Deforestation projections imply range-wide population decline for critically endangered Bornean orangutan

Abstract

Assessing where wildlife populations are at risk from future habitat loss is particularly important for land-use planning and avoiding biodiversity declines. Combining projections of future deforestation with species density information provides an improved way to anticipate such declines. Using the endemic and critically endangered Bornean orangutan (Pongo pygmaeus) as a case study we applied a spatio-temporally explicit deforestation model to forest loss data from 2001-2017 and projected future impacts on orangutans to the 2030s. Our projections point to continued deforestation across the island, amounting to a loss of forest habitat for 26,200 (CI: 19,500-34,000) orangutans. Populations currently persisting in forests gazetted for industrial timber and oil palm concessions, or unprotected forests outside of concessions, were projected to experience the worst losses within the next 15 years, amounting to 15,400 (CI: 12,000-20,500) individuals. Lowland forests with high orangutan densities in West and Central Kalimantan were also projected to be at high risk from deforestation, irrespective of land-use. In contrast, most protected areas and logging concessions currently harboring orangutans will continue to face low levels of deforestation. Our business-as-usual projections indicate the importance of protected areas, efforts to prevent the conversion of logged forests for the survival of highly vulnerable wildlife, and protecting orangutan habitat in plantation landscapes. The modeling framework could be expanded to other species with available density or occurrence data. Our findings highlight that species conservation should not only attempt to act on the current situation, but also be adapt to changes in drivers to be effective.

Orangutan (Pongo pygmaeus ssp. wurmbii) ranging pattern in Punggualas, Sebangau National Park, Central Kalimantan Indonesia

“…Several investigations have identified that the male range is significantly greater compared to females due to the food availability. Despite the increase in deforestation, the orangutan population has shown the opposite trend (Santika et al 2017a;Maria Voigt et al 2021Wich et al 2012).…”

Plant diversity in logged over forest in Mahakam Ulu, East Kalimantan, Indonesia

“…The estimate of collection density in Borneo is much less than Java at a ratio of 35:199 collections per 100 km 2 (Middleton et al 2019). As a biodiversity hotspot, Borneo urgently needs effective conservation actions (Voigt et al 2021). Basic biodiversity research that includes botanical explorations is one crucial activity that will help accelerate the planning and formulation of conservation plans in Borneo (Hairah et al 2017;Sabran et al 2014).…”