See all stories in this edition
Posted 25 February 2009

New research is showing that Australia’s most devastating plant disease is likely to cause a massive collapse of native vegetation under climate change in southwestern Australia.

More than 2200 native plant species in southwest WA, including 800 endemics, are considered susceptible to the dieback pathogen Phytophthora cinnamomi, which kills plants by attacking their roots.

A newly completed two-year study in the Fitzgerald River and Stirling Range national parks by Chris Dunne and colleagues from WA’s Department of Environment and Conservation has delivered an alarming prognosis for these biodiversity hotspots under climate change. The conditions under which the disease thrives will become more frequent.

Dr Dunne told the Invasive Species Council that the pathogen is causing increasing damage as it adapts to the dry Mediterranean environment of southwest WA, which is very different to its original environment in southeast Asian rainforests.

Phytophthora benefits from plant responses to water scarcity — in their quest for water the roots of many species meet together at moist locations, facilitating spread of disease from species to species via their roots. Climate change is predicted to benefit Phytophthora by delivering more rain in summer (most rain falls in winter) through storms linked to northern cyclone activity.

“Over the past decade we have already seen a number of the extreme rainfall events predicted under climate change scenarios for WA’s south coast,” Dr Dunne said.

Zoospores spread in overland water flows and the pathogen infects many more plants under the combination of heat and moisture.

Dr Dunne said the team’s yet-to-be-published study predicts “a collapse of native vegetation” in many sites on the WA south coast and affecting entire ecosystems.

“This will reduce or eliminate some native animals from infested sites,” he said.

Phytophthora causes disease in woodlands, forests and heathlands in all Australian states and the ACT. About 10 per cent of plant species listed as threatened by the Federal Government are at risk or potentially harmed by the disease, recognised by its declaration as a key threatening process.

Sophisticated modelling is required to assess the likely distribution and impacts of Phytophthora under climate change in these areas.

As raised by the ISC in its edition September 2008 edition of the Feral Herald (472Kb pdf), actions under the previous threat abatement plan (2001-2006) for Phytophthora dieback were mostly not implemented because governments failed to fund them.

Chris Dunne says priority actions include immediate management of Phytophthora dieback in threatened ecological communities, threatened species populations and other areas of high biodiversity value using phosphite treatment, hygiene protocols and restoration.

Funding is required to help communities, including industry groups and local governments, to adopt best practice management.

One important message is that all is not lost, as much can be done to avert the worst outcomes.

You can help
ISC asks readers to write to Federal Environment Minister Peter Garrett requesting that his government fully fund actions recommended in the next threat abatement plan (in draft form since 2007).
Take action now

References
Draft threat abatement plan (2007) Disease in natural ecosystems caused by Phytophthora cinnamomi.
http://www.environment.gov.au/biodiversity/invasive/publications/p-cinnamomi-plan.html

Cahill, D.M. et al. (2008). Phytophthora cinnamomi and Australia’s biodiversity: impacts, predictions and progress towards control. Australian Journal of Botany 56: 279-310