Researchers use the power of comparative mapping to uncover specific global and regional threats to reptiles

Global threat maps from A to Z, for logging, pollution, agriculture, invasive species, hunting, climate change, and urbanization. In h, a map showing the highest probability of any of the threats in ag, the black cells contain overlap between different threats as those with the highest probability. Gray indicates areas with 10 or fewer species for which the probability of impact has not been estimated. credit: com.bioRxiv (2023). doi: 10.1101/2023.09.08.556803

According to the International Union for Conservation of Nature (IUCN), 21% of reptile species worldwide are threatened with extinction as of 2022. However, until recently there have been few details on the types of threats affecting different species in specific geographic areas, and As a result, important opportunities for reptile conservation may have been missed.

A team of researchers from Denmark, Mozambique, Spain, Sweden and the United Kingdom aims to provide more precision in this area. At regional levels around the world, the team calculated the likelihood that specific threats to biodiversity would impact endangered species. Their work, “Threats to Reptiles at the Global and Regional Scale,” was published in the journal com.bioRxiv Advance print server.

Reptiles can serve as bioindicators, giving clues to the overall health of ecosystems through symptoms or responses that can be easily measured.

According to IUCN data for 2022, there are 10,196 reptile species in the world, and at least 1,829 of them are listed as threatened with extinction. But as the study points out, a threatened species list by itself is not enough to support effective conservation efforts; We need to know what specific threats are, where they are located, and how likely they are to affect a particular species.

From the IUCN Red List of Threatened Species, the researchers obtained range maps for reptile species, eventually including the ranges of 9,827 terrestrial reptiles in their study (48 species of sea snakes and six species of sea turtles were excluded).

Using information from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) and taking into account IUCN land-use threat classifications, they focused on seven specific causes of biodiversity loss: alien species invasion, climate change, And direct exploitation of natural resources. , pollution; Especially land use, threats to agriculture, logging, and urbanization.

Using species distribution ranges, they then created 50 km x 50 km grid layers for each of the seven threats (excluding cells with 10 or fewer species) and determined the probability of encountering a threatened species in each cell, while at the same time statistically accounting for areas of uncertainty.

For the purposes of this analysis, “threatened” species included those classified by the International Union for Conservation of Nature as critically endangered, endangered, and vulnerable; “Non-threatened” species are those listed as near threatened or of less concern.

To show the intersection of individual threat probabilities affecting threatened species, the researchers created global and regional models, using 12 of the 14 global regions of the International Union for Conservation of Nature. Due to a lack of data, these models did not include the Arctic and Antarctic regions.

Researchers use the power of comparative mapping to uncover specific global and regional threats to reptiles

Results of a linear model of the association between the probability of a species being threatened by various threats (x-axis) and the probability of finding a threatened species (y-axis). In general, there is a positive relationship between threatened species and all threats studied. When looking at different threats and regions, we see different threats impact regions differently. We grouped IUCN regions into biogeographical realms and linked the Australian, Oceanic and Indo-Malay regions for visual purposes. Correlations that were not significant were removed from the plot. credit: com.bioRxiv (2023). doi: 10.1101/2023.09.08.556803

Notably, the results revealed that one or more of the seven threats affected 46% (4,551) of terrestrial reptile species, with agriculture topping the lists for the number of species affected (2,995; 30.5%) and average probability of impact. Other threats showed varying potential for impact compared to the number of species affected.

Regionally, the highest average probability of impact was in Europe, closely followed by Northern Asia and the Caribbean Islands. Global findings showed diverse threats affecting different geographic regions. For example, the threat to agriculture was mostly evident in the Caribbean islands, Central Asia, parts of Europe, and Madagascar, while fishing emerged as a major concern in parts of China, India, and sub-Saharan Africa.

Current research has demonstrated that among vertebrates, terrestrial reptiles are particularly vulnerable to biodiversity loss. The results of this new study are important because they are the first to map the potential for impact from specific threats, paving the way for more effectively targeted conservation initiatives.

The team acknowledges several significant limitations to the study, including the inability to perform a high-resolution analysis, due to the uncertainty associated with IUCN range maps; Inability to ascertain a direct causal relationship between a specific threat and a species receiving a “threatened” designation; and possible under-reporting, uneven sampling, and inadequate fieldwork supporting IUCN Red List-based threat assessments.

However, the researchers say: “Our approach allowed us not only to discover where species are affected by human actions, but also to measure how this potential impact is related to extinction risk,” and reiterate the critical importance of understanding the relationship. Explain the potential threat and its effects on threatened species.

To this end, their work concludes with a call for increased local documentation of biodiversity, “addressing the gap in studies that comprehensively monitor diversity threats.”

more information:
Harith Farouk and others, Threats to reptiles at the global and regional levels, com.bioRxiv (2023). doi: 10.1101/2023.09.08.556803

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