The Indian urban population rose from 17.9% in 1960 to around 34.9% in 2020. The population size in Bengaluru during the same period increased by more than ten folds. Different agencies estimate that by 2030, Bengaluru will be home to 15-20 million people.
This urbanization has resulted in increasing Bengaluru’s Land Surface Temperature (LST) from 33.08°C in 1992 to 41°C in 2017 (a drastic increase of 24%).
Considering the size of the city and the vast number of people, such huge growth will have impacts on our environment, health, ecology, as well as our energy use. In turn, the looming climate crisis would be a game changer in the coming years. Bengaluru, the IT hub, demands voluminous amount of energy for supporting its industries and for basic needs like cooking, transport and construction.
Researchers and climate scientists have reported several factors affecting Bengaluru’s surface temperature due to urban expansion.
Unplanned urbanization
A research study conducted by Indian Institute of Technology, Kharagpur showed that the urban cover of Bengaluru increased by 348% from 1992 to 2017. IT industry after 2000, sprouted in regions like Koramangala and Whitefield, which led to the expansion of areas on larger scale. This in turn raised the real estate prices in and around these locations, thus making them unaffordable for population who relocate here for work. These people thus started settling in the city’s outskirts, creating instances of uncontrolled growth even in these regions. A research study by IISc (Indian Institute of Science) revealed that out of 105 lakes, 98% of them of been encroached upon for the illegal construction of multi-storied buildings and complexes.
Heat islands to climate change
Unplanned urbanization led to the creation of urban heat islands. These islands/ land stretches are areas where the buildings are very closely spaced and the population density is very high. As a result, heat gets trapped in these densely populated areas, especially between the buildings, raising the temperature in these areas as well as the surroundings.
Land Surface Temperature (LST) could be defined as a proxy indicator of urban heat islands. LST is the temperature of the earth’s surface. This in general is more than the surrounding air temperature. If the land is being continuously heated for a long time, then more heat is absorbed by the land surface. The LST, in addition is also linked to climate change in terms of greenhouse effect and global warming. Higher LST values can be attributed to man-made activities such as construction and energy-generation that causes higher pollution and emission of GHGs.
The study report, analyzed from 1992 to 2017 for LST values, using remote sensing technology, found that the urban land use had seen a rise from 5.47% in the year 1992 to around 27.53% in the year 2017, thereby increasing the surface temperature from 33.08°C to 41°C.
The area under vegetation had seen a reduction from 17.01% to 5.79% only due to the urban expansion. The surface temperature of vegetative areas in 1992 was reported to be 31.10°C which rose to 38.78°C in 2017. Moreover, the area of water bodies also dipped from 2.42% to 0.79% with surface temperature cranking from 25.41°C to 35.54°C.
Hotter and cooler clusters
The study also specifies regions with comparatively warmer and lower surface temperature. Jakkur airfield, Kempagowda International airport, HAL airport, goods loading terminal in Kadugodi, the dried Hesaraghatta lake were some of the areas that were reported to show the highest surface temperature in Bengaluru ranging between 44°C to 51°C.
Airports are one of the most densely packed up spaces with air conditioners and closed spaces that trap heat as well as the runways that are constructed with heat-sensitive materials. This is another reason for high temperature around these regions. The vegetation around is also very little with very few water bodies around which could absorb the heat and lower down the temperature.
On the other hand, regions with vegetation covers like Bengaluru Golf Course, Freedom Park and densely covered vegetative patches have comparatively a moderate land surface temperature of 33°C to 35°C. Also, water bodies like Sankey Tank, Ulsoor Lake show low temperatures ranging from 30°C to 33°C.
Cons of High Land Surface Temperature
According to WHO, high temperatures can cause cardiovascular and respiratory illness affecting the health of the people. High LSTs also affect agriculture and aquaculture by disrupting the ecosystem thus making it hard for several micro-organisms to survive. Rainfall patterns are also seen to be altered due to high LSTs. This is due to the fact that higher temperatures cause more evaporation which ultimately leads to higher rainfall, thereby increasing the risks of floods. Alternatively, the warm air can be trapped by the GHGs thus not allowing it to reach the atmosphere. This will prevent cloud formation and could ultimately result in less rain.
Ways to reduce temperature
Some changes cannot be undone. For an instance, the additional one degree warming cannot be reversed. But we can learn from places like Singapore. Planting trees on streets for shade as well as using plants (creepers) at the entries of the buildings could reduce LST to some extent. Developments of gardens and mini-forests around the densely populated regions can lower the micro-climate. Replacing the glass roofs with green roofs can be introduced, which absorb more heat with cooler materials, and this can further cool down interior temperatures.
Further, warming would probably depend on how the city grows in future. The warming which occurred in the past and occurring in the present, is basically due to the built-up areas in the city’s centre. If that continues for the next 3-4 decades, the centre will get even hotter. So, it will all depend on how the built-up area spreads.
A movement to stop the further destruction of lakes is going on in Bengaluru. However, the major focus should be to reduce the total heat generated and to increase the actual cooling processes. We need to move to a new economic system, where both the humans and the nature matters and we create a city with favorable, pleasant and cooler climate for the benefit of all.
Aakansha holds a master's degree in biotechnology and is currently working as a research scholar. An avid reader, Aakansha finds keen interest in reading and writing on areas related to clean energy and zero carbon emissions.
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