ReviewDistribution and conservation status of the orang-utan (Pongo spp.) on Borneo and Sumatra: how many remain? S e r g e A . W i c h , E r i k M e i j a a r d , A n d r e w J . M a r s h a l l , S i m o n H u s s o n M a r c A n c r e n a z , R o b e r t C . L a c y , C a r e l P . v a n S c h a i k , J i t o S u g a r d j i t o T o g u S i m o r a n g k i r , K a t h y T r a y l o r -H o l z e r , M a t t D o u g h t y J a t n a S u p r i a t n a , R o n a D e n n i s , M e l v i n G u m a l , C h e r y l D . K n o t t a n d I a n S i n g l e t o n Abstract In recognition of the fact that orang-utans (Pongo spp.) are severely threatened, a meeting of orangutan experts and conservationists, representatives of national and regional governmental and non-governmental organizations, and other stakeholders, was convened in Jakarta, Indonesia, in January 2004. Prior to this meeting we surveyed all large areas for which orang-utan population status was unknown. Compilation of all survey data produced a comprehensive picture of orang-utan distribution on both Borneo and Sumatra. These results indicate that in 2004 there were c. 6,500 P. abelii remaining on Sumatra and at least 54,000 P. pygmaeus on Borneo.Extrapolating to 2008 on the basis of forest loss on both islands suggests the estimate for Borneo could be 10% too high but that for Sumatra is probably still relatively accurate because forest loss in orang-utan habitat has been low during the conflict in Aceh, where most P. abelii occur. When those population sizes are compared to known historical sizes it is clear that the Sumatran orang-utan is in rapid decline, and unless extraordinary efforts are made soon, it could become the first great ape species to go extinct. In contrast, our results indicate there are more and larger populations of Bornean orang-utans than previously known. Although these revised estimates for Borneo are encouraging, forest loss and associated loss of orang-utans are occurring at an alarming rate, and suggest that recent reductions of Bornean orang-utan populations have been far more severe than previously supposed. Nevertheless, although orang-utans on both islands are under threat, we highlight some reasons for cautious optimism for their long-term conservation.

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The geographic distribution of Bornean orang-utans and its overlap with existing land-use categories (protected areas, logging and plantation concessions) is a necessary foundation to prioritize conservation planning. Based on an extensive orang-utan survey dataset and a number of environmental variables, we modelled an orang-utan distribution map. The modelled orang-utan distribution map covers 155,106 km2 (21% of Borneo's landmass) and reveals four distinct distribution areas. The most important environmental predictors are annual rainfall and land cover. The overlap of the orang-utan distribution with land-use categories reveals that only 22% of the distribution lies in protected areas, but that 29% lies in natural forest concessions. A further 19% and 6% occurs in largely undeveloped oil palm and tree plantation concessions, respectively. The remaining 24% of the orang-utan distribution range occurs outside of protected areas and outside of concessions. An estimated 49% of the orang-utan distribution will be lost if all forest outside of protected areas and logging concessions is lost. To avoid this potential decline plantation development in orang-utan habitats must be halted because it infringes on national laws of species protection. Further growth of the plantation sector should be achieved through increasing yields in existing plantations and expansion of new plantations into areas that have already been deforested. To reach this goal a large scale island-wide land-use masterplan is needed that clarifies which possible land uses and managements are allowed in the landscape and provides new standardized strategic conservation policies. Such a process should make much better use of non-market values of ecosystem services of forests such as water provision, flood control, carbon sequestration, and sources of livelihood for rural communities. Presently land use planning is more driven by vested interests and direct and immediate economic gains, rather than by approaches that take into consideration social equity and environmental sustainability.

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Tropical forests and peatlands provide important ecological, climate and socio‐economic benefits from the local to the global scale. However, these ecosystems and their associated benefits are threatened by anthropogenic activities, including agricultural conversion, timber harvesting, peatland drainage and associated fire. Here, we identify key challenges, and provide potential solutions and future directions to meet forest and peatland conservation and restoration goals in Indonesia, with a particular focus on Kalimantan. Through a round‐table, dual‐language workshop discussion and literature evaluation, we recognized 59 political, economic, legal, social, logistical and research challenges, for which five key underlying factors were identified. These challenges relate to the 3Rs adopted by the Indonesian Peatland Restoration Agency (Rewetting, Revegetation and Revitalization), plus a fourth R that we suggest is essential to incorporate into (peatland) conservation planning: Reducing Fires. Our analysis suggests that (a) all challenges have potential for impact on activities under all 4Rs, and many are inter‐dependent and mutually reinforcing, implying that narrowly focused solutions are likely to carry a higher risk of failure; (b) addressing challenges relating to Rewetting and Reducing Fire is critical for achieving goals in all 4Rs, as is considering the local socio‐political situation and acquiring local government and community support; and (c) the suite of challenges faced, and thus conservation interventions required to address these, will be unique to each project, depending on its goals and prevailing local environmental, social and political conditions. With this in mind, we propose an eight‐step adaptive management framework, which could support projects in both Indonesia and other tropical areas to identify and overcome their specific conservation and restoration challenges. A free Plain Language Summary can be found within the Supporting Information of this article.