empire beginning with the Flora of and ending with the Flora of in. .. Estimates of the number of wild plants in the world and ornamental cultivated plants …Wild plant

The outward journey of westerners in search of garden plants has been divided into a several geographic phases: bulbs from the Near East (1560-1620); herbaceous plants from Canada and Virginia (1620-1686); the Cape of South Africa (1687-1772); trees and shrubs of North America (1687-1772); Australian plants (1772-1820); tropical glasshouse plants and hardy plants from Japan and North America (1820-1900); West China (1900-1930) (Stearn 1965, 1971; Coates ). It is these forays into the unknown that have bequeathed us the familiar garden flora of the western world. The phases of economic plants is less secure … medicinal plants, etc.

To 18^th and early 19^th century Europeans the world still seemed a boundless and bountiful cornucopia of limitless resources and potential, all awaiting the attentions of enterprising merchants, entrepreneurs, adventurers, and scientists. But all too soon planet earth would, in the 20th century, take on the character of a limited and confined space, it would become a global village.

The industrial era changed everything as technology revolutionized daily life in Europe. Engineering created new canals, reservoirs and dams. Wetlands were drained for agriculture. Transport systems were transformed by the combustion engine while railways and steamships were penetrating the inland regions of newly occupied colonial territories from European coastal trading hubs on the continents of America, Africa, Australia, India and elsewhere. Communication engaged more people and travelled faster over longer distances, and this was aided by telegraph and telephone and a now vigorous Republic of Letters. Soon there would be reticulated gas and electricity.

The great seafarers in the Age of Discovery (c.15^th to 18^th centuries) were, first of all, plant hunters engaged in a spice race, explorers and discoverers second. Australian settlement followed in the wake of 16sup>thand 17sup>th century European exploratory mercantilism as first the Portuguese and Spanish, then the Dutch sought to by-pass the Arab and Indian merchant monopoly of overland and Red Sea spice trade by forging maritime trade routes to the Moluccan Islands in the East Indies (Spencer & Cross 2017). Dutch and Portuguese imperial expansion was eclipsed in the 18th century by that of England and France.

From today’s perspective the Enlightenment addition of art and science to former economic and strategic interests seems unusually admirable as botanists, gardeners, and biological illustrators were given pride of place among naturalists on dangerous scientific voyages to record the lands, organisms and peoples of places formerly unknown to them. In the absence of photographers and TV crews of today it was illustrators who could provide tantalizing glimpses of the exotic and new.

Enlightenment gardener-botanists, following in the tradition of Linnaeus’s ‘disciples’ (and earlier) were despatched into the world from Uppsala, were assisting botanists with the collection and transport of herbarium specimens, seeds, and live plants. Most were trained in Europe’s major botanic gardens, notably by Joseph Banks (1743–1820) at Kew Gardens in London, and André Thouin (1747-1824) at the Jardin des Plantes in Paris (Spencer & Cross 2017) but a few were supported by Edinburgh (and other) Botanic Gardens, as well as wealthy nurseries and patrons.

Information about these gardeners is often sparse, and many perished at sea, but among the better-recorded gardener protégés from Paris were: Félix Delahaye (1767–1829) of the Bruni d’Entrecasteaux expedition of 1791–1793. Delahaye was assistant to botanist Jacques-Julien de Labillardière who published what amounted to the first Flora of Australia based on the collections the pair made in Nouvelle Hollande. In 1792 over the 25 days of the first landfall in Recherche Bay, Tasmania, Delahaye established a vegetable garden as a source of food and propagation material for the indigenous people, and potentially a supply of provisions for future visiting European vessels. On returning to France Delahaye became Head Gardener to Empress Josephine at the Château de Malmaison where he specialised in the care of her collection of Australian plants.

Nicolas Baudin‘s scientific expedition (1800–1804) in the corvettes Géographe and Naturaliste, ostensibly to chart the coast of Nouvelle Hollande, make scientific observations and collect natural history specimens, was the grandest and most productive of all the Enlightenment voyages, but extremely costly in human life, only six of the 24 naturalists on the expedition returning home. There was a complement of five gardeners, Head gardener Anselme Riedlé (1775–1801) and assistants Antoine Sautier (?–1801). Also Antoine Guichenot (fl. 1801–1817) who survived to serve on the 1817 voyage of the the Uranie under Louis de Freycinet (who, in 1811, had published the first map of Australia’s entire coastline based on the work of the Baudin expedition), also François Cagnet and one other gardener.

