Trees: The key to climate proofing our cities

Trees: The key to climate proofing our cities Richard Simmons Chief Executive CABE

Summary • Great cities need great trees • We underestimate their value • Don’t overlook the environmental services they provide • Trees are a key ingredient for sustainable cities • They are an integral part of green infrastructure planning

Made beautiful, and good for food, and for building, and for instruments of our hands, this race of plants, deserving boundless affection and admiration, becomes a nearly perfect test of our being in right temper of mind and way of life; no one can be far wrong in either who loves trees enough, and everyone is assuredly wrong in both who does not love them. - John Ruskin, 1819-1900, Modern Painters VI

Planting trees in cities – a practice as old as cities themselves • And the king made silver to be in Jerusalem as stones, and cedars made he to be as the sycamore trees that are in the vale, for abundance • The Bible 1 Kings 10:27

Environmental role of trees • Mature tree transpires 450 litres of moisture a day • Large beech tree produces enough oxygen for 10 people • Single tree has a sun protection factor of between 6 and 10 • Tree lined streets have 10-15% less dust and are up to 6-10C cooler • Trees in the carbon cycle: biofuels and carbon sequestration – some controversy!

Money does grow on trees The plane tree in Berkley Square is valued at £750,000, as calculated by the capital asset value of amenity trees The Times 22 April 2008

Green infrastructure and spatial planning • Developing a green infrastructure strategy puts the natural environment at the heart of urban design and management. • Parks and gardens, allotments and cemeteries, street trees and green roofs should form a network that links the environmental systems of landscapes and urban areas. • Correctly managed, this green infrastructure delivers benefits ranging from creating a sense of place to mitigating the effects of rising temperatures Urban Tree Structure Plan for Western Garden Suburbs, Amsterdam

Green infrastructure and spatial planning • Trees are an integral and visible part of green infrastructure networks • Developing strategies to maximise the value of green infrastructure will require action at a range of different levels and an understanding of the often complex issues involved. • Green infrastructure strategies need to link to policy making and routes for implementation at a range of different levels.

The Urban Heat Island effect • Trees help to moderate the urban heat island effect through evaporative cooling and shading, which create cooler microclimates and make cities more comfortable places to live • Predicted rises in excess of 4°C by the end of the century • A 10% increase in urban canopy cover may be enough to buffer these temperature rises

Water management • UKCIP estimate that UK winters will be 20% wetter by 2050 • Trees play a vital role in managing storm water, • They form integral parts of sustainable urban drainage systems • Help mitigate the effects of flash flooding

Trees at risk • Tree Root subsidence – the number of tree related insurance claims has risen steadily since 1993. However it is estimated that less than one per cent of the total tree population has actually caused damage to properties • London Chainsaw Massacre – risk averse local authorities are replacing large trees with smaller, ornamental species • Proposed new BSI regulations - all trees to be checked by a “trained person” every three years, with a still more rigorous “expert inspection” by an arboriculturist every five years

Managing risk – can we prove we can do better and still keep beautiful street trees? Woman killed as bus hits tree in Tower Bridge Road Tuesday 28 May 2008

Trees in Towns II • This research published in February 2008 builds upon the original Trees in Towns survey undertaken by the Department of the Environment in 1992/93

Trees in Towns II – key issues • An alarming loss of large trees • High rates of urban tree planting undertaken between 1983 and 1992 were not maintained in the1995- 2004 period, resulting in threats to older trees and an imbalanced age structure • Across England just 11% of trees in towns are between 50 and 100 years old and just 2% are over 100 years old • Urban trees being increasingly viewed as a liability by both tree officers and general public

Trees in Towns II • The report calls for a comprehensive tree strategy as the starting point for a modern, planned approach to tree management. • This needs to be integrated and embedded into local development frameworks and other relevant policies

And then some… • Risk limitation strategy for tree root claims A Tree Officers Association guide which advises on the selection of trees and appropriate management • Joint mitigation protocol More robust evidence required before tree removal • Right tree for a changing climate An online tool to ensure that the right tree is planted in the right place • Industry best practice on tree management Right tree right place guidelines for developers Insurer guide to tree risk

What is CABE doing? • A member of the Trees and Design Action Group. The group will produce series of short guides aimed at developers, planners, designers and architects. The first will look at the economic value of large trees within new and existing developments • Working with CIRIA in producing a publication to promote the use of large landscape trees in future new developments, as part of their 'Building Greener' initiative

What is CABE doing? • sustainablecities.org: An online resource which will help decision-makers to use urban design and management to respond to the challenges of climate change • Working with Natural England on developing green infrastructure strategies in all Growth Points • Working with over 120 local authorities to develop green and open space strategies • Promoting good street design through training & advisory support

Thank you. Richard Simmons rsimmons@cabe.org.uk

Trees: The key to climate proofing our cities