Global Ecology and Conservation

Despite islands contributing only 6.7% of land surface area, they harbor ~20% of the Earth’s biodiversity, but unfortunately also ~50% of the threatened species and 75% of the known extinctions since the European expansion around the globe. Due to their geological and geographic history and characteristics, islands act simultaneously as cradles of evolutionary diversity and museums of formerly widespread lineages—elements that permit islands to achieve an outstanding endemicity. Nevertheless, the majority of these endemic species are inherently vulnerable due to genetic and demographic factors linked with the way islands are colonized. Here, we stress the great variation of islands in their physical geography (area, isolation, altitude, latitude) and history (age, human colonization, human density). We provide examples of some of the most species rich and iconic insular radiations. Next, we analyze the natural vulnerability of the insular biota, linked to genetic and demographic factors as a result of founder events as well as the typically small population sizes of many island species. We note that, whereas evolution toward island syndromes (including size shifts, derived insular woodiness, altered dispersal ability, loss of defense traits, reduction in clutch size) might have improved the ability of species to thrive under natural conditions on islands, it has simultaneously made island biota disproportionately vulnerable to anthropogenic pressures such as habitat loss, overexploitation, invasive species, and climate change. This has led to the documented extinction of at least 800 insular species in the past 500 years, in addition to the many that had already gone extinct following the arrival of first human colonists on islands in prehistoric times. Finally, we summarize current scientific knowledge on the ongoing biodiversity loss on islands worldwide and express our serious concern that the current trajectory will continue to decimate the unique and irreplaceable natural heritage of the world’s islands. We conclude that drastic actions are urgently needed to bend the curve of the alarming rates of island biodiversity loss.

Sulawesi is an important island for primates. All 17 species that are found there are endemics. The island also includes contact zones between species of macaques (genus Macaca) where hybrids may arise. Sulawesi continues to be deforested, especially in the lowlands most suitable for estate crops and other agricultural products. We carried out an island-wide review of the current extent and rates of deforestation, and the impact this is having on the habitat available to all primates and within macaque hybrid zones. The provinces of West Sulawesi and Southeast Sulawesi suffered the highest rate of deforestation. Macaca ochreata in Southeast Sulawesi and Tarsius pelengensis on Peleng island in Central Sulawesi have lost the most habitat at 14%, followed by M. hecki and M. tonkeana. Forest loss also occurred in all macaque contact zones. The greatest losses occurred at contact zones between the western population of M. tonkeana and M. ochreata. Corn, coffee, cocoa, and oil palm are commodities that are spreading throughout the island. The extent of deforestation in the hybrid zones is alarming, particularly as none of them are represented in protected areas. To help address these problems, a careful integration of conservation and development is suggested, including making trade-offs explicit, and conducting transdisciplinary research on social-ecological systems at the interface of policy and management at local scales.