Kolkata: A group of tree lovers, mostly in their 70s and 80s now, has been passionately planting trees in a Kolkata locality, which now offers its own challenge to global warming. Kolkata has been listed as one of the 20 cities in the world that have hotted up most in the last six decades by a recent UN report. The city also sports the lowest green cover among Indian mega cities. But the south Kolkata locality of Baishnabghata-Patuli, Patuli in short, is a pleasant surprise. Tall trees cast a fine filigree of shadows on the ground here, and a few minutes of walking into the Patuli area on one side of the E.M. Bypass, where the Patuli fire brigade building is located, you feel a sudden, sharp drop in temperature even on a cool Kolkata December morning.Patuli. Photo: Chandrima S. Bhattacharya.At a time climate change and global warming were distant rumours, residents of the locality began to plant trees. About three decades later, the trees number about 2,000 in an area of about 1.5 sq km, bringing with them a range of climate benefits, finds a recent report by the Kolkata-based environment group The Climate Thinker. “The temperature of the area, in Ward 101 of Kolkata Municipal Corporation (KMC), is cooler the year round by at least 3-5°Celsius in comparison with other city localities and also with the Patuli area on the other side of the bypass in Ward 110 of KMC,” says Srijan Haldar of The Climate Thinker, a biochemistry expert who teaches at Swami Vivekananda University in Barrackpur, near Kolkata. The air pollution levels are lower here compared to other city areas. “Patuli shows a significantly higher level of ‘good’ AQI compared to other localities in the city based on West Bengal Pollution Control data from 2012 to 2018,” adds Haldar. (See chart below) The planted area displays a wide range of biodiversity: Haldar and his team have counted about 30 species of trees and 60 species of naturally grown herbs and shrubs. Halder says that bird watchers have spotted about 60 species of birds in the area and around it. The Climate Thinker report was conducted with the help of satellite data and on-ground observations. “We measured the temperature for six months from September 2024 to March 2025. During the winter months, the Patuli side where trees were planted consistently measured at least 5° Celsius less than the other side. In the summer months the difference went up to about 7° Celsius,” says Haldar.A United Nations Environment Programme (UNEP) report released in November at COP30 points out that the rise of average temperature in Kolkata, at 2.67°C, was highest during 1958-2018 among 20 global cities and regions.The Indian State Forest Report 2023 also shows Kolkata having the least green cover, by far compared to Delhi and Mumbai, among six Indian cities. “A substantial proportion (16.6%) of trees in this region have a height above 10 metres. For a rapidly developing metro city, the high proportion of larger and taller canopies over this area is astonishing,” says The Climate Thinker report. It measures the impact of their shade on temperature through thermal imaging. The writers of the report illustrate (as above) that when you compare the maximum and minimum temperatures of Patuli and Girish Park (the image at the top), a crowded area of the city, measured daily during March 1-15, 2024, the difference is marked. The report cites satellite data of more than three decades to claim that the temperature in the area has not gone up in that time. The satellite data was obtained from a 2022 study by Tania Parveen and Rahaman Ashiq Ilahi on the Kolkata Municipal Corporation area from 1988 to 2021. Going through the study, The Climate Thinker members saw that the temperature had not risen in the Patuli area when almost all other localities showed a sharp temperature rise.Patuli is a model of an urban greening project, small in scale but with big implications, the environmental group feels. What was doneSettlements began from the 1990s in the Patuli township, created from wetlands and agricultural land by the Kolkata Metropolitan Development Authority (KMDA) from the 1970s. Finding the area barren and treeless – an outcome of the development on what used to be wetlands – some residents began to plant trees. It turned into a passion for a few. “The things we used to do get saplings!” laughs Kalyan Sen, 77, a retired public sector employee. With him are R.N. Sinha, 88, another retired public sector employee and Manoj Mukherjee, 77, a retired government employee, and Kalyan Sen’s wife, Nandita Sen, 71, who teaches at an inclusive school. All of them are tree advocates. Patuli’s resident-grown three-layered forestry. Photo: Chandrima S. Bhattacharya.Free saplings would be distributed by the forest department. “We had once collected saplings from Eden Gardens, and had to negotiate hard with the bus conductor to let us carry them,” says Kalyan Sen. “Sometimes we did not know which saplings we were planting,” says Sinha. The trees that they planted were all local species: Chhatim, Palash, Mango, Tamarind, Neem, Jarul, and many more, as local varieties are the most sustainable. They also sustain local ecosystems, when foreign varieties, now often planted for “beautification” in public space by civic authorities, may not survive well and may also interrupt local biodiversity. Mukherjee’s way of planting was unique. From the early 1990s, he would go out every morning on his scooter, carrying saplings, water and compost, and would plant trees wherever he could. This included the narrow divider on the E.M. Bypass along almost a 1km stretch, on the two sides of which Patuli is located. Mukherjee would dig up the hard surface on the divider and plant a sapling, of Debdaru, Arjun, Shishu, Palash, Jaam or Chalta.Trees planted by Manoj Mukherjee on the divider. The image on the extreme right is of a tree cut down in 2023. It had been planted by Mukherjee. Photo: Chandrima S. Bhattacharya.He points at them with pride, walking along the divider, as cars whizz by. Some of the trees are more than 10 feet tall. “I don’t know how many trees I have planted,” says Mukherjee. He tended them every day. To his despair, on the morning of September 12, 2023, he discovered 37 of the trees cut off brutally from the divider from the Patuli crossing to Baghajatin bridge on which he had planted. Only the stumps remained. “We still don’t know who did it,” says Mukherjee. ‘Guerilla tree planting’ and moreHe and the others wrote to the municipal councillors of Wards 101 and Ward 110, on the other side, and the police. The