Andrew Simms: The human race is living beyond its means

In a market economy, the only constraints on what we consume are what we may legally buy and what we can afford.

The result is, as the great environmental economist Herman Daly warned, that we end up treating the planet as if it were a business in liquidation. If you were managing a business, you would be considered grossly negligent if you had no idea of your assets or cash flow. Yet this is how we manage our environmental resources.

When we deplete oil in the North Sea and push fish stocks to the edge of collapse, it is treated as free income to the economy. It is shockingly easy for politicians, economists and planners to forget that the economy is a wholly owned subsidiary of the environment. And, on our island planet, that Earth itself is subject to fuzzy but very real limits.

One of the defining features of life in the UK, the world's fourth-largest economy, is the sheer scale of our material consumption, and the ease with which we ignore the burden that it exports around the globe.

Our high-consuming lifestyle is only possible because the rest of the world supports us with large supplies of their own natural resources.

No individual country has to be self-reliant. We trade what we can't produce locally, and positively enjoy exotic goods that come from all around the globe.

The world as a whole is living beyond its ecosystems' capacity to regenerate, and, looked at in terms of a calendar year, starts living beyond its environmental means on 9 October. Looking back, if the whole world had wanted to share UK lifestyles in 1961, the Earth would just have managed with its available resources - one planet would have been enough. Today we would need 3.1 planets to support them. To live within our overall environmental budget, the UK will have to reduce the burden its lifestyles create; such as the massive growth of leisure flights and subsequent CO2 emissions.

And while our consumption grows, with everything from 4x4s to energy hungry wide-screen TVs, all the academic research shows that consuming more will not make us happier. The same research shows that getting-off the consumption treadmill, finding more time for friends and family, reflection and creative pastimes, can.

Mainstream economics says that nothing must get in the way of economic growth and competitiveness. But in doing so we are inadvertently waging war on the environment, forgetting that, if we win, we will find ourselves on the losing side.

Andrew Simms is policy director at the New Economics Foundation