6 minute read
The benefits of tree cover
Dr Matthew Ling
Dr Matthew Ling is the Project Lead for the Cambridge Canopy Project at Cambridge City Council
Lockdown restrictions resulting from the COVID-19 pandemic forced many of us to stay within the confines of our homes for months. Some of us have houses with private gardens, some with shared gardens, and some with balconies. Others, however, have no access to outside spaces connected to their properties at all. For those of us with limited or no access to the outdoors, public open spaces are an essential asset, providing the opportunity to escape the four walls within which they reside. Increasingly, this was realised during lockdown, with greater numbers of people using parks and greens, and interacting with green spaces in new ways. Such reliance on public open spaces places a lens in front of their quality, as not all spaces are made equal.
The multifaceted benefits we receive from being exposed to natural spaces and features continues to be studied and better understood. But the links to increased physical and mental wellbeing are clear. However, the current crisis has highlighted that barriers exist preventing some parts of society from benefitting equally from those assets.
In Cambridge, UK, there are numerous parks and other green open spaces for the public to access and enjoy. Modelling of visitor numbers, based on data from the ‘Monitor of Engagement with the Natural Environment’ (MENE) survey, shows that Cambridge’s green spaces receive 2.7 million visits annually. The total annual benefits received from these visits is valued at £67 million; – £36 million of which is realised in mental health benefits(1) – underlining the crucial role they provide.
However, even in Cambridge, there is disparity in the level of access residents have to green spaces and features. Using tree canopy cover as a metric, it is possible to observe these differences. Average tree canopy cover across the city is 17%, varying across wards depending on the age of the respective part of the city, and other pressures such as infrastructure. The greatest canopy cover is found in Newnham (22.6%), and the lowest in the Cherry Hinton (12.8%) and Abbey (12.9%) wards (2).
Distribution of Cambridge’s urban forest by ownership type (N.B. Tree canopies not to scale)
© Crown Copyright and database right 2015. Ordnance Survey Licence No. 100019730.
This unequal distribution of trees and green spaces across the city will impact residents in different ways. Citizens residing in more affluent areas with private gardens are likely to be less dependent on public open spaces or tree-lined streets when compared to residents in more deprived areas with limited or no access to gardens or outside space. In areas of deprivation, residents will not benefit from the stress relief, alleviation of depression, nor reduction in crime that trees provide. Very often, it is those in the most deprived areas that benefit from these provisions the most.(3)
Tree canopy cover in Cambridge by ward; overlaid with ownership type
© Crown Copyright and database right 2015. Ordnance Survey Licence No. 100019730. exist preventing some parts of society benefitting equally from these assets.
Yet it is the most affluent parts of Cambridge that are, in fact, most well catered for in terms of tree canopy cover. Every neighbourhood in Newnham ward is classified as being amongst the 20% least deprived in the country. In contrast, using Abbey ward as an indicative example, of its six neighbourhoods, two are in the 20% most deprived in the country, and one in each of the 30%, 40% and 50% most deprived categories.(4)
Research has confirmed this, identifying a positive correlation between tree canopy cover and deprivation in Cambridge, and this pattern has been observed across the UK.(5) The 2019 MENE survey found that the two most deprived sections of society, according to the Index of Multiple Deprivation, had the greatest disagreement with the following statement: ‘Local greenspaces are within easy walking distance.’(6)
This disparity in access to green spaces can be referred to as ‘tree inequity’(7) or the ‘nature gap’(8), and to address it, we must strive for landscape justice.(9) The Cambridge Canopy Project – a Cambridge City Council initiative under the Interreg 2 Seas programme’s ‘Nature Smart Cities’ project – seeks to do exactly that. By analysing existing tree canopy cover against areas of deprivation, it is possible to prioritise areas of greatest need for tree planting and community engagement. By focusing on these priority areas, we aim to increase exposure and access to trees and canopy cover, and the wealth of benefits that they provide, specifically for those that need it the most.