trees would have obscured a large glow sign on Patuli put up by the civic authorities, part of a “beautification” initiative. Bappaditya Dasgupta, councillor of Ward 101, says he is aware of the incident. “We could not find out who was behind the felling of the trees. However, since then we have planted trees and installed CCTV cameras in the stretch and not one tree has been cut since,” he says. Fencing and banner set up by residents at their own cost. The banner talks about the benefits of planting trees, for the young and the old. Photo: Chandrima S. Bhattacharya.The West Bengal Biodiversity Board in its letter dated October 13, 2025, has recommended to the KMC commissioner that a “green patch surrounding a waterbody” in Ward 110, where trees have been planted but not according to a social forestry model, should be “conserved amidst a concrete jungle”. Swapan Biswas, 77, a retired bank official, is another guerilla tree planter. He specialises in Chhatim trees. He does not know how many trees he has planted either, having chosen the bypass, its sides and the divider, and also any empty patch available in the locality. “Cattle don’t eat Chhatim,” explains Biswas. Several other trees chosen to be planted in the area – Sonajhuri, Kadam, Muchkunda Chanpa and Mahua – would also be spared by cattle, though in the residential area the saplings were often fenced.About two years ago, Biswas, too, found more than 80 trees he had planted cut off one day on the bypass, but does not know who did it.The “beautified” stretch of the Bypass along which trees were cut down. Photo: Chandrima S. Bhattacharya.In 2006, when Asesh Lahiri, a former forest officer who had also worked with the Food and Agriculture Organisation (FAO) of the UN, became a resident of the area, a new purpose was added to the plantation. Lahiri, 84, advised a three-layer forestry: a layer of big trees, a layer of smaller trees and shrubs and creepers. According to his advice, roadside space of about 700 m and about 500 sq in the front and backyards of houses were planted, after the first decade of planting. “Large and medium-sized trees number about 430 in these stretches now,” says Lahiri.Saplings of large trees were planted 4 metres apart. Saplings of medium and small-sized trees were planted in the space between them. The planted area was protected by fencing, put up by residents at their own cost. “Clearing of fallen leaves and naturally grown herbs and shrubs were avoided to encourage biodiversity,” says Lahiri, whose words seem to resonate with implications for more than plantations.“With time, much of the space between the planted trees were covered with the naturally grown herbs and shrubs from seeds dispersed by wind and birds and fallen from older trees,” says Lahiri. “The area acquired the appearance of a natural forest and became the habitat of many insects, birds and animals such as squirrels, frogs and mongooses.”Ha has a word of caution about clearing “weeds”. They are often naturally grown herbs with considerable nutritional value and medicinal properties. Lahiri requests municipal cleaners to not clear away the herbs and creepers. Among these in the area he has identified several edible plants with many qualities, such as Punarnabha, Kanta Note, Kalmi, Shantishaak, Kulfashaak, Gandal and Telakucho, some of which are being sold in the area now by vegetable vendors. “Biodiversity plays an important role in nutritional security,” says Lahiri. The white-throated kingfisher, the fulvuous breasted woodpecker, and the coppersmith barbet. Photos: Amit Naskar.Among the 60-odd species of birds here, seven are winter visitors, he says.Yet Lahiri and the tree enthusiasts of Patuli had to constantly encounter a resistance to planting trees. Houseowners would often object, saying a tree would block sunlight or its roots would destroy the foundation of a house. “But a tree needs a few feet to grow and very few trees, other than banyan and ashwattha, can damage the foundation of a house,” says Lahiri.“As for birds and insects coming into the house because of trees, we have to learn to live with them,” says Lahiri. A model for the cityIndependent experts corroborate the usefulness of this model.“The Patuli model of community-led social forestry needs to be replicated in different wards of KMC as a part of Kolkata Climate Action Plan,” says Arunabha Majumder, Professor Emeritus at School of Water Resources Engineering, Jadavpur University, Kolkata, and an expert on urban environmental concerns. He adds that the report prepared by The Climate Thinker highlights the climate benefits of social forestry by assessing all relevant environmental parameters scientifically and by using appropriate methodology. Patuli. Photo: Chandrima S. Bhattacharya.The area, with a tree count of about 2,000, is responsible for a high level of carbon sequestration. “One large tree about 20-feet tall is responsible for carbon sequestration of about 8.15 kg annually and produces an amount of 5.9kg oxygen annually,” says Haldar. “The report provides a thorough analysis of the commendable work done by the community inhabitants of Patuli-Baishnabghata Township,” says Somnath Sen, retired civil engineer, Parks and Squares department, KMC. “It will be highly appreciated if the report can make any positive impact on city-dwellers to come forward with the initiative to create sustainable greenery in the city to the extent possible,” he adds.Arindam Roy of Climate Thinker, an atmospheric scientist, feels that the afforestation at Patuli is a model for the city, as such greening projects help to counter urban heat islands. He reiterates what the tree enthusiasts say: no space is no excuse, because trees need little space to grow, you can find it on pavements, parks, islands on roads, road dividers, house fronts.“The Patuli forestry challenges those who cut trees to promote urbanisation or ‘development’,” says activist Naba Dutta of Sabuj Mancha, an environment platform, and Nagarik Mancha, a citizens’ platform. He points out that an adjacent area, Mukundapur, used to be as green as Patuli. “But it has been destroyed under the weight of so-called development,” he adds. Sen says Patuli reveals that any community, irrespective of its size, can come forward with a positive frame of mind to create sustainable greenery. “We know that Kolkata has a scarcity of open space,” he says. Patuli residents pointed at the importance of the political will. “We don’t need statues or miniatures of Big Ben set up by civic authorities. In their place we should have trees,” says Dutta.