The Bartlett


Sustainable and healthy cities

26 April 2021

Waste management in Kisumu, Kenya - blurred

At a glance

  • Cities are complex systems and climate actions are frequently fragmented, too slow and at too small a scale.
  • Cities are not moving fast enough to reduce their greenhouse gas emissions and address the associated health challenges.
  • Effective city action to move rapidly to net zero carbon will not only reduce the future impacts of climate change but will also provide substantial and more immediate ‘co-benefits’ for health.
  • A systems approach that understands a city as a complex interconnected system, informed by behavioural and implementation science and other forms of knowledge and evidence outside academia, is required to help enable rapid and large-scale change.

What is the problem?

Around the world, cities have not yet been successful in meeting key environmental and associated health challenges [1]. Climate actions have fallen far short of what is required: the 2015 Paris meeting of the UN Framework Convention on Climate Change underlined the importance of action to meet the demanding target of limiting global heating to 1.5°C. Greenhouse gas (GHG) emissions are simply not falling fast enough to meet this target. At the same time, many urban populations suffer, for example, from poor air quality and are vulnerable to extreme weather events. 

What are the key characteristics of the problem?

Action to limit climate change is now recognised as a priority for human societies everywhere. What is often not realised, however, is that there are substantial possible benefits from climate action, not just from reducing future impacts from climate change, but also for human health in moving to a low-carbon economy. There is, for example, huge potential in terms of reducing air pollution, which contributes to millions of premature deaths worldwide each year. Yet cities, climate and health are still largely treated separately and the interactions between them not sufficiently analysed. 

Decisions on urban developments will play a vital role in determining the future of human health and the environment. Population growth is now primarily urban and towns and cities are responsible for a growing share of the world economy and GHG emissions. But opportunities to benefit from policy and infrastructure investments are often overlooked [2]. 

What is the solution?

City actions need to enable change at a pace, scale and degree of integration necessary to address pressing global challenges to the environment and human health. This ambitious aim requires fundamental changes to cities: energy systems need to be decarbonised, buildings need to dramatically reduce their energy demand, transport systems require radical overhaul etc. This will not happen without fundamental changes to the social and political structures, processes and values that underpin individual and collective behaviour.

What is stopping the solution being implemented?

Cities are complex systems. People living in them have diverse priorities and they and the systems that support them (food, transport, buildings, waste management etc.) are interdependent and affect each other in many different ways. Changes tend to be gradual and slow. Too often, the impact of attempts to improve the urban environment and public health is limited because they lose sight of the big picture of change that is required, and as a result are fragmented or too focused on one small area. Big changes often disrupt settled patterns of living and incur some initial cost and unpopularity, which makes them difficult to implement despite their eventual substantial overall benefits.

Waste management in Kisumu, Kenya
Figure 1: In Kisumu, Kenya, participatory approaches are being used to guide new ambitious plans for the sustainable management of waste with benefits for GHG emission reductions and health.

How can these barriers be removed?

Climate action at city level requires clarification of the issues that need to be addressed, by investigating their causes and co-developing integrated solutions with the participation of citizens, focussing on interconnected systems, people’s behaviour and implementation. For example, UK homes are not fit for the future [3]. GHG emissions from UK housing remain stubbornly high and the pace and scale of action to adapt the housing stock for higher summer temperatures, flooding and water scarcity is inadequate. Government action must address retrofitting existing homes alongside building new homes. Performance gaps relating to energy use and indoor environmental quality must be tackled alongside ensuring that the current skills gap is rectified. At the same time there is, for example, a lack of integration with, and development of, sustainable transport infrastructure to encourage active travel (walking and cycling) and the use of public transport and electric vehicles. Current policies are not driving the required changes. Given the complexities involved, innovative policy analysis, design and implementation is needed. Modelling of the interconnected systems involved will help policymakers understand the forces that have influenced sustainability and health outcomes in cities in the past and that will need to be changed for positive outcomes in the future.

Sustainable transport in Rennes, France.

Figure 2: Sustainable transport in Rennes, France. Image credit: Jeremias Gonzalez 


Transforming cities so that they better serve the health and well-being of their communities and help sustain the natural environment, including through reducing climate change, is not easy. Policymakers, planners and the public will need new skills and knowledge, as well as the motivation and opportunities to make these changes in their lives and work. The changes will need to be rooted in an understanding of people’s priorities and decision-making processes and draw deeply on the science of behaviour and behaviour change. The net-zero city will be easier to live in and move around than many of today’s congested and polluted urban areas, keeping us comfortable with less energy use and wasting far fewer resources. But in getting there many of our basic assumptions about cities will need to be re-thought.

Key references for further information

[1] Crane M, Lloyd S, Haines A, Ding D, Hutchinson E, Belesova K, Davies M, Osrin D, Zimmermann, N, Capon A, Wilkinson P, Turcu C, (2021) Transforming cities for sustainability: A health perspective. Environment International,147, Article 106366. 10.1016/j.envint.2020.106366

[2] These opportunities are the focus of the Complex Urban Systems for Sustainability and Health (CUSSH) project (https://www.ucl.ac.uk/complex-urban-systems/).

[3] UK housing: Fit for the future?, (2019) Committee on Climate Change