With temperature peaking, Bengalureans feel trapped in one big ‘heat island’
Recent studies have clearly established that Bengaluru’s average temperature rose by nearly a degree over the last 42 years. The increase has been more pronounced in the last two decades
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 allyear 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 deadend?
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 reemit 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.
Rapid concretisation
The rapid concretisation, dubbed whitetopping of the city’s roads with hardly any option for rainwater to percolate and recharge the groundwater table, might be among the most telltale 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 that.
“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.”
Dire warnings
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, waterbodies 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 heatrelated 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.
He cites the case of the city’s Sarakki Lake, rejuvenated three years ago. “Within a year of that upgrade, the water table rose by 320ft. Today, after three years, there is enough water and the groundwater table is very good. And because of the higher moisture content, the temperature there is two to three degrees lower than the surrounding,” he points out.
To arrest the spread of heat islands, he recommends creation of mini forests of about 23 hectares in each Bruhat Bengaluru Mahanagara Palike (BBMP) ward. “Vegetation, water bodies and mini forests create a heat sink. Our study shows that wherever vegetation is there, temperature is two to three degrees lower than the surroundings. Even the IISc mini forest has shown that. We had planted saplings of native species such as mango, tamarind and jackfruit in a 45acre plot that was earlier partheniuminfested.”
Hot air from ACs
Inevitably, the soaring summer heat has pushed up sales of air conditioners in the city. But this will only aggravate the crisis, warns former Indian Meteorological Department (IMD) Director General Dr. K.J. Ramesh. “The hot air exhaust pushed outside while buildings are cooled inside, will add another 12 degrees to the temperature. There is not enough green cover to absorb this,” he explains.
The mushrooming of massive multistoreyed complexes, shopping malls and steel and glass skyscrapers is bound to amplify this problem. “It has a cascading effect: The power demand increases, and thus also the reliance on fossil fuel coalbased power.”
The construction industry too has not kept pace with the changing climate dynamics. Environmentalists note that glass is used as a popular material to ensure the entry of natural light and aesthetic appeal. However, glass also traps heat leading to excess power consumption to cool the building. Energyefficient building designs consider factors such as sun movement, orientation, wind direction and more.
Cascading heat effects
Most makeshift houses in slum areas have tin roofs, which absorb heat and emit radiation both inside and outside. Dr Ramesh elaborates, “Tiled roof buildings are limited. Our housing construction, new modern builtup area expansion, added power consumption for cooling, all are creating cascading effects for warming. Unless we account for all the factors, you cannot look for a solution. Incrementally, everybody has to contribute.”
The elephant in the room is the dire need to decongest the city so that its infrastructure is not stretched. This, as Dr. Ramachandra points out, can happen only through clusterbased development. “I have been telling the government in various forums to adopt this. This means, locating industries depending on resource availability. If cotton is grown somewhere, it makes sense to locate the garment industry there, not in Bengaluru. This way, we can also reverse the migration,” he elaborates.
How transport helps
He cites an example from Tamil nadu. “If you go to the Thanjavur, Kumbakonam, Thiruvallur triangular junction, because of better connectivity and infrastructure, the youth from the nearby villages travel to the town, work in the industries and go back in the evening. In the process, the three towns are not densified.”
But do these insights make any difference to the policy makers? Most Bengalureans are convinced that once the monsoon sets in and the summer crisis passes over, it would be business as usual.
The official antennas would get worked up only when the next heat record kicks up a storm. Last week, the city recorded its daytime temperature at 37.6 degrees Celsius, the highest in eight years and the third highest for April in the last 15 years. The next record could be just days away!