Sumatran Orangutan Population Declines by 2,700 in a Decade, Habitat Loss Primary Driver

A recent study conducted from 2021 to 2023 by researchers from Indonesia, the UK, and Germany has revealed a continued decline in the Sumatran orangutan (Pongo abelii) population. Over the past decade (2011-2023), at least 19.5% of the population, or 2,700 individuals, has been lost, averaging a decrease of 225 individuals (1.8%) annually. Habitat loss is identified as the primary driver of this decline. Approximately 94,399 hectares of forest, which serves as the habitat for Sumatran orangutans, were lost between 2011 and 2023. This loss accounts for 76% of the variation in population decline across the entire Sumatran orangutan metapopulation. Serge Wich, one of the contributing researchers, emphasized that the Leuser Ecosystem remains a critical stronghold for the survival of the Sumatran orangutan. Around 84% of the species' population resides in West Leuser (4,935 individuals) and East Leuser (4,926 individuals). The highest population density is found in the Trumon-Singkil peat swamp area, with an average of 1.18 individuals per square kilometer. In addition to habitat loss, threats such as poaching, illegal trade, and human-orangutan conflict also endanger the population. Government data indicates that between 2012 and 2024, 319 cases of conflict or orangutan rescue were recorded in Aceh and North Sumatra. Of these, 57 individuals were confiscated from private ownership, with at least 60% being orangutans under four years old. Researchers note that the presence of infant orangutans in illegal trade almost invariably signifies that their mothers have been killed. Another concerning finding is that approximately 18% of the Sumatran orangutan population does not live within conservation areas, including locations like Rawa Tripa. The researchers stress that simply changing the status of forests to protected areas is insufficient. Continued efforts in law enforcement, restoring connectivity between metapopulations, and intervening in landscapes lacking legal protection are crucial. Source: Mongabay Indonesia