Time to apply the brakes before we go over the cliff

If humanity carries on its present course, 11,000 species of plants and animals will be extinct in the foreseeable future. The common analogy is that of the slippery slope steepening until it becomes a precipice. We have not reached the cliff yet, but it will become harder to avoid it. The new "red list" of endangered species, published this week, confirms that the diversity of life on the planet faces its greatest threat since the catastrophe which wiped out the dinosaurs 65 million years ago.

If humanity carries on its present course, 11,000 species of plants and animals will be extinct in the foreseeable future. The common analogy is that of the slippery slope steepening until it becomes a precipice. We have not reached the cliff yet, but it will become harder to avoid it. The new "red list" of endangered species, published this week, confirms that the diversity of life on the planet faces its greatest threat since the catastrophe which wiped out the dinosaurs 65 million years ago.

There are three possible responses to this supremely important environmental crisis, the first of which can be quickly dealt with. That is the view that enough species will adapt to the explosive growth of human population to allow ecological business as usual. While it is true that many life-forms are surprisingly resilient and can adapt to changing conditions, it is a complacent view which cannot be sustained.

Earlier this week we reported that several species of great ape face imminent extinction. Of course, there are many micro-organisms upon whose survival the complex ecology of mammals depends, but apes pose a more immediate and - because of their genetic closeness to humans - more starkly moral challenge.

The second response is to declare that it is already too late for most of the species on the list and to focus the global conservation effort on trying to slow the rate at which species are wiped off the face of the Earth. But this is too pessimistic.

The third response is to seek to save every single species, from the orang-utan to all 100 kinds of moss and liverwort. That would be expensive. The compilers of the red list say that "human and financial resources must be mobilised at between 10 and 100 times the current level". This approach may be derided as unrealistic. But just because something is impossible, does not mean it should not be attempted. We will not succeed, but that objective would help dramatise the scale of the effort needed.

The three causes of extinction, in order of importance, are habitat loss, hunting (and fishing) and the importation of species from their natural areas. In each case, the imperative is to change the economic incentives operating so that local people gain more by preserving habitats and stocks than by depleting them.

As with the attempt to slow down global warming, the bill for the rich countries of the world, including this one, will be high. But it is one that must be paid.