Multiple extreme weather events to impact 36% land animal habitats by 2085: Study

Extreme climate events such as heatwaves, wildfires, droughts and floods driven by climate change are esteemed to affect 36 per cent of the species’ existing habitats by 2085, a new study has revealed.

These impacts have been assessed with the business as usual or high emissions scenario where thousands of terrestrial vertebrates, such as amphibians, birds, mammals and reptiles, globally are likely to get exposed to multiple extreme weather events. 

The study added to the previous research stating that extreme heat may push nearly 8,000 towards extinction. They noted that extreme climate events can have devastating impacts on terrestrial biodiversity.

For example, they noted that the 2019-2020 heatwave reported in Australia killed over 72,000 flying foxes and decimated 17 million vertebrates in Panatanal of Amazon region during the same year. 

“A review of 519 studies found that 57 per cent of studies documented negative responses of species to extreme events, including 100 cases with a population decline of more than 25 per cent and 31 records of local extirpations,” the authors of the report said.

The findings by scientists from multiple countries and led by Potsdam Institute for Climate Impact Research (PIK) were published in Nature Ecology & Evolution. The study was designed with the aim to identify gaps in conservation planning by understanding different species across various geographic regions were most likely at risk to experience from the four extreme weather events. 

The researchers analysed a dataset comprising of 33,936 terrestrial vertebrate species, including 7,605 amphibians, 10,562 birds, 5,476 mammals, and 10,293 reptiles across 794 ecoregions.

They said that by 2050, under a medium-high emission scenario, on average 74 per cent of the area within species’ current geographic ranges are projected to be exposed to heatwaves, 16 per cent to wildfires, 8 per cent to droughts and 3 per cent to river floods. These areas include the species rich  Amazon basin, Africa, and Southeast Asia being the hotspot for threatened species exposure.

“We analysed changes in extreme event exposure between a baseline period centered on 2000 (1985-2014) and future periods, using 30-year moving windows centered between 2030 and 2085,” the scientists noted.

Among the four major extreme climate threats identified by the researchers, heatwaves are projected to rank top with an average of 74 per cent of the species’ geographic range likely to be exposed to heatwaves —  an increase by 56 per cent compared to the year 2000 levels, under the business as usual scenario.

“By 2050, 9,434 (6,864-10,296) bird, 4,729 (3,302-5,299) mammal, 6,849 (5,089-7,384) amphibian, and 9,155 (6,676-9,886) reptile species are projected to have at least 50 per cent of their geographic range exposed to heatwaves,” the study said. By 2085, this area is likely to increase by 93 per cent across all ecoregions.

Followed by heatwaves, extreme wildfires have been ranked as second most prevalent event that is likely to be experienced by the wildlife. By 2050, the study said that 16 per cent area under the species’ range are estimated to be exposed under such conditions scaling up to 25 per cent by 2085. 

Hotspots for increased wildfire frequency in species-rich areas are the Amazon basin, southern Africa, and Southeast Asia. Mid-latitude ecoregions will be increasingly exposed, with 130 ecoregions projected to have at least 25 per cent of the area exposed to wildfires by 2050, under the high emissions scenario, the study stated.

Droughts and river floods were expected to affect eight per cent and three per cent respectively of the species’ range. 

The amphibian habitats are most likely to be the strongest affected due to exposure against other taxa, particularly by 2085. 

Strong increases in flood exposure are projected only for localised areas in Central Africa, taiga and tundra, especially by 2085, according to the study. 

Another crucial aspect of the study assessed by the scientists is that by 2050, 14 per cent of the area within species’ range is expected to be exposed to at least two types of extreme climate events and would more than double to 36 per cent by 2085 under the business as usual scenario. 

This indicates that terrestrial vertebrates could be exposed to multiple extreme events in the same or consecutive years. “However, for 22 ecoregions more than 50 per cent of the area is exposed to at least two types of events already by 2050 in mid-latitude regions. By 2085, this increases to 236 ecoregions,” the researchers noted in the report.

Such compounding effect was demonstrated in a study on the 2019-20 Australian fire recording 27-40 per cent higher declines across flora and fauna when fire was preceded by drought, highlighting the danger of multi- hazard extreme events.

The authors noted that these changes affect positively and negatively to different species, depending on their biological adaptation capacity. But species with limited geographic ranges face the most severe risks as they have less flexibility to move into safer areas, the experts added.

“For example, the ornate chorus frog (Pseudacris ornate) experiences lower predation pressure during droughts. Second, some species and ecosystems are adapted to or even rely on these disturbances. For example, the riffian skink (Chalcides colosii) was only found in forested areas in early postfire years, because it depends on open habitat,” they said. They underlined that as a result, regions with regular flooding or moderate-intensity wildfires often exhibit greater biodiversity.

Speaking on adaptation capabilities they said, “Gorillas (Gorilla beringei) have been shown to drink more frequently with increasing maximum daily temperatures.”

But these physiological adaptive behaviour may come at a cost. For example, while high temperatures can reduce risk of fungal infections in amphibians because these fungi grow more slowly, they do not actively seek out hotter areas likely to avoid desiccation, according to the report.

Further, authors of the study said species with restricted ranges face particularly severe risks, as demonstrated by the Carnaby's Black Cockatoo (Calyptorhynchus latirostris), which experienced a 60 per cent population decline following the 2011 Western Australian heatwave. Meta-analyses indicate native species typically show higher vulnerability to these events than non-native species. 

“Extreme events can also cause abrupt, widespread impacts across taxonomic groups simultaneously — the 2011 Australian heatwave not only led to a crash of the Black Cockatoo population, but also caused high shrub and tree mortality, altering the habitat quality for many species,” they said, adding that such extreme events can amplify other stressors such as habitat loss and disease creating synergetic threats to biodiversity.