Climate Change and the unique biodiversity of the Wet Tropics - Steve Williams

Climate change is expected to significantly affect global terrestrial biodiversity, with 57% of plant and 34% of animal species predicted to lose at least half their climatic ranges by the 2080’s1. Mitigation could reduce these losses by up to 60% if emissions are controlled and reduced over the next decade.1

Australia’s tropical rainforests are not immune to these effects according to a long-term study by Professor Stephen Williams and his team at the Centre for Tropical Biodiversity and Climate Change at James Cook University. Professor Williams says that future predictions of climate change impacts on vertebrates indicate that approximately one third of the vertebrate species in the rainforests of the Wet Tropics World Heritage Area will be severely threatened, one third will be vulnerable and one third will not change or increase.

The study’s latest iteration is funded by the NERP TE Hub, and addresses questions of climate change vulnerability and resilience of tropical animals and habitats. The team is developing strategies to help minimise impacts on the region’s unique rainforest and biodiversity using available knowledge, existing datasets and strategic research. Improving our understanding of which species will be most vulnerable, and why, will help prioritise adaptation, maximise the region’s resilience, and maximise the “bang-for-our-buck” in management and conservation.

Latest results show movements and declines in some bird and mammal species, matching the predictions made by Williams ten years ago. For example, some rainforest ringtail possums have declined, or disappeared, at the lower edges of their ranges, while increasing in numbers at higher altitude. While such mountaintop species are declining in numbers, and contracting further up into the mountains, some widespread lowland species are expanding their ranges to include mountainous areas.

Management may be too late for some populations. In 2005, on one particular mountaintop within the Wet Tropics World Heritage Area (WTWHA), a population of lemuroid ringtail possums crashed after a heat-wave. This possum lives only in cool, misty high altitude rainforests and, according to Professor Williams and his collaborators, has lost the ability to cope with temperatures above 28°C over the course of evolutionary history. Unfortunately for the possums, the frequency, duration and intensity of summer heat-waves have increased over the last 50 years and, during one such event, the temperature rose above that critical level for several hours each day, for 28 days straight. With nowhere to go and no means of cooling themselves the population of possums on that mountaintop declined severely.

With such impacts threatening, it is important to understand the role and function of places in the landscape that act as refuges during extreme weather events. These “refugia” are places a species might survive when threatened by changing climatic conditions, although for species such as the lemuroid possum, such havens may not exist much longer. Professor Williams and team have come up with a number of ways to identify and characterise a variety of different types of climatic refugia. For example, epiphytes or spaces under logs will provide some protection for some species, acting as micro-refugia. Larger landscape refugia, such as cool shady gorges, may provide some short-term buffering of heat waves and droughts. Larger areas of climatic stability provide managers with insights that may help conservation planning at the state and national levels.

Research on the potential of refugia to help protect biodiversity from extreme weather events, and guide our adaptation strategies, is a vital part of the ongoing NERP projects lead by Professor Williams.

Photos:
Male Satin Bowerbird. Credit: Mike Trenerry.
White Lemuroid. Credit: Mike Trenerry.

For further information contact: stephen.williams@jcu.edu.au

Project: 3.1 Rainforest Biodiversity