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Policy Paper Greening the concrete jungle The importance of urban trees and woods February 2010

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Page 1: Greening the concrete jungle - Woodland Trust · Greening the concrete jungle The importance of urban trees and woods February 2010 . ... Economics Foundation, London, p.13. ... Ultraviolet

Policy Paper

Greening the concrete jungleThe importance of urban trees and woodsFebruary 2010

Policy Paper

Greening the concrete jungleThe importance of urban trees and woodsFebruary 2010

Page 2: Greening the concrete jungle - Woodland Trust · Greening the concrete jungle The importance of urban trees and woods February 2010 . ... Economics Foundation, London, p.13. ... Ultraviolet

GREENING THE CONCRETE JUNGLE

Policy briefJune 2010

More than 80 per cent of us live in urban areas,and many more work or spend a substantial partof our lives in and around towns and cities. They

are important for us socially and culturally, theyare the places where we live and work, raisefamilies, socialise and relax, from which we drawidentity and pride. The quality of urban areas is ofgreat importance.

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Good architecture and design are clearlyessential, but of equal importance is the quality ofthe green space. Public parks and gardens, thelandscaping around buildings, street trees andhighway verges, the wilder corners along riverbanks and canals, on railway sidings and industrialsites, and our own gardens.

Trees are often the dominant features of greenspace; their stature and beauty make them thedefining elements of urban spaces. They castshade in the heat of summer, provide shelterfrom the rain and wind, help to keep the air cleanand breathable, support wildlife, and add value tothe culture and economy of our towns and cities.

Trees and woods are vital to health andwellbeing. There is a strong relationship betweenthe quality of urban green space and people’shealth and wellbeing1, 2, 3.

1, 2, 3 Sadler, J.P., Bates, A.J. & Hale, J. (in press) Bringing cities alive:the importance of urban greenspaces for people and biodiversity.Urban Ecology (ed K. J. Gaston). CUP Maas, J., Verheij, R.A., Groenewegen, P.P., de Vries, S. &Spreeuwenberg, P. (2006) Greenspace, urbanity and health: howstrong is the relation? Journal of Epidemiological Community Health,60, 587-592.Maas, J., Verheij, R. A., Spreeuwenberg, P. & Groenewegen, P. P.

(2008). Physical activity as a possible mechanism behind therelationship between greenspace and health: a multilevel analysis.BMC Public Health, 8, 206.

Increasing tree cover mitigates some of theeffects of a warming climate, reduces the impactsof poor air quality, and increases theopportunities for people to adopt a healthylifestyle.

Increasing tree cover in urban areas can helpmitigate the ‘urban heat island effect’. Thisoccurs as the buildings, concrete and otherhard surfaces such as roads act as giant storageheaters, absorbing heat during the day andreleasing it at night. The resultant effects canbe dramatic; on some days there is a differenceof as much as 10oC between central Londonand its surrounding suburbs4. Projections forour changing climate suggest this problem willget markedly worse.

Higher temperatures increase ground levelozone exacerbating the symptoms of chronicrespiratory conditions. In addition prolongedhigh temperature can bring on cardiovascularor respiratory failure or dehydration,particularly amongst the elderly, very young orchronically ill5. In the 2003 summer heat waveover 2,000 people died in Britain alone andmore than 35,000 died across Europe as aresult of the heat.

Green space, and trees in particular, provideboth direct shade and reduce the temperaturethrough the cooling effect of evaporation fromthe soil and plant leaves. One mature treetranspires up to 450 litres of moisture a day –equivalent to five room-sized air conditionersleft on for 19 hours6.4 BBC web site, Urban Heat Islands. Available at:http://www.bbc.co.uk/weather/features/understanding/urban_heat_islands.shtml [accessed 9th June 2010]5 Shaoni Bhattacharya (2003) European heatwave caused 35,000 deaths,

