Heat island push to city’s scorching summer temperature Premium

Bengaluru's worsening Urban Heat Island effect due to deforestation and infrastructure projects threatens residents' well-being.

On a record-breaking spree, the scorching summer heat in Bengaluru feels particularly intense this year for a specific reason: Its Urban Heat Island (UHI) effect has gotten worse, amplified by a widening network of white-topped roads, tree-less layouts, glass-façade highrises and heat-absorbing infra projects. The hottest day of the year on March 14 at 35.4°C could just be the start.

It is mid-April now and the enhanced UHI effect could take the intense heat to record levels this month. Last year, the maximum for the month had hit 38.5° C, less than a degree lower than the highest-ever temperature recorded for April in Bengaluru city: 39.2° C on April 25, 2016. The city’s once-celebrated green cover has depleted dramatically, trapping heat in more localised areas than ever before.

Typically, the UHI effect retains heat within urban areas and halts its dissipation. Heat-absorbing material in both buildings and concrete infrastructure aids this phenomenon significantly. Research shows that the temperature within the UHI areas could be 3 to 5 degrees higher than the surroundings, dramatically worsening citizens’ lives. Bengaluru’s continuing loss of trees and water bodies has only aggravated this trend.

The Bengaluru Metro Rail Corporation Limited (BMRCL)’ s Namma Metro Phase 3 Detailed Project Report (DPR) has lined up a total of 11,137 trees to be felled, making way for two corridors of 44.65 km. But, as environmentalist and legal activist Dattatreya Devare says, there is no information about the location of these trees.

Compensatory plantation is the standard response for the loss of tree cover due to infrastructure projects. But Devare contends that these plants should be planted on the roadside and not in Nelamangala, Gouribidanur or Kolar. “Every quarter, the BMRCL was supposed to submit a report to the court on the compensatory tree plantation for the number of trees cut. They did not submit for almost one and a half years. On a court order, they last submitted a report in September 2024. Two quarters are over now, we are constantly reminding them,” he explains.

The agencies, he points out, argue that there is no space in the city. “I told them there is enough space on the roadsides. Finally, after our continuous efforts, the BBMP (Bruhat Bengaluru Mahanagara Palike) gave an affidavit in the court that in 2025-26, they will plant some 50,000 saplings which can now be taken by BMRCL. Let us see what they do, we are after them.”

Decades of research, both domestic and global, have clearly established the link between green cover and urban temperatures. There is also an existing blueprint on preparatory measures, as articulated by the Karnataka State Heat Wave Action Plan 2023-24. Under city-level medium/long-term measures, the Plan mandates a heat wave risk and vulnerability map for developing a strategic mitigation action plan.