CANBERRA, Aug. 22 (Xinhua) -- Native grass trees that keep Australia's iconic animals safe from extreme weather events are under threat from land clearing and disease.

In a study published on Tuesday, researchers from the University of South Australia (UniSA) discovered that the long, thick and dry grass from Australia's 29 species of yaccas - collectively known as grass trees - insulate animals from extreme weather in summer and winter.

In the Mount Lofty Ranges on the outskirts of Adelaide, the capital city of the Australian state of South Australia (SA), temperatures under yacca canopies were found to be 20 degrees Celsius cooler than under the direct sun in summer and warmer at night in winter, offering shelter to wildlife.

One species was found to keep the soil underneath its thick skirt completely dry during weeks of heavy rainfall.

"Several of the 29 species of Australian grass trees are known to host native bush rats, threatened bandicoots, echidnas and pygmy-possums, among other wildlife," Topa Petit, the lead author of the research, said in a media release.

"The remarkable ability of these grass trees to protect wildlife from deadly climatic extremes - as well as providing effective hiding spots from predators - strengthens the mounting evidence that these plants are keystone species."

However, the same research also found that yaccas on the mainland and on Kangaroo Island - an important sanctuary for biodiversity off the SA coast - are under threat from bushfires, land clearing and the soil pathogen Phytophthora cinnamomi.

Grass trees are commonly burnt in fuel reduction programs and can take decades to recover, but research has shown doing so increases fuel loads.

"Grass-tree resilience to bushfires appears to be overestimated," Petit said.

"Moreover, even if grass trees are not killed by fires, their very old thick skirts of dead leaves burn, leaving no shelter to animals in post-bushfire environments." Enditem

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