The Orangutan Conservancy is a longtime supporter of the work being done by Dr. Anne Russon of the Orangutan Kutai Project in Borneo. Here, Dr. Russon along with colleagues Purwo Kuncoro and Agnes Ferisa offer an eye-opening assessment on what the 2015 El Nino weather system could mean for this already dangerously dry environment. Indeed, reports coming in these past two weeks confirm that 2015 appears to be one of the worst years ever for fires across Indonesia – the home of orangutans.
by Anne E Russon, Purwo Kuncoro, & Agnes Ferisa
At our orangutan research site in Kutai National Park’s Mentoko area, signs of an extreme drought have been evident since July, 2015. We recorded very low rainfall in July, only 30.5 mm, and in August less than 3 mm, our lowest August rainfall since we began research at this site in 2010. Small streams have almost dried up and water levels in our part of the Sangatta River are already so low that we can hardly travel by boat. In the forest, leaves are wilting and falling in large numbers so the forest floor is covered by a thick layer of dead leaves. Other parts of Indonesia have been experiencing similar conditions, making water shortages major features of the nightly national news. El Niño is almost certainly causing this unusual drought. Most people living in East Kalimantan probably know something about El Niño and those who don’t probably will soon because they will experience one in 2015-16, the first since 2009-10. For Kutai NP and surrounding areas in East Kalimantan, questions are what to expect from this El Niño and how it will probably affect the area, including its forest and its wildlife.
El Niño, along with La Niña, are related but opposite climatic events that can cause extreme weather, especially droughts and floods and especially in the tropical Pacific region. Conditions swing back and forth between these two extremes in an irregular, multi-year natural cycle called ENSO, the El Niño Southern Oscillation. The cycle is currently ca 2.5-7 years.
El Niño generally causes prolonged droughts In Indonesia and these are strongest in East Borneo. The worst of these El Niño long droughts on record, in 1982-83 and 1997-88, were famous worldwide because they set the stage for the Great Fires of Borneo. These fires were human-caused but were started and spread easily because of the severe drought. Results in East Kalimantan were widespread and extremely heavy damage. About 50% of Kutai NP’s forest was burned in 1982-83 and about 90% in 1997-98. That damage is a major reason for the common belief that Kutai NP was so badly damaged that it is unrecoverable as a natural area.
El Niño is worth talking about now because the 2015 El Niño is expected to be moderate or possibly greater in strength, to peak in the last quarter of 2015, and possibly to extend into early 2016. Impacts on the Kutai NP region of East Kalimantan would be a prolonged, probably serious drought in 2015 and perhaps in the first quarter of 2016.
El Niño is one event within the ENSO cycle, which refers to fluctuations in the sea surface temperature of the tropical eastern Pacific Ocean (SST) coupled with fluctuations in air surface pressure in the tropical western Pacific (ASP). If the most recent three-month SST average is abnormally warm or cool (more than 0.5 °C above or below normal for that season), an El Niño or La Niña event is considered in progress. They co-occur, respectively, with high and low ASP and can be predicted about 6 months in advance by monitoring SST. During both ENSO events, these ocean and atmospheric changes interact to affect wind, temperature, and rainfall worldwide: they are responsible for some of the extreme droughts, hurricanes, and floods reported globally. Many factors affect global climate, but ENSO is by far the most dominating on multi-year time scales.
ENSO events mostly affect countries bordering the Pacific Ocean because they are products of Pacific ocean-atmosphere interactions, but they also affect countries around the Atlantic and Indian oceans. The 2010-11 La Niña, for example, was responsible for very active hurricanes in the Atlantic and heavy floods in Columbia and Southern Africa. Effects of ENSO events vary considerably with location. El Niño typically causes abnormally low rainfall in Hawaii and the western Pacific (e.g., Phillipines, Indonesia) but excessive rain in the eastern and central Pacific (e.g., California, American Samoa). La Niña causes the reverse: exceptionally heavy rains in the western Pacific but abnormally dry conditions in the central and eastern Pacific.
ENSO effects on Borneo
Although El Niño generally causes abnormally low rainfall across Indonesia, its effects vary by region. Borneo is very strongly affected by El Niño and La Niña, especially in rainfall. Because Borneo is a huge island (the third largest in the world) and because of its mountain ranges and wind patterns, El Niño and La Niña effects on Borneo’s rainfall differ by season and location. In El Niño years all of Borneo becomes unusually dry in SON (Sep–Oct–Nov), but in DJF (Dec–Jan–Feb) the southwest becomes unusually wet while the northeast stays unusually dry. In La Niña years, this pattern reverses. Effects also differ for northern and southern Borneo: the north experiences stronger weather anomalies in SON, the south in DJF.
