The ecological impacts of palm oil industry on avian and mammal biodiversity

Abstract

Industrial oil palm cultivation has become established in large parts of Southeast Asia. New areas of oil palm cultivation result in habitat destruction and local extinction of charismatic fauna (e.g. the Orangutan). The Roundtable on Sustainable Palm Oil (RSPO) has been formed by palm oil producing countries and the World Wide Fund for Nature to certify environmentally friendly palm oil products. To date, few large-scale studies have informed the stakeholders of RSPO on ways to improve biodiversity conservation in existing oil palm landscapes. This thesis aimed to contribute to our understanding of the ecological impacts of the palm oil industry on avian and mammal biodiversity, and to provide strategies for mitigating these impacts. I conducted a field study in the states of Selangor, Perak, and Negeri Sembilan on the west coast of Peninsular Malaysia. I examined 55 oil palm sites, comprising 41 plantation estates and 14 semi-traditional smallholdings. This study is the first to investigate relationships between different management regimes and biodiversity; previous studies mostly referred to plantation estates. The field sites I surveyed were located in 90,000 ha of total planted area of oil palm. I also surveyed a large, logged peat swamp forest covering more than 70,000 ha to compare with oil palm landscapes. I quantified the occurrence and abundance of bird and native mammal species in peat swamp forest and oil palm sites. I measured a number of stand-level characteristics including vegetation cover, undergrowth height, and canopy cover. I used GIS applications to compute landscape metrics including cumulative area of natural forest patches, planted area of oil palm, and distance to natural forests. I recorded types of land-use such as cattle grazing, and the abundance of introduced predators within oil palm plantations. I found that oil palm landscapes, irrespective of different management regimes, supported lower bird species richness than logged peat swamp forest. However, oil palm landscapes were far from devoid of avian biodiversity, sustaining a range of forest-dependent, open-area, migratory, and wetland species. The bird assemblages in logged peat swamp forest consisted of forest-dependant species that some were present, but rare, in oil palm landscapes. Bird species richness in oil palm landscapes was influenced by vegetation cover, canopy cover, and the distance to the nearest natural forest patches. Smallholdings supported more frugivorous birds than plantation estates. I found that oil palm landscapes supported 33 species of mammals, which is approximately two thirds of the number found in Peninsular Malaysia. Smallholdings supported more high conservation value mammal species than plantation estates. Omnivorous mammals occurred in higher abundance in plantation estates. Lastly, I found that smallholdings supported higher mammal abundances than plantation estates. Existing oil palm landscapes supported lower levels of biodiversity than natural forests, but nevertheless provide habitat for some species of native birds and mammals of conservation value. These landscapes can be managed for better conservation outcomes. My study provides important field data on the state of faunal biodiversity in established oil palm landscapes, and highlights some important ways in which palm oil stakeholders can improve biodiversity conservation.