orangutan-climateThe word 'orangutan' is derived from the Malay terms 'orang', meaning person, and 'hutan', meaning forest, and few names could be more appropriate, for the future of the orangutan is intricately linked to the future of their rainforest home, and while forest fires, logging and conversion to agriculture are considered the most immediate threats to orangutan populations, the long term composite effects of these actions on the global climate is likely to bring changes and challenges far greater than those seen today.

The entire planet is a vast network of integrated ecosystems and ecosystem services that control and regulate everything humans, and all other animals, depend on for survival, the most fundamental being the air that we breathe and the water we drink (Sekercioglu, 2010). The air that we breathe is regulated by a system, called the carbon cycle, which incorporates the planets four main reservoirs of carbon: the carbon dioxide (CO2) in the atmosphere, the organic carbon compounds within organisms, the dissolved carbon in water systems, and the carbon compounds found within the earth, as part of soil, limestone, peat, coal, natural gas and petroleum (Alexander at al, 1997). Carbon is the dominant force that both shapes life and regulates the world's climate, and plants, which absorb carbon through a system called photosynthesis, play a major role in fixing the amount of CO2 in the atmosphere, with most terrestrial carbon storage occurring in forest trees (Falkowski et al, 2000). The destruction of these forested areas, and the continued exploitation of buried organic matter, often called fossil fuels, has led to a dramatic increase in the concentration of atmospheric CO2, and a corresponding warming of the world's climate. Since 1750, atmospheric CO2 concentrations have increased by 34% (Millennium Ecosystem Assessment, 2005) and by the end of the century, the average global temperature is projected to rise by 1-8to 6.4 degrees Celsius (IPCC, 2007).

The effects of these rising temperatures are already being felt throughout the world. In Greenland, the melt rate of its glaciers is increasing, and the seismic activity they generate is accelerating (Lovejoy, 2009), and glaciers in most of the world are also in retreat, with those on high peaks in the tropics, like those on Mount Kilimanjaro in Tanzania, receding at such a rate they are unlikely to exist in 15 years (UNEP, 2007). Longer summers and an earlier melt of the snow pack have led to an increase in wildfires in the American West (Flannigan et al, 2000), and many species have been observed changing the timing of their life histories, life cycles and their migration patterns to deal with seasonal changes (Root et al, 2003; Dunn and Winkler, 1999). In the tropical climate of Costa Rica, the Monteverde cloud forest, an ecosystem dependent on condensation from clouds for moisture, has been experiencing more frequent dry days, as the elevation at which clouds form has risen, and there are fears the golden toad that inhabits these forests could be the first documented terrestrial extinction caused by climate change (Pounds et al, 1999).

As an archipelago of 17,508 islands, and with one of the world's highest rates of deforestation (FAO, 2005), Indonesia is both one of the world's biggest contributors to climate change, and one of the country's most adversely affected by it.

Indonesia lies within the inter tropical convergence zone (ITCZ), a belt of low air pressure that runs along the equator, where winds originating in the northern and southern hemispheres meet, and its climate is characterized not by temperature, but by two seasons of varying rainfall. Tropical countries in the ITCZ are some of the wettest on earth, and Indonesia's seasonal patterns of rainfall and winds are strongly related to its location on the equator between mainland Asia and Australia. Monsoons blowing in from mainland Asia bring heavy rainfall from November to March, and southeastern winds from Australia bring a period of infrequent rainfall from June to September (Galdikas, 2009). Indonesia receives an average of 70 to 125 inches of rainfall every year in the lowlands, with some mountainous regions receiving up to 240 inches per year (Galdikas, 2009), but the region is also strongly affected by local weather patterns, known as the El Nino/La Nina Southern Oscillation (ENSO) and caused by variations in sea surface temperatures in the pacific, which causes floods, droughts and variations in annual rainfall.

