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Adapting Cities for Climate Change: The Role of the Green Infrastructure

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Adapting Cities for Climate Change: The Role of the Green Infrastructure

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The urban environment has distinctive biophysical features in relation to surrounding rural areas. These include an altered energy exchange creating an urban heat island, and changes to hydrology such as increased surface runoff of rainwater. Such changes are, in part, a result of the altered surface cover of the urban area. For example less vegetated surfaces lead to a decrease in evaporative cooling, whilst an increase in surface sealing results in increased surface runoff. Climate change will amplify these distinctive features. This paper explores the important role that the green infrastructure, i.e. the greenspace network, of a city can play in adapting for climate change. It uses the conurbation of Greater Manchester as a case study site. The paper presents output from energy exchange and hydrological models showing surface temperature and surface runoff in relation to the green infrastructure under current and future climate scenarios. The implications for an adaptation strategy to climate change in the urban environment are discussed.
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ADAPTING CITIES FOR CLIMATE CHANGE: THE ROLE OF THE GREEN INFRASTRUCTURE
115BUILT ENVIRONMENT VOL 33 NO 1
Adapting Cities for Climate Change:
The Role of the Green Infrastructure
S.E. GILL, J.F. HANDLEY, A.R. ENNOS
and S. PAULEIT
The urban environment has distinctive biophysical features in relation to
surrounding rural areas. These include an altered energy exchange creating an
urban heat island, and changes to hydrology such as increased surface runoff of
rainwater. Such changes are, in part, a result of the altered surface cover of the
urban area. For example less vegetated surfaces lead to a decrease in evaporative
cooling, whilst an increase in surface sealing results in increased surface runoff.
Climate change will amplify these distinctive features. This paper explores the
important role that the green infrastructure, i.e. the greenspace network, of a
city can play in adapting for climate change. It uses the conurbation of Greater
Manchester as a case study site. The paper presents output from energy exchange
and hydrological models showing surface temperature and surface runoff in
relation to the green infrastructure under current and future climate scenarios. The
implications for an adaptation strategy to climate change in the urban environment
are discussed.
Introduction
Much of the emphasis in planning for
climate change is, quite properly, focused
on reducing or mitigating greenhouse gas
emissions. Present day emissions will impact
on the severity of climate change in future
years (Hulme et al., 2002). However, climate
change is already with us. The World Wide
Fund for Nature, for example, has recently
drawn attention to the signifi cant warming
of capital cities across Europe (WWF, 2005).
Due to the long shelf-life of carbon dioxide in
the atmosphere, much of the climate change
over the next 30 to 40 years has already been
determined by historic emissions (Hulme et
al., 2002). Thus, there is a need to prepare
for climate change that will occur whatever
the trajectory of future greenhouse gas
emissions.
With this in mind the UK Engineering and
Physical Sciences Research Council (EPSRC)
and the UK Climate Impacts Programme
(UKCIP) have established a research pro-
gramme into Building Knowledge for a
Changing Climate (BKCC). One project
within the BKCC programme, Adaptation
Strategies for Climate Change in the Urban
Environment (ASCCUE), is developing ways
of preparing for climate change through
strategic planning and urban design. One
important facet of ASCCUE, which is
the subject of this paper, is to explore the
potential of urban greenspace in adapting
cities to climate change.
In 1991, 90 per cent of people in Great
Britain lived in urban areas (Denham and
White, 1998) and it is here that climate
change impacts will be felt. Urban areas
have distinctive biophysical features in
comparison with surrounding rural areas
(Bridgman et al., 1995). For example, energy
exchanges are modified to create an urban
heat island, where air temperatures may
CLIMATE CHANGE AND CITIES
116 BUILT ENVIRONMENT VOL 33 NO 1
be several degrees warmer than in the
countryside (Wilby, 2003; Graves et al., 2001).
The magnitude of the urban heat island
effect varies in time and space as a result of
meteorological, locational and urban chara-
cteristics (Oke, 1987). Hydrological processes
are also altered such that there is an increase
in the rate and volume of surface runoff of
rainwater (Mansell, 2003; Whitford et al.,
2001).
Such biophysical changes are, in part, a
result of the altered surface cover of the urban
area (Whitford et al., 2001). Urbanization
replaces vegetated surfaces, which provide
shading, evaporative cooling, and rainwater
interception, storage and infiltration func-
tions, with impervious built surfaces. How-
ever, urban greenspaces provide areas within
the built environment where such processes
can take place (Whitford et al., 2001). These
ecosystem services (Daily, 1997) provided
by urban greenspace are often overlooked
and undervalued. For example, trees are
felled for the perceived threat they pose near
highways and buildings (Biddle, 1998), infill
development takes place on former gardens,
front gardens are paved over to provide
parking spaces for cars, and biodiverse urban
‘wasteland’ is earmarked for redevelopment
(e.g. Duckworth, 2005; GLA, 2005; Pauliet et
al., 2005).
In a changing climate the functionality
provided by urban greenspace becomes in-
creasingly important. In the UK, climate
change scenarios (UKCIP02) suggest average
annual temperatures may increase by between
1°C and 5°C by the 2080s, with summer
temperatures expected to increase more than
winter temperatures. There will also be a
change in the seasonality of precipitation,
with winters up to 30 per cent wetter by the
2080s and summers up to 50 per cent drier.
These figures are dependent on both the
region and emissions scenario (Hulme et al.,
2002). Precipitation intensity also increases,
especially in winter and the number of very
hot days increases, especially in summer
and autumn (Hulme et al., 2002). It should be
noted that these climate change scenarios do
not take urban surfaces into account. There
is likely to be significant urban warming
over and above that expected for rural areas
(Wilby and Perry, 2006; Wilby, 2003).
Climate change will impact on the urban
environment. These impacts are felt by both
people and the built infrastructure. For
example, it is estimated that the European
summer heat wave in 2003 claimed 35,000
lives (Larsen, 2003). Incidents of flooding
also result in both physical and psychological
illnesses (e.g. Reacher et al., 2004; Baxter et
al., 2002; Shackley et al., 2001). In addition,
buildings are vulnerable to flooding depend-
ing on their location (Graves and Phillipson,
2000).
The biophysical features of greenspace in
urban areas, through the provision of cooler
microclimates and reduction of surface water
runoff, therefore offer potential to help adapt
cities for climate change. However, little is
known about the quantity and quality of
greenspace required. The green infrastructure
is ‘an interconnected network of green space
that conserves natural ecosystem values and
functions and provides associated benefits to
human populations’ (Benedict and McMahon,
2002, p. 12). The green infrastructure should
operate at all spatial scales from urban centres
to the surrounding countryside (URBED,
2004).
