2023-10-05 11:43:00
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And new study published in the magazine Nature reveals that amphibians remain the most endangered class of vertebrates, with 40.7% of species at risk.
The Global Amphibian Assessment highlights that the situation has worsened, especially for salamanders in the Neotropics. Climate change and habitat loss are the main threats, with climate change responsible for 39% of the deteriorations since 2004.
GLOBAL AMPHIBIAN EVALUATION
The Global Amphibian Assessment 2 (GAA2), completed in June 2022, included a review of 8,011 amphibian species, identifying 40.7% as globally threatened. Areas with the highest concentration of threatened species include the Caribbean islands, Mesoamerica, the Tropical Andes, and Madagascar.
Since 1980, documented amphibian extinctions have increased, totaling 37 extinctions through 2022. Diseases, especially chytridiomycosis, and agricultural expansion have contributed to extinctions and declines in amphibian populations.
MAIN CAUSES
The most recent extinctions are Atelopus chiriquiensis y Taudactylus acutirostriswhose populations suffered rapid declines linked to the quitridiomicosis (disease caused by the pathogenic fungus Batrachochytrium dendrobatidis) in the 1990s. On the other hand, Craugastor myllomyllon y Pseudoeurycea expected They were last seen in the 1970s and are believed to have become extinct due to agricultural expansion.
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Declaring a species officially extinct requires meeting strict criteria; therefore, many species that have not been seen in decades are listed as Critically Endangered (CR) and labeled as Possibly Extinct (CR(PE)). In 1980, 24 amphibians were categorized as CR(PE), in 2004 this number increased to 162, and 23 more were added by 2022. Thus, if all CR(PE) species are effectively extinct, the number of known amphibian extinctions could be up to 222 in the last 150 years.
When considering all threatened amphibians, the most documented threats are those related to habitat loss and degradation. The three main types of threats are agriculture (affecting 77% of species), wood and plant collection (53%), and infrastructure development (40%), as illustrated in Figure 2. The Effects of climate change (29%) and diseases (29%) are also common types of threats.
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Although these findings are important, they do not fully reflect the severity and scope of these threats. For example, the data may not capture the intensity of impacts or how these threats could interact synergistically, exacerbating risks to amphibians. This analysis highlights the need to address multiple threats to conserve amphibian biodiversity and ensure the resilience of these ecosystems.
On the positive side, 57 other species (mostly from the Neotropics and Australia) showed improvements without intervention, most of which now persist and, in some cases, are recovering after experiencing rapid decline associated with chytridiomycosis.
It is evident that definitive conservation measures are not yet known to prevent continued decline due to disease in wild populations, although many of these species can benefit from habitat protection.
For example, some species that previously experienced declines due to disease, but which now persist, have improved in status because their habitat has remained protected (e.g. the Australian species Litoria aurea, Litoria dayi, Litoria nannotis, Litoria pearsoniana, Litoria raniformis and Litoria rheocola). While other species that persist after declines associated with B. dendrobatidis may not experience an improvement in status if there are high rates of habitat loss and degradation within their distributions.
TAKE ACTION
The findings of this study confirm that the global amphibian extinction crisis has not abated. Fundamentally, the main driver of status deterioration is the passage of diseases to the emerging threat of climate change. This is especially worrying because it often exacerbates other threats, such as land use change, fire or disease.
Therefore, the GAA2 results highlight the need to research and implement conservation actions that address the species-specific effects of climate change, particularly for species identified as at imminent risk of severe population declines.
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