Human Settlements

Human Settlements and Sustainability

Module Introduction

By Olivia Edwards

Human settlements are permanent or temporary places of any size where people live together. They are made up of both a physical component – the natural and built environment that provide the physical infrastructure necessary for provisioning basic needs like shelter, food, and water–as well as a wide range of economic and social activities that facilitates economic and information exchange, art and culture, education, health, and recreation. From the first towns and villages that formed as populations transitioned from hunter-gatherers to agrarian societies to our present-day global cities, human settlements have provided the infrastructure crucial for social and economic development as well as technological and scientific achievement.

Threats Posed by Urban Growth

Today, 55 percent (4.2 billion people) of the world’s population lives in cities, in contrast to only 30 percent in 1950. The urban population is expected to continue its upward trajectory to 68 percent (6.7 billion people) by 2050. An estimated 90 percent of these new urban citizens will reside in Asian and African cities; many will be refugees from areas devastated by climate change. Meanwhile, the number of megacities with more than 10 million inhabitants is projected to increase from 33 in 2018 to 43 in 2030. As the population of a city grows, ever-more land and resources are required to keep its citizens fed and sheltered, its buildings and electrical grid running, and its infrastructure transporting people and goods. This intensification of resource extraction simultaneously degrades the environment by depleting natural resources and generating pollutants like greenhouse gases and hazardous materials. Currently, for example, cities account for 70 percent of harmful greenhouse gas emissions.

The Nature Conservancy’s 2018 Nature in the Urban Century Report highlights the ecological impact that this sustained urban growth will have over these next two decades. The reach of expanding cities will threaten an estimated 290,000 km2 of habitat, or an area larger than the size of New Zealand. And cities are in increasingly close proximity to protected lands, with 40 percent of strictly protected areas – zones where human access is strictly controlled in order to preserve biodiversity – projected to be within 50 km of an urban area by 2030. This growth will destroy natural habitats that store an estimated 4.35 billion metric tons of C02, or the equivalent of C02 emissions from 931 million cars on the road for one year. There are economic as well as environmental costs associated with unfettered urban growth, with the UN Habitat estimating that, in the U.S. alone, the cost of sprawl stands at approximately $400 billion a year due to higher costs associated with providing infrastructure, public services, and transport.

The Promise of Sustainability 

in Urban Settings

But this does not have to be the future. With thoughtful, inclusive policies and sustainably-minded urban planning, we can build cities that are not only net-zero in their carbon emissions, but that work to protect the environment, promote biodiversity, and cultivate a sustainable and equitable quality of life for all.

Somewhat paradoxically, the key lies in a city’s very size, with greater potential for sustainability found in a grander scale. In contrast to rural areas where there is less density in population and the built environment, the compact nature of cities allows them to more efficiently manage and even reduce natural resource use and waste. Areas in which large cities can be particularly adept at utilizing economies of scale include public transportation, water treatment, and waste recycling. For sustainability efforts to make real change, however, sustainability must be integrated into all planning and policy decisions. It should become woven into the very fabric of the city, both in its built environment and public spaces and in the psyche of its denizens.

There are several variables widely accepted to be necessary (but not sufficient) for sustainability. The city should be compact, favoring density over sprawl. It should promote mixed-use development, advocating for integrated residential, commercial, and cultural infrastructure rather than strict single-use zoning. It must efficiently manage resources and waste, utilizing circular closed-loop systems and passive design as opposed to linear systems and non-renewable resources. And it should invest in rail and other modes of public transportation, instead of fueling the automobile hegemony. While these strategies are some of the most cost-effective methods for reducing a city’s ecological footprint, they are only the start to building long-lasting sustainability.

When a city is informed by the natural landscape and meets human needs while maintaining a respectful and harmonious relationship with the natural world, true sustainability, in all its forms – environmental, economic, social – can arise. This means allowing green space like parks, gardens, green walls, urban farms, waterways and green buffer to permeate the cityscape. Urban green spaces provide a range of critical benefits, including ecosystem services like supplying raw materials for food, water, and medicine and regulating services that include air quality improvement and carbon sequestration and storage. They offer ecosystem supporting services by providing habitats for organisms and maintaining biodiversity, as well as cultural services like recreation and aesthetic appreciation. Meanwhile, bringing food production into urban areas allows the city to become more self-sufficient and to reduce its ecological footprint. Research has shown that vegetation also helps to mitigate the Urban Heat Island Effect (UHI) that adversely affects weather patterns, air quality, and energy costs. Plants provide shade and evapotranspiration that lowers surface and air temperatures, thereby improving thermal conditions and increasing energy savings. 

Promoting Democracy and

Social Justice in Human Settlements

Designing with the climate in mind requires a holistic, multi-disciplinary framework and a debate-and-decide approach that gives space for multiple and diverse stakeholders to shape and contribute to the collective vision of a sustainable tomorrow. Decision-making at all levels must integrate social, economic, and environmental considerations in a process that is democratic, inclusive, and empowering. Historically, low-income and ethnic/racial minority populations have not only been left out of such discussions, but must often live in areas where toxic sites such as landfills and factories are located with negative impacts on their health and social/economic well-being. Residents of rural communities in the United States, for example, are usually poorer and less educated than their urban counterparts, and they suffer from exposure to pesticides, inadequate water systems, and air pollution from crop harvesting and livestock waste, among other environmental threats. Much of the projected urban growth in the developing world will take place in informal settlements where there is often little environmental regulation. These at-risk populations have inadequate access to clean water and waste management systems and are subject to the social ills of marginalization and inequality. Thus, it is important to develop and enforce urban planning strategies and environmental policies that protect all residents of a community, not merely the privileged or dominant segments.



Olivia Edwards, EFI Research Fellow


Case Study: Transportation in Bogotá, Colombia.