Where east meets west, where best to invest?
For species that are increasingly threatened by the combined effects of habitat loss and climate change, we need to identify priority regions where we should be focussing our conservation efforts. In the case of specialist leaf-eaters, considering the effects of climate change on the distributions of their essential food resources should be a key component of conservation planning. The koala (Phascolarctos cinereus) was listed in 2012 as Vulnerable under Commonwealth Government law in the states of Queensland and New South Wales (including the ACT). Yet the synergistic threats to this species continue unabated.
Research reveals ongoing declines in koala populations, primarily attributed to habitat loss in the coastal east (urbanisation) and climate change (more extreme drought and heatwaves) in the more arid west of their range. These declines are often being observed in areas that had previously been considered ‘stronghold’ areas for koalas in Queensland and New South Wales. Compounding the problem are disease and the secondary effects of urbanisation, namely collisions with cars and attacks by dogs.
Food trees and priority regions
We addressed the question of where koalas and their critical habitats are most likely to persist under climate change by incorporating predictive models (that we developed in a previous study) into a conservation prioritization analysis (Adams-Hosking et al, 2014). We used the software Zonation (http://cbig.it.helsinki.fi/software/zonation/).
We developed four scenarios: (1) the probability of occurrence for the koala under the current climate, (2) the probability of overlap for the koala and at least one key food tree under the current climate, (3) the probability of occurrence for the koala under future climate change, and (4) the probability of overlap for the koala and at least one key food tree under future climate change.
We found that the inclusion of key koala food trees affected the identification of priority regions for conserving koalas and those priority regions are predicted to shift considerably, often outside the current range of this species, posing additional challenges for its conservation (Figure 1).
In Queensland and New South Wales, the Australian states where this species is now federally listed as vulnerable, all scenarios predicted that high priority regions will be concentrated eastwards from the western edge of the koala’s current range. However, when we incorporated key koala food trees into the analysis, some high priority regions expanded westwards from the coast in Queensland and New South Wales, although less from the coastal margins under the future climate. In Victoria and South Australia, high priority areas contracted and fragmented when food trees were included.
“The inclusion of key koala food trees affected the identification of priority regions for conserving koalas and those priority regions are predicted to shift considerably.”
A paucity of high priority areas
This is an important planning consideration for conservation. Ongoing urbanization of many coastal regions in Queensland and New South Wales is encroaching into areas that historically also contain strong koala populations. To be able to consider high priority koala conservation areas that are not directly in the path of coastal development, yet are not so far west that increasing droughts and heatwaves will affect them detrimentally, would be very useful in planning and decision-making.
Of concern is the paucity of protected areas in ecologically important areas. When overlaying the Zonation maps with current protected areas it becomes apparent there are few areas of high koala conservation priority under all scenarios, particularly in Queensland (Figure 2). Furthermore, unprotected koala habitats support many other native species and associated ecosystem services.
A key point resulting from our study is the importance of considering, in one prioritization model, not only the specialist species but also its interaction with its critical food resources. Having this knowledge may reduce unwise conservation investment decisions in the future. For example, investing in a region where the food and/or habitat for the species is unlikely to persist under future climatic conditions is not the best use of resources compared to investing in a region where both the species and its essential resources are more likely to persist. This broad-scale study can provide planning guidance for prioritising koala conservation areas at local and regional levels, where other land uses would be taken into account.
More info: Christine Adams-Hosking email@example.com
Adams-Hosking, C, C McAlpine, JR Rhodes, Patrick T Moss & HS Grantham (2014). Prioritizing regions to conserve a specialist folivore: considering probability of occurrence, food resources, and climate change. Conservation Letters. DOI: 10.1111/ conl.12125.
For more on Christine and her co-authors’ work on modelling climate-change impacts on koala food, see her story ‘Food for thought (and survival)’ in Decision Point #59.