Tamil Nadu's first block-level heat stress mapping rings alarm bells

New Indian Express

08-07-2025

CHENNAI: Tamil Nadu released the state's first-ever block-level spatial analysis of heat exposure, on Monday. The decadal study, conducted by the Tamil Nadu State Land Use Research Board and State Planning Commission confirms that rising urbanisation and loss of natural land cover are driving a dangerous surge in local temperatures across the state.
Out of 389 development blocks, the study found that 94 have experienced significant decadal increases in heat stress, while 64 blocks are currently enduring higher-than-state-average temperatures, even if they haven't seen long-term trends.
Critically, 25 blocks which fall under 10 districts -- Chennai, Chengalpattu, Karur, Madurai, Pudukkottai, Ramanathapuram, Sivagangai, Tiruchy, Tirunelveli and Tiruvallur -- fall under the 'extremely heat-stressed' category in both assessments. The study found that many of the blocks that fall under both critical categories are associated with intensive urban development or proximity to industrial belts.
"These blocks are of particular concern as they represent areas where temperatures have both increased significantly over time and are currently above the state average, indicating persistent and intensifying thermal stress," the report states.
The findings draw a direct link between land use change -- especially built-up area expansion -- and temperature rise. For instance, Chennai's built-up area grew from 48% of its total area in 1985 to 74% in 2015. St. Thomas Mount in Chengalpattu district saw a staggering fivefold increase in built-up footprint, surpassing even the capital in relative growth. In these urban and peri-urban zones, temperatures have risen by up to 2 degree Celsius above the state average in just two decades.