The aim of this paper is to explore the
potential of green infrastructure in adapt-
ing cities for climate change. This will be
achieved through a characterization of the
case study site, and quantifying its en-
vironmental functions under both current
and future climate scenarios, as well as with
differing patterns of green cover.
Case Study Site
Greater Manchester, selected as the case study
site, is representative of a large conurbation
(population 2.5 million) in Britain and
Northern Europe. The Metropolitan County
of Greater Manchester, located in north-
ADAPTING CITIES FOR CLIMATE CHANGE: THE ROLE OF THE GREEN INFRASTRUCTURE
117BUILT ENVIRONMENT VOL 33 NO 1
west England, is administered by ten local
authorities: Bolton, Bury, Manchester, Old-
ham, Rochdale, Salford, Stockport, Tameside,
Trafford, and Wigan. There is some coordina-
tion at the conurbation level through the
Association of Greater Manchester Authori-
ties, but planning powers at the larger
scale are vested in the North West Regional
Assembly (NWRA). The NWRA prepares
a Regional Spatial Strategy (NWRA, 2006),
which is the broad planning framework for
the region, whilst the municipalities each
prepare a Local Development Framework
which provides a more detailed template for
development.
Greater Manchester covers an area of
approximately 1300 km
2
and has developed
on a river basin flanked by the Pennine hills.
The altitudinal range is between 10 m and
540 m above sea level. Greater Manchester
offers sufficient size for full expression of
urban environmental character, contrasting
soil types, a range of neighbourhood and
land-use types (including restructuring and
urban extension areas with substantial scope
for climate change adaptation), as well as a
range of built forms.
Manchester was one of the world’s first
industrial cities and the end of that era
was marked by extensive dereliction and
abandoned transport infrastructure. During
the past two decades there has been a change
in the fortune of the conurbation with large-
scale urban regeneration projects transforming
land, water and buildings to new uses.
Urban expansion is restricted by Green Belt
designation and new development is focused
on previously developed, brownfield land.
There is also pressure for infill development
in lower density residential areas, especially
in south Manchester.
Urban Characterization
The fi rst stage of the research was to
characterize the urban environment. This
involved the mapping of urban morphology
types (UMTs) (LUC, 1993) followed by a
surface cover analysis. The UMTs effectively
serve as integrating spatial units linking
human activities and natural processes. The
assumption is that UMTs have characteristic
physical features and are distinctive according
to the human activities that they accom-
modate (i.e. land uses). Greater Manchester
was stratifi ed into 29 distinctive UMTs,
Table 1. Primary and detailed UMT categories.
Primary UMT category Detailed UMT categories
Farmland Improved farmland, unimproved farmland
Woodland Woodland
Minerals Mineral workings and quarries
Recreation and leisure Formal recreation, formal open space, informal open space, allotments
Transport Major roads, airports, rail, river and canal
Utilities and infrastructure Energy production and distribution, water storage and treatment, refuse
disposal, cemeteries and crematoria
Residential High-density residential, medium-density residential, low-density
residential
Community services Schools, hospitals
Retail Retail, town centre
Industry and business Manufacturing, offices, distribution and storage
Previously developed land Disused and derelict land
Defence Defence
Unused land Remnant countryside
CLIMATE CHANGE AND CITIES
118 BUILT ENVIRONMENT VOL 33 NO 1
digitized in ArcView GIS from 1997 aerial
photographs (resolution: 0.25 m, source:
Cities Revealed). These were grouped into
12 primary UMT categories (table 1).
The primary UMT map for Greater
Manchester (figure 1) shows the locations of
the various town centres, grouped under the
primary UMT category of retail, in Greater
Manchester. These are largely surrounded by
residential areas. Higher-density residential
areas are typically located closer to the town
centres. Trafford Park, a major industrial
and retail area, can be seen to the west of
Manchester city centre. The main transport
infrastructure, including Manchester airport
in the south and Manchester ship canal to the
west, are clearly visible. Farmland surrounds
the urban core and in certain instances
extends into the urban areas. Towards the
south of the conurbation the open land of the
Mersey valley forms a greenspace corridor
intersecting the mainly residential areas.
Some 506 km
2
, or just under 40 per cent, of
Greater Manchester is farmland, with the
remaining 60 per cent (793 km
2
) representing
the ‘urbanized’ area. Residential areas account
for just under half of the urbanized area, or
29 per cent of Greater Manchester, and can
thus be viewed from a landscape ecology
perspective as the ‘matrix’ – representing the
dominant landscape category in the urban
mosaic (Forman and Godron, 1986).
Whilst the UMT categories provide an initial
indication of where patches of green may be
expected, e.g. in formal and informal open
spaces, and where green corridors may be
found, e.g. alongside roads, railways, rivers
and canals, they do not reveal the extent
of green cover within the built matrix of
the conurbation. Thus, the surface cover
of each of the 29 UMT categories was then
estimated by aerial photograph interpretation
of random points (Akbari et al., 2003). This
is very important as the surface cover affects
Figure 1. Primary Urban
Morphology Type map of
Greater Manchester.
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119BUILT ENVIRONMENT VOL 33 NO 1
the environmental performance of the
conurbation (Pauliet et al., 2005; Nowak et
al., 2001; Whitford et al., 2001; Pauliet and
Duhme, 2000). Nine surface cover types were
used: building, other impervious, tree, shrub,
mown grass, rough grass, cultivated, water,
and bare soil/ gravel.
The results indicate that on average 72
per cent of Greater Manchester, or 59 per
cent of the ‘urbanized’ area, consists of
evapotranspiring (i.e. vegetated and water)
surfaces (figure 2). All the UMT categories
have, on average, more than 20 per cent
evapotranspiring surfaces. However, there is
considerable variation across the UMTs. Town
centres have the lowest evapotranspiring
cover of 20 per cent compared to woodlands
with the highest cover of 98 per cent. In
general, the proportion of tree cover is
fairly low, covering on average 12 per cent
over Greater Manchester and 16 per cent in
‘urbanized’ Greater Manchester. Whilst the
woodland UMT category has 70 per cent
trees, all other UMTs have below 30 per cent
tree cover. Town centres have a tree cover of
5 per cent.
Particular attention must be given to the
surface cover in residential areas, as these
cover almost half of ‘urbanized’ Greater
Manchester and therefore have a great
impact on the environmental performance
of the conurbation. Approximately 40 per
cent of all the evapotranspiring surfaces
in ‘urbanized’ Greater Manchester occur
in residential areas, with medium-density
residential areas accounting for the majority
of such surfaces. The three types of residential
area have different surface covers from each
other (figure 3). In high-density residential
areas built surfaces (i.e. building and other
Figure 2. Proportion of evapotranspiring (i.e. vegetated and water) surfaces in Greater Manchester.
