Planet Future

This acceleration is caused not only by ever more extravagant overuse in the rich world, but also by increasing numbers of people in poorer countries becoming able to afford a better standard of living.

The consequences of this spiraling mismatch between human demand and planetary limits are most starkly illustrated by climate change.

The choices we make today will shape our opportunities far into the future.

The cities, power stations and homes we build today could lock human society into wasteful use of energy and other resources beyond our lifetimes.

Or they could begin to propel us and future generations towards a new way of more balanced living.

Most climate scientists agree that if we allow global temperatures to rise by more than 2°C above pre-industrial levels, the risk of severe and irreversible changes in the Earth's natural systems becomes increasingly likely. On the face of it, 2°C may not seem like a huge rise. But beyond this limit, truly devastating consequences are expected for humans and the natural systems that sustain us.

Even approaching this threshold, some of Africa's poorest people, living in the arid countries around the Sahara desert, will face impossible pressures on their already insecure livelihoods.

Water will become more scarce and desertification will take yet more of their land.

Beyond the 2°C limit, falling crop yields will affect many more developing countries. The Himalayan glaciers - the vital dry season source of fresh water for over a billion people in south Asia - will disappear. Beyond the 2°C limit, the melting of the Greenland ice sheet will become irreversible, accelerating sea level rises that will affect hundreds of millions of people in coastal cities worldwide, including London.

Coral reef ecosystems will already have been lost. The Amazon rainforest will be permanently damaged and the rate of species extinction will increase dramatically.

Scientists have repeatedly warned that to stay below 2°C global warming, the world's emissions of greenhouse gases will need to peak and start to decline within the next 10 or 15 years. We do not have the luxury of time to prepare more evidence or to wait for others to act first. Every person, every company, every government on the planet has a duty to act now to prevent a crisis that we are causing. But that duty falls most strongly on those of us in the rich countries who are overwhelmingly responsible for emissions.

Until relatively recently, the Earth's natural resources have been more than sufficient to support human needs. In the past, our human activities rarely had global consequences - and the daily struggle by millions of people to secure food, clean water or firewood was never driven by global limits.

Since 1998, we are now living in severe ecological overshoot.

Worldwide, people are consuming about 25% more natural resources than the planet can replace. We are living on ecological credit, drawing down the stock of natural capital while our overall consumption exceeds the planet's ecological limits. As with an increasing bank overdraft, this cannot go on forever.

Our planet is buckling under the weight of the demands we are making on it. The world's population is set to increase to nine billion by 2050 and global consumption levels are already five times what they were just 50 years ago. This overconsumption is leading directly to climate change and species extinctions. We are losing some of the world's richest forests; we are degrading soil and sources of fresh water faster than ever before.

While in the UK live as if we had three planet Earths, two billion people live on less than two dollars a day. While the average British person uses about 150 litres of pure water each day, over a billion people have no access to clean water at all. Yet the consequences of our overconsumption already fall most heavily on the poorest countries.

The impacts on human societies across the world will continue to worsen unless we make some rapid changes. Sir Nicholas Stern, a former World Bank chief economist, argued in his 2006 Review of the Economics of Climate Change that "business as usual" could cause economic impacts greater in scale than the two world wars and the Great Depression put together.

Almost every indicator of the health of our planet's natural systems shows that they are no longer able to adjust to the consequences of human activities. From the collapse of fisheries to the destruction of irreplaceable forests, we are seeing the decline in the Earth's natural capital accelerating alarmingly.

We are driven by a sense of urgency, but not overwhelmed by it.

The kind of action needed will not be generated by guilt, nor by fear.

Just as obesity is best overcome by adopting a nutritious, varied, tasty diet and a healthier lifestyle, so too our global over consumption will be solved by moving to different - but better, healthier and happier - ways of living.

Our vision is for a better quality of life for everyone now and for future generations. People's wellbeing can be improved at the same time as we ease the pressure on the Earth's natural systems. And this can be done while ensuring that our grandchildren will live their lives better than we do ours.

It is because we want everyone to have a better quality of life that we promote a shift towards lighter living, using fewer resources.

Reducing the resources needed to attain a higher quality of life is essential for the eradication of poverty in today's world and will be the foundation for the good quality of life to be enjoyed by future generations. But as long as poverty eradication remains linked to rapidly rising resource use, it will be held back by planetary limits.