The relative importance of aquatic and terrestrial variables for frogs in an urbanizing landscape: key insights for sustainable urban development

Globally, urbanization threatens ∼950 amphibian species with extinction. Yet a lack of knowledge on the factors influencing common and infrequently encountered species in landscapes that are under increasing pressure from urban development is limiting effective conservation. We examined the relative importance of aquatic variables (pond) and terrestrial variables (at three spatial scales: 10 m, 100 m and 1 km), for commonly and infrequently encountered frogs in an urbanizing forested landscape in southeastern Australia. Species richness and the occurrence of four common species were influenced by the aquatic environment (water body size, aquatic vegetation). Species richness also decreased with increasing urbanization within 1 km. This trend was driven by a strong decrease in richness of infrequently encountered species with increasing road length within 1 km from breeding ponds. Richness of infrequently encountered species also decreased with a reduction in forest cover within 10 m to 1 km from breeding ponds. Our findings suggest that frog conservation in urbanizing landscapes requires a mix of strategies across different spatial scales. Maintaining or re-establishing common frogs in urbanizing forested landscapes is likely to be achieved by providing ponds with suitable habitat. However, to conserve several frog species that are sensitive to forest loss and urbanization, breeding habitats need to be maintained within a network of large forest reserves.