CLIMATE CHANGE AND CITIES
120 BUILT ENVIRONMENT VOL 33 NO 1
impervious surfaces) cover about two-
thirds of the area, compared to about half in
medium-density areas and one-third in low-
density areas. Tree cover is 26 per cent in low-
density areas, 13 per cent in medium-density
areas, and 7 per cent in high-density areas.
Quantifying the Environmental Functions
The UMTs, with their distinctive surface
covers, formed one of the inputs into
energy exchange and surface runoff models
(Whitford et al., 2001). The energy exchange
model has maximum surface temperature
as its output and is based on an energy
balance equation (Whitford et al., 2001; Tso
et al., 1990, 1991). The warming of the urban
environment in summer is an important
issue because of its implications for human
comfort and well being (e.g. Svensson and
Eliasson, 2002; Eliasson, 2000). Whilst air
temperature provides a simple estimator of
human thermal comfort, it is less reliable
outdoors owing to the variability of other
factors such as humidity, radiation, wind, and
precipitation (Brown and Gillespie, 1995). In
practice, the mean radiant temperature, which
in essence is a measure of the combined effect
of surface temperatures within a space, is a
signifi cant factor in determining human
comfort, especially on hot days with little
wind (Matzarakis et al., 1999). Whitford et
al. (2001) therefore considered surface tem-
perature to be an effective indicator for
energy exchange in the urban environment.
As well as requiring input of the proportional
area covered by built and evapotranspiring
(i.e. all vegetation and water) surfaces, the
model also requires a building mass per
unit of land, and various meteorological
parameters including air temperature.
The surface runoff model uses the curve
number approach of the US Soil Conservation
Service (Whitford et al., 2001; USDA Natural
Resources Conservation Service, 1986). Again,
surface cover is required as an input along
with precipitation, antecedent moisture
conditions, and hydrologic soil type.
The models were run for the baseline
1961–1990 climate, as well as for the
UKCIP02 Low and High emissions scenarios
for the 2020s, 2050s, and 2080s (Hulme et
al., 2002). Results presented here are for
the 1961–1990 baseline and the 2080s Low
and High emissions scenarios. Temperature
and precipitation inputs were calculated
for the different time periods and emissions
scenarios using daily time series output from
Figure 3. Proportional surface cover in high-, medium- and low-density residential UMTs.
ADAPTING CITIES FOR CLIMATE CHANGE: THE ROLE OF THE GREEN INFRASTRUCTURE
121BUILT ENVIRONMENT VOL 33 NO 1
a weather generator for Ringway (Manchester
Airport) (BETWIXT, 2005; Watts et al., 2004a).
The energy exchange model used the 98th
percentile average daily summer temperature
for its input, or the average temperature
occurring on approximately two days per
summer. The surface runoff model used the
99th percentile winter daily precipitation as
its input, a precipitation event that occurs
approximately once per winter. The 99th
percentile daily winter precipitation is 18
mm for 1961–1990, 25 mm for the 2080s Low,
and 28 mm for the 2080s High. Results of
the surface runoff model presented here are
for normal antecedent moisture conditions.
However, analysis of the weather generator
output suggests that antecedent moisture
conditions in winter become wetter with
climate change.
Model runs were completed for the UMT
categories with their current form, i.e. using
proportional surface covers from the urban
characterization, as well as for a series of
‘development scenarios’ exploring the impact
on environmental functionality of adding and
taking away green cover in key areas in the
conurbation. The ‘development scenarios’
were intended both to help understand
the effects of current development trends
(Duckworth, 2005; Pauleit et al., 2005), as
well as to explore the potential of greening
to help adapt urban areas to climate change.
They included: residential and town centres
plus or minus 10 per cent green or tree cover;
greening roofs in selected UMTs; high-density
residential development on previously
developed land; increasing tree cover by
10–60 per cent on previously developed
land; residential development on improved
farmland; and permeable paving in selected
UMTs. In addition, for the energy exchange
model, runs were completed where grass
was excluded from the evapotranspiring
proportion. This was intended to give some
indication of the impact of a drought, when
the water supply is limited and plants
evapotranspire less, and hence their cooling
effect is lost. Grass may be the first type of
vegetation in which this happens due to its
shallow rooting depth.
Energy Exchange Model
The maximum surface temperature is very
dependent on the proportion of green cover
(fi gure 4). This will become increasingly
important in the future. Currently the maxi-
mum surface temperature of woodlands, the
Figure 4. Maximum surface
temperature in Greater
Manchester for the 98th
percentile summer day in
1961–1990 and the 2080s
Low and High emissions
scenarios.
CLIMATE CHANGE AND CITIES
122 BUILT ENVIRONMENT VOL 33 NO 1
least built up UMT, is 18.4°C, 12.8°C cooler
than that of town centres, the most built
up UMT, at 31.2°C. The maximum surface
temperatures are 19.9°C in woodlands and
33.2°C in town centres by the 2080s Low and
21.6°C and 35.5°C by the 2080s High. Thus,
by the 2080s there are increases in maximum
surface temperature of between 1.5°C and
3.2°C in woodlands and 2°C to 4.3°C in town
centres, depending on the emissions scenario.
The difference in temperatures between these
extreme UMTs also increases to 13.9°C by the
2080s High. In high-density residential areas,
with an evaporating cover of 31 per cent,
maximum surface temperatures increase by
1.7°C and 3.7°C by the 2080s, depending on
emissions scenario; in low-density areas,
with an evaporating cover of 66 per cent, the
increase is 1.4°C to 3.1°C. The temperature
difference between these residential UMTs is
6.2°C in 1961–1990, and 6.5°C to 6.8°C by the
2080s, depending on the emissions scenario.
Adding 10 per cent green cover to areas
with little green, such as the town centre
and high-density residential UMTs keeps
maximum surface temperatures at or below
the 1961–1990 baseline temperatures up to,
but not including, the 2080s High emissions
scenario (figures 5 and 6). In high-density
residential areas, for example, maximum
surface temperatures in 1961–1990 with
current form are 27.9°C. Adding 10 per cent
green cover decreases maximum surface tem-
peratures by 2.2°C in 1961–1990, and 2.4°C to
2.5°C by the 2080s Low and High emissions
scenarios, respectively. Thus, maximum
surface temperatures decrease by 0.7°C by the
2080s Low and increase by 1.2°C by the 2080s
High, in comparison to the 1961–1990 current
form case. This is compared to temperature
increases of 1.7°C to 3.7°C by the 2080s Low
and High if no change was made to surface
cover. On the other hand, if 10 per cent
green cover is removed maximum surface
temperatures by the 2080s High emissions
scenario are 7°C and 8.2°C warmer in
high-density residential and town centres,
respectively, compared to the 1961–1990
current form case (figures 5 and 6).
