Mumbai lost 40% green cover between 1991 and 2018

City witnessed a 2-degree Celsius average temperature rise across 27 years

The extreme heat that one experiences when strolling through any urban landscape is caused by the Urban Heat Island effect, according to experts.

Mumbai lost 81% of its open land (barren spaces without any vegetation), 40% green cover (forests & scrublands) and approximately 30% of its water bodies (lakes, ponds, floodplains) between 1991 and 2018, while the built-up area (areas developed upon) rose by 66% in the same period, says a recent study. It concludes that the city witnessed a 2-degree Celsius average temperature rise across 27 years.

Researchers from the Faculty of Natural Sciences, Jamia Millia Islamia in New Delhi, Osmania University in Hyderabad and Aligarh Muslim University in Uttar Pradesh through their study - Urban Heat Island Dynamics in Response to Land-Use/Land-Cover Change in the Coastal City of Mumbai - published in the peer reviewed Springer Journal of the Indian Society of Remote Sensing found that with this pace of urbanisation and landscape transformation, it is expected that the Urban Heat Island intensity will further increase in the city.

Using satellite imagery (USA-NASA Landsat datasets freely available), the authors studied an area of 603 sq. km of Mumbai region (both city and suburbs) to understand the land-use and land-cover changes, difference in maximum, minimum and average temperatures (for Urban Heat Island intensity), land surface temperatures, changes in vegetation cover versus urban built-up density between 1991 and 2018.

Micro-climatic phenomenon

The extreme heat that one experiences when strolling through any urban landscape is caused by the Urban Heat Island effect, a micro-climatic phenomenon. This is due to a number of causes, the most prominent being the usage of materials such as concrete, according to Atiqur Rahman from the Department of Geography, Faculty of Natural Sciences, Jamia Millia Islamia.

“This will not only deteriorate the urban thermal environment but also increase the serious risks to health for city dwellers,” he said, adding, “This rise in heat intensity in Mumbai is linked to the declining green cover in the city, which is the result of the large-scale transformation of the green cover into built-up land for the infrastructural development in the city.”