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Erratic rain, severe heat may have hit dragonfly count in Delhi: Survey

By, Hindustan Times, New Delhi
Sep 26, 2022 12:07 PM IST

The survey found that there are 25 different species of dragonflies and damselflies in Delhi alone and over 51 species across the National Capital Region.

A dragonfly survey carried out across the seven biodiversity parks in Delhi over the past week suggests significant behavioural changes in the insect’s life cycle, likely due to the climate crisis and erratic rainfall patterns this year, scientists said on Sunday, adding these alterations need to be observed over the next few years.

A Black Ground Skimmer spotted during the survey in Delhi (Biodiversity Parks Programme) PREMIUM
A Black Ground Skimmer spotted during the survey in Delhi (Biodiversity Parks Programme)

The survey, conducted by scientists and technical staff of the Delhi Development Authority’s (DDA) biodiversity parks with students from Hansraj College, Amity University, Jamia Millia Islamia and others between September 19 and 25, found that there are 25 different species of dragonflies and damselflies in Delhi alone and over 51 species across the National Capital Region. The survey counted 5,219 individual dragonflies and damselflies across the seven biodiversity parks in Delhi.

Delhi’s first-ever dragonfly count was held across NCR in 2018, with the Asola Bhatti Wildlife Sanctuary, Okhla Bird Sanctuary, Dhanauri wetland, Surajpur wetland, Najafgarh Jheel, Basai wetland, Lodhi Garden and Sanjay Van surveyed. The biodiversity parks covered then included the Yamuna Biodiversity Park, Aravalli Biodiversity Park and the Neela Hauz Biodiversity Park. The 2018 count, carried out by the Bombay Natural History Society and World Wildlife Fund, led to the discovery of 25 dragonfly species.

Scientists, however, said that the number of dragonflies this year cannot be compared to 2018, as the previous survey was conducted only at three biodiversity parks, but the significant behavioural changes in the insect’s life cycle do need to be observed over the next few years. “There was good rainfall when the monsoon first hit the region, after which there was a long hot and dry spell, leading to the Yamuna river nearly drying up, and then it rained again over the last few days. This has confused the dragonflies as they lay eggs when it rains. So, they laid eggs in the beginning of monsoon and then entered the nymph stage that normally remains underwater for a long time. Because the wetlands dried up, the nymphs grew up quicker and had a shorter lifespan. When it rained again, the dragonflies laid eggs again—which is unusual. It is now a matter of research for the next year to see what will happen to the eggs and how this shift will impact their population. One year’s data is not enough to make a definitive comment,” Faiyaz Khudsar, scientist in-charge of the Biodiversity Parks Programme, said. He added that the nymph stage is the most important regulatory function of the dragonfly as it feeds on mosquito larvae and reduces its population, thereby reducing the possibility of several vector-borne diseases spreading across the region.

Experts believe that a healthy population of dragonflies determines the quality of any ecosystem. The network of seven DDA Biodiversity Parks in Delhi represents both the important ecological landforms—the Yamuna river and Aravalli hill range—in the region. To be sure, any study of these biodiversity parks and its findings represent the true picture of the quality of ecosystems here.

“Effort has been made to assess the population of dragonflies and damselflies in all the biodiversity parks to ascertain the quality of ecosystems, which ultimately provides environmental sustainability and resilience to a city like Delhi. The count of dragonflies and damselflies indicates the quality of water and health of the wetland ecosystem,” Khudsar said.

This year, the 457-acre Yamuna Biodiversity Park reported 23 species of the insect—a drop from 2018, when 25 species were recorded—including 357 individuals. The ditch jewel was the most commonly spotted species here and was also the most spotted species at the 400-acre Kalindi Biodiversity Park, which recorded 16 species and 3,348 individuals. Both of these biodiversity parks represent floodplain ecosystems. While Yamuna Biodiversity Park had the highest number of species, Kalindi had the highest individual count of dragonflies and damselflies. Khudsar, meanwhile, added that a significant change from 2018 was the lack of common picture wing dragonflies in Yamuna Biodiversity Park—a species that was the most common here in 2018.

The 692-acre Aravalli Biodiversity Park recorded 12 species and 555 individuals. The 175-acre Tilpath Valley recorded seven species—an increase from five species in 2018—and 164 individuals. The 320-acre Tughlaqabad Biodiversity Park had seven species and 81 individuals. The 215-acre Kamla Nehru Ridge had 25 species and 291 individuals and the 10-acre Neela Hauz had six species—a drop from nine species in 2018—and 323 individuals. These five biodiversity parks represent the last spur of Aravalli range. While the lowest count of dragonflies was observed in Tughlaqabad, the least number of species was in Neela Hauz, given its small size.

The wandering glider was the most commonly spotted species in the Aravalli and Tughlaqabad, common picture wing in Kamla Nehru, scarlet skimmer in Neela Hauz and granite ghost in Tilpath Valley Biodiversity Park. “This is a good time to survey dragonflies as monsoon is when they can be seen in large numbers as they start breeding. So, any survey needs to be conducted around August-September,” said Aisha Sultana, ecologist, Biodiversity Parks Programme.

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