, 10th October 2003, Available at:http://www.newscientist.com/article/dn4259-european-heatwave-caused-35000-deaths.html [accessed 9th June 2010]6 Nicholas-Lord, D. (2003) NewEconomics Foundation, London, p.13. Available at:http://www.urbanwildlife.org.uk/assets/userfiles/000074.pdf [accessed 9thJune 2010]

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Research at the University of Manchester usingcomputer modelling has shown how increasingurban green space can mitigate urban heatisland effect. Without any increase in greenspace, by 2050 the temperature in Manchesteris projected to rise by 3oC. However if theamount of green space increases by just 10 percent this could potentially eliminate the effectsof climate change on increasing surfacetemperatures. However, reducing tree coverby the same percentage could lead to anincrease of 8.2oC under some scenarios7.

Reducing air temperature is only part of thepicture. Radiant heat – direct sunlight – is oftenmore important in terms of people’s comfort,and carries a health risk when it results insunburn. Children’s skin is more sensitive toUV damage and the amount of sun exposureduring childhood is thought to increase the riskof developing skin cancer in adult life.  Shadingis particularly important in school grounds andwhere children play. Providing direct shadeusing trees in playgrounds reduces the risksfrom UV radiation8.

7 Handley, J and Carter, J (2006), Draft final report to the National Steering

Group, Centre for urban and regional ecology, University of Manchester.Available at:http://www.sed.manchester.ac.uk/research/cure/downloads/asccue_final_report_national_steering_group.pdf [accessed 9th June 2010]8 Heisler, G.M., Grant, R.H., 2000. Ultraviolet Radiation, Human Health,and the Urban Forest. , Newtown Square,PA, General Technical Report pp. 35.

Trees and woodland improve air quality9 byadsorbing pollutants such as sulphur dioxideand ozone, intercepting harmful particulatesfrom smoke, and dust and of course releaseoxygen through photosynthesis. This helps toalleviate the problems caused by chronicrespiratory disease.

Each year, 24,000 people in the UK dieprematurely from air pollution10. Research bythe British Lung Foundation suggests that onein every seven people in the UK is affected bylung disease, almost 8 million people11. The UKalso has one of the world’s highest rates ofchildhood asthma, with about 15 per cent ofchildren affected and a higher prevalence inlower socio economic groups in urban areas12.Columbia University researchers found asthmarates among children aged four and five fell bya quarter for every additional 343 trees persquare kilometre13.

Trees will have a proportionately greater effectin urban areas, where they are close to sourcesof pollution and nearer to people who mightbe affected. Street trees in particular, close tosources of pollution, can intercept particlesfrom traffic and other emissions14. It isimportant to remember that despite thesignificant benefits of trees on air quality, somepeople do suffer allergies to tree pollen,particularly in the early spring15.

9 Nowak, D., Crane, D. & Stevens, J. (2006) Air pollution removal byurban trees and shrubs in the United States,

, pp. 115-23.10 HM Government (1998). . HMSO, London11 British Lung Foundation. Facts about respiratory disease. Available at:http://www.lunguk.org/media-and-campaigning/media-centre/lung-stats-and-facts/factsaboutrespiratorydisease.htm [accessed 9th June 2010]12 Townshend, J., Hails, S. & McKean, M. (2007) Diagnosis of asthma inchildren, ; 335(7612), pp. 198-202.13 Lovasi, G., Quinn, J., Neckerman, K., Perzanowski, M. & Rundle, A.(2008) Children living in areas with more street trees have lowerprevalence of asthma.

(7), pp. 647-649.14 Impens, R.A. & Delcarte, E. (1979) Survey of urban trees inBrussels, Belgium. Journal of Arboriculture, 5, 169-176.15 Allergy clinic. Available at: http://www.allergyclinic.co.uk/pollens.htm[accessed 9th June 2010]

Photo Stephen McLaren

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Proximity of green space to people's homesincreases the likelihood of the residentschoosing walking over other forms oftransport16,17,18. With nearly a quarter of bothmen and women in the UK classed as obese,the Government is looking at the role of trees,woods and other green space in encouragingphysical activity.16,17,18 Humpel, Nancy, Neville Owen and Eva Leslie (20020.Environmental factors associates with adults’ participation in physicalactivity. . 22, 188-199.

