Nina Gallmetzer

Nina Gallmetzer


Impact of oil palm agriculture on amphibians and reptiles.

In the last decades, oil palm plantations expanded rapidly in many tropical regions, including the Neotropics. In this study from the Pacific lowlands of Costa Rica, we quantified the impact on the region’s herpetofauna. Amphibians and reptiles were sampled along transects at five sites in forest interior (FI), at forest margins (FM) and in oil palm plantations (OP), respectively. Besides assessing species richness, we calculated four different functional diversity (FD) measures (FRic – functional richness, FEve – functional evenness, FDiv – functional divergence, FDis – functional dispersion). While no significant differences in species richness were found between FI and FM, OP was characterized by a strongly impoverished fauna. Total species richness of amphibians (28 species) and reptiles (19 species) was reduced to 45.3% and 49.8% compared to FI, respectively. Only 31.8% of amphibian and 30.8% of reptile species found in FI were also found in OP. In both taxa, species composition of OP sites differed significantly from both forest habitats. Species recorded in OP were predominantly disturbance-tolerant species. We did not find differences in FD measures between the FI and FM but a dramatic decline of FRic, FDiv and FDis in amphibians towards OP indicating a decrease in ecological function of amphibian communities in this land-use system. Further, we found a severe loss of endemic species in OP. The almost complete absence of leaf litter, understory vegetation and woody debris as well as the more open canopy may be important drivers for reducing herpetofauna species richness in oil palm plantations. Enhancing understory vegetation could help making plantations a less hostile environment for some species. Still, those management measures might not be enough to promote the occurrence of forest specialists in OP. Therefore, to complement such efforts and prevent losing the majority of the tropical herpetofauna in human-modified landscapes, it is essential to protect any kind of forested habitat ranging from secondary forests to strips of gallery forests and remnants of old-growth forests.

 

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