The political conference season has just finished and the key word lurking behind all the debates and aspirations was a simple one – growth.

It’s something we are used to in our gardens and on farms, it’s acceptable, as each season runs its course and then starts all over again. It’s repetitive, rather than cumulative.

Economic growth is quite a different animal as it assumes that profits, production, material wealth, share prices and house values are just going to keep on increasing, and if they don’t then there’s panic, and the politicians are voted out as they are deemed to have failed.

This greed for material wealth, and power, obscures the reality, and a moment’s thought should show that continuous growth is quite unsustainable and can’t go on forever. A rate of increase as low as one per cent a year would lead to a doubling in 70 years, and an annual rate of growth of three per cent means a doubling in just 20 years. We have been doing the latter for most of the time since 1950.

Because we live in the bubble of the present, and in our own little corner of the planet, we are unable to take the wider view, so we keep on asking for more and expecting the politicians to provide it, otherwise they don’t get our vote. It’s because of this that we haven’t noticed that the world population has increased from two to seven billion, and we have little appreciation of the finite limits of resources that the planet can provide.

It’s interesting that politicians worldwide are seriously worried about their national financial debts, and yet they completely ignore the overdrawn state of the world resources account, where the withdrawals from the seas, forests, soils and minerals point to inevitable bankruptcy.

Mr Micawber would appreciate it if we only consumed the resources that the earth could replace each year, but the last time we did that that was in 1986. By 1987 we had consumed our annual allowance by December 19 and the gap has widened ever since.

This Ecological Debt Day, or Earth ‘overshoot day’, was reached this year on August 22, and it is calculated that annually we consume 40 percent more resources than the earth can provide.

Earlier civilisations than ours have flourished, expanded and then disappeared as they grew beyond the sustainable limit or couldn’t cope with a changing climate. If we are to avoid a similar fate then we need to design a steady state economic system that can be sustained by the natural world.

It would certainly mean there would be no room for more High Speed Rail or an expanded Heathrow.