Smart Guide to 2012: The Rio Earth Summit

• 25 December 2011 by Fred Pearce
• Magazine issue 2844. Subscribe and save
• For similar stories, visit the Climate Change Topic Guide

Rio engineering (Image: NPO Lavochkin/Rex Features)

Read more: "Smart Guide 2012: 10 ideas you'll want to understand"

Spaceship Earth needs a pilot. It's time we stepped into the cockpit and took over the controls. That will be the theme of the Earth Summit in Rio de Janeiro, Brazil, in June. Natural disasters, food and water shortages and biodiversity loss show that humanity is crossing planetary boundaries, making our world more dangerous. At Rio we will have to push for a global system of "environmental governance".

Earth has nine critical life-support systems vital to our survival. They have some resilience to human activity, but the bad news is that going beyond the safe boundaries is all too easy.

We have already bust three of those boundaries. We are eliminating species at 10 times the natural rate of extinction. We have turned up the planet's thermostat higher than it's been in a million years and probably unleashed unstoppable natural feedbacks that will worsen warming. Oh, and our use of fertiliser has pushed the natural nitrogen cycle into hyperdrive, poisoning ecosystems and the oceans.

With three "lives" gone, where else are we approaching Earth's limits? By mid-century we will probably be at or beyond boundaries on the safe extraction of fresh water and will be threatening the last great ecosystems through ploughing land for crops - with serious implications for world food supply. Likewise, the acidification of the oceans will be literally dissolving marine ecosystems.

For two of the three remaining life-support systems - chemical pollution and loading the atmosphere with smoke, dust and other particles - we have yet to figure out where the tipping point to disaster might lie. The last is our solitary success story: fixing the hole in the ozone layer.

Some will call for geoengineering to fix the planet. Whether you buy into that or not, the inescapable message is that we now dominate so many of the planet's life-support systems that simply backing off and reducing our footprint is no longer an option. The planet won't steer itself any more.