A team of Indian scientists in the United States has published a paper, co-authored by an American professor, suggesting that 10 bird species endemic to the Western Ghats face threat levels that are higher than estimated by the International Union for Conservation of Nature (IUCN).
They independently assessed threat levels for 18 species and found that IUCN has overestimated the geographic range for 17 of those, including the 10 for which they have suggested an enhanced threat status, the scientists have reported in the journal Biological Conservation. Geographic range is a key benchmark in assigning a species a threat level in IUCN’s Red List.
IUCN, created in 1948, is a transnational membership union of government and civil society organisations. It is the world’s largest and most diverse environmental network, backed by 1,300 member organisations and 16,000 experts. It describes itself as the “global authority on the status of the natural world and the measures needed to safeguard it”.
IUCN has responded that the team led by Vijay Ramesh, who was with Columbia University at the time of the research, has misunderstood the measures used for assessment of extinction risks. Ramesh, who is now a spatial and computational ecologist with the nonprofit Cary Institute of Ecosystem Studies, told The Indian Express Monday that his team was in the process of drafting a rejoinder.
“We assure you that our results are comprehensive and accurate,” said co-author Trisha Gopalakrishna, who was with Duke University when the study was conducted. Sahas Barve of Cornell and Don Melnick, professor of ecology, evolution and environmental biology at Columbia, are the other authors.
Ramesh said that for birds, IUCN relies on range maps provided by BirdLife International, while their study relied on independently reviewed data from eBird, which he described as the world’s largest citizen science database.
“We found that majority of the maps supplied to IUCN by BLI are largely inaccurate and overestimated. We found that there are areas such as townships within these BLI range maps, where some of these birds definitely do not occur in,” he said by email.
Ramesh conceded that geo-referenced locations of the occurrence of a bird provided by eBird, a portal hosted by Cornell, are not necessarily error-free. “But [this] at least gives us a better picture of where these birds are,” he said. “Records uploaded to eBird are reviewed by eBird regional reviewers… However, BLI merely relies on expert evidence… which can lead to erroneous estimates.”
Priya Ranjan Sinha, IUCN’s India representative, told The Indian Express that the organisation’s Red List head, Craig Hilton-Taylor, has responded to the study. While Hilton-Taylor was yet to respond to questions, Sinha referred to a statement made by his colleague to Mongabay, an environment and conservation news portal.
“Effectively what they’ve come up with is a maximum potential area of occupancy, and they’ve compared that to our Extent of Occurrence thresholds, which are an order of magnitude larger than the Area of Occupancy thresholds that we use,” Mongabay quotes Hilton-Taylor as saying.
“They should have compared their thresholds against our Area of Occupancy thresholds, and then they would have found that most of the species would not qualify for more threatened status, and that in fact we have them correctly listed.”
Hilton-Taylor added, however, that there are two species in the list of 18 “that we do need to look at more carefully”. “Only five species have an Area of Occupancy, from their modelled range, less than 2,000 [in sq km, an IUCN benchmark],” Mongabay quotes him. “Three of those five we have listed as threatened, and they’ve listed them exactly the same way as us. So there’s just two out of the 18 where there’s some discussion to be had about who’s right and who’s wrong.”
Gopalakrishna said they would send their response to Mongabay. Their study, in fact, questions the IUCN model for calculating extent of occurrence, saying it relies heavily on the accuracy of range maps. The team instead used ‘species distribution models’, and says the technique “significantly reduced uncertainty in distribution predictions”.
IUCN’s Sinha referred to an earlier study that had relied on geospatial data, like Ramesh and his team did. That had been published in Science Advances, after which IUCN Red List had issued a statement that the assessment was incorrect.
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