Utilizing Comparative Mapping to Uncover Distinct Global and Local Menaces to Reptilian Species

In 2022, the International Union for Conservation of Nature (IUCN) reported that 21% of reptile species worldwide were under the threat of extinction. However, until recently, there has been a lack of detailed information regarding the specific threats faced by different reptile species in distinct geographic regions. Consequently, important opportunities for reptile conservation may have been overlooked.

A collaborative team of researchers hailing from Denmark, Mozambique, Spain, Sweden, and the U.K. set out to address this knowledge gap. Their objective was to provide more precise insights into the threats affecting threatened reptile species across the world. Their work, titled “The threats to reptiles at global and regional scales,” has been published on the bioRxiv preprint server.

Reptiles play a crucial role as bioindicators, offering valuable insights into the overall health of ecosystems by exhibiting symptoms or responses that can be easily measured.

According to the IUCN’s 2022 data, there are 10,196 reptile species globally, and at least 1,829 of them are classified as threatened. However, as emphasized by the study, merely listing threatened species is insufficient for effective conservation efforts. It is imperative to identify the specific threats these species face, their geographical distribution, and the likelihood of these threats impacting each species.

To conduct their analysis, the researchers obtained range maps of reptile species from the IUCN Red List of threatened species, ultimately encompassing the ranges of 9,827 terrestrial reptiles (excluding 48 species of sea snakes and six species of sea turtles). They focused on seven specific causes of biodiversity loss: alien species invasion, climate change, direct exploitation of natural resources, pollution, and, with regard to land use, the threats posed by agriculture, logging, and urbanization.

Using the distribution ranges of these species, the researchers created grid layers measuring 50 km x 50 km for each of the seven threats, excluding cells with fewer than 10 species. They then calculated the probability of encountering threatened species in each cell, while statistically accounting for areas of uncertainty.

For their analysis, “threatened” species included those categorized by the IUCN as critically endangered, endangered, and vulnerable, while “non-threatened” species included those listed as near threatened or of least concern.

The researchers developed global and regional models, employing 12 of the IUCN’s 14 global regions. Notably, the Arctic and Antarctic regions were excluded due to data limitations.

The study’s key findings revealed that one or more of the seven threats affected 46% (4,551) of terrestrial reptile species, with agriculture being the primary threat, impacting 2,995 species (30.5%). The median likelihood of agriculture’s impact was also high. Other threats exhibited varying median likelihoods of impact in comparison to the number of species affected.

Regionally, Europe had the highest median likelihood of impact, with North Asia and the Caribbean Islands following closely. Globally, diverse threats affected different geographic areas. For example, agriculture was a prominent threat in the Caribbean Islands, Central Asia, parts of Europe, and Madagascar, while hunting emerged as a significant concern in parts of China, India, and Sub-Saharan Africa.

Prior research has established that terrestrial reptiles are particularly susceptible to biodiversity loss among vertebrates. This new study’s significance lies in its ability to map the likelihood of specific threats impacting these species, offering a foundation for targeted conservation efforts.

The researchers acknowledge several limitations in their study, including the inability to perform high-resolution analysis due to uncertainties in the IUCN’s range maps, the challenge of establishing direct causation between specific threats and a species receiving a “threatened” classification, and the potential for under-reporting, uneven sampling, and insufficient fieldwork supporting IUCN Red List threat assessments.

Nonetheless, the researchers emphasize the value of their approach, which not only identifies where species are impacted by human actions but also assesses how this impact potential relates to the risk of extinction. They conclude by calling for increased local documentation of biodiversity, aiming to address the gap in comprehensive studies that capture diversity threats effectively.

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