Abstract

The habitat of Riau pale-thighed surili (Presbytis siamensis cana) located in Riau province of Sumatra island between Siak in the north and Indragiri rivers in the south, has been seriously degraded in the last a few decades. This swampy peat land forest has been degraded by frequent burning during the dry season. These problems originated because of poor governance on the forest management, and the construction of two access roads by the owners of logging concessions and wood pulp plantations. This forest block consists of Tesso Nilo National Park, Kerumutan protected area, Production Forest areas belong to two companies, and a small recreation Park. It also contains one of the most important mixed peat swamp forests. Here, we tracked changes in forest cover before and after road construction using GIS and remote sensing imagery. Deforestation rates have increased from 1.5% per year before road construction to 9.28% per year after road construction, which means that the area of forest has decreased by an annual average of 8156 ha in Tesso Nillo alone. The habitat of Riau pale-thighed surili decreased almost up to 60% in the last decade after companies started their converting forest for oil palm and acacia and roads were built crisscrossed. If the trend of deforestation continues, further decline of population of habitat of this species is unavoided. Researches should be carried out in more details to understand the status of population of this subspecies before this subspecies disappears in the wild.