Heatwave alert: Dhaka's scorching situation and long-term environmental destruction

Dhaka, the capital city of rickshaws and mosques, has lovingly preserved Bangladesh's customs and culture. Dhaka, which was previously enveloped within green, is slowly losing its verdant charm. On the one hand, as Dhaka's air pollution levels rise, so does its temperature. 

In 2022, 40.4 degrees Celsius was recorded in Dhaka on 15 April, while last year 40.6 degrees Celsius was recorded in Chuadanga on 16 April, the hottest temperature since 1965, or 58 years. 

Incidentally, the highest temperature recorded in Dhaka so far was 42.3 degrees Celsius on 30 April 1960. This metropolitan heat has suddenly brought a lot of breath into public life. Dhaka's present sweltering temperatures are the result of long-term environmental degradation. According to the environment, weather, and climate, Dhaka's habitability is presently the primary topic of discussion. Dhaka has been ranked as the most polluted city in recent years. 

Everyone is reconsidering now that the temperature has reached a record high. Whereas the worldwide temperature has risen by 1.5 degrees Celsius, Dhaka's temperature has risen by around 4 degrees Celsius during the previous 20 years. 

If the current situation of heat burning is not addressed, the difference or variation between day and night temperatures in Dhaka and other district cities would decrease. If the existing scenario of heat burning is not regulated, the difference or fluctuation between day and night temperatures in Dhaka and other district cities would decrease, making it seem hot all the time. Rising urban temperatures are a global concern, not just one in Bangladesh. Apart from climate and environmental changes, the temperature of a place depends on population and its density and human activities. Unplanned urbanization, lack of coordination between different agencies in cities and environmental management are more responsible for the increase in temperature than climate change. The temperature of Dhaka city is increasing due to three main reasons: global, regional and local.

Among the worldwide reasons include the loss of the Amazon rainforest, known as the world's lungs, an increase in carbon emissions and fuel use in industrialized countries, and so on. The global temperature is rising owing to business motives. 

Although Bangladesh has little responsibility for this, it is having an influence on Bangladesh. This region was historically traversed by multiple rivers from India, Bangladesh, Nepal, Bhutan, Afghanistan, and China. However, the implementation of numerous projects has gradually destroyed these rivers. As a result, the length and breadth of the rivers have decreased in number. Some of the places where the river receded have been filled with sand and some have new projects there. As a result, a lot of heat is spreading from there. 

On the other hand, due to the presence of sand, a desert condition is created and due to these reasons, the temperature of the surrounding area increases. It is the first regional cause of temperature rise. The second regional factor is the melting of Himalayan ice. 

The temperature is then reflected back into the atmosphere by the Himalayan snow. But now due to the melting of the ice, solid rock is visible. As a result, the temperature stored in these stones is spreading to the surrounding area through air and causing a kind of heat burn. Megacities or cities are growing in these regions, which is followed by an increase in traffic and population. For example, India's population has increased and now it is equal to China. More than one-fifth of the world's total population lives in this region. Temperatures are rising even as this huge population is afforded its civic benefits.

The most vital cause of temperature rise is the local factor which is contributing to the rise in temperature locally. Among these local factors, the main reason for the increase in temperature is the decrease in greening of Dhaka city. At one time there was more than 25% green space in Bangladesh but now its amount is very negligible. Plants provide oxygen by absorbing carbon-dioxide and heat from the environment. As a result, oxygen spreads in the air and keeps the surrounding area cool. But now, in the name of beautification of the city, the big trees dividing the roads are being cut down. As a result, the oxygen and water vapor in the atmosphere are decreasing, the temperature is increasing and due to the same reason, the rainfall is also decreasing.

A second cause of temperature rise is depletion of reservoirs. Research shows that the number of reservoirs or ponds in Dhaka city is decreasing at an alarming rate. The reservoir is being filled with sand instead of soil. This is also one of the reasons for the increase in temperature. A study conducted by the Center for Atmospheric Pollution Studies (CAPS) on 36 places in Dhaka city has shown that the temperature is relatively lower in the areas where greenery is present. Among these 36 places in Dhaka, 9 places had recorded high temperatures because they had less plants in it and in 9 places, the temperature was low due to more trees, lastly 18 other places had average temperature. 

However, the lowest temperature was in the Botanical Garden and National Zoo. Other areas with second lowest temperature were Ramna Park, Dhanmondi Lake Par, some areas including Cantonment. On the other hand, the highest temperature areas were some commercial areas including Tejgaon, Motijheel, Mirpur, Jatrabari. These had a temperature variation of three to three and a half degree. This proves that green swamps are one of the sources of low or rising temperatures. Thirdly, Dhaka's overpopulation is also contributing to the rise in temperature. 

