Importance of small wetlands for the persistence of local populations of wetland-associated animals

Abstract

I simulated loss of small, legally unprotected freshwater wetlands in a 600 km2 area of Maine, USA to examine how loss of small wetlands altered the geometry of the wetland mosaic and thereby might affect the dynamics of metapopulations of wetland-associated organisms. Loss of small wetlands resulted in total wetland area declining by 19% (from 2032 to 1655 ha), total wetland number declining by 62% (from 354 to 136 wetlands), and average inter-wetland distance increasing by 67% (from 0.6 to 1.0 km). Also, average upland-wetland proximity decreased by 50% (0.5 to 1.0 km), such that just 54% of the landscape was within the maximum migration distance (1000m) of terrestrial-dwelling and aquatic-breeding amphibians after loss of small wetlands, versus 90% before loss. A spatially-structured demographic model revealed that local populations of turtles, small birds, and small mammals, stable under conditions of no wetland loss, faced a significant risk of extinction (P > 5%) after loss of small wetlands. No change in metapopulation extinction risk was evident for salamanders or frogs, largely because high rates of population increase buffered these taxa against local extinction. These results suggest that small wetlands play a greater role in the metapopulation dynamics of certain taxa of wetland animals than the modest area comprised by small wetlands might imply. © 1993 Society of Wetland Scientists.