This view has, of course, failed to stem the tiger's decline, that of most other wild animals, or indeed the shrinking of the forests themselves. Wild tigers are down to under 4,000 in number, fragmented into many small populations, and still declining almost everywhere. But in the nick of time, perhaps, the "existence value" argument is being joined by a more pragmatic one.

We have begun to calculate cash equivalent values, if not of tigers and other animals themselves, but at least of the services generated by wildlife habitats. Carbon sequestration, watersheds, prevention of soil erosion; these things are now worth billions. But they are dry and faceless, difficult to relate to. Unlike tigers.

Not only can tigers make forests come alive in our minds, their presence indicates that the ecosystem is healthy, supporting thousands of species of plant and animal. This "flagship" role make tigers the perfect symbol for forest conservation in Asia, the perfect link between saving our planet and saving species. But we have little time, for either the planet or its tigers. If we are to succeed, top-level political will is essential.

The "International Tiger Forum" being held in St Petersburg next week is the first time that leading politicians have joined such discussions, and the juxtaposition of this event and our new economic understanding of the consequences of forest destruction is timely.

It has been a hard road to reach this "Tiger Summit" and it is as yet far from certain exactly what commitments to plan properly the use of natural resources in tiger range states will emerge.

But without top-level agreements, without real political connections between conservation and development, there is little hope for the tigers, the forests, and ultimately, the Earth. If we cannot save this most compelling of beasts, this creature whose power, grace and beauty have captured our hearts and imaginations for centuries, what can we save?

Sarah Christie is a conservationist at the Zoological Society of London