Impact of post-European stream change on frog habitat: Southeastern Australia

Abstract

Stream geomorphology and fluvial processes in Australia have generally been modified substantially since European settlement. In the case of the Southern Tablelands of New South Wales, in southeastern Australia, detailed notes of early explorers and settlers and early survey maps have provided insight into the nature of these changes. Early explorers described most streams in this area as 'chains-of-ponds'. These are ponds connected by short lengths of channel or divided by grassy intervals. Many of these systems were converted to incised channels after Europeans arrived. An examination of the life history characteristics of frogs and their physiological limitations provides insight into how these changes are likely to have affected frog habitat. Chains-of-ponds provided permanent breeding ponds for frog species with extended larval stages. The environment surrounding these ponds flooded regularly, providing breeding habitat for species that can exploit ephemeral waterbodies. Flood waters and saturated soil also created moist, well-vegetated environments for adult frogs during the non-breeding season. Human impacts and landscape modification led to channel incision of chain-of-pond systems and resulted in many physical changes in pond characteristics, including availability, permanency, structural complexity and flow dynamics. The implications of these changes are discussed in this paper. Hypotheses are developed on frog species susceptibility to landscape change associated with channel incision of chain-of-pond systems.