How we are reshaping the Earth system

Human impacts on our life-support system began during the last ice age, with the mass extinction of large animals each time our ancestors arrived in a new continent on their migration out of Africa. Our impacts accelerated with the invention of agriculture and its spread during the Holocene epoch – the last 10,000 years. Populations grew and their material inputs and waste outputs began to accelerate.

We started affecting the vast invisible Earth system in the following ways:

• Irrigation starting around 8000 years ago which led to the salinization of land
• Fertilising crops with animal manure led to water pollution
• Farming led to soil erosion
• Forests were cleared for farming, adding carbon dioxide to the atmosphere
• Farming of rice paddies beginning around 5,000 years ago led to an increase in methane (CH₄) emissions which built up in the atmosphere

When did the Anthropocene epoch begin?

Some researchers argue for an ‘early Anthropocene’ starting with the rise of farming. But a new geological unit of time requires a significant change in the Earth system and a way this can be dated. In 1610 there was a marked drop in atmospheric CO₂ which was recorded in Antarctic ice cores. What caused this? It correlated with the arrival of Europeans in America. They took with them some of the small invisible – including smallpox. This resulted in the death of about 50 million indigenous people and the collapse of farming. The Latin American forests grew back and in doing so absorbed such a large quantity of CO₂ that it was detected in the records.

For many the Anthropocene epoch got underway with the Industrial Revolution:

• The invention of the steam engine (1712, refined in 1769) led to a boom in industry, manufacturing and transport
• We transitioned from burning biomass (wood) and using water and wind energy to burning fossil fuels and in the process transferred fossil carbon into CO₂ in the atmosphere, affecting the vast invisible carbon cycle
• Population, food production, material consumption and the creation and dissemination of waste products all accelerated
• The population grew; 1825 = 1 billion, 1927 = 2 billion, 1974 = 4 billion, 2030 = 8 billion
• Now only 10% of the energy we use is in our food – the rest drives our energy-hungry societies

The best geological marker for the Anthropocene is the ‘Great Acceleration’ – the extraordinary acceleration of human impacts on the planet since the 1950s. This is characterised by:

• An increase in materials flow – especially CO₂
• An increase in material waste (some of which are new materials that we have created) into air, onto land and into oceans
• A marker of our accelerating impact in the radioactive material created by atomic bomb tests
• Now for several of the vast invisible cycles, including nitrogen and phosphorus, our impact exceeds that of all other life on Earth

We have changed the face of the Earth

We are altering the climate, massively accelerating erosion on land and sedimentation in the oceans, acidifying and deoxygenating the oceans, polluting the atmosphere, land and waters with chemicals and waste and leading to the extinction of other species at an unprecedented rate.
Our impact on other life forms is feeding back on us. We depend on the small invisible for the maintenance of the vast invisible cycles, and we depend on these cycles for:

• Fresh air
• Clean water
• Fertile soil
• Nutritious food
• Rich biodiversity
• A stable climate
• A phenomenal recycling system

When we threaten our life support system, we threaten ourselves.