Among Banks’s gardeners were Francis Masson (1741–1805) Kew’s first Enlightenment plant hunter who sailed with James Cook on HMS Resolution to South Africa, landing in October 1772. Masson remained there until 1775 and sent back to England over 500 plant species, in 1776 collecting in Madeira, the Canary Islands, Azores and Antilles ( ). In 1783 he collected plants in Portugal and in January 1786 returned to South Africa, remaining until March 1795 (Coates 1969, pp. 252-259). Anthony Hove was sent to Gujerat, India in April 1787, officially to collect plants for Kew but unofficially to collect seed of cotton. Attention then turned to the Pacific. David Nelson (?–1789) was gardener on Cook’s Third Voyage (1776–1779) and subsequently on William Bligh’s HMS Bounty (1787–1789), surviving a 3800 km journey in a small boat when cast adrift by mutineers, but then dying in Indonesia at Kupang. Peter Good (?–1802) was assistant to Robert Brown, the botanist on Matthew Flinders‘ first circumnavigation of Australia (1801–1803) thus identifying it as a continent who died on the voyage. Then there was the ill-fated George Austin (fl.1780s) and James Smith of HMS Guardian sent to Australia with vital supplies about one year after the First Fleet, but sinking after hitting an iceberg off southern Africa.

This short list of gardener-botanists – there were many more – demonstrates the high value placed on plants at this time. Much of this was a matter of simple economic botany and its search for revenue-generating food crops, fibres, beverages, medicines and structural materials.

As the popularity of spices declined so ornamental plants took over their role as scarce luxury plants that could demonstrate wealth and influence. But this time it was beauty not a connection with the gods that was at stake, as rare plant jewels of distant exotic nature were sought to adorn the gardens of royalty and the social elite.

Gardening & its democratization

Gardens, like cities, require planning, money and labour, infrastructure, and maintenance. When most people have little money or leisure time gardens are an excellent way of demonstrating social status, wealth, and sensitivity to worldly artistic and intellectual predilections of the socially influential. The classical Greeks had pleasure gardens but ‘ … labour in them was despised‘ presumably carried out by slaves in a tradition ‘ … maintained in grand British gardens until the 1920s‘.^[4] Heading the list of Europe’s dignitaries during the Great Divergence were Europe’s royal courts from which fashion and favour flowed.

In the 18th century no garden in Britain could compete with the splendour of the Palace of Versailles or the taxonomic work of French botanists at the Jardin du Roi (later Jardin des Plantes) in Paris. This was a golden age of horticultural and botanical art culminating in the genius of landscape architect André Le Nôtre and his masterpiece created for Louis XIV at Versailles, and the botanical illustration of two noted artists, Pierre Redouté, court illustrator to Marie Antoinette and especially his magnificent watercolour paintings of lilies and roses, and Ferdinand Bauer, court painter to the Prince of Liechtenstein, a travelling artist best known for his work on the floras of Greece, Asia Minor and Australia. In times of poverty ostentatious displays of wealth were just as likely to foment revolution as impress. As absolutist governments stirred up revolution people would try to copy their social superiors, gathering some of the society trappings for themselves. In the 19th century social change was well under way as Kew passed to the state in 1841 and, a few decades later, railways took increasingly affluent workers to the countryside, seaside, and football matches. Today garden styles once named after royal courts, Tudor, Elizabethan, Edwardian etc. are now determined by garden celebrities on television, the internet, and popular magazines as a democratic populism.

