Calls for emergency action plan as myrtle rust pushes plants to extinction
Australia must roll out an emergency national response to an invasive plant disease that is rapidly pushing at least four plant species to imminent extinction, experts have told Guardian Australia.
A draft emergency action plan for the fungal disease myrtle rust proposes that a rapid collection of seeds and plant material needs to be mobilised before several species disappear altogether.
Botanist Bob Makinson, vice-president of the Australian Network for Plant Conservation, has coordinated the action plan with input from about 90 experts around the country. He says the pathogen could result in at least four species becoming extinct within five years – Lenwebbia sp. ‘Blackall Range’ , Lenwebbia sp. ‘Main Range’ and Rhodamnia rubescens (scrub stringybark, brush turpentine, or brown mallet wood), Rhodomyrtus psidioides (native guava) – with others to follow.
“This is extremely urgent. We are almost eight years down the track and we now have species faced with imminent extinction and a problem that’s only going to get worse.”
Myrtle rust, first found at a New South Wales nursery in 2010, attacks trees in the myrtaceae family. In Australia, that includes 2,253 species, including iconic trees such as paperbarks and bottle brush. Many exist only in Australia. About 358 Australian species are already known hosts of myrtle rust, and that number is likely to rise.
Makinson says myrtle rust is now “fully naturalised” from Moruya, 300km south of Sydney, to Cape York, and west to the Great Dividing Range. The disease has also appeared in the north of the Northern Territory and has been found in gardens and nurseries in Victoria and Tasmania.
Andrew Cox, chief executive of the Invasive Species Council, says: “We absolutely need this plan. We could lose an entire series of myrtle plants and we don’t know what could happen then.
“These are complex ecological systems and this could wreak havoc across the Australian plant world. This call cannot be ignored any longer. We could and we should have acted years ago.”
Dr Rod Fensham, of the University of Queensland, is leading a small research effort through the National Environmental Science Program to work out just which myrtaceae are most at risk and what options there might be.
“If you can’t grow, then you die – and with myrtle rust it’s a pretty slow death. Some of these species will just drop of their perch and nobody will notice.
“It’s looking pretty grim so far,” he says, adding about a dozen are heading for extinction.
“That extinction is the end point of millions of years of evolution so, to me, that’s pretty profound.”
Most of those imperilled dozen are absent from state and federal lists of threatened species – such is the relative speed of myrtle rust’s march.
Myrtacea are an “enormously important” family of trees, says Fensham, providing fruit and habitat for native species and, in the wet tropics, stabilising riverbanks.
Some have adapted to quickly colonise gaps in forests caused by events such as cyclones. Once gone, this role, says Fensham, will be filled by another invasive, lantana. “That’s causing enough problems already,” he says.
With no nationally coordinated monitoring program, Bob Makinson says there is still much uncertainty about the true breadth of the pathogen’s impact.
“We have had seven years of encroachment of this disease and the decline of these species with no co-ordination at a national level.
“This is a difficult disease because it is spread by airborne spores. There’s no magic bullet for it, but there are meaningful actions that could be taken.”
One of the worst affected ecosystems, says Makinson, could be the wetlands in the east and north of Australia where broad-leaved paperbark trees that are susceptible to the disease dominate the ecosystem.
“The potential for knock-on impacts in those areas is enormous,” says Makinson.
Priorities for action include a “rapid field assessment” of 45 species, capturing seed and plant material for the most at-risk species, researching resistant plants and preventing the arrival of other strains of the disease.
“Of particular concern is that there are two other strains of the same pathogen – known as eucalyptus rust – and if they were to get to Australia, we could be in very serious trouble,” says Makinson.
The southwest of Western Australia, which is home to more than 1,000 species in the myrtle family, is currently free of the disease, but modelling suggests that area’s climate could suit myrtle rust. Preventing the spread there is another priority.
Makinson says New Zealand’s national response to the 2017 arrival of myrtle rust is “a lesson for Australia”.
“New Zealand has a national approach with a wide range of community stakeholders including Indigenous stakeholders. New Zealand only has about 30 species of native myrtaceae, but they have invested $13m to deal with the problem.
“Australia, by contrast, has no coordinated response and has invested only about $4.2m and has done very little on the environmental aspects of this.”
He says Australia’s response to myrtle rust could aid the country’s ability to respond to future invasive pathogens.
Guardian Australia has approached environment minister, Melissa Price, for comment.