Supplementary Material
Appendix 1: Selection and delimitation of city areas
The 13 study cities used for our analyses were selected on the basis of their associated ‘Urban
Area’ human population size, as recorded during the last census in 2001 (Table S1; [1]). The
boundaries of these 'Urban Areas' were defined by Ordnance Survey for what is now the
Department of Communities and Local Government on the basis of physical urban limits in
2001 [2], corresponding boundaries having been defined for use with the 1981 and 1991
censuses. As these boundaries differ for each period, they cannot be used directly to examine
temporal trends in urban land-use and population size. We therefore defined a fixed sampling
area for each city, including the physical urban area at each census, but extending into the
adjoining administrative area.
Appendix 2: Temporal changes in urban land-use
Landsat Thematic Mapper (TM) images, comprising six spectral bands at a spatial resolution
of 30 x 30 m, were used to explore areal changes in urban land-use. The Landsat data were
acquired for spring/summer (April–September) during the three years for which comparable
data were available: 1991, 2001, and 2006. Eight image scenes were needed to cover the 13
cities in each year. Some data from 2006 images (<5% in total) were not available due to
defective sensors. In these cases, data from 2001 were used to complete the images; changes
in land-use between 2001 and 2006 may, therefore, represent a slight underestimate of that
which actually occurred. The Landsat data were downloaded from the Global Land Cover
Facility (GLCF; http://glcf.umiacs.umd.edu/index.shtml).
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Landsat data were interpreted using the image processing software ERDAS IMAGINE 8.4
(ERDAS Inc). First, the image scenes for each year were combined, prior to overlaying the
urban core boundaries for the 13 cities and extracting the relevant data. The maximum
likelihood method, based on the six spectral bands, was used to classify the images into two
urban land-use types: built-up and greenspace. To assess the accuracy of the classification
procedure, 500 reference points (250 for each category) were generated using the equalized
random sampling method [2]. These were then checked to ensure they had been correctly
assigned to either the built-up or greenspace category using visual image interpretation and
verifying by eye against Google Map 2006. The classification accuracies were 91.4%, 93.2%
and 90.8% for 1991, 2001 and 2006 respectively, indicating that the classified imagery
products were of high quality. Finally, for each year, the areas of built-up and greenspace
within the urban core were analysed in a Geographic Information System (ArcView GIS 3.2;
Environmental Systems Research Institute Inc.).
Appendix 3: Temporal trends in urban EVI
Enhanced Vegetation Index (EVI) satellite data from the Terra Moderate Resolution Imaging
Spectroradiometer (MODIS) sensor were used to examine temporal changes in the
‘greenness’ of our 13 cities. The dataset has a spatial resolution of 250 x 250 m, a temporal
resolution of 16 days (16-day composite period; [3]), and spans a nine year period in England
(18 February 2000 to 19 December 2008). The MODIS-EVI data were downloaded from the
Global Land Cover Facility (GLCF; http://glcf.umiacs.umd.edu/index.shtml).
In order to assess changes in EVI in the study cities through time, comparative baseline data
were needed for adjacent rural zones; these were defined as all non-developed land-uses lying
in a buffer between 2 and 5 km around the urban core boundary. Within the GIS, zonal
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analyses were used to calculate biweekly mean EVI for the rural zone and urban core of each
city, allowing the difference in EVI (EVIdiff) between these two areas to be derived. Annual
EVIdiff was calculated by subtracting the average annual EVI for the urban core from the
average annual EVI for the rural zone.
Appendix 4: Temporal pattern in the human population and number of dwellings
In England, human population and dwelling figures are reported for a hierarchy of statistical
and administrative areas, which change over time. Population and dwelling aggregates for
each study city for 1981, 1991 and 2001 have been constructed from the finest level statistical
units (enumeration districts for 1981 and 1991; output areas for 2001). Additional dwelling
count data for the study cities in 2006 and 2008 have been used by summing numbers of
residential delivery points associated with each unit (i.e. full) postcode within the relevant
areas.
Appendix 5: Corroborating changes in greenspace with existing data
We anticipated that it would be possible to corroborate the increase in greenspace area in our
13 cities, between 1991 and 2001, through a comparison with existing land use data sources.