Giles-Corti, Billie, Melissa H. Broomhall, Matthew Knuiman, CatherineCollins, Kate Douglas, Kevin Ng, Andrea Lange, and Robert J. Donovan(2005). Increasing walking: how important is distance to, attractiveness,and size of public open space.28 (2S2), 169-176. Giles-Corti, B. and Donovan, R. J. (2002). The relative influence ofindividual, social and physical environment determinants of physicalactivity, , 54 (12), 1793-1812.

Around two thirds of the trees in urban areasare in private and less accessible public grounds –gardens, school grounds, allotments and churchyards.Maintaining and increasing this contribution is vitaland provides opportunities for people to take actionto increase tree cover.

Green Streets is a joint Red Rose Forest andCommunity Forests North West project in partnershipwith Manchester City Council, Salford City Council,Trafford Council, the Forestry Commission, NorthWest Development Agency and Untied Utilities.

Green Streets uses tree planting and greening projectsto improve the quality of life for urban communities,fostering a sense of ownership and empowering themto change their neighbourhoods for the better.

Green Streets works at the heart of the communityto promote tree planting as a means of tackling arange of issues. The Green Streets Team has beenworking with local communities in Manchester andTrafford since 2001 and in Salford since 2003. Sincethen the project has been introduced to Merseysideand Teesside.

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Over a third of people are on incapacitybenefits because of mental health problems ormuscular or skeletal disorders – both of whichcan respond to tailored physical activityprogrammes. If just one per cent of people onincapacity benefit could be helped back into theworkplace through active lifestyles, it wouldsave the country £67 million a year19.

The Campaign for Greener Healthcare and theinitiative to establish an NHS Forest20 illustratea growing consensus amongst healthprofessionals of the importance of trees topeople's health and wellbeing. With plans toplant a tree for every one of the 1.3 millionNHS employees, the campaign endorses therole of trees in air quality, improved healthoutcomes and reducing negative environmentalimpact.

With 80 per cent of people living in urban are-as, but fewer than 10 per cent having access tolocal woodland within 500m of their home21 , itis vital that the Government sets targets fornew woodland that will meet the need nearwhere people live.

19 Department of Health press release, 13th August 2009, downloadedat:http://www.dh.gov.uk/en/News/Recentstories/DH_10425420 The Campaign for Greener Healthcare, downloaded at:http://www.greenerhealthcare.org/nhs-forest21 The Woodland Trust (2004) Available at:http://www.treeforall.org.uk/AboutTreeForAll/WhyTreeForAll/Science/spaceforpeople.htm [accessed 9th June 2010]

Greenstreets, Manchester

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There is evidence that trees not only providephysical benefits but can also be important tomental health.

Trees and woods can have a restorative andtherapeutic effect on the mind22. Studies havelooked at the beneficial effects of natural sur-roundings on children with Attention DeficitHyperactivity Disorder23. Trees have beenfound to enhance mood, improve self esteemand lower blood pressure. The quality of natu-ral features and trees in the city helps reducemental fatigue and stress24, and has importantbenefits for child development25.

Research in the Netherlands and Japanindicated that people were more likely to walkor cycle to work if the streets were lined withtrees and feel better and live longer as aresult26.

It is hoped that in coming years there will bean increasing emphasis towards long-termdisease prevention through adopting healthylifestyles. Around £110 billion is spent eachyear in the UK on healthcare, equal to 8.5 percent of all income. It has been estimated that ifevery household in England had good access toquality green space it could save around £2.122 Hartig, T., Evans G.W., Jamner L.D., Davis D.S., and Gärling T. (2003).Tracking restoration in natural and urban field settings.

