Plants have underpinned all the major human socio-economic transformations because they have, until now, provided both the food energy that powers human bodies (as biological energy) and most of the additional energy, mainly as fossil-fuels, needed to build and maintain complex human societies (social energy).
Historically, plants have not only supported the survival, growth, and reproduction of organisms, they have also been the main driver of human social change. Social organization has increased in complexity as existing energy sources were used more efficiently and new, more concentrated, forms of plant energy were discovered. In pre-industrial societies it was mostly biological energy powering the muscles of slaves, workers and domesticated animals that provided the energy needed to maintain economic activity. But it has been the social energy of fossil-fuels that has driven modern industrial economies – their systems of resource extraction, production, distribution, and consumption. The growth and interconnection of widespread populations, and the diversification of economies, then presented the emergent possibilities of social scale, such as the capacity to build ocean-going ships, assemble armies, to mint and exchange coins, to make computers, and develop complex technologies.
During Natura the plant diet was quite varied, consisting mostly of wild greens, fruits, seed, root vegetables, and the meat of hunted animals. Some additional indirect energy was needed to support individual and collective lives – such as that obtained from fires or embedded in the materials used for clothing, and so on. Social activity was achieved mostly using human muscle, so this was a form of existence that benefitted from energy conservation, with minimal possessions, the use of simple domestic and hunting tools, and the highly developed skills of bush craft. The combined total of food energy and social energy required was roughly 5000 to 10,000 kcals/capita/day. The migration of prehistoric hunter-gatherers, walking out of Africa to occupy the world, took about 60,000 years.
The settled farming communities of Agraria, with their domesticated plants and animals arose independently in 6-12 centres of civilization (the exact number is debated) across the world, the first appearing about 13,500 years ago in the ancient Near East. Most people in these communities were engaged in farming based on cereals. Grains were a concentrated source of energy that could be stored for year-round use and, for the domesticated animals, supplemented by fodder. Some settlements thrived to grew into Bronze Age cities that became trade centres for even larger human groupings of nations and empires.
Effectively governed communities with large populations took advantage of new technologies made possible by their scale of operation in a series of changes that increased the complexity of social organization. The sedentary existence facilitated population growth in hierarchically governed urban societies displaying many of the characteristics we associate with the cities of today: a division of labour, coinage, monumental architecture, private ownership, sophisticated legal and economic systems, art, written records etc. as proportionally fewer people worked on the land.
In and around the Bronze Age cities there were now specialized (often enclosed) social spaces that contained cultivated plants, spaces that served different social functions and which have persisted to the present day: fields, public parks, avenues, orchards, vegetable and market gardens, vineyards, gardens – both domestic and royal – and the formal plant decoration used around administrative blocs, temples and burial sites. It was during the Bronze Age interaction of trade, diplomacy and military conquest that occurred between Mesopotamia, Egypt and the Aegean during the third to second millennia BCE that ‘. . . gardens emerge as distinctly meaningful spaces’ (Stackelberg 2013).
The increase in social organization was made possible by the surplus energy from plant and animal domestication and the human population multiplied from a few million people at the dawn of the post-Ice-Age Agricultural Revolution about 10,000 years ago, to around 400 to 500 million in 1550 CE at the first inklings of Industria. The combined total of food energy and social energy needed to produce, store and distribute the grain and sustain communal activity had now increased from about 10,000 to 40,000 kcal/capita/day. Agricultural societies no longer depended on wild plants but used the energy provided by cultivated plants to feed the muscles of man and domesticated beast over a period that lasted about 10,000 years.
Industria, as defined here, lasted about 500 years from around 1550 to 1950 as a time of rapidly increasing social complexity – the advance of science, technology and medicine that was combined with population growth, industrialization, democratization, the development of nation-states, and the global connectivity that flowed from the Age of Discovery and European colonial expansion. This accelerated social change took place when the muscle power of humans and domesticated animals was supplemented by using the concentrated plant energy found in fossil fuels, providing the social energy that powered industry and manufacturing. Industrial agriculture used sophisticated machinery to boost food production in what was, in effect, a second Agricultural Revolution as people moved from farm to factory, from toil on the land to work in the expanding cities. The number of people working in agriculture fell dramatically in technologically developed countries – from over 90% at the beginning of this period to less than 5% today.
It was fossil fuels (fossil plants) – first coal (a convenient replacement for the rapidly diminishing supply of timber fuel) but then gas and oil – that were the drivers of increasing global connectivity and social complexity.
The outcome of Industria was a world that aspired to energy-hungry Western lifestyles that consume around 200 kcal/capita/day, about a 25-fold increase over that of hunter-gatherers. Plant-based energy use increased from about 38 kcals/person/day in 1800 at the start of the Industrial Revolution to around 92 kcals/person/day in 1900, and 230 kcals/person/day in 2000.
Phase four (Informatia) followed in the wake of the devastation of two WWs as economic recovery gathered pace around 1950. Increasingly sophisticated science and technology accelerated globalization and the more efficient extraction of planetary resources that produced unprecedented economic and population growth – the Great Acceleration – as the world population soared from 2.5 billion in 1950 to 6 billion in the year 2000. It had taken about 200,000 years for the human population to reach 1 billion around the year 1800 and then, fired by fossil fuel social energy, only 200 years more to reach 7 billion.
Cities expanded upwards with the advent of skyscrapers, and outwards as domestic houses and gardens multiplied to form sprawling suburbs. In 1800 about 3% of the world population lived in cities but by 2017 this had increased to 55% (Index Mundi World Demographic Profile 2018) as more land was appropriated to provide the food needed to feed the growing population. Human appropriation of plant net primary productivity (HANPP) almost doubled from 1910 to 2005, from 13% to 25% while population grew 2.7 times and GDP grew about 17 times (Krausmann et al., 2013; Haberl et al., 2014). The increasing harvest from forests and the additional land occupied by infrastructure added little to HANPP. It is agriculture that dominates HANPP globally, representing 84–86% of total appropriation of plant growth over the entire period, with 42–46% on cropland and 29–33% on grazing land. We must also consider the impact of plant-energy-dependent domesticated animals. The ‘MacCready explosion’ claims that 10,000 years ago humans, their pets and livestock comprised around 0.1% of the terrestrial vertebrate biomass. Today this total has rocketed to 98% (MacCready 2004). Though a statistic that is difficult to substantiate, this is a stark reminder that beyond human demands for plant food and other resources are the demands on planetary ecosystems resulting from animal domestication.
But there is much more to the social, economic, and environmental dimensions of post-industrial Informatia with its knowledge economy and service sector generating more wealth than the manufacturing sector. There has been decolonisation, the geopolitical dominance of America, the formation of the United Nations and, latterly, the rise of Asia, particularly China. Environmentally it has been marked by a new epoch called the Anthropocene. Socially the most obvious transition is from printed to digital communication with the advent of computers and the internet. Many forms of knowledge, once only available to the privileged few and therefore a form of social distinction, is now available to all who have access to computers or smartphones. Scientifically Informatia is strongly associated with the penetration of the last major scientific frontier – the human mind, consciousness, mental and other forms of computation, and artificial intelligence.
Throughout history humans have been totally dependent on plants as a source of energy, both the energy that supports biological metabolism and the energy that builds societies. This energy came first from wild plants (Natura), then cultivated plants (Agraria), then the additional energy of fossil fuels (Industria) that facilitated globalisation and increasing social complexity.
Today, in Informatia, our dependence on plants for social energy is waning as the world economy transitions from plant-based fossil fuels to renewable energy sources like wind, solar, biomass, nuclear and hydro as, it seems, we approach a new milestone for humanity, peak per capita energy use.