In the 18^th century there was a special excitement associated with maritime exploration and trade – the possibility of windfall profits and discovery of botanical novelties in distant lands. This translated into advances on many fronts – in taxonomic botany, economic botany, ornamental horticulture, and the role and objectives of botanic gardens. The world of plants became a preoccupation of high society including royalty, the wealthy, and leading intelligentsia, this engagement of influential personalities investing botany with a scientific and social prestige that it had never had before, and which it is unlikely to see again. Perhaps the culmination of these times occurred when the influential administrator Joseph Banks was president of the Royal Society from 1778 to 1820, presiding over the worlds largest collections of living and dried plants and the economic botany of Kew Gardens, the leading botanical institution of an empire that spanned the world.

Commercial plant nurseries proliferated, and women now joined men in nature studies and botanical art. Plant treasures from overseas were lovingly described and illustrated in the new garden periodicals. Overseeing much of this excitement were the scientists and gardeners of Europe’s major botanic gardens.

Though small in quantity, ornamental plants were dispersed in great variety to European colonies sharing a gardening obsession as commercial plant nurseries proliferated, and gardening was democratized.

The narrow academic interest in natural history broadened out into a much wider societal preoccupation as the Botanophilia of the 18^th century. Spurred on by the Enlightenment’s dedication to science, progress and learning the scholarly approach to plants was now combined with a lust for exotica, the thrill of travel and exploration, the enhancement of aristocratic gardens, and the possibility of windfall profits from new plant products. With an increasing distaste for privilege, especially that of royalty (this was also an Age of Revolutions), there was also an increasing popularisation and democratisation of science, scientific education and gardening.

Botany became the first publicly accessible science as, in the 19^th century interest in nature study, plants and gardens would pass from the educated and well-to-do to a much wider public as the consequences of economic botany would transform peoples’ lives. Botany would attract and accept the some of the first female scientists.

By the mid-19^th century industrial agriculture could boast sowing and harvesting machines and horticulture had lawn mowers. Improvements in the manufacture of glass and cast iron made the construction of the magnificent Crystal Palace possible for London’s 1851 exhibition demonstrating the British Empire’s economic and industrial progress, and the potential use of glasshouses for protected plant production. The Royal Society and other scientific institutions now connected the scientific community. Photography had begun and the world was on the brink of its first cars.

Botanic gardens

The role of botanic gardens has been a common link through this brief account of economic botany, plant exploration, plant geography, wild and artificial landscapes, social rituals associated with horticultural crops is now abundantly clear. It is in the broad context of the aims of plant globalisation – of spices and medicinal plants, cereals and staple crops, horticultural crops, timber trees, and ornamental plants – that colonial botanic gardens were born and, since this is reflected in their objectives today, it requires closer examination.

Today’s seemingly inconsequential medicinal plants had initiated the establishment of the first Renaissance botanic gardens in Italian universities where plant medicine would be transformed into modern plant science: and today’s seemingly inconsequential spices initiated the global economy.

Through the 16^th to 18^th centuries, which included the European Scientific Revolution, the Ages of Discovery and Enlightenment many botanic gardens had changed from Hortus medicus to Hortus botanicus as medicinal gardens became repositories for the flood of plants harvested from around the world during the European colonial expansion. While these plant novelties needed scientific classification and description, they also vastly extended the palette of ornamental plants available to western gardeners, their introduction stimulating the combination of art and science that we associate with today’s botanic gardens.

The 17th century Dutch botany and horticulture admired across Europe during the Dutch Golden Age was surpassed in the 18th century by that of Britain and France. At this time no garden in Britain could compete with the splendour of the Palace of Versailles or the taxonomic work of French botanists at the Jardin du Roi (later Jardin des Plantes) in Paris. However, Kew Gardens, during Banks’s watch from 1773-1820, under his program of imperial economic botany, would become the world’s pre-eminent Botanic garden.

At the time of Australian settlement botanic garden administration across the world was passing from royal patronage to the state. Absolute monarchy was under challenge and, though universal suffrage and fully democratic institutions were some way off, public opinion mattered. During the 19th century, the practice of science became professionalized and institutionalized, including the botany in practised in botanic gardens. But scientific work here was tempered by public impatience with the pursuit of narrow academic interests, leading botanic gardens to adopt thematic collections that leaned towards attractive design and display.

