Habitat Loss Major Threat to Australian Birds

[Cara J]

The Threatened Species Recovery Hub study, conducted by University of Queensland scientists and published in the journal Conservation Biology, found that half of all native bird species have each lost almost two-thirds of their natural habitat across Victoria, parts of South Australia and New South Wales.

Lead researcher, Dr Jeremy Simmonds, said the team looked at both threatened and non-threatened birds, including common species: “While more attention is usually paid to threatened species, common species, like many of our familiar fairy-wrens, pigeons and honeyeaters, are crucially important. Common species play a vital role in controlling insect pests and pollination and their decline through loss of habitat has implications for the health of ecosystems. Along with feral and invasive species, habitat destruction is among the greatest threats facing biodiversity in Australia, so it is important to understand how big the problem of habitat removal is: our research developed a method to do this, called the Loss Index.”

The team looked at how the amount of habitat available for each of Australia’s 447 different land bird species had changed since 1750. In places like Queensland’s south-east and the Wet Tropics, each hectare of forest cleared can affect up to 180 different native bird species.

Dr Simmonds continued: “Habitat loss has been particularly devastating for birds from south-east Australia; more than half of the 262 native birds in this region only have a small fraction of their natural habitat remaining in this part of the country. Northern Australia and Australia’s arid zone have had the least habitat loss, as there has been much less vegetation clearing across that region. We also looked at different bird groups and found that Australia’s parrot species are more impacted by habitat loss, compared with birds of prey, like eagles and owls.”

One such parrot is the orange-bellied parrot, a migratory species, listed as critically endangered. The 2016 to 2017 breeding season saw just 16 confirmed individuals in the wild. The Norfolk parakeet is listed as endangered and is found only in a small region of Norfolk Island. Numbers had dwindled to less than 50 birds by 1970, primarily due to the loss of large old trees with suitable hollows for them to breed in.

Dr Simmonds said the index provided a tool for conservation managers and planners to better understand how habitat loss affects all birds, and not just the endangered ones. He says: “It helps to show that every hectare of native vegetation that is removed chips away at remaining habitat for dozens and sometimes hundreds of species, including common species which typically do not receive conservation attention. The quality of the remaining habitat is often reduced, due to weeds, grazing and changed fire patterns, such as more and hotter fires, and this can further reduce the number and type of birds that an area can support.”

The Loss Index can also be applied to other species like mammals or plants to summarise and communicate how human actions affect whole assemblages, not just threatened species.

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