There is still some debate about where and when exactly, but the idea that humanity can and has changed the direction of planet Earth is hardly controversial today. We are a force of nature, and have left our imprint on the geological record. Some scientists argue that we are now living in the Anthropocene era, where human actions are the primary driver of planetary change.
Can human actions really add up to global change? Here are five ways that we’ve already shifted the future of the planet.
1. The extinction of the megafauna. Every continent used to have big animals, varieties of elephant, giant sloths, giraffes and hippos. Now they are largely gone, only surviving in India and Africa. Their disappearance from the fossil record consistently comes shortly after early humans arrive. We cross a land bridge and reach a new continent for the first time, and the big animals disappear. “The few million people alive at the end of the Pleistocene killed a staggering one billion very large animals” write Lewis and Maslin in their book The Human Planet.
The altering of the planet’s zoology had knock-on effects too, because large animals manage their ecosystems in a variety of ways. The loss of the megafauna would have turned grasslands to forest in some places, which would have altered weather and climate.
2. The discovery of agriculture. Our second big interference is the evolution of settled farming, which began around 10,500 years ago. Among the many reasons for the shift are that we didn’t have large animals to eat any more. Vast tracts of forest were burned and cleared to be planted with crops. The cleared forests and the methane from rice growing added greenhouses gases to the atmosphere. After thousands of years of gradual cooling, the climate slowly began to warm. Looking at the cycles of warming and cooling that preceded the discovery of agriculture, it appears that they have been interrupted. If the pattern had continued, we’d be in an ice age right now, but the wide adoption of farming has postponed it.
3. Domestication. On a related note, those early farmers began to tweak the genetics of plants an animals – not that they understood genetics of course, but that’s what they were doing. Traits that benefited humans were prioritised, leading to domesticated plants and animals. Take maize. In its original wild form, it produced a single cob about an inch long per stem. A big yellow corn on the cob is a total freak by comparison, an entirely human creation. Domesticated animals changed too – all dogs, in all their different breeds, share a common ancestor in ancient wolves.
Having settled on around 100 plants and 14 big animals (nobody has added to that list in 5,000 years), they were shared around the world. In what is known as the Columbian Exchange, America plants such as maize and potatoes were adopted in Europe, Asia and Africa. Wheat, rye, and animals such as pigs and horses went the other way, creating a global farming culture. Life on Earth was fundamentally tilted to serve human needs.
4. The discovery of fossil fuels. This change is more familiar to us, because we’re living through it on a daily basis. Humans have used fossil fuels for a while. China was using coal a thousand years ago, and European explorers found an oil industry in Burma in the 1700s. Once combined with the industrial expansionist culture of Britain, Europe and then America, fossil fuel use ramped up dramatically. It fuelled the industrial revolution, and then reached consumers through domestic heating and lighting, and then through public transport and cars.
Today the world runs on oil, coal and gas – and the carbon dioxide from burning fossil fuels is changing the atmosphere. More heat is trapped close to the Earth’s surface, raising the temperature. The planet has gone through many changes in the past, usually over thousands or millions of years. The warming effect of fossil fuels is incredibly fast by comparion, and as weather patterns change and sea level rises, we are changing the climate faster than we can adapt. As climate change affects water supplies, biodiversity, ocean acidification and many other natural systems, it may turn out to be our most significant impact so far.
5. Novel entities. Finally, the advent of modern science has brought new elements and materials into being. Substances that never existed in nature begin to appear in the fossil record. Geologists can pinpoint the first tests of nuclear weapons, for example. Soot is laid down in ice layers. There are new chemicals and nuclear isotopes, and of course plastic. It’s such useful stuff that we’ve created over 8 billion tonnes of plastic since it was invented in the 1950s. Since it’s not biodegradeable, it’s still with us – scattered in flakes through land, air and ocean, on every continent. It’s in the food chain, it’s in tap water, and we’re only now waking up to the problem.
In answer to our earlier question, yes: humans can and have caused planetary scale change – and this isn’t an exhaustive list. Other questions should follow. How are we effecting it today? Are we affecting it in positive or harmful ways? If our effect is negative (hint: it is), what is driving that harm and what is preventing us from changing course? How are we going to cooperate to ensure that the planet is managed for everyone?