The general character of modern botanic gardens, including the modern functions of HB and CPT, are largely a product of European aspirations developed during this Age of Plants. Their contemporary relevance arises out of the peculiarly Western attraction to the system of science which, as botany, translated into the desire to collect plants in museums, herbaria, and botanic gardens where they could be named, classified, described, illustrated and cultivated as objects of novelty, utility, decoration, and scientific interest. Exploration of new territories and the discovery of the limits of the world’s land masses had increased the urge to catalogue and illustrate the natural world at all scales, from local to global. It was a desire that was embraced most enthusiastically by society as a whole during the Enlightenment with the excitement of its voyages of scientific exploration.

Botanic gardens could engage in a reciprocal exchange of both living plants and seed (the botanic garden International Seed Exchange had begun in the late 17th century, see Spencer & Cross 2017).

This was also a time of accelerating plant globalization, facilitated by botanic gardens, in an exchange that occurred between Europe, the colonial Neo-Europes (Crosby 2004), and the tropics.

It is now possible to list some of the major elements that, in combination, add up to an Age of Plants: the spice race that led to a mostly plant-based Atlantic and subsequently global economy; a second agricultural revolution this time based not on solar agriculture but, in addition, the fossil fuel needed for industrial agriculture; the initiation of modern botanic gardens and plant science aligned with the appointment of botany professors to the medical gardens of university medical faculties in early modern Renaissance Italy; an unprecedented phase of plant globalization resulting from the international dispersal of herbs and spices, the establishment of a Columbian Exchange of biota between the Old and New Worlds; the spread of temperate agriculture to temperate European colonies, the formation of a cosmopolitan tropical crop flora, the development of plantation economies based on socially transforming beverages like tea, coffee, cocoa and cola, the social drugs of tobacco, sugar and rum, and materials like cotton and Rubber; a global phase of European exploration, again based strongly on plants of economic, ornamental and scientific interest that moved first out of the Mediterranean into the Atlantic, then into the Indian and Pacific Oceans and opening up of China; an era of intrepid plant hunters; botanophilia.

Plants played a key role in this opening up of the world to the West was crucial, and it is from this phase of history that HB and CPT draw their inspiration.
This, then, is some of the big picture background to Australia’s botanic gardens, their historical raison d’être and early priorities.

Botanic gardens played a significant role in modern era globalization sometimes referred to as the Great Divergence which extended from roughly 1550 to around the time of World War 1 (Pomeranz 2000). This was a period when north-west European countries entered a period of colonial expansion as the West surged ahead of the rest of the world in political and economic power as the cities of coastal Western Europe benefitted from thriving trade, first between the Old and New Worlds across the Atlantic Ocean but then between countries on maritime trade routes across the Indian and Pacific Oceans. Colonial expansion culminated in the formation of the British Empire.

The Great Divergence produced a not only a global economy, it was also a period of unprecedented social change in science, technology, the arts, commerce, and more. During this period the world population more than doubled, this growth alone placed a great demand on the world food supply and ultimately on plants as primary producers while also making accessible many countries, peoples, cultures and plant treasures previously unknown in the West. Along with the globalization of Western institutions came that of biological globalization of human commensals – the migration of animals, plants, pathogens and diseases so closely associated with human activity.

Though botanic gardens were a part of the organizational structure that helped disperse various crops around the world their involvement with agriculture today is only incidental.

Botanic gardens, and by implication horticultural botany and cultivated plant taxonomy (and their hybrid, horticultural taxonomy) played a significant role in this social transition contributing to the general process of globalization but especially that relating to the British Empire and its network of colonial botanic gardens.

Commentary & sustainability analysis

Inanimate plants might appear uninteresting, inconsequential, and unlikely historical agents, They are, nevertheless, not only the life-support system for the entire community of life, they have underpinned the modern human cultural phenomena of globalization and industrialization.

Today most of the world’s population live in cities. Here we are not only divorced from wild nature but also increasingly ignorant of the cultivated plants of our rural surroundings, not knowing whether the vegetables and fruits we buy in supermarkets were grown nearby or in another country. The tomato we associate so closely with Italian cuisine is native to South America; chilli peppers of South America are widely cultivated in India; Australia’s most significant native commercial crop, the macadamia was, until recently, mostly sourced from Hawaii; the oil palm grown so widely in Indonesia and Malaysia is native to West Africa; the sugar that was grown in slave plantations in the Caribbean in the 16th century had first found its way from its origin (we think) in New Guinea to China, India, and Europe.