Cambridge is the UK’s most unequal city – income in the city is more unevenly distributed among its residents than in any other city measured, including London – and the third least affordable.(10) In terms of figures, the Centre for Cities think tank states that the top 6% of earners in the city receive 19% of the total income, in contrast to the bottom 20%, who take home only 2% of the total.(11)
Factors including affluence and quality of local environment act in combination to impact upon quality of life and, indeed, life expectancy. Data presented by the Consumer Data Research Centre, showing estimated life expectancies for children born between 2009 and 2013, reveal an almost 10-year disparity between the most and least affluent parts of the city. Newnham ward has an average life expectancy of 87.3 years, whereas in King’s Hedges it is 78.2 years (12). Tree planting in the areas of greatest need could help to redress the balance. Researchers in Philadelphia found that 403 premature deaths could be avoided annually if tree canopy cover in areas of lower socioeconomic status were to be increased to a minimum of 30%.(13)
Medium density residential housing, Romsey ward, Cambridge. Average tree canopy cover in this land use type across the city is c. 20%.
2013 aerial photography © Bluesky International Limited
Despite Cambridge’s unequal and unaffordable nature, it continues to grow. From 2014-2018, it was the fastest growing city in the UK in terms of year-on-year employment growth.(14) This looks set to continue, with the share of jobs in occupations likely to shrink calculated as 12.9%, with only Oxford scoring lower (12.8%).(15) With jobs, come houses; alongside Telford, between 2015 and 2016, Cambridge topped the figures for housing stock growth, expanding by 1.7%.(16)
Relative tree canopy cover (%) by ward in Cambridge.
Cambridge City Council, 2016
As cities continue to grow and densify, and new threats like zoonotic diseases emerge, it is increasingly important to consider the quality of our urban environments to deliver on multiple fronts. Specifically, we must consider the climate and ecological emergencies, and seek to benefit the physical and mental wellbeing of city users. The coronavirus pandemic has placed greater focus on this, with people realising that there is an alternative to the ‘business as usual’ approach of cities globally. The way in which this will manifest itself is not yet clear, but people have placed much more importance and value on accessing green spaces, having clean air, being able to hear birds singing instead of engines idling, and feeling a greater sense of community that these factors encourage. And this must all be managed in a way that delivers across all parts of the socioeconomic spectrum.
The Cambridge Canopy Project is part of the Interreg 2 Seas 2014-2020 Programme’s ‘Nature Smart Cities across the 2 Seas’ project, which is co-funded by the European Regional development Fund under subsidy contract No. 2S05-048.
References
1 Vivid Economics. (Undated, unpublished).
2 https://www.cambridge.gov.uk/tree-data
3 https://assets.publishing.service.gov.uk/ government/uploads/system/uploads/ attachment_data/file/904439/Improving_access_to_ greenspace_2020_review.pdf
4 http://dclgapps.communities.gov.uk/imd/iod_index. html
5 https://www.cambridge.gov.uk/media/8131/theimportance-of-neighbourhood-trees-for-quality-of-life. pdf
6 https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/828552/Monitor_Engagement_Natural_Environment_2018_2019_v2.pdf
7 https://www.csmonitor.com/Commentary/themonitors-view/2020/0727/A-protest-against-oneracial-inequity-tree-deserts
8 https://www.americanprogress.org/issues/green/ reports/2020/07/21/487787/the-nature-gap/
9 https://www.communitylandscotland.org.uk/wpcontent/uploads/2017/09/Landscape-justice.pdf
10 https://www.centreforcities.org/wp-content/uploads/2018/01/18-01-12-Final-Full-Cities-Outlook-2018.pdf
11 https://www.theguardian.com/uk-news/2020/ jan/12/beyond-cambridge-spires-most-unequal-citytackles-poverty
12 https://maps.cdrc.ac.uk/#/metrics/lifeexpectancy/ default/BTTTFFT/14/0.1182/52.2055/
13 ttps://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(20)30058-9/fulltext
14 https://www.equalitytrust.org.uk/resource/choicelook-inequality-cambridge; https://irwinmitchell.turtl.co/story/uk-powerhousejanuary-2020
15 https://www.centreforcities.org/wp-content/uploads/2018/01/18-01-12-Final-Full-Cities-Outlook-2018.pdf
16 https://www.centreforcities.org/wp-content/uploads/2018/01/18-01-12-Final-Full-Cities-Outlook-2018.pdf
