This book contains a selection of revised papers that were presented during the Heart of Borneo conference in Leiden in 2005. This conference was organised jointly by the World Wide Fund for Nature (WW Netherlands), the International Institute for Asian Studies (IIAS) and the Institute of Environmental Sciences (CML) as a follow-up of another conference organised in Brunei in April 2005. During that meeting political leaders of Malaysia, Indonesia and Brunei, together with scientists from the region, as well as representatives of the major international conservation agencies discussed the need to collectively take responsibility for the protection of the Heart of Borneo, the large transborder area of high conservation value shared by the three countries.