Plot showing the observed up-slope shift and slight increase in population size of Grey-headed Robins, (Heteromyias albispecularis) based on 15 years of monitoring in the Australian Wet Tropics.
At ATBC in Cairns this year I am lucky enough to have the opportunity to present two papers. The first, entitled “Rapid Population Shifts in Australia’s Tropical Montane Avifauna: Monitoring Responses to Climate Change” is in the Symposium entitled “Impacts of climate change on tropical birds: Current knowledge and pressing uncertainties” (organised by Jeffrey D. Brawn & Cagan Sekercioglu), and draws on the results of a large collaborative project at the Centre For Tropical Biodiversity and Climate Change where I did my PhD, completed in 2011, and first short Post Doc, completed in 2013.
Abstract:Montane tropical rainforests are critical reservoirs of endemic bird diversity, while narrow thermal tolerances and restricted distributions make these faunas particularly vulnerable to climate change. In the Australian Wet Tropics, climate niche modeling has been used to predict range contractions of cool-adapted upland endemic species, and expansion of lowland generalists. Actually detecting these changes however has proved challenging, as population densities and hence patterns of distribution and abundance in rainforest birds are difficult to quantify. Efforts focused at range margins face the challenge of detecting rare colonization events, and demonstrating absences at the trailing edge is similarly problematic. By focusing on estimates of density and models of elevational abundance response, we have overcome some of these challenges for a suite of rainforest specialist species in the Australian Wet Tropics.
Using long-term monitoring data we show that climate change predictions are rapidly materializing, with significant changes in the distributions of 28 of 56 species with sufficient data. Integrating models of abundance response with available habitat area in elevational bands, we highlight synergistic effects of up-slope shift and declining habitat area in driving rapid population declines in 14 species, 6 of which are endemic to the region. In contrast, a further 14 species show population increases, all of which are lowland species adapted to warmer climates. Challenges remain in measuring shifts at the upper extremes of these gradients, where species are most at risk, and in understanding the repercussions of these assemblage changes in terms of ecosystem function.