Potential Impacts of Climate Change on Wet Tropics Biodiversity

Tropical Ecosystems Hub researchers have drawn chilling conclusions for the future of specialist rainforest vertebrate species in the Wet Tropics region in a changing climate.

In its fifth Assessment Report, the Intergovernmental Panel on Climate Change (IPCC AR5) adopted four Representative Concentration Pathways (RCPs) for estimating the trajectory of greenhouse gas concentration in the atmosphere. The four pathways, RCP 2.6, RCP 4.5, RCP 6 and RCP 8.5, are effectively measures of the extent to which the Earth’s energy budget will be out of balance in the year 2100 relative to pre-industrial values.

The team from Project 3.1 Rainforest Biodiversity have concluded that, under a low emission scenario (RCP 4.5), about 10% of endemic rainforest vertebrates in the Wet Tropics are expected to be critically endangered by 2085. However, under a high emission scenario (RCP 8.5), similar to what we are currently tracking, nearly 60% of these species will be critically endangered.

Whilst the big challenge is to reduce global greenhouse gas emissions, the challenge for local land use managers and planners is to determine which areas provide refuge for species in a changing environment to maximise conservation of biodiversity.

Identifying areas with high species richness, species turnover or species endemism is an important first step in determining likely refugia both now and in the future. By using conservation prioritisation software, the team ensure that the areas of highest priority incorporate complementarity across both species and sites.

The project team’s analysis included 202 species across taxonomic groupings of birds, reptiles, amphibians and mammals from the Centre for Tropical Biodiversity and Climate Change long term monitoring database. The team assessed climate change impacts on individual species and biodiversity as a whole against the RCP emission scenarios for decadal time steps from present to 2085.

The modelling produced a suite of predictive metrics for use in understanding future impacts on species distributions and the ecology of the animals of the Wet Tropics. The project team focused on two variables from the models, “change in abundance” and level of future “habitat fragmentation”.

The results largely paint a grim picture for the survival of the endemic vertebrates of the rainforests of North Queensland if global greenhouse gas emissions continue to rise rapidly.

The results indicate that, with the “business-as-usual” worst-case scenario (RCP 8.5), great losses in species are predicted to occur by 2085. Coupled with these predicted losses in vertebrate populations in the future, results indicate that populations will be highly fragmented.

Mitigating greenhouse gas emissions and increasing carbon sequestration on a global scale is necessary to avert the worst of the scenarios modelled under IPCC AR5. However, the results of the current research emphasise the importance of identifying local, critical climate change refugia early and maintaining or enhancing connectivity between sites in anticipation of future climate scenarios.

To this end, the Queensland government is now using the methodology developed through this research to identify climate change refugia in the Wet Tropics region with the intention of purchasing land where necessary.