Trial by Fire

by Carey Yeager & Anne Russon

International Primatological Society newsletter, 1998

Fires and droughts have ravaged Borneo repeatedly over the past two decades (1982-1983, 1987, 1991, 1994). They swept the island again in 1997-1998, from August to December then February to April, at the worst levels seen this century. Sumatra had been spared such disasters until recently, but the 1997-1998 droughts and fires threatened its forests and their inhabitants as well. Throughout this period, fires blanketed the islands in smoke, euphemistically termed `haze'. At the height of the fires, smoke reduced visibility to approximately 5 m in some parts of Borneo. It reached neighboring countries like the Philippines, Singapore, Malaysia, and as far north as Thailand, affecting them to the degree that they lodged formal international complaints. Flight delays and even cancellations were the norm for weeks and one airliner crash over Sumatra was attributed to the smoke. The health hazard posed was considered so severe that businesses and schools were closed, residents were advised to remain indoors, face masks were issued free of charge, and employees of international corporations were evacuated overseas. The devastation for nonhuman primates and their habitat may be unparalleled.

In Borneo alone, millions of hectares of forest were destroyed by fire, including primary forest. Much of the area burned was already degraded; however, some fires did invade good quality forest as well. GTZ (a German non-governmental organization involved in fire prevention) has estimated that 8 to 10 million hectares of land burned in the fires. Four million hectares burned in East Kalimantan alone and 95% of that area had some type of forest cover previously. A WWF-Indonesia survey of the 1997-1998 fire damage found that in burned swamp areas, approximately 80% of all trees died, and that even in unburned areas, significant amounts of forest cover were lost due to drought effects. Kutai National Park in East Kalimantan, Indonesian Borneo, an area of some 200,000 ha, was decimated. Approximately 95% of its lowland forest was burned. Before the fires, it had supported an orangutan population estimated at 1200-2000. Herman Rijksen has estimated that the disaster cost the Bornean orangutan population up to 30% of its numbers, reducing it from about 21,000 to about 15,000.

El Nino played an important role in the lengthy 1997-1998 drought but humans seriously exacerbated the devastation. Poor land use policies, poor enforcement of existing laws, and increased levels of forest degradation all made the forests more vulnerable to drought and fire. However, almost all the fires were human caused and many were set intentionally. Fires in dry swampland are often set to improve fishing conditions once the water rises and to provide new grass shoots for deer, which are hunted illegally. In addition, people clear areas to facilitate illegally mining gold. Fires often originated near forest edges, along roads and rivers, for instance. Primates and other species have been affected on a host of levels. Among the most direct results are that their habitat and predations problems have increased. As proboscis monkeys, a threatened species, are restricted to river and coastal edges, they appear to have lost the greatest amount of remaining habitat of any primate species in Kalimantan. Orangutans lost significant numbers, both from the fires and from poaching after they were driven out of the forest. Long-tailed macaques, an opportunistic species known to exploit degraded habitats, will probably recover relatively quickly.

Food resources will be strained this year and beyond, for several reasons. Apart from the obvious loss of trees, vines, and shrubs, the haze caused light reduction and particulate deposition on surviving leaves. This affects the primary productivity of the forests (plants were left with less time to photosynthesize), so overall food availability and abundance will be lower this year. Changes in the resource base may lead to increased metabolic expenditure, as some animals are forced to increase their travel time in order to find sufficient food resources.

Those animals able to disperse will be concentrated at higher densities in forest fragments (compression effects). With increased numbers of animals being supported by the remaining areas, resources may not be sufficient to support them long term. They may exceed the carrying capacity of the area, and in fact, with their over-extraction of resources, actually lower the carrying capacity of the area. Orangutans, for example, turn to eating bark during times of food stress; this often leads to death of the tree and a subsequent further decline in available food resources.

Primates that survived the drought and fires may suffer nutritional deficits, both in terms of total caloric intake and vitamin and mineral deficits in coming years. Diet composition may change, with lower quality food sources like foliage and bark potentially becoming a larger part of the diet. Lower quality foods are those with few nutrients and those which contain high fiber levels or toxins which interfere with digestion. The poor nutrition may affect conception rates (rate at which females become pregnant), the amount of time between births, individual growth rates, infant death rates, and population growth rates. This is true for all animals, including orangutans and proboscis monkeys. Social structures may be altered due to changes in the sex/age composition of populations, although additional data are required to establish to what extent and in what ways. How far individuals travel per day, the total area required by an individual or group, and the pattern of which age/sex class leaves their natal group (e.g., male juveniles may typically leave but during times of food stress, both male and female juveniles may leave) may all be affected.

It will be an incredibly long time to recovery for many parts of Indonesia. Peat swamps may never recover their original vegetation cover, given the fragility of their soils. It will very likely be necessary to undertake habitat restoration to help restore the carrying capacity of the park and reserve system and assure the survival of the threatened species found within them. A host of animal species, including primates like proboscis monkeys and orangutans, may have their preferred habitats permanently reduced in size. El Nino events are predicted to occur more frequently in the future and Indonesian policies still promote the conversion and degradation of forested land, so droughts and fires remain a looming threat. As the Indonesian islands support one of the world=s richest diversities of primates, all efforts should be made to assist the development of strategies for preventing or limiting similar disasters in the future and safeguarding remaining primate populations.