Why cities are the best weapon against climate change

When we think of the effects of climate change we usually conjure up haunting images of coastal areas, melting icebergs, deserts littered with animal carcasses, and drought-hit territories with burnt trees.
But we rarely think of the city as an affected area due to climate change or, more importantly, as a cause of it. There is an ongoing disconnect between the discussions on global climate-related vulnerabilities and the processes of urbanisation. This is perplexing because urbanisation has become one of the most powerful and visible anthropogenic effects on Earth. The world's urban population will rise from less than 30% in 1950 to 75% by 2050. Cities are the engines of economic growth. South Korea's 50% GDP is attributed to Seoul; in Bangladesh, 36% to Dhaka. However, the flipside of the city's heroic economic narrative is that cities are also the most corrosive pollutants of the planet's environment. They produce more than 75% of the world's total greenhouse gas emissions. With their industrial activities, population density, transportation, and energy usage, they are key contributors to global warming.
Mitigating climate change problems, thus, requires a sustained engagement with the ways cities are designed, governed, maintained, and developed.
Bangladesh has missed this policy focus so far. Here, the climate change conversation has been singularly dominated by the specter of a “southern threat.” That is, with ongoing global warming and the resultant sea-level rise, a significant landmass of Bangladesh's coastal south would disappear under water. And, a vast coastal population would lose their livelihood and become climate refugees, destabilising local and regional security. Al Gore's Oscar-winning documentary, An Inconvenient Truth (2006), helped popularise this particular view of Bangladesh among the global community concerned with climate change and its disastrous effects on such low-lying countries as Bangladesh and Maldives.  
The susceptibility of Bangladesh's southern seaboard to global climatic catastrophes cannot be underestimated. But a linear emphasis on the southern threat, unfortunately, blurs the urgency of the country's more immediate environmental threats due to rapid, ecology-defying urbanisation. An immediate environmental menace with long-term climatic implications lurks at the geographic centre of the country because of the monstrous urban growth of Dhaka and its deleterious effects on the fragile land-water ecosystem that has historically sustained the capital and its surrounding regions. Dhaka's frenzied growth in all directions, devouring rivers, water bodies, and agricultural lands, is as serious an environmental threat as the sea-level rise due to global warming.
The capital's urban growth not only exemplifies the dire environmental consequences of uncontrolled and profit-driven urbanisation in Bangladesh, but also alarms us, more generally, about the collective need to view cities as the frontier of climate change. With sustainable environmental policies cities present the single most potent weapon to combat climate-related environmental problems.
Three urban policies, by no means exclusive, should be considered for cities to be an efficient defense against climate change.
First, a city's growth must take into consideration the ecology of the place. Altering the fundamental geography of a place in the name of development would mean tampering with nature's balance which is essential for a place's continued ecological harmony. Consider Chittagong. Rampant hill-cutting in the port city changes its land form (which is nature's trial-and-error method of perfecting a geographic condition through millions of years), exposing it to natural calamities caused by climatic abnormalities. River-filling in Dhaka would mean fewer drainage arteries for the snow-melted water that descends from the Himalayan plateau and passes through the flat Bengal delta.
Second, cities must be compact, so that they can foster walkable communities and a culture of smaller carbon footprints. Compact cities are served well by a mass transit system, reducing the need for personal cars and carbon emissions from them. A compact metropolis with an urban growth boundary stops sprawl, generates fewer heat-producing surfaces, and preserves carbon-reducing agricultural fields. Lest we forget, buildings and transportation together account for 37% of global carbon emissions. A perpetually expanding city, with its built-up area and dependence on personal transportation, is basically a heat island and a carbon factory. Consider the devastating possibility of a Dhaka extended up to or beyond Aricha in the north and Mawa Ghat in the south, and all the rivers, canals, wetlands, and arable lands in between are filled up to create buildable lands (this is already happening). Urban compactness has become one of the essential mantras of sustainable urbanism and an efficient strategy against global warming.
Third, implementation of environmental laws should be a top-down urbanisation policy to ensure the preservation of a city's “lifeline” like rivers, hills, wetlands, etc. The protection of natural resources provides cities and their regions with the best ability to be resilient in the face of natural disasters. Cities provide easy access to transportation hubs. Thus, factories tend to flock to cities, so that they can easily and quickly export their products. But, as much as they are stimulants of national economy factories are also environmental pollutants, unless strict environmental laws are enforced. Consider the air-polluting brickfields of Ashulia on the outskirts of Dhaka. Their environmental hazards may seem local and temporary, but they severely harm the region's long-term climate resiliency.
The best way to tackle climate-induced vulnerabilities is to protect and preserve nature's way of balancing itself. When excessively profit-driven human actions take precedence over nature's balance, when human activities radically alter a place's elementary geography, their environmental consequences are bound to be calamitous. Since the future of the world is urban, the best place to ensure the planet's ecological wellbeing is the city. This basic understanding should frame Bangladesh's urbanisation policies.

The writer is an associate professor of architecture and planning in Washington, DC, and
author of Oculus: A Decade of Insights into Bangladeshi Affairs.