Adding green roofs to all buildings can
Figure 5. Maximum surface temperature for the 98th percentile summer day in high-density residential
areas, with current form and when 10 per cent green cover is added or removed. Dashed line shows the
temperature for the 1961–1990 current form case.
ADAPTING CITIES FOR CLIMATE CHANGE: THE ROLE OF THE GREEN INFRASTRUCTURE
123BUILT ENVIRONMENT VOL 33 NO 1
have a dramatic effect on maximum surface
temperatures, keeping temperatures below
the 1961–1990 current form case for all time
periods and emissions scenarios (figure 7).
Roof greening makes the biggest difference
in the UMTs where the building proportion
is high and the evaporating fraction is low.
Thus, the largest difference was made in the
town centres followed by manufacturing,
high-density residential, distribution and
storage, and retail. The difference made by
the roof greening becomes greater with the
Figure 6. Maximum surface temperature for the 98th percentile summer day in town centres, with
current form and when 10 per cent green cover is added or removed. Dashed line shows the temperature
for the 1961–1990 current form case.
Figure 7. Maximum surface temperature for the 98th percentile summer day in selected UMTs, with
current form and when all roofs are greened.
CLIMATE CHANGE AND CITIES
124 BUILT ENVIRONMENT VOL 33 NO 1
time period and emissions scenario. For
example, in 1961–1990, greening roofs results
in maximum surface temperatures of 24.6°C
in town centres, a decrease of 6.6°C compared
to the current form case of 31.2°C. By the
2080s High, greening roofs in town centres
results in temperatures of 28°C, 7.6°C less
than if roofs are not greened and 3.3°C less
than the 1961–1990 current form case.
In contrast, when grass dries and stops
evapotranspiring, rivers and canals become
the coolest UMT, with maximum surface
temperatures of 19.8°C in 1961–1990 and
22.9°C by the 2080s High, followed by wood-
lands. The UMTs experiencing the biggest
change in maximum surface temperature
when grass dries out are those where it
forms a large proportion of the evaporating
fraction (figure 8). For example, in schools
which often have large playing fields, the
Figure 8. Increase in
maximum surface
temperature for selected
UMTs for the 98th percentile
summer day when grass
dries out and stops
evapotranspiring.
Figure 9. Runoff coefficients for selected UMTs under normal antecedent moisture conditions on a fast
and slow infiltrating soil. Vertical dashed lines show the 99th percentile daily winter precipitation for
1961–1990 (18 mm), the 2080s Low (25 mm), and the 2080s High (28 mm).
ADAPTING CITIES FOR CLIMATE CHANGE: THE ROLE OF THE GREEN INFRASTRUCTURE
125BUILT ENVIRONMENT VOL 33 NO 1
maximum surface temperature increases by
13.8°C in 1961–1990 and 15.6°C by the 2080s
High.
Surface Runoff Model
In general, the more built up a UMT category
is the more surface runoff there will be.
Additionally, soil type is very important
(fi gure 9). Faster infi ltrating soils, such as
sandy soils, have lower runoff coeffi cients
than slower infi ltrating soils, such as clays.
The runoff coeffi cients display the largest
range on high infi ltration soils and the
smallest range on low infi ltration soils. For
example, for an 18 mm precipitation event on
sandy soil, low-density residential UMTs will
have 32 per cent runoff compared with 74 per
cent from the more built up town centres,
which have the highest runoff coeffi cients of
all the UMTs. On a clay soil this changes to
76 per cent and 90 per cent respectively, much
higher values and with a smaller difference
between them. Thus, surface sealing has a
more signifi cant impact on runoff on a sandy
soil with a high infi ltration rate than on a clay
soil with a low infi ltration rate.
With the increasing precipitation expected
by the 2080s there will be increased surface
runoff (figure 10). Not only will there be
higher precipitation but a larger percentage
of the precipitation will contribute to
surface runoff. The total runoff over Greater
Manchester for an 18 mm rainfall event, the
99th percentile winter daily precipitation in
1961–1990, is 13.8 million m
3
. Yet for the 28
mm rainfall event, expected by the 2080s
High, which has 55.6 per cent more rain
Figure 10. Surface runoff over Greater Manchester from 99th percentile daily winter precipitation with
normal antecedent moisture conditions in 1961–1990 and the 2080s Low and High emissions scenarios.
CLIMATE CHANGE AND CITIES
126 BUILT ENVIRONMENT VOL 33 NO 1
than the 18 mm event, the total Greater
Manchester runoff increases by 82.2 per cent
to 25.2 million m
3
. The total runoff from
‘urbanized’ Greater Manchester is 8.9 million
m
3
for an 18 mm rainfall event compared to
16.0 million m
3
for a 28 mm rainfall event.
Increasing green cover by 10 per cent in the
residential UMTs reduces runoff from these
areas from a 28 mm precipitation event,
expected by the 2080s High, by 4.9 per cent;
increasing tree cover by the same amount
reduces the runoff by 5.7 per cent (figure
11). While increasing green or tree cover by
10 per cent helps to deal with the increased
precipitation, it cannot keep the future runoff
at or below the runoff levels for the baseline
1961–1990 current form case. In fact, runoff
from high-density residential areas will still
be approximately 65 per cent higher by the
2080s High even when green cover is added,
when compared to the 1961–1990 current
form case. This ‘development scenario’ does
not have a very large impact on the total
runoff over Greater Manchester; however,
it must be remembered that residential areas
cover 29 per cent of Greater Manchester.
Thus, changing 10 per cent of the surface
cover in residential areas in fact only alters
2.9 per cent of the surface of the conurbation.
Adding 10 per cent tree cover to residential
areas reduces total Greater Manchester runoff
by only 1.9 per cent for a 28 mm event.
Figure 11. Runoff from
high-density residential
with current form and
plus or minus 10 per cent
green or trees, with normal
antecedent moisture
conditions. Vertical dashed
lines show the 99th
percentile daily winter
precipitation for 1961–1990
(18 mm), the 2080s Low (25
mm), and the 2080s High
(28 mm).
Figure 12. Runoff for
selected UMTs with and
without green roofs added,
vertical dashed lines show
the 99th percentile daily
winter precipitation for
1961–1990 (18 mm), the
2080s Low (25 mm), and the
2080s High (28 mm).
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127BUILT ENVIRONMENT VOL 33 NO 1
Adding green roofs to all the buildings
in town centres, retail, and high-density
residential UMTs significantly reduces runoff
from these areas (figure 12). The effect is
greatest where there is a high building cover.
When green roofs are added, the runoff from
an 18 mm rainfall event for these UMTs
is reduced by 17.0–19.9 per cent. Even for
the 28 mm event runoff can be reduced by
11.8–14.1 per cent by adding green roofs.
