As league tables go, the WWF’s ranking of planetary profligacy is not the most precise. Citizens of the United Arab Emirates may or may not be guzzling slightly more ecological resources than citizens of the United States of America, and almost twice as many as people in the UK. But the WWF’s Living Planet Report seeks to establish an important concept: that humans are living beyond the means of the planet. Even countries that seem to make more efficient and sparing use of resources — such as Finland — cannot afford to feel smug. For it seems that we are collectively running an ecological deficit.

It is almost 20 years since the Brundtland Commission, led by the eponymous Norwegian Prime Minister, defined sustainable development as that which “meets the needs of the present without compromising the ability of future generations to meet their own needs”. Since then the growing human population has continued to encroach upon land, forests, ecosystems and other species. Between 1970 and 2000, the 1,000 species studied by WWF have declined by an average of 40 per cent.

Does this matter? Is it merely romantic to worry about losing the sea turtles, the polar bears and tigers, which are all now on the endangered list? At what point will their loss, and those of the ecosystems on which they depended, ultimately have consequences for our own survival? We cannot be sure. Man’s growing ecological footprint might not be cause for alarm in itself — industrialisation has lifted far more people out of grinding poverty than any aid programme — but it becomes deeply worrying when set against increasingly strained biological capacity. Even taking into account the ingenuity of humans in increasing the Earth’s biological capacity, for example by reclaiming land, WWF calculates that by 2050 we will need three Earths to keep our children in the style to which we have become accustomed.

The model is inevitably simplistic. But given that functioning ecosystems are a prerequisite of a healthy economy, it makes sense to try to place a value on them. The problem, however, is not as straightforward as suggested by the WWF spokeswoman who made the ludicrous claim that the Ugandan hippo and the Brazilian rainforest people are paying the price of Western consumption patterns. The WWF should stick to facts and leave the emotional nonsense to lesser organisations. Poor people have benefited enormously from globalisation and from the opening up of export markets to the West. Their environment may be degraded as a result, but they have not yet seen the economic consequences of that degradation.

One partial solution is to use resources far, far more efficiently. Even Wal-Mart, much derided by campaigners, is finding that energy efficiency saves money. The time has come to rethink the design and use of buildings and transport. When in ecological overdraft, it is surely wise to take action to keep the next generation out of bankruptcy.