The living wealth of South Asia

Why conservation in a crowded subcontinent has had to invent its own methods

A The band of mountains running down the western edge of the Indian peninsula occupies less than six per cent of the country's land area and contains a very large proportion of its plants and animals, including several hundred species found nowhere else. The reason is climatic rather than accidental. The range intercepts the monsoon arriving from the south-west, forcing the air upwards and wringing the moisture out of it, so that the western slopes receive extraordinary quantities of rain while the plateau immediately behind them lies in a rain shadow. A wall of wet forest beside dry country creates an island, and islands generate species. The effect is amplified by the shape of the range itself, which is broken by gaps and valleys that isolate one block of forest from the next, so that populations of the same animal separated by a few dozen kilometres of dry ground have diverged into distinct species along its length.

B The isolation is older than the mountains' present appearance. The landmass carrying India travelled north for tens of millions of years as a fragment separated from other continents before colliding with Asia, and its cargo of organisms evolved in seclusion during the journey. Several lineages of frogs and caecilians found in these hills have their closest relatives not in Asia but in Africa and Madagascar, which are the traces of that voyage. The pattern was noticed long before anyone accepted that continents move, and was explained at the time by land bridges that would have had to cross oceans; the distributions that seemed absurd under a fixed geography turned out to be some of the better evidence for a mobile one. A purple frog described only in this century, which spends nearly the whole year underground and emerges for a few days to breed, represents a lineage that separated from its relatives before the collision.

C The eastern side of the subcontinent presents an entirely different arrangement. The delta where two great river systems meet the sea supports the largest continuous mangrove forest in the world, a landscape of salt-tolerant trees, tidal channels and shifting mud that lies partly in India and partly in Bangladesh. It is nursery to a substantial fishery, a barrier that measurably reduces the damage inflicted by cyclones on the settlements behind it, and the only mangrove system in the world with a resident population of tigers, which swim between islands and have acquired a reputation for hunting people that is unusual among the species.

D Conservation in this region cannot be practised as it is in much of the world, and the difference is demographic. Reserves in southern Africa or the American west can be large and effectively empty; here the human population density is among the highest on earth, and no protected area is more than a short walk from a village. Every conservation decision is therefore also a decision about people's fields, firewood and livestock, and approaches that assume otherwise fail quickly. The corollary is that the region has been forced to develop methods of coexistence that other places may need later.

E The clearest success is also the clearest illustration of that difficulty. A national programme launched in the 1970s to protect the tiger has raised numbers substantially, and India now holds most of the world's remaining wild population. It achieved this partly through strict protection of core areas and partly through relocating villages out of them, a process that has been voluntary in law and less clearly so in practice, and which is the subject of continuing dispute between conservation authorities and organisations representing forest-dwelling communities. Legislation recognising the rights of those communities to the forests they inhabit exists and is implemented unevenly, and the resulting arguments are conducted between two groups who both regard themselves as protecting the forest from the other.

F A quieter case has produced a more interesting result. Leopards, unlike tigers, live in large numbers outside protected areas, in agricultural landscapes and even on the edges of major cities, subsisting largely on domestic dogs and livestock. Attempts to solve the resulting conflict by capturing animals and releasing them elsewhere were found to make matters worse: translocated leopards travel long distances, are more likely to attack people while doing so, and vacate territory that is promptly occupied by another animal. The policy was revised in favour of managing the circumstances rather than removing the animal, and attacks declined.

G The region also supplies the most dramatic wildlife collapse of recent decades, and its cause was pharmaceutical. Vulture populations across the subcontinent fell by more than ninety per cent within about a decade, and the agent proved to be an anti-inflammatory drug given to cattle, which causes fatal kidney failure in birds that feed on the carcasses. The consequences extended well beyond the birds: carcasses that vultures had disposed of within hours instead rotted or were consumed by feral dogs, whose numbers rose accordingly, with measurable effects on rabies transmission. The drug has been banned for veterinary use and the populations are recovering slowly. The episode remains the standard illustration of how a species performing an unnoticed service can be removed almost accidentally, and how expensive the resulting gap turns out to be.