Habitat loss

More on illegal trade here
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There are still parts of South-east Asia not yet reached by the recent explosion of trade-driven hunting. Animals like rhinoceroses, which have fetched high prices for many decades, have been sought in even the most remote parts of South-east Asia. But some areas remain so remote that bulk hunting of ordinary-value wildlife is not economically feasible within them. But, as stocks deplete of species after species, the harvest in even the remotest areas become more viable. Where 20 years ago only a handful of species where worth extracting from any given area, now a different selection drives entry (and these species were much more common 20 years previously) and, if the situation continues, in 20 years’ time, various species now considered common will be the targets of the future hunters. This predictable progression can be speeded up greatly by enhancement of access. Anything which allows easy vehicle access into an area previously reachable only by a couple of days, or more, of arduous march alters the cost/benefit balance. If, rather than carrying out one’s haul on one’s back it is possible to load up a pick-up (courtesy of a road) or a boat (thanks to a dam that has rendered passable a stretch of river previously riddled with rapids), the per-unit-weight price above which it is sensible to collect drops greatly. About the worst thing that can happen for any remote wilderness in South-east Asia is for it to be opened up to boats, cars or even just motorcycles.

A focus on trade-driven hunting risks overlooking the other threats that are driving some of the region’s species ever closer to extinction. Habitat loss is, rightly, given great prominence. The percentage of South-east Asia that supported largely natural habitat 150 years ago was much higher than today. Losses have been especially severe since the 1960s, and while in some areas (e.g. the state of Sabah, in Malaysia) it seems unlikely that much more old-growth forest will be cleared, in other areas the conversion of huge areas to cash-crop plantations (notably palm oil) proceeds apace. However, for most forest types, there is an adequate number and distribution of protected areas for the survival of habitat and its wildlife if hunting is controlled. Most South-east Asian countries retain higher, mostly much higher, percentages of natural or near-natural habitats than most European countries.

Most worrying about ‘habitat’ is the ‘empty forest syndrome’: a term coined in the 1980s, as survey after survey found that large tracts of little-degraded habitat survived, but were largely bereft of their hunting-sensitive wildlife. The long-term effects of this on the forest are not precisely known but are unquestionably negative, given the vital role many large animals play in seed dispersal, habitat engineering and as predators. While it is true to say that for many forest-types in the region, the habitat changes over the last 150 years have reduced massively the area available to forest-dependent species, and thus the maximum potential population of such species, they have not reduced habitat so much that extinction is a significant likelihood on habitat grounds alone. The central issue is that there are fewer, often many fewer, animals that the available habitat can support, and so, again, the imperative in preventing extinction comes back to the control of illegal hunting.

In some areas, and for some habitats, the situation is much less rosy. In some areas, although many fewer than with hunting, habitat conversion and degradation proceed unrestrained by the management agreements for the area. At the local level the (illegal) losses of habitat within some protected areas are driving many local extirpations, but the fact that many protected areas are not suffering severely in this way means that for most species somewhere in their range, adequate suitable habitat persists. The major exception to this is in the Philippines: each island of this archipelago supports species found nowhere else in the world, and thus the typical total size of distribution range for Philippine species is much lower than for continental species. High rates of deforestation on many of the Philippine islands mean that many large animals are threatened by this factor. Large animals tend to have larger area needs than smaller species, meaning that they are particularly at risk.

Wetlands

Much more seriously, and this is probably a consequence of the protected areas systems of most countries having originated within their forest departments, non-forest habitats such as grasslands, bushlands and wetlands receive very little, and in some areas, effectively no, protection. In some areas they are still seen by most land-use decision-makers as wastelands presenting the challenge of finding a tree species which will grow in them and make them ‘useful’. While grasslands are naturally extensive in some other parts of Asia, most of South-east Asia was naturally forested, with grasslands restricted to small areas. Moreover, as with wetlands, they often offer prime farmland, and so many were converted centuries ago. While there has been a focus in the western world on the need for ‘tropical rainforest’ to be conserved, the conservation status of tropical grasslands and wetlands in South-east Asia is far, far, worse.

There may be only one large floodplain still mostly under natural processes left in tropical mainland Asia – that in the Hukaung valley of Myanmar. The other formerly great plains, such as Thailand’s lower central plain, the Red River Delta (Vietnam), the Mekong Delta (Cambodia/Vietnam) and the Irrawaddy Delta (Myanmar) are now largely or entirely agricultural. The process of conversion is increasingly removing the last vestiges of natural habitat on smaller plains. The consequence of this is that, when animals fetching enormous prices in the trade are dropped from consideration (e.g. rhinoceroses), most of the extinctions (such as Schomburgk’s Deer, formerly of the lower central plain of Thailand) and species now on the edge of regional extinction (such as Hog Deer, which formerly inhabited parts of most mainland Southeast Asian countries but is now reduced to a handful of known populations there, all small) are wetland/grassland species, not forest species.

A special case of habitat change relates to the large fish of the region’s large rivers. Many species of the Mekong and other large rivers of those parts of South-east Asia with a strong wet-season–dry-season cycle are migratory and the stimulus to start moving may be extreme water levels. With increasing regulation of flow, through dams in tributaries and headwaters, there is a risk that migration will cease. Mainstream dams are particularly threatening and there is good evidence from neighbouring China that the Three Gorges Dams across the Yangtze extinguished the Chinese Paddlefish, one of the world’s largest freshwater fish, and the Yangtze River Dolphin. Various mainstream dams are proposed for the Mekong (which has a particularly rich species community of giant fish) and South-east Asia’s other rivers. It is difficult to think of any effective mitigation, should mainstream dams go ahead.