Ecology always deals with the nexus between nature and living organism. Ecology of urban settlement is the scientific study of the relation of living organisms with each other and their surroundings in the context of an urban environment. The urban environment refers to environments dominated by high-density residential and commercial buildings, paved surfaces, and other urban-related factors that create a unique landscape dissimilar to most previously studied environments in the field of ecology.
Setting the Scene
Urbanization is one of the 21st century’s most transformative trends. Cities are the dominant force in sustainable economic growth, development and prosperity in both developed and developing countries. In developing countries, urbanization is taking place at a rapid pace. Currently 54% of the world’s population (4 billion people) resides in urban areas. By 2030, 2 billion people will have migrated to cities, placing unprecedented pressure on infrastructure and resources, particularly those related to water, soil etc. Both local shipping and long-distance trade are required to meet the resource demands important in maintaining urban areas. Carbon di-oxide (CO2) emissions from the transport of goods also contribute to accumulating greenhouse gases and nutrient deposits in the soil and air of urban environments. In addition, shipping facilitates the unintentional spread of living organisms, and introduces them to environments that they would not naturally inhabit.
In Dhaka city, Around 250 industries are discharging chemical pollutants into the Buriganga and Sitalakkhya rivers. Every day 4,000 tons solid waste & 22,000 tons tannery waste mixes with water in Buriganga River. Different industries and their contribution to pollution in Dhaka are: Pulp & paper – 47.4 per cent; pharmaceuticals – 15.9 per cent; Metals – 14 per cent; Food industry – 12.1 per cent; Fertilizers/pesticides – 6.6 per cent. In urban areas, sewages are discharging directly into the rivers and low-lying part around the urban areas.
Status of Urban Ecology in Dhaka
Wetlands around our city are being shattered through land development and dumping of toxic effluents and untreated sewage. In Bangladesh, cities have sprung up alone the banks of different rivers. Industrial effluents have totally destroyed the biota in the rivers near these large urban areas. In Dhaka, 20 canals have lost her life out of 42. Liquid, solid wastes and heavy metals – copper(CU), iron(Fe), lead(Pb) and nickel(Ni) are distressing the Biological Oxygen Demand(BOD), Chemical Oxygen Demand(COD), (Dissolved Oxygen)DO, (Total Dissolved solids)TDS, (Acidity or Alkalinity)PH of water.
According to World Health Organization (WHO), the estimated number of death as of pollution is 37,000 per year in Bangladesh. A fourth of the death in Bangladesh and a sixth in the world’s total death result from environmental contamination, mostly caused by air pollution. Particulate matter 2.5 and 10, which is responsible for causing many lung diseases – such as asthma, asphyxia, Pneumonia, obstructive lung disease, bronchitis, lower respiratory infection, lung cancer, etc – is found on an average 7 to 8 times higher in public areas where the permissible limit of PM (particulate matter) 10 is 65 micrograms per cubic metre and for PM (particulate matter)-2.5, it is 150 micrograms per cubic metre. Major air pollutants in Dhaka city are suspended particulate matter, hydrocarbons, carbon monoxide, nitrogen oxides, lead, carbon dioxide, methane, etc emitted from the motorized vehicle. Alien species often have no natural predators and pose a substantial threat to the dynamics of existing ecological populations in the new environment where they are introduced. Alien species are populations of organisms living in a range in which they did not naturally evolve due to intentional or inadvertent human activity. The urban planning act (1919) specified that the city should have a green belt and they prescribed the number of trees that should be planted within the belt.
But we are cutting down a huge amount of trees without planting like that. In addition, planting or cultivation of non-native/ invasive alien species has become a widespread culture in Bangladesh. There are more than 300 exotic plant species in Bangladesh which is assumed to be cultivated as economic crops? Mahogony (swietenia mahagoni), Eucalyptus (eucalyptus globulus), Minzium (acacia mangium) and Akashmoni (acacia auricoliformis) are some examples. Basically, if we plant these trees in urban areas, these trees create environmental insurgencies.
