Almost a quarter of banksia species are
threatened with extinction by the
Phytophthora infestation.
Image: iStockphoto

ONE of the world’s most important biodiversity hotspots is under renewed threat due to a tiny introduced water mould that is devastating the flora of southwestern WA.

A major study has found that more than one million hectares, or 10 000 square kilometers, of the southwest are now infected with Phytophthora cinnamomi otherwise known as Phytophthora dieback, an introduced microorganism that kills by destroying the root systems of plants.

A team of scientists working on Project Dieback, a study supported by the state government and the Federal Government’s Natural Heritage Trust, has mapped the spread of Phytophthora dieback from Eneabba to Esperance.

Their findings were released in Perth on June 4 in the run up to World Environment Day.

Project Dieback team leader Dr Joanna Young says the extent of Phytophthora dieback infestation in the southwest is an environmental disaster.

She says the invasive pathogen is threatening to wipe some of the state’s most iconic species off the face of the earth.

Of particular concern are banksias, with up to 24 species under threat of extinction from Phytophthora dieback alone.

“Five million hectares of remnant bush and the conservation estate has been assessed for dieback occurrence using on-ground observation, aerial photography and remote sensing,” Dr Young says.

“The project team estimates that in the order of one million hectares have been infested by Phytophthora dieback in the wetter areas of the southwest.”

Dr Young says many national parks, including the Stirling Range National Park, are already so damaged by Phytophthora dieback that their value as conservation areas is being undermined.

“Some south coast banksia species will only survive in the wild if the Fitzgerald River National Park remains free of extensive Phytophthora infestation.”

She says that once an area is infected with Phytophthora dieback it is not possible to rid it of the disease.

Project Diebacks’ four-year study described the plants susceptible to Phytophthora dieback, finding that of the 5700 described plant species in the southwest, 2300 are susceptible.

Half of the state’s 383 threatened plant species are included in the list of flora susceptible to the disease.

Dr Young says areas of the state could be saved from Phytophthora dieback if preventative action is taken immediately.

“There is currently no known cure for Phytophthora dieback. Recovery from disease impacts is costly and in some cases not feasible. The best method we have is to protect areas of bushland not currently infected.”

Dr Young says more than one fifth of the southwest, an area classified internationally for its biodiversity value, has now succumbed to the deadly pathogen and at least another one million hectares is under threat from the disease.

The Project Dieback team has completed its study but wants to ensure that further Phytophthora dieback research and preventative action continues.

Dr Young says now that the location of Phytophthora dieback infestations are known, a concerted effort to retain those areas identified as free of the disease is needed to save what is left of one of the world’s most important biodiversity hotspots.