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Climate Change Threatens Frogs and Toads
Context:
Recent research published in the journal Nature has highlighted a grim outlook for frogs and toads, known collectively as anurans, as climate change intensifies.
Projected Habitat Changes:
- Under the intermediate warming scenario, 6.6% of currently occupied anuran areas will become arid by the century’s end.
- Under the high-emission scenario, this could rise to 33.6%.
- 15.4% of regions inhabited by anurans are expected to experience intense, frequent, and prolonged droughts between 2080 and 2100.
Key Findings:
- The study examined two climate scenarios: Intermediate warming (2°C above pre-industrial levels) and High-emission scenario (4°C rise).
- Amphibian Threat: According to the 2023 Second Global Amphibian Assessment, nearly 41% of amphibian species are at risk of extinction, making them the most threatened class of vertebrates.
- Water Loss and Vulnerability: Arid conditions are projected to double amphibian water loss rates, adversely affecting their movement and reproduction and increasing their susceptibility to diseases.
- Geographical Impact: Regions at risk include the Americas, southern Africa, Europe, and southern Australia, with the Amazon and Atlantic forests facing the highest threats.
Specific Case Studies:
- In India, droughts in the Western Ghats have already led to habitat loss and a shortage of breeding pools during monsoon seasons.
- Additionally, climate change could shrink the geographic range of the Malabar tree toad by nearly 70%.
Physiological Impacts:
- Physiological Effects: The combination of warming and drought reduces frogs’ thermal tolerance and preferred body temperatures, leading to dehydration and impaired locomotion.
- Activity levels for tropical frogs dropped significantly, with warming alone causing a 3.4% decrease and drought leading to a staggering 21.7% decline. The worst-case scenario, combining both stressors, could decrease activity by 26%.
Balancing Heat Regulation and Survival:
- Evaporative Water Loss (EWL): Frogs utilise EWL to regulate their body temperature in extreme heat, maintaining their skin temperature around 35°C even in air temperatures ranging from 40°C to 50°C.
- However, this mechanism leads to dehydration and increased energy demands, creating a challenging trade-off that impacts their dispersal, breeding opportunities, and overall activity levels.
- Water stress also impairs critical bodily functions, including blood flow, oxygen transport, and brain function, which are essential for muscle contraction, mate-seeking, and foraging.
Adaptation and Resilience:
- Amphibians have some capacity for phenological plasticity, allowing for resilience against climate change. However, the study warns that their ability to acclimate will ultimately determine survival in increasingly arid environments.
- Notably, stream-dwelling and semiaquatic species are at greater risk of desiccation stress compared to their arboreal or burrowing counterparts.
Urgent Conservation Strategies:
- Habitat Restoration: Efforts to restore and protect existing habitats are crucial.
- Legal Protections: Enhancing legal frameworks for amphibian conservation is necessary.
- Scientific Action Plans: Developing targeted actions to mitigate climate threats.
- Community Engagement: Promoting awareness and education to foster collective action.
Broader Ecosystem Implications: Frogs and toads serve essential roles in their ecosystems:
- Predators and Prey: Their presence helps control insect populations, reducing vector-borne disease spread.
Environmental Indicators: Declining amphibian numbers signal broader ecological distress.
