Chilling Prospects: Nature-based solutions to reduce the urban heat island effect in Mumbai, India
India is home to 309.2 million people at high risk due to a lack of access to cooling. Mumbai, the most heavily populated city in the country, has undergone rapid urbanization, converting natural land cover with soil, water and vegetation into urban paved areas. Consequently, it has developed a pronounced urban heat island effect (UHIE).
Measured land surface temperatures in Mumbai demonstrate that areas with low built-up density experience temperatures around 28°C, whereas high built-up urban areas exhibit significantly higher temperatures of approximately 34°C. In contrast, on the city's outskirts, where vegetation density and water coverage are more abundant, temperatures range from 21°C to 23°C. [1] Discover more urban land use and heat analysis for Mumbai here and in the WRI Working Paper Urban Blue-Green Conundrum: A 10-City Study on the Impacts of Urbanization on Natural Infrastructure in India.
The impact of Mumbai’s UHIE was particularly noticeable in the suburb of Andheri East, specifically at the Marol Co-op Industrial Estate, following the construction of a metro line. Before the metro’s construction in 2005 and 2010, average temperatures recorded were 29.27°C and 33.4°C, respectively. However, after the construction, the average temperature rose to 38.8°C. [2]
In response to this, the Brihanmumbai Municipal Corporation (BMC) and Marol Co-op Industrial Estate initiated the development of a 3.2 acre Urban Forest and Nature Conservancy Park in Marol along the Mithi river to increase green cover in this heat-stressed part of Mumbai. On World Environment Day in June 2023, the BMC carried out a tree plantation drive supporting this initiative. [3]
Based on studies of the cooling intensity of trees in an urban environment, the temperature reductions achieved could range from 0.4° C to 3.0° C. [4] More cooling may be achieved with a higher density of the proposed green space. Once complete, the Urban Forest and Nature Conservancy Park is expected to serve up to 172,824 people who can access the green space within a 15-minute walk. [5]
This nature-based initiative was made possible by the Mumbai Climate Action Plan (MCAP). The MCAP includes a priority action track to ‘increase vegetation cover and permeable surface to 30-40 percent of the city surface area by 2030 to tackle flood- and heat-related disaster risk’ with sub-actions that include developing low-cost nature-based solutions to reduce heat stress in low-income neighborhoods and an increased budget allocation for urban green development and maintenance to tackle heat. Furthermore, India is establishing nationwide strong nature-based solution networks for the peer-to-peer exchange of best practices, technical training and knowledge sharing, such as the India Forum for Nature-based Solutions.
Mumbai is demonstrating that evidence-based policymaking, sub-government actions and practice-based change can help reduce the impact of excess heat on its citizens through nature-based solutions.
Notes and references
[1] Grover, Aakriti & Singh, RB. (2016). Monitoring Spatial Patterns of Land Surface Temperature and Urban Heat Island for Sustainable Megacity: A Case Study of Mumbai, India Using Landsat TM Data. Environment and Urbanization Asia. 7. 38-54. 10.1177/0975425315619722.
[2] https://www.knocksense.com/mumbai/bmc-to-develop-urban-forest-in-marol-industrial-area-to-reduce-heat-island-effect-in-the-region
[3] https://www.linkedin.com/posts/wri-india_worldenvironmentday-worldenvironmentday-activity-7072092710051938306-L4py/?originalSubdomain=in
[4] Planting Healthy Air: A global analysis of the role of urban trees in addressing particulate matter pollution and extreme heat. The Nature Conservancy (2016)
[5] SEforAll analysis using catchment for locations within a 15-minute walk captured from https://app.traveltime.com. Estimated population taken from https://www.freemaptools.com/find-population.htm using 0.9 km radius catchment.
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