However, in practice it is difficult to measure reliably the extent of informal areas of
greenspace in cities, despite the existence of two potentially comprehensive data sources; the
first consists of records of previously developed land parcels held within the National Land
Use Database (NLUD-PDL), and the second is the Land Use Change Statistics (LUCS), both
collected for the UK government’s Department of Communities and Local Government
(DCLG). NLUD-PDL relies on returns made voluntarily by local authorities and is therefore
not complete for every year. In practice different authorities may be represented within these
data in different years. If examining a whole city (which will often include several local
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authorities) change due to variation in coverage must be distinguished from underlying
change in the stock of vacant land. LUCS, on the other hand, although providing no measure
of vacant land stock, potentially measures both land becoming vacant and land ceasing to be
vacant. There are, however, significant difficulties in knowing when changes actually
occurred. Therefore, while the approach to data collection underpinning LUCS allows for
relatively robust measurement of land ceasing to be vacant through development, it implies a
systematic tendency to under-record flows into vacancy, making it inappropriate for
comparisons between time periods [4].
The NLUD-PDL does allow such comparisons to be made, but only for years after 2000.
Prior to this the areas covered by the dataset varied between years. To allow comparison with
the remote sensed data, we used NLUD-PDL to compare vacant land stocks in 2000/1 and in
2005/6 in the 13 cities. Individual parcel records were aggregated to the city level, the
individual land-use and site descriptions being used to estimate the balance between
redundant buildings and vacant land where this was not explicitly indicated in the database.
This analysis indicated that between 2000/2001 and 2005/2006 there had been a net reduction
of roughly 2 km2 (5.7%) of vacant land across the thirteen cities; evidence that is consistent
with the findings from the remote sensed data.
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Table S1: Characteristics of England’s largest ‘Urban Areas’, in descending order of size,
from the Office for National Statistics [1].
Urban Area
City
Zone
Population
Area (km2)
Density (pop/km2)
Greater London
London
South
8,278,251
1,623.37
5,099
West Midlands
Birmingham
Central
2,284,093
599.72
3,809
Greater Manchester
Manchester
North
2,240,230
556.72
4,024
West Yorkshire
Leeds
North
1,499,465
370.02
4,052
Tyneside
Newcastle
North
879,996
210.91
4,172
Liverpool
Liverpool
North
816,216
186.17
4,384
Nottingham
Nottingham
Central
666,358
158.52
4,204
Sheffield
Sheffield
North
640,720
162.24
3,949
Bristol
Bristol
South
551,066
139.78
3,942
Brighton/Worthing/Littlehampton
Brighton
South
461,181
94.09
4,902
Portsmouth
Portsmouth
South
442,252
94.52
4,679
Leicester
Leicester
Central
441,213
101.64
4,341
Bournemouth
Bournemouth
South
383,713
108.15
3,548
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Table S2: The greenspace coverage within the urban core of each of the 13 study cities in
2006, derived from Landsat Thematic Mapper data.
City
Zone
Greenspace coverage (%)
London
South
27.5
Birmingham
Central
21.4
Manchester
North
29.1
Leeds
North
40.7
Newcastle
North
28.4
Liverpool
North
26.1
Central
19.3
Sheffield
North
22.9
Bristol
South
18.0
Brighton
South
16.9
Portsmouth
South
20.7
Central
20.2
South
23.7
Nottingham
Leicester
Bournemouth
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Figure S1: The location of the 13 study cities in southern (black circles), central (mid-grey
circles) and northern (light-grey circles) England: Bi, Birmingham; Bl, Bristol; Bn, Brighton;
Bo, Bournemouth; Lc, Leicester; Ld, Leeds; Li, Liverpool; Lo, London; Ma, Manchester; Ne,
Newcastle; No, Nottingham; Po, Portsmouth; Sh, Sheffield.
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Figure S3: (a) The previous status of land converted to residential use between 1989 and
2009 across England (solid line, previously undeveloped land; dashed line, previously
developed land; from [5]); (b) density of new dwellings built in England between 1990 and
2009 (from [5]).
(a)
Land-use change (%)
80
60
40
20
0
1989
1994
1999
2004
2009
2004
2009
Year
(b)
Dwellings per hectare
50
40
30
20
10
0
1989
1994
1999
Year
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References
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Newport: Office for National Statistics.
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Roy, D.P. & Morisette, J.T. 2002 An overview of MODIS Land data processing and product
status. Remote Sens. Environ. 83, 3 -15. (DOI:10.1016/S0034-4257(02)00084-6).
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