Fragmentation from hydropower: impacts of forest edges and isolation on rainforest mammals

Abstract

Rising energy demands have unleashed a tidal wave of hydropower development throughout the tropics, creating reservoirs that flood large forest areas and isolate different forest patches. Small forest fragments support a small fraction of forest dwelling species, but even large forest areas can suffer great biodiversity losses along habitat edges. We quantify this loss through camera trap surveys conducted in and around Chiew Larn, a 165 km2 hydroelectric reservoir in Thailand. We placed cameras on islands in the reservoir and in the mainland forest surrounding the reservoir, along transects from the reservoir edge into the interior forest. We measure what fraction of biodiversity is lost – and which species survive – in forest fragments and edges, and then summarize any particular characteristics shared by the survivors. We also compare the relative impacts of (1) distance to forest edge and (2) distance to dam wall on the richness of carnivores, ungulates, and other groups of mammals. As deforestation rates continue to rise in the tropics, our findings will help us to predict how biotic communities will respond to ongoing fragmentation due to agricultural expansion, hydropower development, or other infrastructure growth. These findings are particularly relevant to biodiversity conservation in South America, where hydropower development is accelerating in some of the most remote and most biologically rich parts of the Andes and Amazon.