During El Nino years, dry season rainfall can be less than half of normal (Harrison et al, 2009), and particularly severe El Nino years have seen huge fires devastate Indonesia's forests. Once thought to occur around once every seven years, there is evidence that climate change is causing an increase in the frequency and severity of El Nino southern oscillations (Yeager et al, 2003), with Indonesia experiencing drought conditions and corresponding forest fires in 1972-73, 1982-83, 1987, 1991-92, 1997-1998, 2002, 2006 & 2009. The results were devastating. Forest fires in 1982 and 1983 burned around 3.6 million hectares of forest in East Kalimantan alone (Leighton & Wirawan, 1986), and forest fires in 1997 and 1998, usually started by local farmers or plantation companies and exacerbated by drought conditions, are believed to have destroyed at least 9.7 million hectares of forest throughout Indonesia (Case et al, 2009), significantly affected 36 of the 45 major forest blocks in Kalimantan, and devastated the country's national parks (Yeager et al, 2003). It is believed that thousands of orangutans died as the forests burned in 1997/98, with a survey in 2003 showing the wild population in the Sebangau area of central Kalimantan had decreased by 49%, from a total of 13,000 in 1996 (Suhuh & Saleh, 2007). Hundreds of adult orangutans were also killed by villagers as they fled and wandered in to villages in search of food, and orangutan rehabilitation centres were inundated with orphaned babies and infants, otherwise destined for the illegal pet trade (Barber & Schweithelm, 2010).

Of great concern is the amount of carbon dioxide the fires released in to the atmosphere. During the 1997-98 fires, 2 million hectares of the forest burned was carbon rich peat swamp forest (Page et al, 2002), which is believed to have released 0.81-2.57 billion tonnes of carbon in to the atmosphere (Rieley, 2002). The surface air temperature in Asia has already increased by approximately 1-3 degrees over the last century, and annual precipitation has decreased by two to three percent across the whole of Indonesia over the same period (Case et al, 2009). It is feared that the increased frequency of El Nino impacted forest fires could create a positive-feedback loop, whereby increased burning increases atmospheric CO2 concentrations, which raises temperatures, and increases the frequency and severity of ENSO events, thereby increasing the incidence and severity of future fires (Harrison et al, 2009). Additionally, forests that have burned once are then more susceptible to future fires, as the reduced canopy cover reduces humidity levels in the forest, increasing the rate at which biomass dries, and therefore increasing the forests fuel load (Yeager et al, 2003).

While the increase in drought conditions and forest fires is considered one of the most immediate threats to the future of wild orangutan populations and wild orangutan forest habitat, the long term effects of the fires on the quality of the forest, and its susceptibility to future climate change, is also a concern. Orangutans are frugivorous primates, and are known to feed on up to 400 different types of fruit. Their very survival depends on there being enough fruit, and other forest products, to sustain them. During and after the 1997/98 El Nino fires, fruit was abundant in the Kayan Mentarang National Park in East Kalimantan in the months of January to March 1998, but then plummeted and remained low during 1999 and 2000, with some species of the Artocarpus genus failing to produce any fruits from July 1998-October 1999 at all (Suhud & Saleh, 2007). Studies in Tanjung Puting National Park in Central Kalimantan after the same fires revealed the burned peat swamp had between 13.1-68.9% fewer tree species than unburned forest in the same area, with similar findings for other areas of peat swamp forest in East Kalimantan, and follow up surveys in the same forest eight months later showed tree mortality had increased significantly (Yeager at al, 2003).

Warming temperatures and changes in precipitation and seasonality are likely to affect the phenology of fruiting trees, and the seasonal activities of the forests' flora and fauna (Saleh, 2009). It has been predicted that temperatures in Asia will increase by between 0.72-3.92 degrees between now and the end of the century, and the annual monsoon in Indonesia could be delayed every year by 30 days due to changes in the regional climate (Chase et al, 2009). A longer, more severe dry season is likely to reduce the abundance of fruits (Saleh, 2009), and although orangutans have been shown to store fat during periods of low fruit availability (Knott, 1998), longer periods like these will force orangutans to rely more heavily on low quality fall back foods, such as bark, and struggle to maintain their body weight. This is also likely to have an effect on orangutan reproduction, as females are less likely to conceive during periods of low fruit abundance (Saleh, 2009), and orangutan ranging patterns and social systems, as orangutans change their behavior and locations to deal with the scarcity of suitable forest foods (Suhud & Saleh, 2007).

Orangutans have become the most high profile victim of climate change in Indonesia, but they are not the only species to have suffered over the last few decades, nor is their habitat the only one to have been damaged. Coral reefs are under threat from warming sea-surface temperatures and bleaching, and an increase in extreme weather events, warming temperatures and changes in ocean circulation and salinity patterns may impact Indonesia's marine turtle populations (Case et al, 2009). It is estimated that 34% of Asia's coral reefs were lost during the El Nino fires of 1997/98, and increased temperatures are expected to severely alter fish habitat in the equatorial pacific (Case et al, 2009). Indonesia's coastal mangroves are also threatened by sea-level rises, reduced freshwater flows and salt-water intrusion, and projected changes in the level of precipitation, temperatures and seasonality are expected to adversely affect the regions amphibians, reptiles, birds and mammals, including humans (Case et al, 2009).

