Connectivity among wetlands matters for vulnerable amphibian populations in wetlandscapes

Wetlands have been degraded and destroyed, resulting in the decline of many wetland-dependent species populations. Many conservation efforts are based on protection of individual wetlands; however, fluxes of energy, materials and organisms between wetlands create important structural and functional connections upon which several species depend. We investigated the role of individual wetlands within a wetlandscape in sustaining an amphibian population. Wetlandscapes were represented as networks, where nodes were wetlands and links were flows of organisms described by an amphibian population model. Relationships between a wetland's connectivity to the other wetlands and the abundance of amphibians under different wetland management strategies were examined. The first finding was that wetlands within a network can be classified into sinks (where local mortality exceeds birth rate), sources (where local birth rate exceeds mortality), and pseudo-sinks (where excessive immigration maintains the population above the carrying capacity). These three wetland classes have low, medium, and high Indegree (a parameter reflecting a wetland's connectivity), respectively. The second finding was that management interventions in wetlands have different consequences according to the wetland's Indegree: wetland removal has the worst impact on amphibian populations if the wetland is a source, and wetland restoration has the best impact if the wetland is a pseudo-sink. These findings provide support for policies that managing wetlands not as independent objects but as integral parts of the wetlandscape.