Increased catchment erosion and nutrient loading are commonly recognized impacts of deforestation on global wetlands. In contrast, an increase in water availability in deforested catchments is well known in modern studies but is rarely considered when evaluating past human impacts. We used a Budyko water balance approach, a meta-analysis of global wetland response to deforestation, and paleoecological studies from Australasia to explore this issue. After complete deforestation, we demonstrated that water available to wetlands increases by up to 15% of annual precipitation. This can convert ephemeral swamps to permanent lakes or even create new wetlands. This effect is globally significant, with 9 to 12% of wetlands affected, including 20 to 40% of Ramsar wetlands, but is widely unrecognized because human impact studies rarely test for it. This research was part of an Australian Research Council Discovery Project (DP 110103081) and was also partly supported by the Australian Institute for Nuclear Science and Engineering (grants ALNGRA11068 and ALNGRA12071). The database used for the meta-analysis of Holocene records of catchment deforestation and wetland change can be downloaded from the Dryad Digital Repository at http://dx.doi.org/10.5061/dryad.m62gj.
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