According to the US-EPA, average temperatures in any given area could increase by 1.8 - 5.4 degree Fahrenheit for every 100,000 people. Again, the human body has its own temperature which is called metabolic heating and the amount of this temperature in every person is 100 watts. That is, the more people there are in the same place, the higher the temperature will be. The current population of Dhaka city is more than 2 crore which is directly increasing the temperature. Apart from this, a large part of the people in the city burn wood for cooking. Apart from this, there are about 20 lakh families in the city with 20 lakh stoves that cook for at least 3 hours a day on an average. 

The fourth reason for the increase in temperature in Dhaka is the widespread burning of waste. As a result of burning the plastic inside the waste, various polluting gases and micro plastic particles mix with the air and pollute the air. These plastic particles floating in the air are trapping heat and warming the atmosphere. The theme of this year's environment day was plastic pollution with the aim of banning single-use plastics and reducing the use of plastics. This year marks the 50th anniversary of Environment Day. For the last 50 years, Environment Day is being celebrated on June 5 to demand the protection of the environment. But day by day environmental pollution and other important elements of the environment are changing which are affecting our way of life. One example of this is the intolerable change in temperature.

Fifthly, the capital's heavy traffic and congestion problems are also contributing to the rise in temperature. Which includes about 52 lakh vehicles plying in the capital. One-third of which are walking without fitness. Due to traffic jams, cars have to stand on the road for hours with their engines running. This causes huge amount of heat released from the engine which is spread with the help of wind and heats up the city environment. 

The sixth reason includes the steep roads of Dhaka city. This road heats up during the day and retains heat until the early part of the night. Then when it releases it contributes to the increase in heat in the city. This requires trees on road dividers. Which is helpful in reducing heat. But now the divider trees are being cut down in the name of beautification of the city. The temperature is increasing. 

The seventh reason is the use of extra glass and AC in newly constructed multi-storied buildings and narrow roads inside the buildings. By doing this, the heat contained in the glass and the heat released from the AC spreads to the air and increases the temperature. Again, the narrow streets inside the building obstruct the normal movement of air, resulting in the extreme afternoon heat being trapped inside the buildings and suddenly the temperature in the area is observed to be higher in the evening. On the other hand, instead of grass, the sidewalks are now paved, which prevents water from seeping into the ground. As a result, the soil under the plant also gets heated. Which contributes to increase in temperature. All in all, unplanned development activities in the current urbanization, industrialization and communication systems are mostly responsible for the increase in temperature.

A study shows that by 2050, heat waves will seriously affect the lives and livelihoods of more than 3.5 billion people worldwide, and more than half of them will live in cities. Extreme heat waves are more dangerous for cities and the risk continues to increase in cities every year. Recently, a report titled 'Hot Cities, Chilled Economies: Impacts of Extreme Heat on Global Cities' by the US-based 'Adrienne Arsht-Rockefeller Foundation Resilience Center' stated that Dhaka is losing 6 billion dollars every year due to altitude and by the year 2050 this loss may exceed 8 thousand 4 billion dollars. As compared to any other city, the labor productivity of people in Dhaka is affected more by altitude. 

This loss could rise to 10 percent by 2050 if no action is taken to reduce the temperature. The number of hot days is estimated to double by 2050. It is expected to adversely affect the vulnerable population, especially women, children and the elderly. Survivability of novel viruses and pathogens is increasing due to heat wave in Dhaka city. It is increasing dengue, chikungunya, respiratory illness and other infectious diseases. High temperature causes dehydration, allergy, heat cramps, heat stroke etc. The summers are getting longer and the rainy season is frequent starting lately.

To control the rising temperature of Dhaka city, the first step to be taken is to plant trees in every vacant space of the city (at least 20%). Apart from the ornamental trees in the road dividers, different types of useful trees such as different fruit trees, medicinal plants, timber trees should also be planted based on the types of land. Roof garden should be increased. A forest area directly reduces heat and carbon emissions. 

All existing wetlands should be conserved and new reservoirs should be created. Encroached wetlands should be recovered. No structure can be constructed by filling the wetlands. Appropriate measures should be taken through law enforcement if necessary. Concerns needs to be aware while constructing infrastructure and newly proposed buildings should be maintaining a certain distance. Population must be controlled and overcrowding from urban areas must be reduced. Burning of plastic and other waste should be avoided everywhere and plastic waste should be properly managed. The use of fossil fuels should be stopped and the use of renewable energy should be increased instead. 

In emergency situations, all educational institutions should be declared closed. It is important to take plans keeping in mind the local, geographical features and natural environment and public policy of the city. Above all, everyone must work together to reduce this heat flow.

Professor Dr Ahmad Kamruzzaman Majumder, is the dean of Faculty of Science, Stamford University Bangladesh, and Joint Secretary, Bangladesh Poribesh Andolon (BAPA)