The urban areas of the world take up less than 3% of the land surface Liu & He, 2014). The vast areas taken up by the few but geographically widespread species used in the monocultures of agriculture and forestry contrast with the species-rich menu of ornamental plants cultivated in our urban parks and gardens. Garden plants are also, for both better and worse, globalized. As we have seen, we owe much of this to the English who remain the world’s greatest gardeners: ‘Other countries have quickly acquired (doubtless with the help of the RHS Plant Finder) the same plants we grow here, resulting in the internationalization of the world’s garden flora.’ (Lord, 2017). Just as uniting the world in trade has given us food choice, so the ‘internationalization’ of garden treasures has given us an almost infinite plant palette for our cities, streets, parks, and gardens.

But all too soon planet earth would, in the 20th century, take on the character of a limited and confined space, it would become a global village.

The Great Divergence was a dramatic increase in social organization as human society became more complex, interconnected, and interdependent. This process of globalization was closely associated with growth – of human population, knowledge, economies, political influence and more. The most obvious social change was the transition from rural agrarian societies towards urban industrialized societies powered by the energy of fossil fuels. There is a key historical causal link here between the mode of energy capture and the social organization on which cultural change and development depends or, in other words, the change from the life-sustaining energy provided by cereal crops and the way this can defer to other cultural pursuits when supplemented by the energy of fossil fuels.

Plant significance – meaning & symbolism

By the time of World War 1 folklore had become ancient superstition, religion was beginning its own decline into superstition with community traditions like harvest festivals and plant symbolism losing relevance. Shakespeare, so full of plant symbolism and meaning, would be superseded by cultural tropes of a different kind. Popular music, for example, does not compare beautiful women to flowers. Today plant common names are just as likely to be extracted from plant databases as discovered within the rural community. Natural vegetation had been replaced by cultural landscapes, the former passion for herbs and spices had dwindled to be replaced a new passion for ornamental plants and gardening, former society gardening fashions were more widespread across society, science in general flourished and plant medicines were being replaced by synthetic medicines, structural materials now included the wider use of metals and the first plastics were beginning to replace plant products. Direct contact with plants now mostly occurred when buying food from the grocer, and when spending time in parks and gardens.

Key points

The following list includes both key plant-related impacts on sustainability . . . that is, on the social, economic, and environmental conditions of the Great Divergence. It is also a summary of the many factors that warrant the rubric ‘Age of Plants’ for a medium time-period lasting several hundred years from approximately 1550 to 1950.

Agriculture

• The transition to industrial agriculture from solar agriculture which released people from toil on the land while facilitating many technological and other social benefits created an industrial society that was made possible by the use of plants as fossil fuels
• The emergence of industrial agriculture brought the world population from about 480 million in 1550, to 1 billion in 1800, and 2 billion in 1930 in a social transition referred to as the Second Agricultural Revolution
• The rapidly expanding European population was fed from crops grown on arable land annexed as colonial land grabs in the Great Plains of the United States, Canada, SW Australia, Tasmania, New Zealand, also parts of Africa, Argentina, Uruguay, Brazil, central India and elsewhere

