Pollution, invasive species and disturbance

More on illegal trade here
More on habitat loss here

The other three factors mentioned in the introduction this threats section — pollution, invasive species (species introduced from other parts of the world) and disturbance — are of much lower significance in terms of short- and mid-term extinction risk for the large animals of South-east Asia. In part this is because they tend to occur around concentrations of people, which are not generally the areas holding many large animals anyway. Nonetheless, a few examples can be found. Banteng, a wild cow occurring widely in mainland South-east Asia, parts of Borneo, and Java has been hunted out of most of its range. Baluran National Park, Java, formerly held a large and stable population, even during the 1990s when most other populations were in free-fall decline; yet the tree Acacia nilotica, introduced from Africa, has now taken over much of the prime Banteng habitat. Vultures were formerly among the most abundant large birds of tropical Asia.

The South-east Asian populations declined to rarity over the last few decades, through the overhunting of wild herbivores and changes in domestic carcase disposal practices, perhaps compounded by direct persecution of the vultures themselves. They remained abundant in India until the 1990s, when a sudden, very rapid decline occurred. This ongoing decline is due to poisoning through veterinary medicine residues; by chance, the medicine responsible is not used in South-east Asia. The South-east Asian vultures are now an invaluable resource in case the Indian populations disappear before the veterinary pollution issue can be solved. Yet they are themselves at permanent potential high risk of pollution: should veterinary drug-use patterns change in South-east Asia, the vultures could disappear within a couple of years. However, examples such as these are very much the exception to the general pattern of high extinction risk through trade-driven hunting and, in a few cases, habitat factors.

To these threats to the animal populations can perhaps be added an additional factor: that the situation can seem so depressing that some conservation personnel will give up, and the threat allowed to continue and indeed intensify. This absolutely need not be so. There are a sufficient number of cases where highly challenging situations have been tackled and stability, then increase, brought to populations that seemed doomed to extinction. These even include the most highly-sought animals in the trade: the Javan Rhinoceros population of Ujung Kulon National Park, Java, has been stable for some decades, reflecting effective protection. The ingredients of success are elusive, but with the right people and enough funding, there is no reason to believe that any land-based situation is beyond solution.