Frogs and toads could experience severe water stress due to climate change, with up to 33.6 per cent of their habitats becoming arid by 2080-2100, according to new research.
A study published in the journal Nature revealed that between 15.4 per cent and 36.1 per cent of anuran (frogs and toads) habitats will be subject to worsening drought conditions under two scenarios: An intermediate warming scenario with temperatures 2 degrees Celsius above pre-industrial levels and a high-emission scenario with a 4°C rise.
The 2023 Second Global Amphibian Assessment, featured on the International Union for Conservation of Nature’s Red List of Threatened Species, highlighted that nearly 41 per cent of amphibian species are at risk of extinction, making amphibians the most threatened class of vertebrates.
The study’s authors warned that arid conditions in current habitats will likely double water loss rates among amphibians. This will severely affect their movement, reproduction and make them more vulnerable to diseases.
The research also mapped the combined effects of drought and warming on the physiological functions and survival of anurans. Under the intermediate warming scenario, 6.6 per cent of areas currently occupied by anurans will face arid conditions by the century’s end. Under the high-emission scenario, this figure could rise to 33.6 per cent.
Between 2080 and 2100, 15.4 per cent of regions inhabited by anurans are projected to experience a combination of more intense, frequent and prolonged droughts.
Regions at risk include the Americas, southern Africa, Europe and southern Australia, with the Amazon and Atlantic forests facing the highest threats.
In 2023, Down To Earth reported how droughts in India’s Western Ghats led to habitat loss and a shortage of breeding pools during the monsoons. Another study indicated that climate change could shrink the geographic range of the Malabar tree toad by nearly 70 per cent .
The new study also examined water conservation strategies in ground-dwelling, arboreal and burrowing frogs through biophysical simulations.
“In the tropical biome, their activity decreased for all scenarios across the year, where warming alone decreased by 3.4 per cent, drought alone decreased it by 21.7 per cent and the combination of warming and drought decreased it by 26 per cent,” the study noted.
The combination of warming and drought affects frogs’ physiological functions by reducing their thermal tolerance and preferred body temperatures. Dehydration from these conditions also worsens locomotor functions, further hampering their survival.
Scientists observed that amphibians use evaporative water loss (EWL) to regulate body temperature when exposed to air temperatures between 40°C and 50°C. While frogs can maintain their skin temperature at around 35°C via EWL, this leads to dehydration and increased energy demands.
The trade-off in regulating body temperatures affects frogs’ dispersal abilities, reduces breeding opportunities and diminishes activity levels. Water stress also causes reduced blood flow, oxygen transport and brain function, impairing muscle contraction, mate-seeking and foraging.
“Stream-dwelling and semiaquatic ecotypes are expected to be at greater risk of desiccation stress than arboreal or fossorial ecotypes, due to differences in adaptation to varying water exposure in their environments,” the study stated.
While frogs can show phenological plasticity, allowing some resilience to climate change, researchers noted that their capacity to acclimate will ultimately determine their ability to survive increasing environmental aridity.
“These findings underscore the pervasive synergistic threat of warming and environmental drying to anurans,” the study stated.