Habitat loss, alterations in ecosystems and invasive species are among major threats
A ringtail possum. Photo: iStock Climate change has pushed 25 per cent more organisms in Australia’s biodiversity-rich northern rainforests into the list of threatened species since 2020, a new report showed. The rainforests are world heritage sites.
The new report State of the Wet Tropics was prepared and submitted by the management and conservation authority for the UNESCO-listed Queensland wet tropics to the state government. It highlighted the growing threats and declining health of species such as ringtail possum.
The species was given international protection in 1988, but climate change, habitat loss and degradation of supporting ecosystem poses threats.
Invasive species and diseases also threaten the existence of these species, the authors of the report noted. “The insidious and damaging threat posed by invasive species and diseases, and the impacts of climate change present real danger to the continuing integrity of the area’s biodiversity.”
It further stated that a number of other species, specifically the endemic rainforest frogs, high-altitude birds, ringtail possums and plants of the Myrtaceae family that were considered secure while listing, “now face significant challenges from accumulated and compounding threats”.
The country is home to about 600,000 native species and a high proportion of them endemic to the region.
The Wet Tropics bioregion contains 26 per cent of Australia’s vascular plant species. Some 314 of these are classified as Vulnerable, Endangered or Critically Endangered, according to the Nature Conservation Act (NCA) or Environment Protection and Biodiversity Conservation (EPBC) Act with a further 98 species listed as Near Threatened.
It is a similar story for vertebrates, with at least 25 per cent of the area’s fish, amphibians, birds and mammals having some level of conservation significance. The report observed that information on the region’s invertebrate taxa is not adequate.
“The Euastacus crayfish of upland streams are vulnerable with restricted distributions. Robert’s crayfish (Euastacus robertsi) and one butterfly, the Apollo jewel (Hypochrysops apollo apollo), are the only Wet Tropics invertebrates listed as Threatened,” it stated.
The authors attributed this significant increase in threat to climate change and its impact on the species at multiple levels. The extinction of endemic vertebrate fauna in the region was predicted to occur by more than 50 per cent about 15 years ago, they noted.
The area’s distinctive upland flora and fauna were specifically affected as the protection of suitable climate offered for cool-adapted species is declining and further impacting their ability to adapt due to natural geographic barriers and modified landscapes, the report added.
“Species already restricted to the highest elevations have nowhere further to go and face an ‘elevator to extinction’,” the authors said.
As many as nine species and subspecies of birds endemic to Wet Tropics now stand classified as threatened as per the International Union for Conservation of Nature criteria and additional five are Near Threatened due to climate change, the findings suggested.
Upland populations were impacted with increasing temperature and changing rainfall patterns, while the lowland populations are experiencing heatwaves, the authors pointed out.
“The region’s iconic ringtail possum species have also undergone rapid and severe declines, with some species most affected by increasing average temperatures and others impacted by increasingly frequent heatwaves. The lemuroid ringtail possum (Hemibelideus lemuroides), now Critically Endangered, has been most affected, losing nearly 70 per cent of its population in little more than a decade,” it mentioned.
Climate change could further alter waterflows, threatening freshwater species with reduced runoff in headwater streams, the researchers warned. The upland spiny crayfish which depends on clear, cool and fast-flowing water is an example of a species that can be affected this way.
Apart from changes in water regimes, climate change may affect the food supply and add nutritional stress among species.
The researchers pointed out that extreme weather events induced by climate change can trigger abrupt changes in the ecological systems. A one-third decline in the populations of flying foxes (Pteropus conspicullatus) was observed in 2018, when 23,000 of the species died during a period of three days.
Bushfires in 2019 affected 53 per cent of the Gondwana World Heritage Rainforests and 80 per cent of the Greater Blue Mountains World Heritage Area, the report stated. Moreover, severe tropical cyclones further threaten the species.
“Tropical Cyclone Larry, for example, caused a broad-scale redistribution of spectacled flying foxes seeking alternative supplies of blossom and fruit, and delayed and reduced tooth-billed bowerbird (Scenopoeetes dentirostris) bower residence and display, presumably because the cyclone caused direct mortality and severely reduced the fruit supply,” it stated.
It also noted that 82 per cent of the threatened taxa as per the Environment Protection and Biodiversity Conservation Act faces common pressure from invasive species.
“Invasive species can outcompete and displace native species, and severely disrupt the ecological interaction networks that sustain the habitats that provide essential ecosystem services, including changes in the behaviour of native fauna,” the report said.
It said that species like lianas (woody vines) benefit from increased temperatures due to climate change and displace trees and shrubs. Some vegetation in riparian zones have become vulnerable as invasive species germinate earlier and grow faster after events such as floods, the authors added.
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