Cities must align climate and health actions to tackle urban challenges

Cities are at the forefront of addressing climate impacts and play a key role in cutting the greenhouse gas emissions that cause climate change. Previous evidence from the Pathfinder Initiative shows that climate action can deliver major health benefits, and that cities are uniquely positioned to drive the transition towards a healthier, more sustainable future.

A new study by researchers from the Pathfinder Initiative at the London School of Hygiene & Tropical Medicine (LSHTM) builds on this evidence, highlighting that more ambitious cross-sectoral urban policies are needed to achieve climate targets and large-scale health benefits. The study looks at published evidence on the effects of implemented city-level climate mitigation and adaptation actions and their impacts on health, identifying implementation gaps and measures that can be taken to accelerate effective action.  

The researchers carried out an umbrella review (a review of systematic reviews) to bring together data and insights from global evidence on the climate and health effects of implemented city-level actions. Forty nine reviews published between 2009 and 2024, summarising evidence from 1,900 individual studies, were included in the review, which is the first comprehensive analysis of its kind focusing on climate and health action in cities. 

Most of the reviews included in the analysis focused on actions in the transport and buildings sectors, as well as changes to urban form (how a city is designed or laid out). Evidence showed that health benefits resulted mainly from active transport, such as walking and cycling, reductions in air pollution and improved housing. However, the analysis found that health co-benefits were inconsistently quantified, which is important as it has been shown that it is easier to motivate people and policymakers to act when they understand the substantial health co-benefits of many actions. The review also found that in studies where health impacts were the primary focus, environmental impacts were not directly assessed, and in studies focusing on environmental impacts, health impacts were not explicitly reported, suggesting missed opportunities to capture the full range and scale of benefits. 

In the transport sector, the most frequently reported interventions were traffic control policies, including traffic restrictions and congestion charging zones, and improvements in public transport infrastructure. Good urban design was a key factor in influencing behaviour changes towards increased use of public transport and active travel, and away from private vehicle use. Interventions such as speed restrictions and traffic lane separation were also shown to prevent potential increases in road injuries from active travel. Switching to electric vehicles was shown to reduce  CO₂ emissions, while measures to cut emissions, such as low-emission zones, were linked to reductions in air pollution. However, switching from petrol to natural gas did not reduce levels of harmful air pollution. 

In the buildings sector, most evidence related to home energy efficiency improvements, which were linked to health benefits largely from improvements in thermal comfort, as well as improvements to social conditions. Two reviews included in the analysis highlighted that implementing such measures without ensuring adequate ventilation could increase indoor air pollution, showing the need to consider and mitigate potential trade-offs when implementing interventions. Evidence showed that green roofs and walls resulted in environmental benefits, including reduced heat exposure, energy use, and air pollution, with implications for health. 

There was limited evidence in the waste and food sectors, with no reviews on implemented actions relating to sustainable diets. All food-related reviews included in the analysis focused on sustainable urban agriculture. These studies showed that increased production and consumption of locally sourced food can reduce emissions and energy use and enhance biodiversity, but would only significantly benefit health if accompanied by dietary changes. 

Urban planning, street redesign and improved access to recreational facilities could improve liveability and were associated with increased physical activity and fewer road traffic injuries. Increased access to green space was shown to improve social connectedness and mental health. Urban greening was also linked to reduced energy use and environmental benefits. 

The researchers identified several barriers to policy implementation, including a failure to consider relevant costs and benefits systematically. For example, the authors say that travel policy assessments should encompass the evaluation of public health benefits and greenhouse gas emissions reductions rather than focusing on a single metric such as travel time. The researchers highlight a lack of robustly designed impact evaluations, with most studies assessing the implementation of a technological solution rather than the implementation of a policy that aims to support the uptake of a solution. They also note that considering trade-offs is essential to prevent negative impacts and subsequent pushback from those affected by a policy. 

Dr Emma Hutchinson, Assistant Professor at LSHTM and lead author of the review, said: ‘Our review provides further evidence that many urban climate actions have substantial health benefits, including through increased physical activity, cleaner air, and reduced heat exposure. It also highlights the need for more ambitious, cross-sectoral, city-wide policies to maximise climate and health benefits, as well as rigorous evaluation of implemented actions to understand what works and why.’

Dr Hugh Sharma Waddington, Associate Professor at LSHTM and part of the Pathfinder Initiative team, said: ‘Cities need stronger governance systems working across different sectors and scales to embed health and environment into the planning, implementation and evaluation of urban policies. There is a need for more focus in research and policy on how interventions are implemented, including barriers, enablers and context-specific outcomes, to determine the systems changes needed to scale up effective action.’