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Savar is not light years away from Dhaka, just a little over 30 kilometers separate the satellite town from the Bangladesh capital. But the former normally has temperature 3.0 degree Celsius lower than in the megacity. Still more significant is the fact that in the commercial areas of Dhaka, the temperature is 2.0 degree Celsius higher than in green covered Ramna and Dhaka University area. In case of the temperature variation between Dhaka and Savar, the deciding factor naturally is local ecosystem.
While Savar boasts 50 per cent vegetation and 22 per cent water bodies and wetlands of its total area, the unplanned and world's third most densely populated city Dhaka is almost barren with a measly 2.0 per cent cover of lush and eco-friendly greeneries although it still has 8.0 per cent of its area covered by vegetation. A recent research study by the Institute of Remote Sensing and GIS of the Jahangirnagar University confirms this.
When it comes to water bodies in central Dhaka, its coverage has drastically declined to just 5.0 per cent. The same microclimate differentiation is responsible for the 2.0 degree Celsius variation between commercial hubs and Ramna-Nilkhet area where sprawling parks, lakes and a profuse tree cover of the university campus and residential area for ministers and high government officials lend it its soothing environment. One can even feel the difference at the time of passing the area from any other direction.
If the trees, parks and lakes in an area help keep its environment comparatively cooler, the residential buildings and other accommodations also play a decisive role in determining a locality's level of temperature. For example, in the Dhaka University area, the few tall buildings are students' dormitories and those keep a healthy distance from each other. Moreover, rows of very big trees hide many of those out of sight. In areas surrounding Ramna, the accommodations are even of lower height and sparsely distributed. Population density there is the thinnest in this capital city.
Contrast this with the area's neighbourhood Lalbagh which is the densest urban settlement on this planet with 181,340 people living in one square kilometre. According to the Population and Housing Census 2022, the population density in Dhaka South City Corporation is 39,353 and in Dhaka North City Corporation it is 30,474 per square kilometre. No wonder, Dhaka was found to be the 7th least liveable city in the world by the Economist Intelligence Unit in that year. The institute of Economics and Peace considered Dhaka the fourth global mega-city to face the biggest challenges in terms of population boom, high disaster risks and vanishing green spaces.
Abnormal crowding of people of such an astounding order is good enough to expose Dhaka's position as an unliveable place. The current heat waves have caused what looks like 'wet-bulb temperature' that claimed 11 lives in nine days. For long the city has turned out to be a 'heat island' in the parlance of environmentalists. According to a 2021 study by Md Imran Hosen, a researcher at the University of New South Wales, Australia, Dhaka's surface temperature rose by a mean of 6.43 degree Celsius or 0.24C per year between 1993 and 2020. Consequently, 60-70 per cent of Dhaka residents now suffer from heat stress. There are other risks such as from precarious fall of the underground water table and impermeable land surface because of unplanned concrete structures with little grass lands and open space. This makes the city a veritable heat trap.
Now the question is, if there is any way of transition from this terrible situation. From its current mess, there is no easy route for escape. But Savar and Ramna along with Dhaka University area offer some redeeming features. Tree plantation is certainly a viable option, although it is not the only one. Under a DNCC tree plantation programme, a target of planting 200,000 saplings was taken, courtesy of the first chief heat officer recruited by the Adrienne Arsht-Rockefeller Foundation Resilience Centre.
Launching programmes with fanfare in this part of the world is hardly followed by post-launch follow-up and required care. The median of the widened road between Agargaon metro rail station and Shishu Mela should by now have become a host to young trees if saplings were planted at the time the road got its spacious shape. Similarly, other roads such as Rokeya Sarani, once a proud host to some indigenous select trees, could be given its green cover back. Shrinking roadside green spaces can be revived or even reversed. The incumbent mayor of Rajshahi has proved it beyond doubt. Let the cheap heat officer take short- mid- and long-term programmes in order to work wonder in this regard.
About reviving wetlands, water bodies such as ponds, not much can be done because many of those have long vanished and on their places multi-storied buildings now stand. Yet Rajuk marked a total of 3,364 ponds, of which 250 are in central Dhaka, in its jurisdiction of 1,528 square kilometre. Even if one-third of those can be restored, things can be better. Tree shade and surface water together can cool the city to a large extent. At least 20 per cent green cover can do the trick.
By its own admission, the government revealed in its "Mujib Climate Prosperity Plan", Bangladesh could lose 5.0 per cent of its working hours equal to 3.83 million jobs and GDP loss of 4.9 per cent by 2030. The worst can still be averted if remedial action plans such as administrative decentralisation and the city's physical recovery are started with utmost seriousness.