Bengalureans feel trapped in one big ‘heat island’ Premium

Unprecedented in scale, unrelenting in its intensity, the hottest summer in recent memory has caught Bengalureans in a tizzy. But how did the city, celebrated for its all-year generosity in weather, get reduced to one big heat island? Concretised beyond limits, polluted by an explosive vehicular onslaught, parched and clueless, has Bengaluru reached a dead-end?

Unprecedented in scale, unrelenting in its intensity, the hottest summer in recent memory has caught Bengalureans in a tizzy. But how did the city, celebrated for its all-year generosity in weather, get reduced to one big heat island? Concretised beyond limits, polluted by an explosive vehicular onslaught, parched and clueless, has Bengaluru reached a dead-end?

Heat islands are called so for a reason: They experience temperatures higher than the outlying areas, a trend fuelled by a high concentration of buildings, roads and other concrete infrastructure that absorb and re-emit the sun’s heat more than green expanses and water bodies. This ‘heat island effect’ in areas across the city has amplified the already unbearable summer discomfort.

Recent studies have clearly established that Bengaluru’s average temperature has risen by nearly a degree over the last 42 years. The increase has been more pronounced in the last two decades. Inevitably, this has spiked the evaporation rate of water bodies. Reduced rainfall over the last three years has directly impacted groundwater recharge and replenishment of reservoirs, a perfect recipe for the current water crisis.

The rapid concretisation, dubbed white-topping of the city’s roads with hardly any option for rainwater to percolate and recharge the groundwater table, might be among the most tell-tale signs of a policy gone haywire. But this trend has been going on for decades, as a recent revision by the Indian Institute of Science (IISc) of its earlier findings clearly indicates.

“Unplanned developmental activities leading to rapid changes altering land uses in the region had adverse ecological and environmental impacts, evident from the decline of forest cover (by 26%), agricultural lands (by 23%), with a sharp escalation of paved surfaces (urban area 34% increase in five decades),” notes the study, “Environmental Consequences in the Neighbourhood of Rapid Unplanned Urbanisation in Bangalore City.”

If this trend continues, the warnings are dire for the city’s future. “The city of Bengaluru will be choked with paved surfaces (to the extent of more than 98%) and 69.9% of the landscape in the Bangalore Urban district would be paved areas,” says the study. Combined with the loss of vegetation, water bodies and open spaces, the study warns that the urban heat island effect will enhance ambient temperature and humidity levels and lead to heat stress and heat-related illnesses including behavioural changes.

“We need to plan for water urbanism by making the city’s landscape porous. Our study shows that in areas with vegetation of native species, about 55 to 60% of the rainwater gets infiltrated. When vegetation cover is less than 30%, only about 25% of the water gets infiltrated. But concretisation completely stops infiltration,” notes Dr. T.V. Ramachandra, who authored the report, along with three other researchers.