A multi-scale, multi-species approach highlights the importance of urban greenspace and pond design for amphibian communities

Abstract

Urbanisation threatens species through habitat loss, isolation and fragmentation. Greenspace in urban landscapes often provides connectivity and habitat for wetland-dependent species. Accessible greenspace measures the combined effects of movement barriers (e.g., roads) and the total amount of greenspace on populations. I determined whether accessible greenspace was a better predictor of amphibian occupancy at ponds than the total amount of greenspace, and at what spatial scale. I also assessed the relative importance of habitat variables at the local pond-scale. Frog surveys were conducted at 65 ponds distributed along an urban–rural gradient over two breeding seasons in the greater Melbourne region, Australia. Accessible greenspace was mapped around ponds at varying spatial scales (250 m – 2000 m) using potential barriers to amphibian movement. The best-ranked multi-species occupancy model included the proportion of total greenspace within a 1000-m radius of a pond and four local-scale covariates (presence of mosquitofish, pond permanence, vertical pond walls and water conductivity). There was no support for models containing accessible greenspace. There was a positive relationship between the probability of community and species-level occupancy and total greenspace within 1000 m of a pond. There was a negative relationship between mean community occupancy and the presence of a vertical pond wall at a site. There was no apparent effect of barriers on occupancy, indicating that urban areas may be more permeable for movement by some species than predicted. Individual species responses demonstrated that management actions are required at fine and broad spatial scales to benefit amphibian communities in urban landscapes.