23, 109-123.23 Taylor, AF et al (2001) ‘Coping with ADD, The Surprising Connectionto Green Play Setting’ , Vol. 33, January 2001,pp 54-7724 Ulrich, R.S., Simons, R.F., Losito, B.D., Fiorito, E., Miles, M.A. andZelson, M. (1991). Stress recovery during exposure to natural and urbanenvironments. 11: 201-23025 Kaplan, R. and Kaplan, S. (1989).

. Cambridge University Press, Cambridge26 Van den Berg, A.E., Koole S.L., and van der Wulp N.Y. (2003).Environmental preferences and restoration: (how) are they related?

23, 135-14627 Natural England (2009)

. Page 8. Available at;http://www.naturalengland.org.uk/Images/nhsmanifesto_tcm6-12022.pdf[accessed 18th May 2010]

An increase in hard surfaces in urban areas,unable to absorb rainfall, often means drains areoverwhelmed and water quickly collects on thesurface rushing down streets and over paving.Following the 2007 flooding, paving over ofgardens was identified as having a major impacton drainage of surface water in urban areas.

Around two-thirds of the 2007 flooding was aresult of surface water, with 3.8 million homes inEngland susceptible28, 29. The insurance cost ofthe 2007 floods was thought to have beenaround £3 billion30, but the Environment Agencyexpects the regular annual cost of damage toproperty alone to be in excess of £1 billion.When the cost of further disruption, damage toinfrastructure and loss of business is added thisincreases to £2.5 billion and could rise to £4billion by 203531.

Interception of rainfall by trees in urban areascan be critical in reducing the pressure on thedrainage system32 and lowering the risk ofsurface water flooding. Slowing the flowincreases the possibility of infiltration and theability of drains to take away excess water.Scientific modelling in Greater Manchestersuggests that increasing or decreasing theamount of tree cover affects surface water run-off - increasing tree cover in urban areas by 10per cent reduces surface water run-off by almost6 per cent33, 34.28, 29 Environment Agency (2009)

, downloaded 29th July 2009. Available at:http://publications.environment-agency.gov.uk/pdf/GEHO0609BQDS-E-E.pdf [accessed 9th June 2010]

, Cabinet Office. Available at:http://archive.cabinetoffice.gov.uk/pittreview/thepittreview/final_report.html [accessed 9th June 2010]30 Newratings, 24th June 2007, UK floods likely to cost £3bn ininsurance. Available at:http://www.newratings.com/en/main/company_headline.m?&id=1577047 [accessed 9th June 2010]31 Environment Agency, ‘New reports highlight GBP20Bn investmentover 25 years is needed to protect England from flooding’ downloaded29th July 2009 at: http://www.environment-agency.gov.uk/news/108705.aspx [accessed 9th June 2010]32 Gill, S (2009) ‘The Essential role of trees – adapting cities to climatechange by managing high temperatures and reducing pressure ondrainage systems’, in proceeding

19th November 2009

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The financial benefits of tree cover in watermanagement have been quantified for towns inCalifornia35. This suggests that broadleaved treesin urban areas in the UK are already playing animportant role in moderating run off andreducing expenditure on other forms of watermanagement, in addition to the other benefitstrees bring.

Many places have seen a decline in numbers ofolder trees with large spreading crowns,replaced with smaller, more manageablealternatives. These smaller crowned trees haveless capacity to intercept rain. A report forGovernment during 2008, ‘Trees in Towns II’challenged this trend highlighting the“undeniable” importance of mature and ancienttrees36.

Recent years have also seen a decline in thenumbers of trees planted in urban areas which,combined with a loss of trees planted during theVictorian era, should send a warning signal aboutthe future for urban tree cover37. Around twothirds of the trees in urban areas are in privateor less accessible public grounds – such asgardens, school grounds, allotments andchurchyards. Maintaining and increasing treecover is vital.