Global warming, or climate change, is one of the most challenging and controversial threats facing the planet. Although there are many who claim human activities are unlikely to be the cause of this warming, the overwhelming scientific consensus suggests otherwise, and the effects are largely to be felt everywhere. Conserving tropical rainforests, their plants, leaves and peat bogs, is one of the most effective ways of decreasing the amount of carbon released in to the atmosphere, and is the only way of securing the future of the orangutan species.




Alexander, S.E., Schneider, S.H. and Lagerquist, K. (1997). The interaction of climate and life. In: Nature's Services: Societal Dependence on Natural Ecosystems. Daily, GC, editor, pp. 71-92. Washington, DC: Island Press.


Barber, C.V. & Schweithelm, J. (2010). Trial by Fire. World Resources Institute.


Case M., Ardiansyah, F. & Spector, E. (2009). Climate change in Indonesia: implications for humans and nature. WWF Indonesia.


Dunn, P.O. & Winkler, D.W. (1999). Climatic change has affected breeding date of tree swallows throughout North America. Proceedings of the Royal Society of London, 266, pp. 2487-2490


Falkowski, P., Scholes, R.J., Boyle, E., Canadell, J., Canfield, D., Elser, J., Gruber, N., Hibbard, K., Hogberg, P., Linder, S., Mackenzie, F.T., Moore, B., Pedersen, T., Rosenthal, Y., Seitzinger, S., Smetacek, V. & Steffen, W. (2000). The global carbon cycle: a test of our knowledge of earth as a system. Science, Vol 290, No 5490, pp. 291-296 

FAO. (2005). Global Forest Resources Assessment. Food and agricultural Organization of the United Nations, Rome


Flannigan, M.D., Stocks, B.J. & Wotton, B.M. (2000). Climate change and forest fires. The science of the Total Environment, Vol 262, pp. 221-229

Galdikas, B. (2009). The climate of Indonesia. Orangutan Foundation International.


Harrison, M.E., Page, S.E. & Limin, S.H. (2009). The global impact of Indonesian forest fires. Biologist, Vol 56, 3, pp. 156-163


IPCC (2007). Fourth assessment report: climate change 2007, the physical science base. Cambridge University Press.


Knott, C. (1998). Changes in orangutan caloric intake, energy balance & ketones in response to fluctuating fruit availability. International Journal of Primatology, Vol 19, No 6, pp. 1061-1079


Leighton, M. and N. Wirawan. (1986). Catastrophic drought and fire in Borneo tropical rain forest associated with the 1982-1983 El NiƱo Southern Oscillation event. In G.T. Prance, editor, Tropical rain forest and the world atmosphere. Westview Press, Boulder Colorado, USA, pp 75-102 .


Millennium Ecosystem Assessment (2005). Ecosystems and human well being; synthesis. Island Press


Page, S.E., Siegert, F., Rieley, J.O., Boehm, H-D.V., Jaya, A. & Limin, S. (2002). The amount of carbon released from peat and forest fires in Indonesia. Nature, Vol 420, pp. 61-65


Pounds, J.A., Fogden, M.P.L. & Campbell, J.H. (1999). Biological response to climate change on a tropical mountain. Nature, Vol 398, pp. 611-615


Rieley J. (2002). Kalimantan tropical peat swamp forest project. Orang Utan Tropical Peatland Project Press Release.


Root, T.L., Price, J.T., Hall, K.R., Schneider, S.H., Rosenzweig, C. & Pounds, A. (2003). Fingerprints of global warming on wild animals and plants. Nature, Vol 421, pp. 57-60


Saleh, C. (2009). Climate change and orangutans. WWF Indonesia.


Sekercioglu C.H. (2010). Ecosystem functions and services. In Sodhi, N.S. & Ehrlich, P.R.,editors,  Conservation biology for all. Oxford University Press, UK


Suhud, M. & Saleh, C. (2007). Climate change impacts on orangutan habitats. WWF Indonesia.


Yeager, C.P., Marshall, A.J., Stickler, C.M. & Chapman, C.A. (2003). Effects of fires on peat swamp and lowland diptercarp forests in Kalimantan, Indonesia. Tropical Biodiversity, Vol 8, pp. 121-138