Climate change affecting birds in Australian rainforest
Study finds great declines for birds native to higher elevations
A recent study of bird populations in the northern rainforests of Australia has found that global warming is imperiling bird species that live in these rainforests.
The scientists, Steven E. Williams and Alejandro de la Fuente, both of whom are associated with the Center for Tropical Environmental Science & Sustainability at James Cook University in Townsville, Australia, conducted their research in the biodiverse Australian Wet Tropics World Heritage Area, examining the shift in the abundance of 42 bird species. The two scientists conducted 1977 bird surveys at 114 sites from 2000 to 2016. They published their findings in PLOS ONE on December 22 of last year.
It’s easy to imagine Australia as a huge desert, with Sydney and other major cities tacked on to the continent’s edges. But rainforests exist in Australia. Located at the northern end of Queensland, the Australian Wet Tropics World Heritage Area is found in that stretch of land that juts up from Australia and points north to Papua New Guinea.
The Wet Tropics World Heritage Area occupies 2.2 millions acres along the northwest coast of Australia. The mountains of the Heritage Area stand over 5,000 feet. The changes in elevation of that magnitude can have a number of transitions from one bioregion to another. As such, it is recognized that mountain regions such as this one are particularly vulnerable to climate change.
The Heritage Area is also quite wet. Bellenden Ker, a small town (pop 252) adjacent to the Heritage Area, is the wettest place in Australia, drenched with nearly 500 inches of rain a year. One day in January of 1979, 76 inches of rain fell there in just one day.
The rain and topography make for a rich biodiversity, with an estimated 2,800 vascular plants, 700 of which are endemic and found nowhere else. The Heritage Area has 230 butterfly species and 222 species of snails. It contains 227 plant species and 47 animal species listed as Threatened.
Because of climate change, species are on the move. The trend is that species are moving north (or south in the Southern Hemisphere) or to higher elevations as their environments warm. Species are moving, but their existence has become precarious as well. In the Australian study, the scientists found that populations of birds declined by about 12 percent for all 42 species that they studied.
Looking more closely at the bird species and where they live in the mountains, birds that live at mid and high elevations had decreased by more than 40 percent. Particularly troubling was the decline—34 percent—of the regionally endemic birds. Lowland species had moved up the mountains with the warming weather, and their populations had increased by up to 190 percent in the higher elevations.
Generally, the higher up a mountain a bird species lived the greater the population decline for that species. Among the higher elevation birds that were studied are the bridled honeyeater, Atherton scrubwren, and the grey-headed robin. The scientists theorize that the decline in higher elevation bird species is due more to climate change affecting their resources (their food, resources for shelter, etc.) than from competition from the lowland birds moving into their territory.
Species moving up mountains due to global warming has been part of the thinking of biologists for quite some time, and some biologists have referred to this phenomenon as the “escalator to extinction.” After all, once species migrate to the highest regions, where do they have to go after that? What I find remarkable is how quick and profound these changes are. The study was conducted over 16 years. That is not a long time.
As the scientists point out, it’s easy to feel assured that the living things in a nature preserve or wildlife refuge are safe from the meddling of humans, yet they found that the planetary warming we have caused and continue to cause has had a profound effect on the bird populations they studied. They add that other phenomena exacerbated by climate change, such as drought, could further plague the birds and other wildlife of the Heritage Area. They add that other species that live in mountainous regions throughout the world are probably experiencing much the same as the birds living in the rainforest mountains of Australia.
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