Black-necked cranes at Tso Kar, Ladakh. Photo: Dibyendu Ash/Wikimedia Commons, CC BY-SA 3.0.
Black-necked cranes are iconic birds of the Tibetan Plateau, and are of great spiritual and cultural significance to Tibetan Buddhism as well as are integral to the landscape’s biophysical ecosystem.
These medium-sized alpine cranes, weighing about 5 kg each and standing about 115 cm tall, have a patch of red on their crowns, grey bodies and a characteristic black-neck. Meadows are their favoured habitat, where they can feed on roots, insects, snails, fish, frogs, small birds and rodents.
They breed exclusively in alpine meadows, at altitudes of 2,600 to 4,900 m, and as a protection from predators nest in marshes where the water is about 30 cm deep. In winter, they migrate to river valleys at lower altitudes, preferably to areas near crop fields.
These birds are endemic to the Tibetan Plateau, and are threatened by human- and climate-change-induced habitat loss, and of late also by free-ranging dogs in their breeding areas and food shortage in wintering areas. As a result, they are currently listed as ‘vulnerable’ in the IUCN Red List.
The IUCN Red List of Threatened Species is a comprehensive source of information on the conservation status of wild species around the world. It provides important information on the health of the world’s biodiversity and is useful to plan conservation policies and make policy changes in species-range countries. It has also proved a powerful tool to persuade governments to protect threatened species.
The list’s makers use a fixed set of criteria – including population size, rate of population decline, geographic distribution and population and area fragmentation – to group species by risk of extinction. The risks range from ‘critically endangered’ at worst to ‘least concern’ at best. The makers also periodically reassess the response of species to protection measures to update their risk status.
Because the IUCN Red List informs conservation policy in species-range countries, its critics have already warned that governments could misinterpret changes in the list to justify destructive projects in critical habitats.
Based on reports of recovery and perceived reduction in the risk of extinction, a review of IUCN Red List status of the black-necked crane (BNC) is currently underway. BirdLife International, the official IUCN Red List authority for birds, has proposed down-listing BNC from ‘vulnerable’ to ‘least concern’, and the proposal was uploaded to its website for public comments in June. Its last assessment of this kind happened in October 2016.
According to the proposal, the BNC “species is responding well to conservation action throughout its range” and “may warrant a change in Red List status”. But conservation scientists and naturalists working in BNC range areas don’t agree. While certain global population estimates have reported species recovery, they have proved controversial even as others have noted that the BNC’s threats have only multiplied and become more dangerous.
The principal contention with the reassessment’s conclusion is that BirdLife is going by overall population trends instead of local threats to habitats.
Population estimates lack rigour
To evaluate ‘rate of population decline’, ‘geographic range’ and ‘population size’, BirdLife members rely on reports of “absence of a continuing decline” of the population.
This is a faulty premise, according to Neeraj Mahar, a researcher at Wildlife Institute of India working on high-altitude wetland birds. “The estimated global population of around 10,000 individuals is not based on a rigorous scientific method,” he told The Wire Science. “The population size was earlier assumed to be 8,000 individuals. Hence, a reliable global population trend can’t be evaluated without scientifically sound long-term monitoring.”
Depending on the topography, a climate-change-induced glacial melt could deepen water bodies, rendering once favourable habitats now unsuitable to BNCs. Ahead of IUCN’s 2016 assessment, researchers noted in a study that Tso Moriri – a lake in the Changthang Plateau – “showed a rise in water between 2000 and 2006 and then it started decreasing, whereas Tso Kar [has been] regularly shrinking”. These changes to the Changthang’s wetlands continue to this today.
Glacial melts may create new lakes or increase the size of existing ones. But a suitable habitat also depends on anthropogenic factors, habitat type, water depth, etc. In Ladakh, for example, “more water in wetlands submerged established nesting sites, and this pattern was observed over three years of my study from 2015 to 2017,” Mahar said.
Tsewang Namgail, director of the Snow Leopard Conservancy India Trust also said “global warming is enabling cultivation of crops like barley in areas where previously it was difficult, due to early frost. People therefore divert water from prime BNC habitats to irrigate the barley fields, which often leads to habitat shrinkage.” Namgail has edited a book entitled Bird Migration Across the Himalayas.
Risk of local extinction
Some experts have said that BNC has too large a range – but this also means the birds are exposed to a wider range of threats, and currently face the possibility of local extinctions. In India itself, the BNC has disappeared from some of its wintering sites in Arunachal Pradesh and is currently threatened in Ladakh, where it breeds.
“Being the largest of the alpine cranes and [given its] small brood size – usually two – the BNC has [experienced[ a decrease in breeding success in Ladakh despite increase in population,” by fewer than 100 individuals, according to Mahar.
Studies (such as this and this) in Ladakh have shown that the bird’s breeding success has correspondingly declined from 60% in 1995 to 29% in 2016. Most of the blame lies with free-ranging dogs, which collect in the area fed by trash from tourist camps and military outposts in border areas.
As a result “down-listing would be imprudent because the threat of mortality to BNC from predation, accidents and indirectly through habitat destruction have not seen any decrease – and have rather increased since the last assessment in 2016,” Namgail said.
It was in similar conditions that the BNC was classified as ‘vulnerable’, forcing – with help from the conservation community – governments to respond to concerns about infrastructure development projects in BNC habitats, the threat of free-ranging dogs, and tourism in BNC habitats across its range. The BNC’s wintering areas are small and particularly vulnerable to linear projects like power lines, highways and railways. Policies to convert grassland and farmland to forests in China could destroy the species’s preferred habitats.
All these ‘pressures’ will vanish if the species is listed as being of ‘least concern’.
The Red List review committee has to consider these challenges, as well as secure stopover sites1 across its range, instead of overlooking them in favour of an overall, population-based assessment. Easing the Red List status of the BNC without discussing all these aspects could lull us into a false sense of security and increase the birds’ risk of extinction.
Narendra Patil has worked for Wildlife Conservation Society (India Program) for a decade and with an NGO towards snow leopard conservation.
Where birds pause during migratory flights ↩