The last time our planet entered a new geological age was around 10,000 years ago and it had a profound effect on the survival and success of our species. As the last ice age ended, a new epoch of global warming called the Holocene began. Ice sheets retreated to the poles and the tropics became wetter. People came out of their caves and began taking advantage of the new conditions: grasses proliferated and those with nutritious seeds, like wheat and barley, could be farmed. Around the world, people began settling in larger communities and processing food rather than simply hunting and gathering. This stability led to the development of culture and civilisations – our species became more populous and so successful we spread across six continents. The impacts of the Anthropocene will be just as profound.
It was Nobel laureate Paul Crutzen who came up with the term Anthropocene. The Dutch chemist was sitting in a scientific conference, he told me, when it occurred to him that all the biophysical changes that researchers were discussing ‘meant we weren’t in the Holocene any more. The planet had changed too much from what would be considered normal for the Holocene.’ Crutzen made a case for the Anthropocene in an article in Nature in 2002, and over the past decade the term has gained use in the scientific community.7 Now, the British Geological Society is beginning the slow process of formally deciding and listing this new epoch, based on the changes humans are making to the biosphere that will be preserved in the geology, chemistry and biology of our planet for thousands or millions of years.8 These include land-use changes, such as the conversion of forest to farmland, and radioactive fallout particles. Boundaries between geological times are fuzzy and often span thousands of years, as scientists try to calculate them from stripes in rocks around the world. The geologists will have to decide when the epoch started – was it thousands of years ago with the advent of farming, a few generations ago with the industrial revolution, or the 1950s with the Great Acceleration? That decision will depend on which marker the geologists use to define the Anthropocene: the atomic tests of 1949, say, or the rise in atmospheric carbon dioxide concentration around 150 years ago.
But while the geologists battle the conceptual difficulty of palaeontological dating for an era whose palaeontology and geology are still being created, the Anthropocene has escaped the confines of academia and been embraced by a far broader section of society. The idea that humanity is having a truly planetary effect has aroused the interest of artists and poets, sociologists and conservationists, politicians and lawyers. Scientists are using the term to describe multifaceted changes to our planet and its life. And it is in the spirit of this broader definition – and the growing consensus that we are now crossing the boundary into the Anthropocene epoch – that I write this book.
So how can we recognise the Anthropocene – what are the signs that we’re entering a new geological age? In the atmosphere, carbon dioxide levels are almost 50% higher than the Holocene mean – our industrial and domestic emissions of greenhouse gases are warming the atmosphere, changing the climate and disrupting weather patterns across the globe.9 The impacts of climate change are planetary and affect all life on Earth to some degree. The atmosphere has also newly become a repository for a range of other chemicals. Mountains are losing glaciers that have covered them for many thousands of years, causing them to crumble faster – and they are also being hacked at by miners. Rivers are rerouted, dammed, drained and exhibiting a dramatic reduction in sediment flow. Farmlands have appeared out of the natural landscape and there has been an explosion in the amount of available nitrogen on the planet because of the fertilisers we’re adding. This nitrogen has increased crop yields, which has allowed human populations to soar, doubling in the last fifty years, with far-reaching consequences for the entire planet. The oceans are becoming more acidic as they dissolve our carbon dioxide emissions from the atmosphere, and they are becoming less biodiverse as coral dies and we lose fish through overfishing, pollution and warming waters. The Arctic is melting and coastlines are eroding as storms increase in frequency and violence, the sea level rises and protective sediments, mangroves and wetlands vanish.
Deserts are spreading across savannahs, forests are drying and being logged. Wildlife is being hunted and dying because of habitat loss, climate change and species invasions, pushing the planet towards the sixth mass extinction in its history. Meanwhile, we are causing the proliferation of our domesticated species and indiscriminately scattering others around the globe. We are disembowelling the Earth through mining, drilling and other extractions, littering the planet with novel compounds and materials, devices and objects, that could never have occurred naturally. And we are building enormous steel, concrete and glass cities that light up the night sky and are visible from space.
And what about the impacts of our changed planet on us? After all, we’ve evolved and adapted to a life in the Holocene, and the new changes have occured very rapidly. The transformations we have made to our planet have been key in enabling us to become this superspecies – and they have also been a consequence of our extraordinary ascent. In changing the Earth we have been able to thrive, to live longer and healthier, in better comfort even in greater numbers than ever before. However, for now, at least, humans are still of nature – we evolved on this living planet, we are made of cells, we breathe air, drink water and eat protein. We rely on the biological, chemical and physical parts of our planet to provide everything, including all our materials, fuels, food, clothes, and to clean our air, recycle our water and manage our waste. Our growing population and the way we live in this new human world are making us more demanding than ever of our planet’s resources and processes. But, as we continue to change Earth, we reduce its ability to meet these needs and, as a result, we are facing crises in fresh-water availability, food production, climate change and ‘ecosystem services’, the immeasurable functions that the biosphere performs to enable our survival.
In the Anthropocene, we have already started to push global processes out of whack. In some cases, just tiny further changes could spell disaster for humans; for others, we have quite a bit of leeway before we face the consequences. Most of them have some sort of tipping point beyond which it will be almost impossible to return to Holocene-like conditions. For example, glacier melt at the poles could reach a tipping point at which sudden runaway melting occurs and sea level rises by metres. Fears of big changes like these have led some scientists to describe ‘planetary boundaries’ – biophysical limits for human safety, such as the extent of land-use change and biodiversity loss – some of which they say we’ve already exceeded.10 In leaving the relative safety of stable Holocene conditions, it is clear that humans face unprecedented challenges.
The key here is how we will deal with the consequences. It may have been desirable to keep within the internationally agreed ‘safe’ global-warming limit of 2°C (above pre-industrial levels), for example, but we will almost certainly exceed that by the end of this century, and so the question becomes how we can live in the warmer Anthropocene environment.11 We have always altered ecosystems to serve our needs and presumably will continue to do so. Our habitable range, for example, is not limited to the tropics, because we invented clothes and other ways to keep warm, just as air-conditioning technology keeps us cool. We have improved the planet for our survival in a number of ways, including by staving off the next ice age, but we have also made it worse. Some of those negative consequences we can overcome through technological advances or migration or other adaptations. Others we will need to reverse; some others we will need to learn to live with.
The good news is that some problems are already being brought under control. Pollution is being curbed in many countries through laws and technological improvements; radioactive pollution has been limited through the international nuclear test ban treaty. The growth in the ozone hole has also started to slow because of the Montreal treaty banning ozone-destroying chemicals. Crucially, the rate of population growth is also slowing, with many countries now in negative growth.12 Other problems, however, remain increasing and significant threats. And, while science may be able to identify biophysical issues, it cannot tell us how to react – that is for society to decide. Humans are no longer just another animal, we have specifically human rights that are expected to be achieved through development, including access to sanitation and electricity – even the Internet.13 Delivering social justice and protecting the environment are closely linked; how poor people get richer