Conservation news

Overestimated range maps for endemic birds in India’s Western Ghats lead to underestimated threats, study finds

  • In a paper published earlier this week in the journal Biological Conservation, researchers detail their findings that suggest the IUCN has “vastly” overestimated the geographic range sizes for 17 of 18 endemic birds studied in the Western Ghats.
  • In some cases, the researchers write in the study, the range maps supplied by BirdLife International (BLI) and used by the IUCN for its threat assessments of birds in the Western Ghats included “large areas of unsuitable habitat” and were so off that the threat status should be changed “for at least 10 of the 18 species based on area metrics used by the IUCN for threat assessment.”
  • The head of the IUCN Red List says that the study’s authors made a “fundamental error” in applying threat assessment criteria to their datasets, however, adding that just two of the 10 birds identified in the study need to be examined more closely.
  • The key to the updated range maps created by the researchers behind the Biological Conservation study is citizen science. In particular, the researchers used data from eBird, an online checklist program created by the Cornell Lab of Ornithology. And on the point of the usefulness of citizen science, the researchers and the IUCN are in full agreement.

New research suggests that the International Union for the Conservation of Nature (IUCN) is overestimating the ranges of several bird species endemic to the Western Ghats mountain range in India, which can have major implications for determining the extinction threat faced by those species.

The IUCN is an international organization that counts over 1,000 governments and NGOs amongst its members and works with more than 11,000 scientists and other experts to assess the conservation status of species around the globe. Best known to the public as the publisher of the IUCN Red List of Threatened Species, the organization’s work is highly influential among businesses, governments, and other decisionmakers.

In a paper published earlier this week in the journal Biological Conservation, researchers detail their findings that suggest the IUCN has “vastly” overestimated the geographic range sizes for 17 of 18 endemic birds studied in the Western Ghats.

In some cases, the researchers write in the study, the range maps supplied by BirdLife International (BLI) and used by the IUCN for its threat assessments of birds in the Western Ghats included “large areas of unsuitable habitat” and were so off that the threat status should be changed “for at least 10 of the 18 species based on area metrics used by the IUCN for threat assessment.”

Range overestimation for 18 species of Western Ghats endemic birds. White portion of pie chart shows percent suitable habitat within IUCN range, blue portion shows percent of the range where unsuitable or no habitats are predicted. Red arrows indicate species with potential need for IUCN threat status uplisting. Blue ‘equal’ signs indicate species where no uplisting is currently needed. Asterisk for Kerala Laughingthrush (KLT) indicates that it is estimated to be found in an area larger than current BLI range maps. Acronyms used in this figure: NP = Nilgiri pipit, WLT = Wynaad laughingthrush, MGH = Malabar grey hornbill, RB = rufous babbler, GFGP = grey-fronted green pigeon, WBTP = white-bellied treepie, GHB = grey-headed bulbul, MP = Malabar parakeet, NWP = Nilgiri wood pigeon, NF = Nilgiri flycatcher, BTG = broad-tailed grassbird, BRF = black and rufous flycatcher, BCLT = black-chinned laughingthrush, CBS = crimson-backed sunbird, WBS = white-bellied shortwing, NS = Nilgiri shortwing, WBBF = white-bellied blue flycatcher, KLT = Kerala laughingthrush. Image Credit: V. Ramesh et al. / Biological Conservation.

“Our study highlights the importance of using a data-driven approach in estimating ranges for species,” Vijay Ramesh, the study’s lead author and a Spatial and Computational Data Manager at the Cary Institute of Ecosystem Studies in New York, told Mongabay. “We show that ranges have been overestimated by BirdLife International for 17 of the 18 species that we considered and are largely inaccurate. This means that the threat status designation by the IUCN is inflated and species that are in immediate need of protection are listed as species of Least Concern (we show in this study that many of the Least Concern species are actually threatened).”

Many of the endemic bird species Ramesh and team looked at are highly forest-dependent and can only survive when their natural habitat remains undisturbed. One of those birds is the Nilgiri pipit (Anthus nilghiriensis), whose range BLI has overestimated by a “staggering” 88 percent, according to Ramesh. The bird is found in high-elevation grassland habitats in the Western Ghats that are threatened by economic development projects. But while BLI lists the Nilgiri pipit’s range as encompassing 11,558 square kilometers (4,463 square miles), Ramesh and colleagues determined that the species actually occurs in a much smaller range of less than 1,392 square kilometers (537 square miles).

That means that even as the bird’s habitat is being slowly lost to deforestation and other changes caused by human activities, the species has been listed as Vulnerable on the IUCN Red List instead of Endangered, which Ramesh said it would qualify for based on his team’s findings. “If you take climate change into account, which we haven’t done in this study, it paints a bleak picture for some of these species,” Ramesh added.

Study co-author Don Melnick, a professor of conservation biology and the director of the Center for Environment, Economy, and Society at Columbia University, is quick to caution that the intent of the research is not to criticize the IUCN or BLI, but to improve the quality of the data being used in IUCN’s threat assessments.

“IUCN does great work,” Melnick told Mongabay, “and not only that, but the criteria that they’re using for assessing whether species are endangered, threatened, vulnerable, or whatever it may be, those criteria are excellent. We’re neither criticizing the criteria that they’re using, nor are we criticizing the IUCN as an institution and the work they’re doing, because we think they’re both really good. What we’re actually disagreeing with is the basic data they’re feeding into their criteria.”

