It is widely acknowledged that trees and green spaces have a big role to play in addressing climate change. A lot has been written about how large-scale tree planting is essential for reducing atmospheric carbon dioxide levels, and the UK government has committed to planting ten million rural and 130,000 urban trees by 2022 as part of the plan to reach net zero carbon emissions by 2050. In addition, we need to adapt the ways we live to deal with the impacts of climate change which have already been set in motion. Trees and green spaces can help by moderating extreme temperature and reducing the risk of flooding.
Heatwaves, like that of summer 2018, are now 30 times more likely to happen than if there had been no man-made climate change through emission of greenhouse gases. Urban trees and green spaces can help regulate air temperatures, therefore helping communities deal with periods of extreme heat. This is self-explanatory in many ways – we all can appreciate the shade provided by a tree on a hot day. But trees also cool down the environment through their evapotranspiration process, which intercepts radiation energy from the sun before it reaches the ground. Importantly, this is only really effective when the trees are healthy and flourishing – so they must be well cared for and planted in a thoughtful and well-designed scheme, not just plonked in at the end as an afterthought and forgotten about.
The cooling effect of trees is particularly important in towns and cities, which warm up more than the surrounding countryside (heat is stored for longer in concrete and added to by artificial heating/cooling of buildings and from vehicle exhausts). Greenery around buildings (trees and green roofs and walls) can also provide insulation to buildings, thereby saving heating and air conditioning costs.
Many cities are planning to use greenery in their urban areas as a cooling mechanism and to create shaded areas. For example, in the Zuidas business district of Amsterdam, up to 25,000m2 of insulating green roofs will be created by the end of 2020 as part of the “Zuidas Vision”, designed to keep the buildings warm in winter and cool in summer as well as providing outside space for employees, storm water storage and many other benefits. Projects like this will help the 270-hectare district to continue to provide a suitable and pleasant working environment, which is crucial to its long-term success as a business and financial centre.
Green space can also reduce the risk of flooding, particularly from very heavy rainfall, because it allows the water to soak into the ground rather than running across the surface. The UK Climate Change Risk Assessment shows that by the 2050s the UK population living in areas of flood risk will increase from 1.8 million currently to 2.6 million.
When Beam Parklands in London was revamped in the late 2000s, the floodplain of the River Beam was restored and it can now store 45,300m3 of water (as well as providing high-quality public green spaces in one of the most deprived areas of the city). This means that nearby homes are much less likely to flood as the water has somewhere else to go, and as a result, this has led to investment in the area.
Our green spaces and trees have the potential to play a huge role in the future of our communities. They must be protected and invested in to maximise the benefits they provide. In the post Covid-19 recovery, the government’s “Build, Build, Build” campaign must not just result in a frenzy of building poorly planned new homes. As we can all appreciate now more than ever, homes must be comfortable and safe to live in, both now and for at least 100 years in the future. Setting all new and existing development in the context of a high-quality, green environment that is designed with the future climate in mind is an essential measure that will determine the resilience of a place, something that will be crucial to being able to secure future insurance and investment.
Jessica Fieth is projects and policy manager at the Town and Country Planning Association.