Transportation Health and High-rise Buildings
Increasing in urban population has created a tremendous pressure on the existing network of intra-urban and inter-urban roads and highways as both the number and the volume of vehicular of traffic increases within the city or in its outskirts at specific time of the day, especially during rush hours. The number of motorized vehicles plying in streets of Dhaka was around 140,000 in 1995, 185,000 in 2000 and 290,000 in 2007. Now it is around 3, 85,000. Apart from that, there is a question of registration and non-registration. Bangladesh Road and Transport Authority mentions, there are almost 29.48 lakh registered vehicles in the country. At this moment high-rise buildings dominate many regions of Dhaka city. These buildings have enormous dissident reservoirs to hold water. The pressure of water in the distribution pipes of WASA is not enough to fill these huge reservoirs? Water is tired from these pipes by illegally connecting water pumps straight on WASA lines. As a result, other houses in the neighborhood undergo from water shortage. Dhaka city is merely served by a sewerage system, which is not able of accommodating huge loads of sewage at specific points.
The high-rise apartment buildings are creating extra load of sewage at specific points at specific times of the day. This teeming may debilitate the whole system. Where there is no sewerage line, huge septic tanks need to be erected to clutch the sewage. If constructed in dangerous revitalize areas, this may contaminate the groundwater, pollute the land and lake ecology. Dhaka suffers from traffic congestion, which is deteriorating, despite its low level of motorization. This horrible situation prevails largely due to absolute lack of roads, deficient road network configuration and inefficient traffic management. The existing public transport system, bus transit operations in particular, is characterized as far short of the desirable mobility needs of the people in terms of reliability, comfort, speed and safety. In Dhaka, buses are generally considered unreliable and time-consuming to reach one’s destination. It is one of the very few megacities in the world without a proper public transport system.
The present public transport system in Dhaka city consists of only conventional bus services (buses and minibuses) and para-transits (e.g. rickshaws, auto-rickshaws, taxis, battery bikes, etc.). Lack of effective public transport system and preference of door-to-door services influence the augmentation of private cars and other forms of transport. The railway was very popular and still is a relatively safer and cheaper transport system in Bangladesh; as a consequence of the absence of proper initiatives and investment in the urban corridors, it could not play the expected role in Dhaka’s public transport system. Moreover, rail tracks run through the Central Business Districts (CBDs) and congested areas of the city with numerous level crossings which result in enormous congestion.
All these factors have created a situation where cars and motorcycles are increasingly becoming a necessity for the middle class to get around in Dhaka. As a result, there is further congestion in roads and worsening air and noise pollution and safety issues. The number of registered motorized vehicles stands at 1,255,402 as of April 2018, an increase from 303,215 in 2003 (a fourfold increase in 15 years). More than 36 percent of all registered vehicles are in Dhaka (a total of 3,419,884 in Bangladesh) (BRTA 2012, 2018). During this period the percentage of buses and minibuses has remained almost the same; private vehicles, particularly the number of cars and motorcycles, have almost tripled. Public transport such as buses and minibuses has grown at a very insignificant rate even though the demand for public transport services is increasing. Motorcycles and cars constitute around 54 percent and 26 percent of total motorised vehicles respectively.
To improve the current situation and reorganize the existing traffic system methodically, the government prepared the Strategic Transport Plan (STP) for Dhaka (2005) which has been recently revised (it has now become Revised Strategic Transport Plan, RSTP since 2015). It recommended a package of comprehensive programs for the development of transport infrastructure over a 20-year period. This strategy includes various types of development agendas, such as three Bus Rapid Transit (BRT) and Mass Rapid Transit (MRT) (Metrorail) routes, more than 50 highway projects, expressways, flyovers, etc. But unfortunately, the implementation of the components of STP or RSTP does not reflect the intention to mitigate transport problems of the masses. Ignoring the needs of non-motorized travelers and pedestrians, recent policies at all levels of the decision-making processes have focused mostly on trying to lessen the travel time for the motorized elite of the city by putting preference on the construction of numerous grade-separated flyovers, overpasses and interchanges (e.g. Jatrabari-Gulistan flyover, Kuril interchange, Banani overpass, expressways, etc).