Craig Hilton-Taylor, who heads up the Red List Unit at the IUCN, said that the paper does point out some issues with the data used in the IUCN’s species threat assessments: “It’s great to have that feedback, and we will look into some of those issues.”

But Hilton-Taylor said that there’s a “fundamental error” in the methodology used by Ramesh and team in their study. “They’ve misunderstood the two measures we use for criteria in extinction risk assessments, they’ve misunderstood Extent of Occurrence and Area of Occupancy,” Hilton-Taylor told Mongabay. “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. 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.”

(Ramesh and team used a similar approach and came to similar conclusions as researchers who published a study in the journal Science Advances in December of last year, Hilton-Taylor said. You can read IUCN’s full response to that study here.)

Hilton-Taylor adds that there are two species in the list of 18 “that we do need to look at more carefully.” To be considered “Vulnerable” by the IUCN, a species has to have an Extent of Occurrence of less than 20,000 square kilometers (around 7,720 square miles) or an Area of Occupancy of less than 2,000 square kilometers (about 770 square miles). “Only five species have an Area of Occupancy, from their modeled range, less than 2,000,” he noted. “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.”

Re-evaluating those two species’ threat status will require incorporating some of the IUCN Red List sub-criteria pertaining to environmental factors like forest fragmentation and declines in habitat, Hilton-Taylor said. “And they mention in the paper that they haven’t delved into any of that at all, so they just purely used the range thresholds, and not the sub-criteria, which are a critical part of the assessment process. So they’ve used the wrong measure for extent of occurrence, and they haven’t applied that measure against area of occupancy thresholds, so that’s where they’ve gone wrong in their process.”

Range maps have been overestimated by BLI and NatureServe for both high-elevation specialists such as the Nilgiri pipit (Anthus nilghiriensis), shown on the left, to low-elevation species such as the Malabar grey hornbill (Ocyceros griseus), shown on the right. The black outline represents the range polygon used by IUCN for threat assessment and the range in purple represents the range modeled in this study. The dust brown color represents the boundary of the Western Ghats. Image Credit: V. Ramesh et al. / Biological Conservation.

Citizen science emerging as key source of data for future threat assessments

The key to the updated range maps created by Ramesh, Melnick, and team is citizen science. In particular, the researchers used data from eBird, an online program created by the Cornell Lab of Ornithology.

On this point, at least, Hilton-Taylor is in full agreement — and he even says that the IUCN itself is increasingly turning to citizen science to inform its work. “We strongly support and encourage those kinds of initiatives, and we feel that that data is really good to use,” he said. “IUCN is teamed up with iNaturalist to gather citizen science data and help in some of our assessment projects. iNaturalist has an app that we use to help with some of our assessment processes. iSpot, which is another one of these initiatives, that data is used to feed into Red List assessments.”

Citizen science has grown rapidly over the past several years, and the data citizen scientists are uploading to the internet is “improving at a tremendous rate,” Ramesh said. For instance, he points out that “In the period between the start of this study and its acceptance, eBird has [implemented] separate columns in their data that now show ‘APPROVED’ and ‘REVIEWED,’ which essentially means that these datapoints are being vetted thoroughly by experienced naturalists, reducing the room for error.”

As it has grown in popularity, citizen science has increasingly been used in hard scientific research. It has led to the rediscovery of a snail species not seen for over 100 years, for instance, and has been called “the best way to identify and tackle the causes and to guide river restoration” in Malaysian Borneo.

It’s important that citizen science data be filtered and checked by experts from the particular area being studied, Melnick says. “In other words, you don’t just dump the citizen science data in, you actually go through and filter it using experts and other kinds of filtering processes, to make sure they’re not double-counting the same bird, or that they misidentified the bird, or mis-identified where they were.”

The approach used for the Biological Conservation study combined citizen science data with high-resolution, geo-referenced ecological data on biotic and abiotic factors that affect whether a species is at a particular location, all of which was run through the latest species distribution modeling software.

“If you put that all together, you can come up with a more refined estimate of where a particular species is at the moment,” Melnick said. “And you can do that annually so you can not just see where they are now but you can see where they were 10 years ago, and 20 years ago — because a lot of that data still exists. And you can monitor it going forward at a fairly precise level, without necessarily having that many boots on the ground. That is a tremendous source of information for what IUCN is doing.”

Melnick argues that the method used to revise bird range maps in the Western Ghats is actually the conservative approach, as opposed to how the IUCN does it now. “I say that because if we have underestimated the range, and therefore exaggerated the threat status, that can’t harm the species, it just means we’re applying extra care to the species,” he said. “However, if you overestimate the range, and therefore underestimate the threat status, that could harm the species.”

Because global range size is an important factor used by the IUCN in assigning threat status for a species, the authors write in the study, “The methods used here to significantly revise range estimates have important conservation management implications not only for endemic birds in the Western Ghats, but for vertebrate and invertebrate taxa worldwide.”

Ramesh adds that there are two chief implications of the study, the first being: “We are able to use an approach that uses freely-available citizen science data, along with freely-available information on climate, land cover, elevation etc. to arrive at accurate ranges that seldom exist for many endemic birds of the Western Ghats.”

And Ramesh says of the second: “There are many development projects underway in the Western Ghats and by demonstrating that species in this region are already far more threatened than currently stated by the IUCN, our models could strengthen the case of those who are petitioning against development in sensitive habitats.”

A Nilgiri pipit (Anthus nilghiriensis) in the Western Ghats, a mountainous biodiversity hotspot in southern India. Photo Credit: Adesh Shivkar

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