CONTEXT 180 : JUNE 2024 21 WHERE HERITAGE AND NATURE MEET or in public parks that developed from earlier landscape parks, or they may have been retained as street trees in areas later developed for housing. The ancient sweet chestnuts in Greenwich Park, survivors of avenues created for Charles II in the 1660s, are one famous example. These trees, collectively part of our living, green heritage, are in some cases as old or older than the historic buildings that surround them. They are also as irreplaceable. Historic trees should be considered in the context of their cultural and design interest and the many environmental benefits that they provide. Trees planted in 19th-century parks and green spaces were valued for their aesthetic contribution and for the improvements they brought to public health. They still deliver all of this, as do the many trees planted since. But today, we also understand their wider contribution to environmental quality and management. Helping to filter particulates, trees make an important contribution to air quality. They provide shade, helping reduce the impact of high temperatures and urban-heat-island effects. They take up and lock in carbon for the duration of their lifespan. They help reduce flooding by improving soil structures below the hard surfaces of the urban environment. They benefit urban nature, providing food and shelter. They have cultural and heritage value, and they support our physical and mental wellbeing. Together, these benefits can be considered as part of the ecosystem services that trees provide. A study by Forest Research and Defra estimated that the value of trees outside of woodlands, both urban and rural, for the provision of ecosystem services to be approximately £3.8 billion². In the context of rising average and peak temperatures, trees are key, alongside other green infrastructure, to mitigating overheating in urban areas. A recent study found that botanic gardens and parks provided a cooling benefit of nearly 5º C to surrounding areas. Street trees were found to provide nearly 4º C of cooling³. A recent Environmental Audit Committee inquiry (http://bc-url.com/ctx80a) into heat resilience and sustainable cooling recognised the contribution that trees make to passive cooling as part of nature-based solutions to climate change. The committee recommends in its report that the government adopts a range of measures to protect and expand green spaces, particularly in urban areas, and that these must prioritise areas that are disadvantaged and currently under-served by green space. The greatest benefits are generally provided by mature, large-canopied trees. We need to look after the trees we have, which provide such a wide and important range of benefits already. We need to consider succession: the trees that will take the place of existing trees when they reach the end of their lives. And we need to A yew in Church Cemetery, Nottingham (Photo: Erika Diaz Petersen) A former parkland oak in Mapperley Park Conservation Area, Nottingham (Photo: Erika Diaz Petersen) ² www.forestresearch. gov.uk/research/ valuing-non-woodlandtrees/ ³ www.sciencedirect. com/science/article/pii/ S2666675824000262
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