The rapid motorization and heavy infrastructural development which promote cars come with the depletion of transportation equity in a city. For example, from an environmental and equity perspective, major concerns exist regarding the unwanted increase of motorized two-wheelers. Some have even characterized the motorcycle as likely the “most challenging” transport problem that Asia will face in the next decade. The rise of private transport and current prevalence of NMT (Non Motorized Traffic, mostly rickshaws) are not a sustainable solution although they may help to increase mobility in the short term. Already authorities tried to and have been successful in banning NMT from some parts of the city. So, like other developing cities around the world, NMT will be restricted in near future for Dhaka too.
Environmental Hazards and Climatic Impacts in Urbanization
Global climate change and its current and potential consequences for life, property and prosperity are now accepted as the major challenge for human society in the next 100 years. By 2030, without significant investment to improve the resilience of cities around the world, climate change may push up to 77 million urban residents into poverty (UN, 2017). So, developing a sustainable city along with its basic infrastructure is of utmost important to ensure future sustainability. Building cities that “work”—are inclusive, safe, resilient, and sustainable—requires intensive policy coordination and investment choices. Therefore, city-level actions will be a central part of sustainable development initiatives, where the world needs inclusive and sustainable urbanization as a milestone in the path towards socio-economic growth, as documented by SDG Goal 11: Sustainable Cities and Communities.
Transport is the life of a city and choices on public transit options are fundamental decisions about a city’s future growth and development. It is a key infrastructure sector that acts as a stimulus to economic growth and development, and an important element of strategies for poverty reduction, regional integration and national development including the environmental objective of limiting GHG emissions. As transport is one of the major contributors to global warming through burning fossil fuels, this sector could be one of the prime sectors where policies aiming to reduce GHG emissions will be most important. Sustainable transport that emphasizes the use of public transport, bicycles and walking, and discourages the use of individual motorized vehicles like cars and motorcycles is essential to achieve many of the proposed SDGs and the 2030 agenda for sustainable development and it is, therefore, mainstreamed across several SDGs and targets, especially those related to food security, health, energy, infrastructure, cities, and human settlements (UN, 2017).
Environmental hazards are one of the unfortunate by-products of 21st-century urbanization and industrialization. World Bank report has analyzed on environmental crises in Bangladesh— the report titled “Enhancing Opportunities for Clean and Resilient Growth in Urban Bangladesh” clarifying the integration of boosting economic growth and attention to the environmental security. The data shows that deaths caused by pollution in 2015 in Bangladesh stand at 28% —the highest in South Asia. In the same year, there were around 234,000 deaths due to environmental pollution and related health risks, including 80,000 in urban areas. This is more than ten times the number of deaths resulting from road accidents in 2015.
Water Security & Flooding
Water security should be ensured for all citizens before it is too late In urbanization, all processes are viewed in relation to the city. Generally, better food supply, good medical care, education, jobs, industrialization, commercialization, electrification, specialization of professions, and entertainment are the basic causes of urban growth. Accessible energy plays an important role in our development — with this, people can enjoy all the modern facilities. By establishing road communication, an undeveloped area may be connected with a developed area. It helps the people of the areas, the use of information, technology, and media for an improved standard of living.
From 2016 to 2030, a 35% population increase is expected in the top ten megacities. Forecasts indicate cities in developing countries including Karachi, Lagos, and Dhaka will surpass cities like New York, Osaka, and Sao Paulo by 2030. This represents a 50% increase in demand for energy and water, generating challenges that exert pressure on water resources and threaten global water security. This has a palpable effect on public health, economics, and development. Local solutions for local problems are most suited to meet these challenges. As more than three-quarters (76%) of the world’s mega-cities are coastal; there will be a considerable impact on water eco-systems from ridge to reef. Because of this, local and regional authorities lead initiatives targeting water-related obstacles, including housing gaps, climate change, and an increased demand for food, energy, and water.
Climate change, in particular, represents a daunting challenge for cities, as 40% of the world’s population will live in river basins under severe water stress, while 20% will risk floods by 2030. Flooding and droughts have increased globally, and the impact is devastating.
Are We Breathing Toxin through Nose?
