As oil palm plantations expand across the tropics, questions about their impacts on the local landscape continue to grow. Often embedded among the sprawling plantations are forest fragments that act as refuges for native flora and fauna, who become surrounded by the monotonous matrix of oil palm. But is it possible that these forest fragments can act as sources for functionally important species that might spillover into palm plantations and provide ecosystem services?
In their upcoming paper in Biological Conservation, Gray et al. test this idea in Malaysian Borneo by surveying for invertebrates that provide important ecosystem functions such as dung and necromass removal. They examine how the biodiversity and ecosystem function of these two taxa differ in palm plantations, specifically when there is an adjacent riparian reserve to act as a population source.
After sampling almost 10,000 individuals from over 90 species of dung beetles and ants, they found that spillover from riparian areas into adjacent oil palm areas was limited for dung beetles and non-detectable for ants. They also found no evidence that proximity to a riparian reserve enhanced the activity of dung beetles or ants in nearby oil palm.
Their results suggest that in oil palm landscapes, the dispersal ability of forest-dwelling invertebrates is very limited, and plantations experience very little benefit in terms of biodiversity and ecosystem services from spillover. The authors conclude with the recommendation that forested corridors would be crucial for maintaining individual movement and gene flow between populations in forest fragments, since spillover is unlikely to maintain biodiversity throughout the region.
Gray, C. L., B. I. Simmons, T. M. Fayle, D. J. Mann, and E. M. Slade. 2016. Are riparian forest reserves sources of invertebrate biodiversity spillover and associated ecosystem functions in oil palm landscapes? Biological Conservation. DOI 10.1016/j.biocon.2015.12.017.