Evidence from ‘Trees in Towns II’38 shows alack of sufficient investment and planning fromsome local authorities in maintaining andexpanding the tree cover. The reporthighlights the need for specialist staff and aclear tree strategy in order to take fulladvantage of the many benefits trees can bringto people living in urban areas.35 Xiao, Q and McPherson, E.G. (2002) ‘Rainfall interception by SantaMonica’s municipal urban forest, 6, pp 291-30236 Trees in Towns II, a report for Department of Communities and LocalGovernment. Available at:http://www.communities.gov.uk/publications/planningandbuilding/treesintownsii [accesses 9th June 2010]37 Britt, C. and Johnston, M. (2008)

, a report forthe Department for Communities and Local Government. Available at:http://www.communities.gov.uk/documents/planningandbuilding/pdf/treesintownsii.pdf [accessed 9th June 2010]38 Britt, C. and Johnston, M. (2008) , DCLG,downloaded at:http://www.communities.gov.uk/documents/planningandbuilding/pdf/treesintownsii.pdf [accessed 9th June 2010]

The world is losing biodiversity at an acceleratingrate, due largely to a combination of habitat lossand climate change. Aside from any intrinsic value,biodiversity is important for helping to maintain thestability of natural systems and in the supply of arange of ‘ecosystem services’. These include floodattenuation, pollination of crop plants, soilconservation and climate regulation. Native woodsand trees in urban areas, including gardens can bevital to a wide range of wildlife, providing food,shelter and places to breed.

As well as remnant pockets of woodland and morenatural space, urban areas have parks, privategardens and planted shrubberies which cansupport a large number of invertebrate and birdspecies, especially in the suburbs. These includeuncommon species, including for example juniperfauna which has adapted to garden junipers39.

An important characteristic of urban areas is theirmosaic of habitats. Industrial sites such as demoli-tion sites, disused railway lands or unused industrialland can be rich in species. Later stages of succes-sion through to woodland contain many uncom-mon invertebrates with flies, bees and wasps,including some parasitic species and sawflies.

Trees in urban areas support a wealth of wildlife,from the  common, such as robins, blackbirds andtits, to bats and bees, many of which are in de-cline.  Native tree species are particularly impor-tant in supporting wildlife – native willows forinstance may support over 450 species, many ofwhich are insects that provide food for birds40.

The Convention on Biological Diversity is aninternational agreement to which the UK issignatory. The UK Biodiversity Action Plan is thegovernment’s response to the convention, andfinds local expression in local biodiversity actionplans (LBAPs).

The LBAPs include measures to maintain andincrease managed urban green space as part ofprotecting and improving biodiversity. Theseinclude opportunities to enhance biodiversity in allmajor developments through provision of greenspace, and working with local communities toidentify and develop new and existing managedgreen space.39 UK Biodiversity Action Plan. Habitat Statement – Urban. Available at :http://www.ukbap.org.uk/ukplans.aspx?ID=754 [accessed 10th June 2010]40 Trees for Cities. Trees and urban biodiversity. Available at:http://www.treesforcities.org/page.php?id=490 [accessed 10th June 2010]

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Floodplain woodland can reduce and delay flood flows

The planning system should protect andmaintain existing areas of conservation interest,but should also provide opportunities fordeveloping wildlife and its habitats. Tree plantingand woodland creation, including by individuals,local communities and schools, can help tocreate new habitat to meet targets under theLBAPs.

The beauty of towns and cities arises from a mix ofgood architecture and design, and the landscape ofpublic spaces. There is strong evidence thatimproving green infrastructure and the urbanenvironment helps promote inward investment bycreating a more attractive environment forbusinesses and their staff41.

Trees are a vital element in providing structure andtexture to green infrastructure, and yet this hasbeen eroded in many places. Maintaining what wehave, ensuring future generations of trees toreplace those that are being lost, and imaginativecreation of more places rich in trees is central tomaking towns and cities places people want to livein, visit and do business in.

Trees are multi-purpose tools for urban adaptationand design. Any measures which underminecurrent levels of tree cover are likely to bedamaging to adaptation, whereas well planned andwell maintained urban tree cover can greatlyincrease the adaptive capacity and resilience of thecity.

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,Commissioned from ECOTEC by The Mersey Forest on behalf of NaturalEconomy Northwest

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