Growing a resilient urban forest in Cambridge

Summary

The project strategically uses trees as a form of nature-based green infrastructure to build climate resilience, primarily by combating the urban heat island effect and reducing surface water flood risk. Recognising that the majority of land is privately owned, the project’s core strategy relies on engaging residents to plant and care for trees in their own gardens, complementing the council’s efforts on public land.

Introduction

The Cambridge Canopy Project – part of the Interreg 2 Seas ‘Nature Smart Cities’ project – seeks to grow Cambridge’s urban forest, increasing tree canopy cover from 17% to 19% by the 2050s. The project uses trees as a form of green infrastructure to make the city more climate-resilient for the future, helping to combat the urban heat island effect and lowering the risk of flooding. By utilising a nature-based solution like this, the Cambridge Canopy Project is helping the city adapt to, and mitigate against, the likely impacts that will be brought about under future climate change scenarios.

Key Messages

• Nature-based solutions in practice: The project is a clear example of using green infrastructure – the urban forest – to adapt to and mitigate key urban climate challenges like extreme heat and flooding.
• Engaging residents is crucial: With 77% of the city’s land privately owned, the council cannot achieve its canopy target alone. Empowering residents to plant trees in their gardens is the central pillar of the project’s strategy.
• Beyond planting: Protection and diversification: A successful urban forest strategy involves more than just planting new trees. The project also focuses on reducing the unnecessary removal of existing trees and encouraging greater species diversification to build long-term resilience.
• Multiple co-benefits: The project delivers benefits far beyond climate adaptation, including storing over 88,000 tonnes of carbon, removing 64 tonnes of air pollutants annually, and contributing positively to residents’ physical and mental health.

A key insight driving the project is that the greatest opportunity for increasing canopy cover lies in private hands. With residential gardens making up the single largest land use in Cambridge, resident action is essential to the project’s success.

Three priority challenges addressed by the project

The project’s design directly responds to the practical challenges of greening a built-up urban environment.

1. The challenge of space constraint

Cambridge is a relatively small and compact city, which limits the potential for large-scale tree planting on public land. This creates a significant challenge of scale.

• The problem: The council identified 2,000 locations on its own land for new trees. However, modelling showed that 16,000 new trees are needed to meet the 2% canopy increase target. Public planting alone would fall short by 14,000 trees.
• The solution: The project pivots to focus on the city’s largest land resource: its 40,000+ residential gardens. Through free tree giveaways and awareness campaigns, the project taps into this distributed network of private spaces to achieve a city-wide goal that would be impossible on public land alone.

2. The challenge of a “Leaky Bucket”

Simply planting new trees is an ineffective delivery model if mature, healthy trees are simultaneously being lost elsewhere in the city. This is like trying to fill a leaky bucket.

• The problem: The project recognised that its canopy targets could be undermined by the “gradual diffusion” of canopy cover over time due to the unnecessary removal of existing trees. Losing a large, mature tree takes decades to replace in terms of canopy benefit.
• The solution: The project’s strategy is twofold: plant new trees and protect existing ones. By running awareness campaigns that champion the virtues and benefits of trees, the project aims to catalyse residents not only to plant new trees but also to value and care for the ones they already have, thereby plugging the leak.

3. The challenge of a non-resilient forest

A narrow vision for an urban forest might focus only on the quantity of trees, not their collective strength. An urban forest with low species diversity is vulnerable to being wiped out by new pests and diseases, a risk magnified by climate change.

• The problem: The long-term success of the urban forest depends on its resilience. A lack of species diversity creates a “brittle” system that is not well-adapted to future shocks.
• The solution: The project’s scope extends beyond simple planting targets to include the need for a more resilient urban forest by encouraging “greater diversification of species to be planted”. This ensures that the new trees being planted contribute to a more robust and future-proof city-wide ecosystem.

Lessons Learned

• Long-term awareness is a vital investment: The project identified that raising public awareness is essential for the urban forest’s long-term health and protection. This is not a one-off campaign but a continuous process needed to ensure trees are “understood, appreciated, valued, and protected into the future”.
• Plan for aftercare: Young trees are extremely vulnerable to drought. The project learned that budgeting and planning for watering newly planted trees is critically important for their successful establishment and long-term survival.

Suggested Citation

Cambridge City Council (2021) Cambridge City Council: the Cambridge Canopy Project – building climate resilience for the future. Available at: https://www.local.gov.uk/case-studies/cambridge-city-council-cambridge-canopy-project-building-climate-resilience-future (Accessed: 4 September 2025).

Contact

matthew.ling@cambridge.gov.uk

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