By the 2080s High, when compared to the
1961–1990 current form cases, adding green
roofs to town centres, retail, and high-density
residential UMTs limits the increase in runoff
to 43.6 per cent, 47.2 per cent and 44 per cent,
respectively. This is compared to 65.5 per
cent, 67 per cent and 67.6 per cent for these
areas if no green roofs were added.
Green roofs reduce the total Greater
Manchester runoff for an 18 mm precipitation
event by 0.6 per cent, 0.1 per cent, and 1.0 per
cent when added to town centres, retail, and
high-density residential, respectively; for a
28 mm event the reductions are 0.4 per cent,
0.1 per cent, and 0.7 per cent, respectively.
Whilst these figures seem small, it must be
remembered that town centres, retail, and
high-density residential cover 2.1 per cent,
0.5 per cent and 3.7 per cent of Greater
Manchester, respectively.
Climate Adaptation via the
Green Infrastructure
The modelling work presented here suggests
that the use of urban greenspace offers
signifi cant potential in moderating the
increase in summer temperatures expected
with climate change. Adding 10 per cent
green in high-density residential areas and
town centres kept maximum surface tem-
peratures at or below 1961–1990 baseline
levels up to, but not including, the 2080s
High. Greening roofs in areas with a high
proportion of buildings, for example in
town centres, manufacturing, high-density
residential, distribution and storage, and
retail, also appeared to be an effective
strategy to keep surface temperatures below
the baseline level for all time periods and
emissions scenarios. On the other hand,
the modelling work highlights the dangers
of removing green from the conurbation.
For example, if green cover in high-density
residential areas and town centres is reduced
by 10 per cent, surface temperatures will
be 7°C or 8.2°C warmer by the 2080s High
in each, when compared to the 1961–1990
baseline case; or 3.3°C and 3.9°C when
compared to the 2080s High case where green
cover stays the same.
Thus, one possible adaptation strategy to
increasing temperatures is to preserve existing
areas of greenspace and to enhance it where
possible, whether in private gardens, public
spaces or streets. For example in Housing
Market Renewal Areas or in the Growth
Areas, significant new greenspaces should
be created. These initiatives are part of the
UK government’s Sustainable Communities
Programme. Nine Housing Market Renewal
Areas have been identified by the govern-
ment across the North of England and the
Midlands, including Manchester/Salford
and Oldham/Rochdale, with the objective of
renewing failing housing markets through
refurbishment, replacement and new build of
houses. The Growth Areas are in South East
England and will provide as many as 200,000
new homes to relieve housing pressures in the
region (DCLG, no date). Given the long life
time of buildings, from 20 to over 100 years
(Graves and Phillipson, 2000), it is crucial to
take opportunities for creating greenspaces
as they arise.
However, in many existing urban areas
where the built form is already established,
it is not feasible to create large new green-
spaces. Thus, greenspace will have to be
added creatively by making the most of
all opportunities, for example through the
greening of roofs, building façades, and
railway lines, street tree planting, and con-
verting selected streets into greenways.
Priority should be given to areas where the
vulnerability of the population is highest. A
CLIMATE CHANGE AND CITIES
128 BUILT ENVIRONMENT VOL 33 NO 1
study in Merseyside found that vegetation,
and in particular tree cover, is lower in
residential areas with higher levels of socio-
economic deprivation (Pauleit et al., 2005).
The socio-economic deprivation index used
included variables relating to health depri-
vation. Such populations will therefore be
more vulnerable to the impacts of climate
change.
One caveat to the potential of green cover
in moderating surface temperatures is the
case of a drought, when grass dries out
and loses its evaporative cooling function.
Output from the daily weather generator
used suggests that with climate change
there will be more consecutive dry days and
heat waves of longer duration in summer
(BETWIXT, 2005; Watts et al., 2004a, 2004b).
Similarly, research undertaken as part of the
ASCCUE project to map drought risk through
the combination of available water in the
soils, precipitation and evapotranspiration,
suggests a significant increase in the
duration of droughts with climate change.
Thus, it is likely that there will be more cases
when the grass loses its evaporative cooling
function unless counter measures are taken.
In such situations the role of water surfaces
in providing cooling and trees in providing
shade become increasingly important. The
modelling work presented here does not
include the effect of shading on surface
temperatures. A pilot study undertaken by
the ASCCUE project suggests that the shade
provided by mature trees can keep surfaces
cooler by as much as 15.6°C.
One possible adaptation strategy would
be drought-resistant plantings. In Greater
Manchester this would involve planting
vegetation, such as trees, that is less sensitive
than grasslands to drought. Trees are common
in open spaces in the Mediterranean. Tree
species which are less sensitive to drought
can be chosen from temperate zones, such
that they will still evapotranspire and
provide shade. Site conditions for trees in
streets may need improving so that there
is sufficient rooting space. In addition,
irrigation measures must be considered to
ensure that they have an adequate water
supply. This could be through rainwater
harvesting, the re-use of greywater, making
use of water in rising aquifers under cities
where present, and floodwater storage.
Unless adequate provision is made there
will be conflict as greenspace will require
irrigating at the same time as water supplies
are low and restrictions may be placed on its
use. Ironically, measures which are currently
in hand to reduce leakage in the water supply
system may reduce available water for street
trees which are critically important for human
comfort in the public realm.
There may be other potential conflicts
arising from planting trees in proximity to
buildings. On clay soils in particular, changes
in soil moisture content, as may occur with
climate change, result in dimensional changes
in the soil (Percival, 2004). If changes occur
below the foundation level of the buildings,
this can result in damage. However, the
persistence of a moisture deficit beyond
seasonal fluctuations only occurs in extreme
cases. Tree roots are involved in at least 80
per cent of subsidence claims on shrinkable
clay soils, yet even on clay soils the risk of a
tree causing damage is less than 1 per cent
(Biddle, 1998). Biddle (1998) argues that,
due to the importance of trees in urban
environments, a proper understanding is
required of the mechanism of damage, how
this can be prevented, and of appropriate
remedies if damage occurs. An approach
which accepts that minor damage may
sometimes occur, and then remedies the
situation if it does, is the most appropriate.
In addition, new buildings should include
precautions in the design and construction
of foundations to allow for tree growth near
buildings (Biddle, 1998).
The modelling work suggests that
greenspace on its own is less effective at
moderating the volume of surface runoff
under climate change. While greenspace
helps to reduce surface runoff, especially at a
local level, the increase in winter precipitation
ADAPTING CITIES FOR CLIMATE CHANGE: THE ROLE OF THE GREEN INFRASTRUCTURE
129BUILT ENVIRONMENT VOL 33 NO 1
brought by climate change is such that runoff
increases regardless of changes to surface
cover. Thus, in order to adapt to the increased
winter precipitation expected with climate
change, greenspace provision will need to be
considered alongside increased storage. There
is significant potential to utilize sustainable
urban drainage (SUDS) techniques, such as
creating swales, infiltration, detention and
retention ponds in parks (Mansell, 2003;
CIRIA, 2000). There is also an opportunity to
store this excess water and make use of it for
irrigating greenspaces in times of drought.
