Dhaka, the bustling capital of Bangladesh, has long been a symbol of rapid urbanization and economic growth. With a population now exceeding 24 million, the city has transformed from a modest urban center in the 1970s to a sprawling megacity. However, this growth has come at a steep environmental cost. The relentless expansion of concrete infrastructure-roads, high-rise buildings, and industrial zones-has turned Dhaka into a heat island, exacerbating the frequency and intensity of heat waves. As temperatures soar, the city faces a public health crisis, ecological degradation and a looming threat to its sustainable future. Immediate action is needed to mitigate this escalating disaster.
The phenomenon of rising heat in Dhaka is not solely a consequence of global warming; it is deeply tied to the city's infrastructural choices. Over the past few decades, Dhaka's landscape has undergone a dramatic shift. Wetlands, which once covered 20% of the city in the 1980s, have dwindled to a mere 2% by 2025. These water bodies, with their high heat capacity, acted as natural air conditioners, absorbing heat during the day and releasing it slowly at night. In contrast, concrete, which dominates Dhaka's modern landscape, has a heat capacity 4.75 times lower than water, trapping and radiating heat with devastating efficiency. Areas like Mirpur and Banani, now concrete jungles, are 5-7°C hotter in summer than locales with water bodies like Dhanmondi Lake or Ramna Park.
The transformation has exacerbated the Urban Heat Island (UHI) effect, causing urban regions to become considerably warmer than their rural counterparts. Over the past 25 years, Dhaka's UHI intensity has increased by 0.21°C per ten years, with an average intensity of 0.48°C. As concrete surfaces release stored heat, this effect peaks in the winter around 0.95°C, making nights very unpleasant. The city's land surface temperature has risen 6.43°C between 1993 and 2020, or 0.24°C each year on average. This is much more than the 1.2°C global average temperature increase since the pre-industrial period. Dhaka's average temperature has increased by 2.74°C in the last 20 years alone, and if current trends continue, it could rise by an additional 5°C during the next 20 years. Such a path could lead to Dhaka becoming unlivable, a serious warning that requires immediate action.
The health implications of this heat crisis are alarming. In 2022, heatstroke claimed 112 lives in Dhaka, a 300% increase from 2015. Cases of heat rash, dehydration, and respiratory issues among children and the elderly have risen by 40% between 2010 and 2023, driven by increased humidity and air pollution. The International Labour Organization (ILO) forecasted that by 2030, Bangladesh might experience a loss of 4.84% of its total working hours as a result of heat stress, which translates to millions of job losses, especially in outdoor industries such as agriculture and construction. Day laborers, who form a significant portion of Dhaka's workforce, are especially vulnerable. The heat index, combining temperature and humidity, has reached dangerous levels, with "felt" temperatures hitting 47°C in recent years, even when air temperatures were around 39°C. This cumulative physiological stress exacerbates chronic health conditions, increases mortality rates, and pushes low-income families deeper into poverty as they struggle with medical costs and lost productivity.
Dhaka's infrastructural development, heavily reliant on concrete, is a primary driver of this crisis. Concrete buildings, asphalt roads and dark surfaces absorb solar radiation during the day and radiate heat at night, creating urban hotspots. Between 1993 and 2020, the city's built-up area-which includes low-lying areas, green spaces, and water bodies-grew by 67%. In just three decades, this has resulted in a 56% decline in green space, leaving Dhaka with only 7-8% tree cover, well below the 20% that is advised for ecological health. The lack of vegetation, which cools the environment through transpiration, compounds the problem. A Dutch study noted that a 10% increase in urban greenery can reduce the UHI effect by 0.6°C, yet Dhaka's urban planning has prioritized concrete over green infrastructure.
The energy implications are equally concerning. As water bodies disappear, the demand for artificial cooling has skyrocketed. In 2022, Dhaka's peak electricity demand reached 3,800 megawatts, a 60% increase from 2015, driven largely by the use of air conditioners. This surge in energy consumption not only strains the city's power grid but also increases carbon emissions, creating a vicious cycle that further intensifies the heat. The loss of rivers and canals, which have seen a 30% reduction in water flow since 2010, has also increased humidity by 18%, pushing the heat index to dangerous levels and making the city feel even hotter.
Beyond health and energy, the heat crisis threatens Dhaka's ecosystem and economy. The city's rivers, part of the second-largest river system in the world, have been filled or covered to accommodate urban sprawl, disrupting the microclimate. Wetlands, which are more effective than parks at mitigating heat, have been sacrificed for development. Water absorbs and holds more heat than concrete, regulating air temperature, yet urban planners have ignored this natural solution.
To address this crisis, Dhaka must adopt a multi-pronged approach centered on nature-based solutions. First, the restoration of water bodies and wetlands is critical. Protecting existing waterways and reviving lost ones can significantly lower temperatures. Second, urban greenery must be prioritized. Increasing tree cover to 20% through afforestation, rooftop gardens and city parks can mitigate the UHI effect. Native, pollution-resistant trees like mango, banyan and jackfruit should be planted along the city's 200 km of roadways. Third, urban planning must shift away from concrete-heavy development. Policies promoting greenbuilding materials, green roofs and sustainable infrastructure can reduce heat retention. Finally, public awareness campaigns and heat adaptation plans, similar to those implemented in Ahmedabad, India, should be introduced to educate residents and build institutional capacity to tackle heat waves.
Dhaka's authority has outlined plans to create parks and eco-parks in its urban plan through 2035, but implementation lags. However, these measures are insufficient without a systemic overhaul of urban planning. The city must balance its growth with sustainability, ensuring that development does not come at the expense of its residents' well-being. As temperatures continue to climb, the city stands at a crossroads: it can either continue down the path of unsustainable growth or embrace nature-based solutions to build a resilient, livable future. The time for action is now-before Dhaka's heat crisis becomes an irreversible catastrophe.
The writer is a Ph.D. researcher, University of Dhaka
