Evaluating At-Risk Black Ash Wetlands as Biodiversity Hotspots in Northern Forests

Black ash (Fraxinus nigra) forests, which cover over 1.2 million hectares in the Great Lakes Region, are threatened by emerald ash borer (EAB; Agrilus planipennis), which is eliminating native populations of ash throughout the region. Understanding the contribution of black ash wetlands to local and regional species richness is critical in forming effective conservation policies and informing management plans for these imperiled habitats. We measured breeding bird and anuran communities in black ash wetlands and compared them to nearby non-black ash habitats for each taxa: aspen-dominated upland forest for birds and emergent wetlands for anurans. Our results showed black ash wetlands support unique communities of birds but not of anurans. For birds, black ash wetlands had higher species richness and a greater number of birds that were indicator species compared to upland forests; this is likely due the presence of a water component and more structural diversity in black ash wetlands compared to aspen-dominated aspen forests. In contrast, emergent wetlands had higher richness of breeding anurans and greater number indicator species than black ash wetlands; this reflects a general preference by North American anurans to breed in more open canopy habitats. If EAB invades these systems, expected increases in ponding and canopy openness may be beneficial for some anuran species during the breeding season, but loss of the forest canopy could result in significant changes in bird community composition. Our results indicate that implementing management strategies that focus on emulating structural complexity of black ash wetlands will be beneficial for conserving wildlife diversity.

Automated summary

Black ash wetlands support unique bird communities, while emergent wetlands have higher richness of breeding anurans. Invasion of emerald ash borer may lead to significant changes in bird community composition.