Human-induced deforestation increases extinction risk faster than climate pressures: Evidence from long-term monitoring of the globally endangered Milne-Edward's sifaka

Anthropogenic pressures continue to drive the decline of animal populations and loss of ecosystems they inhabit, as is the case for many nonhuman primates. Climate change can significantly exacerbate ongoing human pressures and therefore mitigating actions are urgently needed if we are to avert impending extinctions. Quantitative extinction risk assessments of threatened species are crucial but rarely done due the lack of long-term monitoring of populations in the wild. We assessed the risk of decline and extinction for the endangered Milne-Edward's sifaka (Propithecus edwardsi) – a primate endemic to southeastern Madagascar experiencing deforestation of its habitat which is also affected by cyclones and drought. We built stochastic population models for the species using 34-year population demographic data together with climatologies of cyclones and drought from the same period and the information on anthropogenic pressures within its range. Our results revealed that human-induced deforestation is the most influential variable affecting species decline over the next two decades, with the species becoming more susceptible to cyclones and drought towards the end of the 21st century. Against this backdrop, forest law enforcement, community forest management and economic incentives for community-based conservation must be implemented to tackle proximate deforestation causes. We additionally found that expansion of protected areas could support the recovery potential of Milne-Edward's sifaka from anthropogenic pressures, and therefore further investment in protected area establishment and management, with explicit consideration of the wellbeing of local communities, must be a priority.