Science

• The birth of botany as a rejuvenation of Theophrastus’s plant science and its development including the in-principle resolution of plant structure and function up to the micro and macro scales
• The appointment of professors of botany to the medical faculties of universities (the physic gardens and herbaria of the first early-modern botanic gardens) in mid-16^th century Renaissance Italy
• The transition from plant descriptions listed in printed medicinal herbals (c. 1470-1670) to medical pharmacopoeias and botanical descriptions in regional floras
• Linnaeus (1707-1778) produced an international consensus on a methodology for biological inventory (taxonomy) – a revolution in plant classification, nomenclature, and description
• The microscope had opened up the discipline of plant anatomy in the 17th century and experimental botany advanced in the 18^th century as plant physiology united with anatomy to elucidate the mysteries of translocation, respiration, photosynthesis, and reproduction
• The establishment of plant collections of various kinds in museums, botanic gardens, cabinets, herbaria, private gardens (a mostly western phenomenon associated with the development of science and especially encyclopaedic descriptive science)
• Global biological inventory begins with estimates of wild plant numbers in 1500 (c. 1000), 1623 (c. 6000), 1753 (10,000) then rapidly expanding; cultivated plant; botanic garden living collections in 1660s Jardin du Roi c. 4000, 1720 Leiden c. 5846, 1770 Chelsea Physic Garden 5000, 1789 Kew‘s Hortus Kewensis 5500 and in about 1813 11,000
• Britain contributed to the global advance of plant science by instituting several of the world’s most influential plant academies: Kew Gardens (1759), the British Linnean Society (1788), The Horticultural Society of London (1804, Royal Charter granted in 1861). The location of the world’s most extensive living and dried plant collections in London in the early 19th century ‘… sets Britain above all other nations in the Botanical Empire’ (Wulf 2009, p. 223)

Cultivated plant globalization

• A Columbian exchange of crops between the Old and New Worlds including horticultural crops, the cereals of temperate agriculture, the exchange of tropical crops between the East and West Indies and ornamental plants
• Botanist-gardeners and plant hunters would serve on Enlightenment voyages of scientific discovery and exploration in a tradition continuing into the 20th century

Economics

• The desire for spices, whose trade and sources were controlled by Indian and Arab middle-men, prompted a spice race between Spain, Portugal, and Holland with the establishment of maritime trade routes westward to the New World (leading eventually to a lucrative Atlantic economy) and eastward to China and the East Indies. It was this early spice trade and later trade in plantation crops like tobacco, sugar, and cotton that would help forge a global economy
• World beverages based on grapes (wine) and cereals (beer) would now be supplemented by new socially important beverages like tea, coffee, and cocoa, all sweetened with sugar
• The Atlantic economy involved a two-way exchange of plants between the Old and New Worlds that became known as the Columbian Exchange (after Columbus) and it involved not only plantation crops but ornamentals, cereals, and their associated organisms
• Today’s seemingly inconsequential medicinal plants had initiated the establishment of the first Renaissance botanic gardens in Italian universities where plant medicine would be transformed into modern plant science: and today’s seemingly inconsequential spices initiated the global economy

Exploration

• First global circumnavigation, the delimitation and mapping of the world’s major landmasses and thus the definition of a finite world amenable to a global bio-inventory
• Establishment of the first modern botanic gardens
• The development of a global economy prompted by a spice race between European colonial powers that would settle much of the world
• A Second Agricultural Revolution as a transition from solar agriculture to industrial agriculture based on fossil fuels and the appropriation of large areas of colonial arable land to feed a world population that doubled from 1 billion in 1800 to 2 billion in 1930
• An unprecedented period of plant globalization as temperate crops were spread to colonized temperate regions of the world, an intermixing of tropical crops, the generation of wealth from plantation crops and new beverages, collection ornamental plants eventually widely dispersed through a commercial nursery network; ……..
• Extensive global plant prospecting and exploration by merchants, adventurers, governments, religiosi, scientists in foreign lands for both economic and ornamental plants
• The development of landscape gardening into a fine art to produce some of the world’s most outstanding garden art, the zenith of botanical illustration
• The democratization of horticulture that included the proliferation of commercial nursery networks
• The early stages in the development of a global garden flora

Botanophilia

• Joseph Banks (effective director of Kew Gardens 1773-1820-president of the Royal Society from 1778 to 1820) over this period presided over the worlds largest collections of living and dried plants and a vibrant economic botany at Kew Gardens, the leading botanical institution of an empire that spanned the world

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First published on the internet – 31 August 2020

Anthropogenic biomes datasets describe potential natural vegetation, biomes, as transformed by sustained by human population density and land use including agriculture and urbanization. Anthropogenic biome categories (Anthromes) are defined by population density and land-use intensity. The data consists of 19 anthrome classes in six broad categories.