Two contradictory ideas shape UK politics. First, the argument for austerity, that the nation cannot and should not live beyond its financial means. Second, the notion that we can and must, in effect, live beyond our environmental means. That is why any increase in our spending and consumption is hailed as economic success.

Today, the world goes into ecological debt, or "overshoot" – an estimate of the moment in the year when humanity has consumed more natural resources and created more waste than our biosphere can replace and safely absorb over a 12-month period.

Since the 1970s we've been living beyond our means, going into ecological deficit before the end of each year. And, the day when we hit "overshoot" has been creeping ever earlier. This year it falls two days earlier than in 2012. It now takes about 18 months for the biosphere to compensate for a year's worth of human consumption and waste. Conservatively, here in the UK we're using the equivalent of three and a half times the natural resources we have as a nation. For a country like Japan the figure is seven times. Many low-consuming countries in Africa are ecological creditors. Indonesia has been a creditor, but rising consumption and deforestation are running down its natural assets and pushing it over the brink.

For how long we can get away with not balancing the ecological books is a question that exercises many scientific minds, if unfortunately few political and economic ones. It's a bit like Jenga, the game with the tower of wooden blocks; you can keep taking them away for a while until, with a suspenseful amount of uncertainty, the whole thing collapses.

Later this year the IPCC releases its next major report on global warming. It may suggest that the climate is slightly less sensitive to rising emissions (although others say the opposite may be true) but with a likely prognosis that we are still on course to go over the edge and soon become locked into long-term, worsening climatic upheaval.

The contradiction between our approach to good financial and ecological management is stark enough, but even worse than it appears at first glance. Money is not like soil, or forests or fossil fuels. It is not a bounded thing in the way that a natural resource or ecosystem is. It is a social contract, a measure of trust, a promise to pay, long since separated from any underpinning finite material such as gold. Therefore, in some senses, it is unlimited. That's why in both the US and the UK governments were able to magic hundreds of billions of dollars and pounds from thin air, through the magic of double-entry book keeping, to bail out failed banks and pull the economy back from the brink. As an advocate of local currencies once put it, a lack of money should no more stop us doing something than should a lack of inches prevent us from building a house.

The Earth's ecosystems can be more or less productive depending on how well we care for them, but they are ultimately finite. So, we have chosen to ignore the idea of living within our means in the one arena, the ecological, where it is critical for our survival. Conversely, politicians obsess about the idea of living within our means in the economic arena, where it is debilitating to society in practical terms, and theoretically flawed. Obliviousness to ecological debt is characteristic of an economic system in which the interests of finance come first and which fails to recognise the environmental foundations of prosperity.

As a result, money flows into things that maximise short-term financial returns, rather than optimising overall value for the economy and society. Tax breaks go to the oil and gas industry while renewable energy is starved of investment and undermined by a hostile chancellor of the exchequer.

One problem has always been how to bring such ideas home. That is beginning to change. The fracking debate is reminding many that the energy we take for granted actually comes from somewhere. Using less, or having more clean, community-owned renewable sources suddenly seems more attractive than injecting chemical cocktails into the ground not far from your home to push more carbon out of it. These reactions are in Conservative heartlands. And, it was a Tory minister, Lord de Mauley at the Department for Environment, Food and Rural Affairs, who recently reminded us that rampant consumerism is not very conservative. Buying second-hand and repairing things, he said, would tackle scandalous levels of waste and leave you better off.

"Live without limits" is the slogan of Jeep, makers of archetypal, gas guzzling off-road vehicles. However, if you tried to, you wouldn't live very long. By accumulating too much ecological debt, we are losing the climate to which we are adapted. Historically speaking, the public debt is at relatively low levels, while our ecological debt is larger than ever and growing. That is the issue that should be at the top of the political agenda.