Relative effects of landscape-scale wetland amount and landscape matrix quality on wetland vertebrates: a 'meta-analysis.

Conservation management of wetland-dependent species generally focuses on preserving or increasing wetland habitat. However, the quality of the landscape matrix (the intervening non-wetland portion of the landscape) has been shown to be more important than wetland availability for some wetland-dependent species. We used meta-analysis to compare the effects of wetland amount (measured as the area of wetland habitat in a landscape) and matrix quality (measured as the area of forest cover in the same landscape) on the population abundance of wetland-dependent vertebrates. We combined data across 63 studies conducted in forested ecoregions worldwide and extracted 330 population responses for 155 species, at the spatial scale that best predicted the effects of wetland. amount and forest amount for each response. In addition, to ensure that our results were not biased by the scale selected, we assessed whether the relative effects of wetland and forest amount were scale dependent. We found that the amount of wetland in a landscape had a larger effect than the amount of forest on the abundance of mammals and birds whereas, surprisingly, for amphibians the amount of forest in a landscape was more important than the amount of wetland. For reptiles, both wetland amount and forest amount showed only weak,effects on abundance. These results were not scale dependent, i.e., they were consistent across spatial scales. Our results suggest that the population distribution of wetland-dependent amphibians is more strongly related to landscape matrix quality than to wetland availability in a landscape, likely due to their requirement for access to terrestrial resources. We conclude that conservation policies for wetland biodiversity that focus only on wetland habitat will be ineffective in conserving many of these species. In addition, population viability analyses based only on wetland amount may overestimate the capacity of a landscape to support populations of wetland-dependent species.