Multidimensi Perubahan Iklim pada Distribusi Orangutan Sumatera di Ekosistem Leuser untuk Perencanaan Konservasi

Abstract

Sumatran orangutan (Pongo abelii) is one of the three orangutan species (Pongo spp. – Tapanuli: P. tapanuliensis; Borneo: P. pygmaeus) from the great ape family group (Hominidae) that lives in Indonesia. Sumatran orangutan current population in 2015 reached 14,613 individual species based on field survey. Currently, Sumatran orangutans suffered a population declining over the past year due to altered habitat. Climate change also would be expected to increase the extinction risk of the species – thus, many biodiversity, particularly primates will redistribute their habitat. Most Sumatran orangutans (82.5%) are only found in the Leuser Ecosystem, Aceh Province. Due to the range contraction and many threats towards Sumatran orangutans, the species have been considered critically endangered (CR) species based on the International Union for Conservation of Nature (IUCN) red list. Species distribution modelling has been already used for various applications, such as conservation management towards non-human primate species within the protected areas – e.g., the Sumatran orangutan. Nevertheless, there is still a lack of research and information that elaborates climatic shifting effects and habitat degradation towards Sumatran orangutan distribution. The Leuser Ecosystem is the essential habitat for Sumatran orangutans; thus, understanding the climate effects for this species within the area is crucial. In general, the objectives of this research were a) to estimate Sumatran orangutan distribution within the Leuser Ecosystem using species distribution model, b) to identify and quantify exposure of Sumatran orangutan towards climate change and altered habitat, and c) to design conservation strategies for the species. The novelties of this research were: a) Research approach: species distribution modelling approach for Sumatran orangutan within the Leuser Ecosystem using ensemble-method of machine learning (e.g., RF, SVM, MaxEnt, and GLM) based on shared socio-economics pathway with the spatial resolution 100-m; and b) Problem solving: evaluation of Sumatran orangutan vulnerability under climatic pressures, altered habitat, and deforestation using bioclimatic velocity. Furthermore, conservation planning – e.g., habitat restoration and creating the wildlife corridor using least-cost path analysis. In addition, we also provide a new method to estimate the extinction rate of Sumatran orangutans using a macro-ecological approach to assess species adaptivity. This research revealed that the ensemble model from several algorithms (i.e., GAM, GLM, Maxent, Random Forest, and SVM) had outperformed the other algorithms based on discrimination metrics (i.e., AUC, TSS, Kappa, Jaccard, Sørensen). The bioclimatic factor was the essential variable to capture the fundamental distribution of Sumatran orangutan. Orangutan distribution within the Leuser Ecosystem was strongly correlated with the precipitation in the driest quartal and temperature range, affecting food abundance, activity budget, and habitat quality. This result shows that the current Sumatran orangutan distribution covered 37% of the landscape (9915.63 km2). Furthermore, this study also used species distribution model output to estimate population density and metapopulation within the habitat patches. The density model of Sumatran orangutan has a relatively similar pattern to the previous study. Climate and habitat changes jeopardized tropical biodiversity, including Sumatran orangutan within the Leuser Ecosystem. This landscape will suffer a tremendous climatic anomaly (i.e., precipitation and temperature) in the northwest, southeast, and montane areas of the Leuser Ecosystem. Besides, high-temperature anomalies will lead to a novel local climate disturbance, particularly in the high-altitude areas. BAU scenario showed more significant climate shifting than mitigation scenario. This environmental disturbance will create the downsizing and downgrading of the protected areas within the Leuser Ecosystem. Therefore, proper conservation planning should be performed to maintain the Sumatran orangutan populations. For orangutans, strategic and conservation actions in Indonesia were still focusing on habitat alterations and fragmentation – i.e., oil palm plantation expansion. Integrating climate aspects that can affect extreme events and natural disasters should be elaborated in preparing a conservation plan document for the Sumatran orangutan. Therefore, Sumatran orangutan’s conservation strategy can be more realistic and aligned with the Post-2020 Global Biodiversity Framework. Habitat refugia and restoration identification based on climate and vegetation components should be elaborate in conservation planning. Furthermore, wildlife corridor creation can function as habitat connectivity – thus, the Sumatran orangutan can survive under unprecedented global environmental changes.