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Trees: The key to climate proofing our citiesRichard 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 treesThe 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 RoadTuesday 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