Another way of exploring possible
climatic adaptations is to consider the green
infrastructure of the conurbation from
the perspective of landscape ecology. The
modelling work has concentrated on the
environmental performance of the UMTs
regardless of their spatial context. However,
the functionality of the green infrastructure
will be dependent on its location. Thus,
the green infrastructure can be viewed as
consisting of corridors, patches, and the
overall matrix (figure 13) (Forman and
Godron, 1986).
These components of the green infra-
structure play different roles in terms of
climatic adaptation (table 2). For example,
flood storage is especially important in
corridors, but also has some importance as
SUDS in the patches. In Greater Manchester,
for example, green spaces such as golf
courses and nature reserves alongside the
River Mersey are used as flood storage basins
at times of high river flow (Sale Community
Web, no date). On the other hand, the matrix
is especially important when it comes
to rainwater infiltration, as are patches.
Greenspace is most effective at reducing
surface runoff on sandy, faster infiltrating
soils. There may be a case for adapting to
climate change through preserving and
enhancing vegetated surfaces on such
soils, for example, through the creation of
Conservation Areas. Infill development could
be restricted in lower density residential areas
where soils have a high infiltration capacity.
Evaporative cooling is very important in
the patches which provide green oases with
cooler microclimates and also in the matrix
where people live. Greenspaces develop
a distinctive microclimate when they are
greater than 1 hectare (von Stülpnagel et
al., 1990). Similarly shading is required in
the matrix and patches, especially within
residential areas.
In addition to providing climate adapta-
tion, the green infrastructure offers a range
of other benefits in urban areas (e.g. URBED,
2004; Givoni, 1991). The combination of
these functions makes the use of green infra-
structure an attractive climate adaptation
strategy. Moreover, the use of green infra-
structure may help in reducing greenhouse
gas emissions, or in mitigating climate
Figure 13. Elements of the green infrastructure from a landscape ecological perspective.
CLIMATE CHANGE AND CITIES
130 BUILT ENVIRONMENT VOL 33 NO 1
change. For example, vegetation can reduce
solar heat gain in buildings and can thus
reduce the demand for mechanical cooling
through air conditioning, which contributes
both the greenhouse gas emissions as well as
the intensification of the urban heat island
through waste heat (e.g. Niachou et al., 2001;
Onmura et al., 2001; Papadakis et al., 2001).
Conclusion
The research fi ndings presented here are
signifi cant because they begin to quantify
the potential of the green infrastructure to
moderate climate change impacts in towns
and cities. Such claims are often made for
urban greenspace (e.g. Hough, 2004) but
the introduction of a modelling approach
clarifi es the magnitude of the effect and
allows adaptation strategies to be tested. We
do not suggest that the model outputs can be
directly translated in practice, for example it
would be quite unrealistic to green all roofs
in city centres and high-density residential
areas. However, the model runs indicate
which type of actions are likely to be most
benefi cial and in which locations. Urban
greenspace from street trees, to private
gardens, to city parks provide vital ecosystem
services which will become even more critical
under climate change.
Within urban centres green spaces therefore
constitute critical environmental capital that,
once developed, is difficult to replace. This
green-space needs to be strategically planned.
The priorities for planners and greenspace
managers is to ensure that the functionality
of greenspace is properly understood and
that what exists is conserved. Then it should
be possible to enrich the green cover in
critical locations, for example the planting
of shade trees in city centres, schools and
hospitals. Opportunities to enhance the green
cover should also be taken where structural
change is taking place, for example, in urban
regeneration projects and new development.
The combination of the UMT-based modelling
approach with the patch-corridor-matrix
model may help in the development of
spatial strategies for the green infrastructure
to preserve existing greenspace and create
new greenspace such that a functional
network is formed. This approach, however,
requires further exploration.
Mature trees will be very important for
the roles they play in providing shade and
intercepting rainfall. Also, in times of drought
they may provide a cooling function for
longer than grass, which will dry out faster.
At present, those areas experiencing highest
surface temperatures and socio-economic
disadvantage also have the lowest tree
population and here urban forestry initiatives,
such as the Green Streets project of the Red
Rose Forest of Greater Manchester (Red Rose
Forest, no date), are beginning to redress the
balance. During periods of water shortages,
as for example in South East England at the
time of writing, urban vegetation is often the
first target of a ‘drought order’. The research
suggests that the benefits of greenspace go
well beyond consideration of amenity and
that opportunities will have to be taken
to ensure an adequate water supply to
vegetation in times of drought.
Climate change is already with us and
there is an urgent need to develop adaptive
strategies. The creative use of the green
Table 2. Climate adaptation via the green infrastructure – an indicative typology.
Corridor Patch Matrix
Flood storage ••• ••
Infiltration capacity •• •••
Evaporative cooling ••• ••
Shading • •• •••
ADAPTING CITIES FOR CLIMATE CHANGE: THE ROLE OF THE GREEN INFRASTRUCTURE
131BUILT ENVIRONMENT VOL 33 NO 1
infrastructure is one of the most promising
opportunities for adaptation and this needs
to be recognized in the planning process at
all scales from the Regional Spatial Strategies,
through Local Development Frameworks to
development control within urban neighbour-
hoods. Within the government’s Sustainable
Communities Programme there is real scope
to ‘climate proof’ new developments in the
Growth Areas and to reintroduce functional
green infrastructure during the redevelop-
ment process in areas subject to Housing
Market Renewal.
