Humans and the Earth system

Human activities are upsetting the Earth's cycles.

Too much carbon dioxide:

• the oceans absorb more of it and become more acidic, which threatens plankton and coral reefs;
• but warmer water absorbs less, so the ocean becomes a weaker carbon store;
• burning fossil fuels and cutting forests overload the natural carbon stores (forests and oceans), making global warming worse.

Too much fertiliser: rain washes nitrates from fields into rivers and lakes. Algae feed on them and grow out of control (an algal bloom). The water then runs short of oxygen, and fish die. This is eutrophication, and it harms lakes and coastal fishing.

Cutting forests (deforestation) affects every sphere:

• less photosynthesis and transpiration, so less local rain;
• the ground's albedo changes;
• without roots to hold it, soil washes away;
• animals lose their homes and biodiversity declines.

Smog. Fumes from vehicles react with sunlight to form smog and ozone at ground level, which is harmful to breathe. (Ozone high up in the stratosphere protects us; ozone down here harms us.)

Fixing it together. The Montreal Protocol has started the ozone layer's recovery. The Kyoto Protocol and Paris Agreement, in which countries promised to cut carbon dioxide, have been less successful. What helps:

• saving energy, and switching to renewable energy (solar, wind);
• planting trees;
• saving water and food;
• sustainable farming;
• reducing waste, reusing and recycling.

India has planted billions of trees and greatly expanded solar energy.

Mission LiFE (Lifestyle for Environment), an India-led global initiative launched at the UN climate conference in 2021, asks every person to live in an earth-friendly way: switch off lights you are not using, save water, avoid waste. Small habits, multiplied by millions of people, help keep the Earth in balance.