Dhaka has been historically infamous for being heavily polluted. It was termed as the most polluted city when the presence of lead (Pb) in the air was reported to be higher than in the atmosphere of any other place in the world back in 1997. Pollution from traffic and brick kilns has been identified as two of the most significant factors by studies. In the late 1990s and early 2000s, in order to improve the severe situation, the authorities took some important decisions (e.g. banning two-stroke engines, introducing Compressed Natural Gas (CNG), etc). Other than numerous sporadic studies and projects, there has been little systematic research or successful project implementation on air pollution in the city. Unless the situation becomes extremely hazardous or almost uninhabitable, what the authorities usually do is adopt the “do nothing” approach.
The main culprits for air pollution are large numbers of high-polluting vehicles, impure fuel, inefficient land use, overall poor traffic management, and industries (especially brick kilns). The most important pollutants have been identified as carbon monoxide, sulfur dioxide, lead, nitrogen oxides, ozone, hydrocarbons, suspended particulate matter and last but not least, particulate matter with an aerodynamic diameter of less than or equal to 10µm (PM10 and PM2.5). Observations show that the concentration of sulfur dioxide, ozone, carbon monoxide and nitrogen oxides goes up in the dry season significantly. The same is true for PM2.5 and PM10.The estimated PM emissions from different modes indicate that around 54 percent emission contribution is from buses/minibuses, followed by trucks and tankers (26 percent). The black spot areas for PM were located in the intercity routes and the major bus terminals. The bus terminals (Gabtoli and Sayedabad) showed average estimated values above 110 ?g/m3 of PM. Locations with highest concentrations of PM are Sheraton, Farmgate, Sonargaon, Mohakhali-Gulshan intersection and Banglamotor.
When a team of researchers performed field studies in the 90s, to measure ambient NO2 concentration in 51 street locations, one residential area and four personal exposures, 35 of them were identified as black spots. Most polluted locations of nitrogen oxides were Sayedabad bus stand, Sheraton hotel roundabout, Sonargaon hotel roundabout, Farmgate intersection and Moghbazar intersection. The calculation of nitrogen oxides indicated that buses and minibuses (diesel operated) and motor cars have a significant contribution of nitrogen oxides (30 percent), followed by heavy-duty vehicles (trucks and tankers) (28 percent). The situation has gotten much worse now after 20 years, as there have been no visible steps to improve the situation. Researchers found that nitrogen oxide and sulfur oxide emissions from transportation systems in national pollution averaged 34 percent and 47 percent, respectively. In case of sulfur dioxide in Dhaka, the contribution mainly comes from high sulfur content in the diesel fuel. It was estimated that buses powered by diesel fuel contribute 58 percent sulfur dioxide emission followed by trucks and tankers at 34 percent.
At present, air pollution in metropolitan Dhaka has been increasing at a steady rate for more than three decades. Annual average increases of 6.5 percent in nitrogen oxides, 5.8 percent in hydrocarbons, 5.9 percent in carbon monoxide, 5.6% in PM and 6 percent in sulfur oxide emissions were observed from 1981 to 1996. These rates have certainly not gone down, as the number of motorised vehicles is rapidly increasing, which results in chronic congestion almost at every intersection, resulting in more and more emissions. It is proven that the impact of policy decisions (e.g. banning of two-stroke engines and leaded gasoline, introduction of CNG, etc.) can have far-reaching effects in a positive way. The ever-increasing amount of PM2.5 and PM10 is getting out of hand, and making the city one of the most polluted in the world. If we do not take proper effective measures to mitigate the problem now, we will face grave consequences.
Dhaka is probably one of the very few megacities in the world without any properly planned design or guideline for expansion of the mass transit system. There are few others like us such as Lagos, Karachi and Kinshasa, but none of them has a population density of about 50,000 people per square kilometer. According to some projections, approximately 24 million and 35 million people will reside in Dhaka by 2030 and 2050 respectively. So, if Dhaka is to survive the juggernaut called “development” and “urbaniation”, it must have a proper plan not only to provide guidelines on paper but also for implementation in reality—and there is little scope for mistakes.
The writer is environmental analyst & Associate Member of Bangladesh Economic Association.