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ACKNOWLEDGEMENT
This research is funded by the Engineering and
Physical Sciences Research Council and the UK
Climate Impacts Programme. Information about
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Technical Report
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Soil and water are two key resources that directly or indirectly affect our everyday activities. Until recently, soil has predominantly been perceived in the context of its agricultural production function but healthy soils provide many more goods, services and societal function e.g. for flood protection and maintenance of natural landscapes; and water is necessary for all the provisioning, regulating, supporting and cultural services it provides. Mismanagement and/or intensive use of soil and water put at risk the maintenance and resilience capacity of our natural capital. Our economies have increasingly relied on technologies and innovations to cope with environmental degradation, rather than on optimising the ecosystem services (ESS) provided by our environment. For example, in the agricultural sector, irrigation and drainage can be used intensively to cope with the degradation of soil hydrological functions. In the urban environment, storm-water channels and other hydraulic works allow tackling the risks of flooding linked to rainwater runoff on impervious surfaces. The necessity to preserve the important contribution of soil to the water cycle, in particular through the soil water retention (SWR) capacity, is still not fully recognised in EU policies. Soil and water are mostly treated as independent subjects, although an integrated approach of soil and water management is emerging in the EU, as illustrated in the Floods Directive 2007/60/EC, the Communication “Addressing the challenge of water scarcity and droughts”, the Thematic Strategy for Soil Protection and the Draft Framework Directive for the protection of soils. Today, a large number of research publications investigate the issue of soil-water dynamics. Although they shed light on some of the scientific aspects, the overall knowledge of SWR remains scattered and there is no clear overview of the trends in SWR at EU and Member State (MS) levels, their causes and environmental, socio-economic and political implications. There is a need to explore these aspects, put in a global perspective and explain to policy makers and public society. In particular, a better understanding of the mechanisms and drivers of SWR will empower policy makers and stakeholders to take informed decisions about how to maintain, restore or improve the SWR capacity. This study bridges the science-policy gap and enhance the current evidence base about SWR capacity by gathering and synthesising the available information. Through key messages and recommendations, the study further aims to help policy-makers take appropriate actions to maintain or restore SWR. Overall, it aims to answer the following questions: What is SWR capacity and how does it work? Why is it important? What are the EU major trends? What are the environmental and socio-economic implications of a reduction in SWR capacity? What are the key drivers behind these trends and which practices allow enhancing SWR capacity?
... In a study by Gill et al. (2007), the surface runoff model predicted that by adding green roofs to all buildings in town centres, retail, and high density residential areas in Greater Manchester, the runoff for an 18mm rainfall event is reduced by 17.0-19.9%, and for the 28mm event by 11.8-14.1%. ...
Chapter
Cities’ increasing vulnerability to the effects of climate change calls for greater attention to urban transformational adaptation as a path towards environmental and social resilience. Through the initial Superblock project in the Poblenou neighbourhood of Barcelona – whereby traffic pacification is combined with new open space and transit network improvements – we analyse municipal efforts aligning transformational land use planning with climate adaptation objectives and the pushback again them. The initial opposition to the project embodied the everyday political struggle for municipal authority, that is, clashes over visions for the future Barcelona and who can define them and own them. Urban transformation – and the contestation around it – is thus not only about negotiating environmental and quality-of-life benefits that are ostensibly the target of interventions, but also competitive urbanism and related short-term political gains. Of particular importance is how civic and political contestation over the authority of climate champions can jeopardise not only transformational adaptation achievements, but also the political survival of those champions. Transformational adaptation can be slowed down not only by the fear for the material and political effects of transformation per se, but also because of how key stakeholders and the residents around them contest who has the authority to decide for the common good. This chapter is a modified and updated version of the Zografos et al (Cities 99:102613. Copyright (2020), with permission from Elsevier, 2020) article previously published in Cities, Elsevier.KeywordsTransformational adaptationCompetitive urbanismMobilityPublic spaceSuperblocks
Article
This research deals with the issue of the recovery of the historic urban fabric with a view towards ecological transition, nowadays considered the preferable direction of sustainability for the reform of the house–city–landscape system. The massive incentives provided by the Italian government for sustainable building, in view of the post-pandemic economic recovery, risk being reduced to mere support for the real estate sector, which turns the financial transfer from the public into an increase in asset value for the private sector. Such an incentive system could contradict the original function of the city, which is to be the privileged place for social communication and the creation of the identity of settled communities. A process of property development that disregards the distribution of income favors the most valuable property, thus increasing the socioeconomic distance between centrality and marginality. The latter is a condition that often characterizes the parts of the historic city affected by extensive phenomena of physical and functional obsolescence of the built heritage, and it is less capable of attracting public funding. The increase of building decay and social filtering-down accelerates the loss and involution of neighborhood identities; the latter constitutes the psycho-social energy that helps preserve the physical, functional and anthropological integrity of the city, due to the differences that make its parts recognizable. This study, with reference to a neighborhood in the historic city of Syracuse (Italy), proposes a model of analysis, evaluation and planning of interventions on the buildings’ roofs, aimed at defining the best strategy for ecological–environmental regeneration. The model presented allows one to generate a multiplicity of alternative strategies that combine different uses of roofs: from the most sustainable green roofs, but that are less cost-effective from the identity and landscape point of view; to the most efficient photovoltaic roofs from the energy–environmental point of view; and up to the most cost-effective ones, the vertical extensions with an increase in building volume. The proposed tool is an inter-scalar multidimensional valuation model that connects the multiple eco-socio-systemic attitudes of individual buildings to the landscape, identity, energy–environmental and economic overall dimensions of the urban fabric and allows one to define and compare multiple alternative recovery hypotheses, evaluating their potential impacts on the built environment. The model allows the formation of 100 different strategies, which are internally coherent and differently satisfy the above four perspectives, and it provides the preferable ones for each of the five approaches practiced. The best strategy characterizes most green roofs, 427 out of 1075 building units, 277 blue roofs, 121 green–blue roofs and 46 grey roofs.
Article
Transportation agencies rely on scientific information to design and site infrastructure, plan operations, and make policies. However, the ways in which science interfaces with transportation policy are not straightforward: political incentives, usability challenges, implementation failures, and capacity limitations all shape how public organizations use scientific information. To build stronger connections between transportation-relevant science and policy it is necessary to better understand current patterns of scientific information use in practice, particularly as transportation agencies address an expanding purview of policy issues, such as climate change mitigation and intelligent transportation systems. This paper measures science use observed in transportation planning and project documents–plans, proposals, impact assessments, and other deliverables that agencies are required to produce as part of the policy process. Using state, regional, and county transportation agencies in the state of California as a focal sample, this paper applies automated natural language processing (NLP) tools to analyze documents and identify references. Our sample includes 5080 documents from 59 organizations involved in transportation governance in the state of California. We observe that the transportation science-policy interface is a cyclical system in which public agencies act in varying (and simultaneous) capacities as consumers, producers, funders, and brokers of scientific information. For instance, documents produced by state-level entities draw more heavily on academic literature, while regional and county-level agencies rely most heavily on reports produced internally by state agencies and by state-funded research institutes. Understanding where different transportation agencies access scientific information, and how scientific information flows between entities at different levels of government, can help researchers and science-policy boundary organizations increase the uptake of scientific products and design interventions to improve information access and use.
