Rising average temperatures in the Himalayan region have driven several dozen species of butterfly and moth to habitats higher up the mountains, a new study commissioned by the government has found.
The findings of the study will be used as a baseline indicator to track the impact of climate change on animal species over the coming decade, officials said. The Himalayas are home to more than 35 per cent of Lepidoptera — the order of insects that includes butterflies and moths – species found in India.
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The survey, funded by the Ministry of Environment, Forest and Climate Change and carried out by the Zoological Survey of India (ZSI), identified at least 49 species of moth and 17 species of butterfly that have shown “considerable new upward altitude records”, with a difference of more than 1,000 metres between their current and previously recorded mean habitat altitudes.
Seven species in particular have started to inhabit altitudes more than 2,000 metres higher than the previous mean, officials said. These include the moth species Trachea auriplena (Noctuidae), Actias windbrechlini (Saturniidae), and Diphtherocome fasciata (Noctuidae), with mean altitudinal differences of 2,800 m, 2,684 m and 2,280 m respectively.
“The Common Map and Tailless Bushblue butterflies were previously found at 2,500 m, as has been recorded in historical data. During our survey we recorded them at 3,577 m at the Ascott wildlife sanctuary in Uttarakhand, Dr Kailash Chandra, director of ZSI, told The Indian Express.
“In Ladakh, the Indian Red Admiral butterfly was historically found at 3,900 m; it is now found at 4,853 m, an altitudinal increase of 950 m,’’ Dr Chandra said.
The study found that eight moth species, including the mulberry silkworm moth and tiger moth, which would historically be found at 2,000 m, are now typically found at 3,500 m or higher altitudes.
“The extension of the range of Lepidoptera due to climate change has been observed all over the world,” Dr Chandra said. “The data and evidence-based study (in India) confirms this trend, and shows us which species are moving, and how. This will be the baseline by which we can track changes in biodiversity due to climate change over the years.”
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Butterflies are sensitive species that are extremely susceptible to changes in climate. They are, therefore, good indicators of long-term change in climatic conditions, Dr Chandra said.
The four-year study tracked 1,274 species of moth and 484 species of butterfly in Jammu and Kashmir, Himachal Pradesh, Uttarakhand, Sikkim, North Bengal, and Arunachal Pradesh. It also identified 80 new species of butterfly and moth.
The tracking of the insects’ movement was possible because the ZSI has historical records of many species since 1865. Records from 1865 to 2015 were scanned and examined to make a comparative assessment.
Receding ice caps and glaciers leading to a scarcity of water in the Himalayas has been a major reason for the altitudinal shift of the Lepidoptera. The increase in average temperature has also resulted in an altitudinal shift in vegetation – trees, shrubs, and plants that once grew at lower altitudes in the Himalayas are now found only higher up in the mountains.
Increasing human habitation too, has contributed to the shift, Dr Chandra said. “For instance, Shimla and Darjeeling were two big hotspots of rich butterfly diversity. But expanding towns have encroached on virgin territory, and the space for the butterfly has shrunk,’’ he said.
The study identified two species richness hotspots – one in West Bengal’s Darjeeling hills, where more than 400 species records were documented, and another in Kumaon, Uttarakhand, where more than 600 species records were found. In Himachal Pradesh, two high diversity areas were identified – Dharamshala and Shimla.
The study revealed an increase in the richness of Lepidoptera biodiversity from the Western to the Eastern Himalayas – it found 211 species of butterfly in the West, and 354 in the East.
But the Lepidoptera habitat is shrinking. The ZSI predicts a decline of as much as 91 per cent for example, in the suitable area for the Notodontidae family of moths in J&K, Himachal, and Uttarakhand by 2050.
“Butterflies like the Red Apollo are highly prized by collectors and are often poached. One butterfly sells for up to £100 on the international market. We have to devise some stringent mitigation measures to protect butterflies and moths from both human beings and the changing climate,” Dr Chandra said.