Wildlife Disease Association - Australasian section statement on climate change 

22 March 2022

Climate change poses an urgent and substantial threat to wildlife, biodiversity and ecosystem health worldwide. From devastating wildfires to prolonged droughts, more frequent disease spillover events, unpredictable rainfall and rising sea levels, the impacts of climate change on wildlife health are increasingly clear. WDA-A acknowledges the overwhelming scientific evidence that anthropogenic climate change is significantly affecting our wildlife, and calls for a response that matches the scale and urgency of this accelerating crisis. 


Climate change is already having profound impacts on the world’s ecosystems. 


The latest Intergovernmental Panel on Climate Change (IPCC) report concludes that rising CO2 emissions from human activities are resulting in significant, quantifiable impacts on the global climate, including drought, extreme heat events and altered rainfall patterns.(1) These changes are already apparent with a 1.1°C temperature increase since industrialisation, and will only increase in severity as greenhouse gas levels in the atmosphere continue to rise.(1)


The central aim of the Paris Agreement was to limit warming to well below 2°C, and preferably to 1.5°C.(2) Projections show that under current government policies worldwide, global temperatures will increase by 1.5°C by 2030 and by 2.7°C by 2100.(1,3) In the unlikely event that all non-legislated pledges from COP26 are enacted in full in the timeframes specified, global temperatures will still increase by 1.8°C – a level which will have profound ecosystem impacts.(1,4) Climate change is also predicted to have significant effects on human health. More than 60% of emerging infectious diseases are of zoonotic origin, and the majority of these have originated in wildlife.(5) As we have seen with SARS-COV-2, these pathogens have the potential to have enormous impacts on human populations. 


The effects of climate change on wildlife health are far-reaching. 


Wildlife health is affected by a diverse range of processes including infectious disease, trauma, poor nutrition, altered reproduction and other physiological stressors. Many of these processes are closely related to ecosystem health and are directly and indirectly influenced by climate change. Direct and easily observable effects on wildlife include death and trauma from increasing frequency and intensity of bushfires, and habitat loss from rising sea levels resulting in local extinctions. Warming sea temperatures cause coral bleaching and have significant impacts on reef ecosystems.(6) More subtle effects include changes to host-pathogen interactions leading to unprecedented infectious disease outbreaks, and increases in physiological stress due to thermal extremes or resource limitations, both of which can result in increased mortality.(7)


Evidence indicates that climate change affects arthropod vector distribution and parasite transmission.(8) Warmer temperatures have also been linked to changes in animal migrations resulting in the introduction of pathogens to previously unexposed populations.(9) Furthermore, climate change can combine with other environmental stressors including anthropogenic habitat alteration, the presence of invasive species and the development of pesticide-resistant vector populations to induce cumulative effects on infectious disease distribution and wildlife health.(10,11)


Climate change is already affecting the health of Australasian wildlife species.


An estimated three billion animals died or were displaced by the 2019-2020 bushfires, which also affected the habitat range of more than 14,000 invertebrate species.(12,13) Smoke inhalation from these events also resulted in substantial pulmonary pathology in affected animals.(14) Over the same period, an estimated minimum 72,000 flying foxes died in Australia in extreme heat events.(15) Flying fox mortalities may also have zoonosis transmission implications for humans, with increased contact and stress driving potential viral spillover.(15,16,17) 


Climate change induced alterations in habitat suitability are also occurring. In Australia, storm surges and rising sea levels on Bramble Cay in the Torres Strait have significantly reduced vegetation cover. The resulting extinction of the Bramble Cay melomys (Melomys rubicola) is regarded as the first documented mammalian extinction due to human-induced climate change.(18) Drought has reduced the grass available for Bogong moth (Agrotis infusa) larvae, causing a decline in moth numbers and resultant reduction in food supply for several species including the critically endangered mountain pygmy possum (Burramys parvus).(19) In New Zealand, temperature increases are likely to result in more favourable conditions for the migration of mosquito vectors, which are predicted to drive the emergence of infectious diseases in avian species, as encountered with avian malaria in Hawaii and West Nile Virus elsewhere in the world.(20) 


The physiological stress caused by direct impacts of climate change is likely to make wildlife more susceptible to disease and extinction. In koalas, the stress imposed by drought and high temperatures is predicted to increase susceptibility to Chlamydiosis.(21,22) On their current trajectory of population decline, koalas will become extinct in New South Wales by 2050.(23) More subtle population level effects of climate change can also occur. In green turtles (Chelonia mydas) and tuatara (Sphenodon punctatus) offspring sex is determined by temperature, with warmer areas producing more female turtles or more male tuatara. Skewed sex ratios have already been observed in turtles on the northern Great Barrier Reef and in tuatara on North Brother Island, with the potential for these changes to significantly impact population viability and increase extinction risk.(24,25)


Using current trends and modelling techniques, broad predictions can be made about the future impacts of climate change on wildlife and ecosystem health. Globally, 7.9% of species are predicted to become extinct due to climate change, increasing to 14% in Australia and New Zealand.(26) Of a representative set of 213 threatened species in Australia, 45% are considered moderately to highly vulnerable to climate change.(27) Even in a scenario where the global mean temperature rise is constrained to 2°C, Southwest Australia – one of the most biodiverse regions on Earth – is still projected to become unsuitable for 30-60% of species across all groups (birds, mammals, amphibians, reptiles).(28)




WDA-A recognises the magnitude and impact of the current climate emergency. Our response must match the scale and urgency of this accelerating crisis. Current Australian and New Zealand Government policies, including “net zero by 2050” without significantly strengthened emissions cuts by 2030, are grossly inadequate. They fall far short of achieving the emissions reduction necessary to protect wildlife populations and preserve healthy ecosystems. WDA-A calls for immediate action to mitigate climate change and its impacts, with a particular focus on limiting threats to wildlife and the emergence and effect of disease on wildlife populations. This requires a large-scale, interdisciplinary effort involving individuals, organisations and governments. To limit warming to 1.5°C, drastic cuts in emissions are required by the end of this decade.(29,30,31) Based on targets and recommendations from multiple sources,(30,31,32,33) WDA-A calls on the Australian and New Zealand Governments to act urgently to:


  • Legislate to reduce greenhouse gas emissions to 75% of 2005 levels by 2030

  • Rapidly adopt 100% renewable electricity generation

  • Commit to no new or expanded fossil fuel extraction and infrastructure

  • End deforestation and land clearing, and restore damaged landscapes

  • Support less developed nations to achieve the same


Concluding statement


WDA-A accepts the overwhelming scientific evidence that human activities are the primary driver of climate change. Scientific evidence alone has not been enough to promote the changes necessary to halt ecosystem degradation and reduce greenhouse gas emissions to levels that support a sustainable future. As experts in wildlife health, we must take urgent action to bring the scale and impact of this crisis to the attention of the public and policy-makers. Only by doing this can we hope to preserve our unique species and the ecosystems they and we depend on for survival.

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Literature cited

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