Article
Increasing urban sprawl has caused many severe problems like surge in pollution, rapid climatical variations, and the intensification of temperature in the urban areas, termed Urban Heat Islands (UHI). Population density has caused theconversion of most land areas into cities, and cities have expanded vastly. UHI phenomenon has caused temperature rise in the cities. Most of the metropolitan regions of India are experiencing consequences of UHI and the severity of pollution formation, which is a crucial research area. Since the rising temperature has a direct linkage with urban air pollution; the mitigation measures for UHI are also linked with urban air pollution mitigation; efficacy of mitigation measures of UHI phenomenon in correlation with urban air quality is being studied extensively, which emphasizesthescientific approach and planning concerns of implementation agency to consider the same into urban design and planning aspects. Ahmedabad is one of the growing metropolitan regions of India. The city has grown economically and physically by expanding its boundaries in a radial pattern. This study has attempted temporal assessment of remote sensing data to derive the UHI and the city's growth, and its changing land uses. Assessment has been performed from2008 to 2018 from Landsat data for temperature profile at surface level and type of usage of land of the study area. The spatial profile of Particulate Matter (PM2.5 and PM10) has been generated based on data from the state pollution control board. Four variables, LST, PM2.5, PM10, and LULC, are taken to establish the relationship between all variables present in different layers withthehelp of regression statistical analysis. A strong positive correlation between PM2.5, PM10, and LST has been discovered, which was eventually used to assess the impact of mitigation strategies of UHI, specifically urban greening and a white roof to particulate matter concentrations.
Preprint
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Urban grasslands are crucial for biodiversity and ecosystem services in cities, while little is known about their multifunctionality under climate change. Thus, we investigated the effects of simulated climate change, i.e., increased [CO2] and temperature, and reduced precipitation, on individual functions and overall multifunctionality in mesocosm grasslands sown with forbs and grasses in four different proportions aiming at mimicking road verge grassland patches. Climate change scenarios RCP 2.6 (control) and RCP 8.5 (worst-case) were simulated in walk-in climate chambers (ca. 7.7 m2), and watering was manipulated for normal vs. reduced precipitation. We measured eight indicator variables of ecosystem functions based on below- and above-ground characteristics. Recently established grassland communities responded to higher [CO2] and warmer conditions with increased vegetation cover, height, flower production, and soil respiration. Lower precipitation affected carbon cycling in the ecosystem by reducing biomass production and soil respiration. In turn, the water regulation capacity of the grasslands depended on precipitation interacting with climate change scenario, given the enhanced water efficiency resulting from increased [CO2] under RCP 8.5. Multifunctionality was negatively affected by reduced precipitation, especially under RCP 2.6. Trade-offs arose among single functions that performed best in either grass- or forb-dominated grasslands. Grasslands with an even ratio of plant functional types coped better with climate change and thus are good options for increasing the benefits of urban green infrastructure. Overall, we provide experimental evidence on the effects of climate change on the functionality of urban ecosystems. Designing the composition of urban grasslands based on ecological theory may increase their resilience to global change.
Article
Plants are able to exercise a positive influence on both the climate and the air in the surroundings. Through transpiration the humidity is increased (often it is too dry in the towns), and the heat required for the evaporation puts a slight brake on excess temperatures. Thus green areas can help to produce cool air, which is a necessary compensation in highly built-up areas. In addition plants in vegetation belts help, to some extent, to absorb noise. Dust and pollutants settle out on the vegetation, an effect which is greater for trees and bushes than for lawns. Small green areas of only one hectare or less have no clear effect on an urban climate individually. Nevertheless they can develop their own microclimate if thick bushes and trees screen them from the surroundings, which can at least be of benefit to those seeking relaxation in or near the green area. -from Authors
Book
"Green infrastructure" is a term becoming more commonly used among natural resource professionals. While it means different things to different people, depending on the context in which it is used, for the purposes of this article, green infrastructure is an interconnected network of green space that conserves natural ecosystem values and functions and provides associated benefits to human populations. Green infrastructure is the ecological framework needed for environmental, social and economic sustainability- our nation's natural life support system. Planning utilizing green infrastructure differs from conventional open space planning because it looks at conservation values in concert with land development, growth management and built infrastructure planning. This article introduces green infrastructure as a strategic approach to land conservation that addresses the ecological and social impacts of sprawl and the accelerated consumption and fragmentation of open land. It describes the concept and value of green infrastructure and presents seven principles for successful green infrastructure initiatives.
Conference Paper
With clay soils and temperate climatic conditions, trees are the biggest cause of soil drying and subsidence, resulting in foundation movement and damage. Understanding how trees dry the soil, and how this drying can be controlled, is essential for decisions on methods of preventing or remedying this damage.
Book
Presents a detailed study of the potential impacts of anthropogenic climate change in one region of England (the East Midlands), drawing together different disciplinary perspectives from meteorology, climate change, hydrology, physical and human geography and stakeholder perceptions and responses.
Article
According to projections by the United Nations, 60% of the world’s population will reside in urban areas by 2030. Studies of the ecology of cities and ecology in cities will therefore assume increasing relevance as urban communities seek to protect and/or enhance their ecological resources. Presently, the most serious threats to wildlife include the degradation and/or loss of habitats, the introduction and spread of problem species, water pollution, unsympathetic management, and the encroachment of inappropriate development. Climate change could add to these problems through competition from exotic species, the spread of disease and pests, increased summer drought stress for wetlands and woodland, and sea-level rise threatening rare coastal habitats. Earlier springs, longer frost-free seasons, and reduced snowfall could further affect the dates of egg-laying, as well as the emergence, first flowering and health of leafing or flowering plants. Small birds and naturalized species could thrive in the warmer winters associated with the combined effect of regional climate change and enhanced urban heat island. This article reviews the range of climate-related threats to biodiversity in the aquatic, intertidal and terrestrial habitats of urban areas. London is used as a case study to illustrate potential impacts, and to contend that ‘green spaces’ in cities could be used by planners to counter climate-related threats to biodiversity, as well as to improve flood control and air quality, and reduce urban heat island effects.
Article
Analytical solutions are presented to the near-neutral atmospheric surface energy balance with the new approach of including the participation of heat storage in the building substrate. Analytical solutions are also presented for the first time for the case without heat storage effect. By a linearization process, the governing equations are simplified to a set of time-dependent, linear, first-order equations from which explicit solutions are readily obtainable. The results compare well with those obtained by numerical solutions upon the set without linearization when applied to the tropical city of Kuala Lumpur, Malaysia.
Article
The paper discusses the impact of urban planted areas: public parks and private planting around individual buildings, on various aspects of the quality of the urban environment. Specific issues discussed are: •functions and impacts of urban planted areas;•effect of plants on the climatic characteristics of an area;•climatic impacts of private planted areas around buildings;•experimental studies on the thermal effect of plants;•public parks and the urban climate;•range of the effect of urban parks;•impact of green spaces on air pollution;•planted areas as noise;•social functions of urban parks;•parks as social interaction areas between neighborhoods; and•summary: Climatic guidelines for parks design: ◦Parks in hot, dry regions;◦Parks in hot, humid regions; and◦Parks in cold regions.Comment: This paper is based on a book by the author, published by the World Meteorological Organization (Givoni, 1989, Urban Design for Different Climates, WMO).