Climate change impacts on Australia’s Wet Tropics freshwater fishes
The freshwater fish fauna of the Wet Tropics region has faced substantial, and often dramatic, climatic changes in the past. For example, during the early to mid Holocene (9.5 – 6ka BP), a dramatic rate (>1cm/yr) and amount (~60-70m) of sea level rise resulted in a major loss of floodplain habitats, accompanied by the reworking of coastal soils and a corresponding reduction in water quality. These changes may have increased the potential resilience of the Wet Tropics fish fauna to the effects of future human-induced climate change. However, certain areas have been buffered from past climatic variability and are now characterised by high levels of endemism. In particular, the Bellenden Kerr and Bartle Frere mountain ranges have provided relatively stable hydrological conditions for a number of endemic riffle dwelling gobies, such as the undescribed Mulgrave River goby (Glossogobius sp 4), scaleless goby (Schismatogobius sp.) and the very rare Stiphodon alleni. If future climate predictions are correct, such species may be lost and overall species richness in individual river basins is expected to decline, due to a reduction in dry-season base flows and catchment area due to sea level rise. In addition, fish communities in the main channels of lowland rivers may be affected by changing flow regimes and productivity dynamics. For the first time, the Wet Tropics fish fauna faces major climate change coupled with the additive pressures of anthropogenic disturbance.