Van Walt Environmental Connect Issue Two

Studying Soil Properties to Help Conserve Orangutans

The Borneo Nature Foundation (www. borneonaturefoundation.org) has been working in Borneo since 1999, in an effort to help protect Borneo’s incredible biodiversity and in particular to conserve its imperilled orangutans. This mission began in the Sabangau Forest, a 6,000 km2 area of tropical peat-swamp forest that is the largest continuous lowland forest block remaining on Borneo and is home to the world’s largest orangutan population. The peat soils in this forest are incredibly carbon rich, storing around 20 times more carbon than other forest types (where carbon is mostly stored only in trees). This is due to the naturally waterlogged conditions, which restrict the decomposition of dead vegetation, leading to formation of the thick peat layer, on top of which the jungle grows. Our work in Sabangau continues to date, with illegal logging patrols, fire fighting, forest restoration and research work all helping to protect the area’s orangutans and other forest wildlife. Over the last year, we have become increasingly involved in efforts to protect another important rainforest area in southern Borneo: the 2,000 km2 Rungan Forest. This area of forest stretches in a long band from the flat south to the hillier north, and so covers a variety of different soil and consequently forest types. The far south is relatively poorly drained and so is dominated by peat-swamp forests, similar to those in our Sabangau study site. As you move north, gentle hills begin to emerge and the soil becomes increasingly sandy, leading to a mixture of sandy heath soils on the hills/slopes (known locally as “kerangas”, meaning soil on which rice cannot grow) and peat forest in the flatter areas between hills. Continuing north, the land becomes increasingly undulating and mineral soils begin to dominate, upon which dry lowland (dipterocarp) forests are found. Our knowledge of the exact distribution and nature of these soil and forest types, and how this affects the distribution and abundance of endangered species such as the orangutan in the area, is extremely poor. The village of Mungku Baru is found in the central part of this forest, in the mixed heath- peat forest zone. The forest here has been and still is threatened by logging and oil palm conversion, but the local village are eager to protect their forest, which is important both for local livelihoods and forms an important part of the traditional local culture (a belief exists that, if certain trees are cut in the forest, the people cutting those trees will die). The local

Local research staff using soil kit. Photo by Bernat Ripoll Capilla / BNF

Wild Bornean orangutan infant. Photo by Erik Perlett / Borneo Nature Foundation

University Muhammadiyah Palangkaraya have established an Education Forest near to this village, where they aim to conduct research and education activities. To help support these activities, the Borneo Nature Foundation signed a MoU with the University Muhammadiyah Palangkaraya last year. To formally launch this collaboration, we began a joint research expedition in July 2016, which was the first detailed scientific study in the region. Our primary aims in this expedition were to begin describing the forest in this area, including the extent, type and distribution of forest types; their abiotic determinants; the abundance and diversity of forest wildlife; and the influence of habitat and soil type variations on these. The expedition involved around 45 people, including international and local scientists, students and volunteers, plus local village assistants. The basic forest camp was built especially for this expedition

The link between studying soil properties and conserving orangutans in Borneo is not immediately obvious. Most people likely use Van Walt’s soil testing equipment to monitor soil properties for commercial applications, such as establishing the optimal growing conditions for crops, and most users are likely concentrated in developed temporal regions. Orangutans, on the other hand, live in tropical rainforests, preferring pristine forest areas that have not been disturbed by humans. So, why the connection? Well, as for crops, the condition and productivity of a rainforest depends to a large extent on its soil properties. Better soil means that trees can grow quicker and taller, and produce more flowers and fruits, enhancing their reproductive success. Orangutans are almost exclusively vegetarian, feeding on fruits,

flowers, leaves, barks and piths, supplemented by the occasional insect, fungi and rarely vertebrates (consumption of bird eggs and even squirrels and slow lorises has been observed). The bulk of their diet – around two thirds – is fruit, however, and it is for this reason that orangutans are restricted to the tropical jungles, where forest trees produce fruit throughout the year. In theory, higher quality soil should therefore result in greater production of fruits (and flowers) for orangutans in the forest, which would be expected to lead to higher orangutan population densities. This is potentially very important, given that orangutans are threatened by human activities across their range – they have recently been classified as “Critically Endangered” by the International Union for Nature Conservation (IUCN).

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