A recent study finds expansion of reserves for critically endangered fairy possums may come at the expense of other threatened forest species.

 

• Fairy possums are dependent on montane ash forests in Victoria's central highlands. But these forests are threatened by fire and logging.
• A severe fire season in 2009 led to a more than 40 percent decline in fairy possums.
• Protected area expansion is seen as one way to help fairy possums survive. But a recent study finds if reserves are expanded with solely the fairy possum in mind, other species could lose out because their habitats may not overlap.
• The researchers say their analysis technique could be used generally to more effectively plan protected areas.
• Empics

 

In the highland forests of central Victoria, Australia, lives a marsupial with big eyes and an uncertain future. Fairy possums need big, old trees to survive, which are dwindling due to fire and logging. Conservationists are urging for the expansion of protected areas to help the possums survive, but a recent study published in PLoS ONE finds that doing so for this one species may put others at risk.

 

The fairy possum (Gymnobelideus leadbeateri), also called Leadbeater’s possum, is a relic from the past and the sole member of its genus. Averaging about 13 inches (33 centimeters) long, they emerge at dusk to feed, running along the upper canopy branches of some of the tallest trees in the world.

Fairy possums shelter in tree-hollows and are dependent on old trees in montane ash forests. This has been their downfall as fires, farming, and logging felled the forests of this region of central Australia, restricting the species to a fragment of its former range and driving down its numbers.

 

Listed as Endangered by the IUCN since 1982 (with a temporary respite to Vulnerable from 1988 to 1994) the fairy possum was elevated to Critically Endangered after a heavy spate of wildfire in 2009. Satellite imagery shows large burned areas within the possum’s range, and data from the University of Maryland indicate the area lost around 15 percent of its tree cover from 2001 through 2014 – most of that due to fire. Scientists say that, as a result, the population has declined more than 40 percent since 2009.

Timber harvesting threatens remaining fairy possums – so much so that the Threatened Species Scientific Committee concluded in its 2015 evaluation that the best way to prevent further decline would be to cease logging in the region’s ash forests. The species also stands to be affected by global warming, according to researchers.

 

Another idea touted by conservationists is setting aside more protected areas. In a recent PLoS One study released in January, scientists from Australian institutions attempted to figure out just where these should be to best help fairy possums. They gauged the effectiveness of the region’s existing reserve network, then looked for possible areas for expansion based on habitat suitability.

They found existing protected areas currently cover around 30 percent of fairy possum habitat. With expansions, they calculated this could be increased to between 34 percent and 62 percent.

But the researchers warn that prioritization of protected areas for fairy possums may not help other wildlife.

“We found an acute trade-off between conserving key areas for [fairy possums] and conserving habitat for other forest-dependent species,” the authors write in their study. “This arises because their habitat requirements do not strongly overlap.”

The researchers included three other species in their analysis: greater gliders (Petauroides volans), yellow-bellied gliders (Petaurus australis), and sooty owls (Tyto tenebricosa). The glider species are listed under the IUCN Red List of Threatened Species.

 

Greater glider

While all four species live in forests, the researchers found differences in range and condition preferences made it so that expansion of protected areas based only on habitat suitability for fairy possums led to tradeoffs for the other species. Ultimately, their results indicate that a much larger reserve network would be needed to equally protect all species.

For their study the researchers used a combination of a population viability analysis and spatial prioritization, and say their technique could be broadly used when planning protected area expansions.

“Given the current state of knowledge and the urgency with which decisions about the conservation of a critically endangered species must be made, this study provides crucial and tangible recommendations about where to implement conservation action,” they write.