ENSO-related droughts in Borneo have a long history, so native Bornean flora and fauna may be adapted to them. (Fires that have occurred during El Niño droughts, however, do not appear to be natural events but rather recent products of human activities like deforestation and deliberate fire setting.) El Niño droughts typically cause prolonged food shortages for plant eating wildlife but also trigger mast fruiting, the mass synchronized fruiting of many individuals of many species. New plant growth is also rapid once the drought breaks. So rapid relief from food shortages and ultimately a fruit feast follow El Niño droughts. East Bornean wildlife may be adapted to this bust-boom seesaw in food availability. Although all orangutans are primarily fruit eaters, for example, East Bornean orangutans can survive for unusually long periods on poor quality, non-fruit foods; probably for that purpose, they have especially robust jaws.
ENSO effects in and around Kutai NP.
Kutai NP is located in a region that is one of the driest in Borneo in normal (non-ENSO) years and that experiences the most prolonged droughts in El Niño years (Figure 1). The Kutai NP authority reports the average annual rainfall in the park is 1543.6 mm. With this little rain its habitat barely qualifies as rainforest and its orangutan research sites are the driest of all wild orangutan research sites. The severe damage to Kutai NP following the 1982-83 and 1997-98 El Niño droughts illustrates how much ENSO events can affect this region’s flora and fauna, and could be interpreted as showing their great vulnerability. On the other hand, other evidence suggests just the opposite: flora and fauna native to the Kutai NP region may be exceptionally resilient because they are adapted to ENSO extremes.
First, the Kutai NP region supports exceptional biodiversity. This was recognized in the 1930s, when 2,000,000 ha were formally protected as a Nature Reserve, and more recently when a core portion of this reserve was designated a national park. Kutai NP’s current ca 192,000 ha represents a rich lowland tropical rainforest ecosystem that includes mangrove, mixed dipterocarp, heath, floodplain and freshwater swamp. Recent biodiversity estimates are 1,148 plant, 80 mammal and 368 bird species, a considerable number of them protected and/or endemic to Borneo. Rich biodiversity could be interpreted as one expression of this resilience.
Second, although fire damage to Kutai NP was widespread and extreme, burned forest areas have now been regenerating from 1997-98 fires for over 17 years. We assessed how well our Mentoko orangutan study area forest supported orangutans after 12-15 years’ natural regeneration. We found orangutans in strong numbers and all appeared to be healthy, behaving normally, and reproducing normally, so the forest is supporting them well. Many of the original tree species have survived, but the forest has changed considerably in composition and is now dominated by fast-growing pioneer species. These changes appear to benefit orangutans, probably because pioneer species produce large crops of foods attractive to them. Wildlife species believed to have gone extinct in Kutai NP have also recently been found to have survived, notably banteng and berangat (Presbytis hosei). Studies of similar damaged East Bornean forests have likewise shown relatively rapid and strong recovery (ca 15-20 years) of forest structure and biodiversity plus especially strong orangutan recovery, although recovery is much slower for tree species composition and distribution.
Last, Kutai NP’s orangutans belong to the East Bornean subspecies, Pongo pygmaeus morio, which is known for exceptional resilience in the face of habitat damage and loss. A considerable amount of the evidence for morio’s great resilience is from studies conducted in the Kutai region. As one example, most orangutans known in the Mentoko area of Kutai NP before the 1982-83 fires destroyed it survived: they were resighted in the same area, alive and reproducing, within 2-3 three years after the fires. This suggests morio has special adaptations or abilities for surviving the unusually difficult conditions that characterize their habitat.
For the Kutai NP region, the 2015-16 El Niño could be a disaster in the making. The drought had already started in our Kutai NP study area in July and is predicted to continue until the end of the year or even longer. For the park’s orangutans, other fauna and flora, prolonged drought undoubtedly causes hardships, possibly extreme ones this year, and probably higher than normal mortality. On the other hand, El Niño events are normal for this region, the orangutans we have seen during this drought to date are individuals we recognize and all have appeared healthy and have behaved normally, and these forests are known to recover well and relatively rapidly from drought-related damage. Kutai NP’s flora and fauna should then be able to cope with and recover from these hardships. Finally, for conservation, this El Niño is an opportunity to improve understanding of how Kutai NP’s orangutans and its other native fauna and flora cope with extreme climate conditions. Where do ‘our’ orangutans go when they are not in our study area, for instance, and what do they eat when conditions become very poor? Improving knowledge and understanding of such responses is important to protecting Kutai NP’s natural resources because it is critical to developing effective management practices.
Figure 1: Kutai National Park location. Kutai National Park is located about midway up the east coast of Borneo (see green label and arrow) within an unusually dry region of the island (rust circle). Grey scale variation on the map shows elevation (meters above sea level).
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