In a record carnival, Bengaluru’s hot summer heat this year is for a specific reason: its urban heat island (UHI) effect gets worse, expanded by enlarged white top roads, treeless layouts, glass fenders, glass-style high-rises and heat-absorbing Infra Infra Infra project. March 14th The hottest day of the year at 35.4°C may just be the beginning.
It’s mid-April and the enhanced UHI effect could lead to strong caloric record levels this month. Last year, the highest level this month reached 38.5°C, down from the highest ever recorded in the city of Bangalore on April 25, 2016: 39.2°C. The city once heavily harbored green cover has been a huge depletion, capturing heat in more localized areas than ever before.
Typically, the UHI effect retains heat in urban areas and stops its dissipation. Heat-absorbing materials in buildings and concrete infrastructure can contribute to this phenomenon. Research shows that temperatures in UHI areas may be 3 to 5 degrees higher than the surrounding environment, which greatly deteriorates citizens’ lives. The continued loss of trees and water bodies in Bengaluru has only exacerbated this trend.
A total of 11,137 trees were cut down in the Namma Metro Phase 3 Detailed Project Report (DPR) of Bengaluru Metro Corporation Limited (BMRCL, paving the way for two 44.65 km corridors. But, as environmentalist and legal activist Dattatreya Devare said, there is no information about the location of these trees.
Flower suppliers use umbrellas to protect themselves from the intense heat of Bengaluru. |Photo source: Sudhakara Jain
Compensatory plantation with skew
Compensatory plantations are standard responses to tree cover due to infrastructure projects. But Devare believes that these plants should be planted on the roadside, not in Nelamangala, Gouribidanur or Kolar. “Each quarter, BMRCL should file a report to the court on compensatory tree plantations for the number of trees cut down. They haven’t filed for almost a year and a half. On the court order, they filed a report for the last time in September 2024. Now there are two quarters that are over and we keep reminding them,” he explained.
He noted that the institutions believed the city had no space. “I told them there was plenty of room on the roadside. Finally, after our continued efforts, BBMP (Bruhat Bengaluru Mahanagara Palike) issued an affidavit in court that in 2025-26, they will plant about 50,000 slims and can now bring the BMRCL to the BMRCL. Let’s see what they will do and we will be on them.”
Heat Wave Action Plan
Decades of domestic and global research have clearly established the link between green coverage and urban temperature. Karnataka State Heat Wave Action Plan 2023-24 also expressed an existing blueprint for preparatory measures. Based on medium/long-term measures at the city level, the plan calls for the development of a heatwave risk and vulnerability map of strategic mitigation action plans.
The plan is also part of mapping out hot spots within the city and integrating them into a vulnerability assessment. It also requires the reduction of temperatures at these hot spots by developing vertical gardens, small parks with fountains and other related features. The program further aims to establish environmental assessments through the coordination of different research and educational institutions. The Heat Wave Action Plan says the findings of the assessment should be incorporated into urban planning and design policies to curb the future emergence of urban heat islands.
Within a year when Sarakki Lake was rejuvenated three years ago, the groundwater table there was improved by 300 feet. Last year, when the entire city faced a water crisis and higher temperatures, the lake had enough water, with the groundwater tables less than 500 feet. |Picture source: K. Bhagya Prakash
Porous landscape dropped to 6.02%
The Ecological Science Center of the Indian Academy of Sciences (IISC) tracks land use patterns in Bangalore, showing a sharp decline in green coverage in the city. The proportion of porous landscapes (vegetation and water bodies) in the city fell from 68.2% in 1973 to 6.02% in 2025. During the same period, the Bengaluru Urban Information System Portal pointed out that the share of paved landscapes (buildings, roads, etc.) rose from 7.97% to 87.97%.
TV from CES, IISC, Dr. Ramakandra pointed out that this stark trend is emerging, “No groundwater charging occurs due to the dominance of the paved surface. Since the landscape does not hold any water, the heat in the system also rises. The city’s temperature reached 19 degrees Celsius in 1990s in the 1990s and is 22 degrees Celsius to 22 degrees Celsius. 38 degrees,” he explained.
But as a person moves away from the city center in any direction, the temperature drops at least two to three degrees in areas of water and parks. He cites the Sarakki Lake case about three years ago. “In a year, the groundwater tables there were 300 feet higher. Last year, when the entire city faced a water crisis and higher temperatures, the lake had enough water, and the groundwater tables were less than 500 feet. In addition, the high moisture content ensured that the temperature in the area was at least 2-3 degrees lower than the rest of the city.”
Heating materials in buildings and concrete infrastructure contribute to the impact of urban heat islands (UHI). |Picture source: K. Bhagya Prakash
Glass facade building with longing
It is well known that in many tech parks and office buildings, glass facades are a preferred option to increase thermal radiation in the surrounding area. Dr. Ramachandra draws attention to another frequently signed factor: higher power consumption. “In ordinary buildings, if 1,400 vehicles are consumed per year, within glass facade buildings, it increases to 14,000 to 17,000 vehicles. The consumption is 10 times higher, leading to global warming, which inevitably raises the temperature.”
As reiterated in a study at Curtin University, temperature increases due to the UHI effect can affect human thermal comfort. This can cause hot air, dyspnea, heat cramps, dehydration, and even heat-related mortality. Especially vulnerable are children, the elderly and those with health problems. Increased temperatures at night may lead to further thermal stress.
In January 2025, the Academy of Wood Science and Technology Workshop on “From Concrete to Canopy: Urban Forestry in Green Cities” emphasized the need to view urban green infrastructure as a holistic system. Retired IFS official Dr. Kn Murthy stressed the need to connect green patches across the city and become part of the planning process.
He stressed regular visits to each tree in the city for maintenance, while suggesting vertical green coverings of buildings with glass facades to reduce heating impacts. Other speakers drew attention to the World Health Organization (WHO) standard that requires everyone to have 9 square meters of urban green space.
publishing – April 17, 2025 06:19 AM IST
