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FEATURE ARTICLE: SUBURBAN LANDUSE CHANGE ADELAIDE

INTRODUCTION

As with most Australian cities, Adelaide has a vision to promote a significant shift in the pattern of suburban growth towards infill development and urban renewal in activity centres located along transit corridors (Table 1).

For Adelaide, The 30-Year Plan for Greater Adelaide identified planning for net growth of 258,000 dwellings over thirty years. The focus of future growth will be away from urban sprawl to protect food growing areas and natural landscapes (Department of Planning and Local Government 2010). The 30 Year Plan proposes a shift towards smaller medium-high density dwellings, with a move away from larger detached dwellings, as projected in Table 2.


Table 1 Infill targets for selected Australian cities/regions

City/region	Timeframe	Target dwellings	Percentage from infill
		No.	%
Sydney	2005-31	640 000	60 to 70
Melbourne	2009-30	600 000	53
South-East Queensland	2009-31	754 000	50
Perth	2009-31	328 000	47
Adelaide	2010-40	258 000	moving from 50 to 70

	Business As Usual		30 Year Plan
	No. Dwellings	%	No. Dwellings	%
High Density	10 000	4	36 000	14
Medium Density	52 000	20	93 000	36
Detached	196 000	76	129 000	50

Dwelling Type	2006		2011		2006 to 2011
	No.	%	No.	%	No. Change
Separate house	381 218	76.2	404 212	75.8	22 994
Medium density	107 725	21.5	116 337	21.8	8 612
High density	9 024	1.8	10 908	2.0	1 884
Caravans, cabin, houseboat	1 358	0.3	1 196	0.2	-162
Other	778	0.2	616	0.1	-162
Not stated	294	0.1	240	0.0	-54
Total private dwellings	500 397	100.0	533 509	100.0	33 112

House to Block Size Ratio	Frequency	Average block size	Change from 1980	Average house size	Change from 1980	Mean Adjusted Area Ratio	Change from 1980
	No.	square meters	%	square meters	%		%
prior to 1980	200 928	779	0	143	0	20	0
prior to 1990	237 544	779	0	147	2	20	3
prior to 2000	278 473	759	-3	151	6	22	11
prior to 2010	321 784	732	-6	157	10	24	23
prior to 2014	340 099	718	-8	159	11	25	28

Table 5 shows the largest increase in mean house to block size ratio occurring between the end of the 1990s and the end of the first decade of the 2000s. The mean house to block size ratio for new dwellings built between 2010 and 2014 was nearly double the mean house to block size ratio of dwellings built in the decade to 1990. This increase in mean house to block size ratio over the past couple of decades has not been restricted to the city centre and inner metropolitan suburbs (see Figures 1-4).


Table 5 House to block size change, New dwellings, Adelaide UCL, 1980 - 2014

House to Block Size ratio	Frequency	Average Block Size	Average House Size	Mean Adjusted Area Ratio
	No.	square meters	square meters
prior to 1980	200 928	779	143	20
1980 to 1989	36 616	780	165	23
1990 to 1999	40 929	644	177	31
2000 to 2009	43 311	560	196	40
2010 to 2014	20 389	466	182	44

DENSIFICATION AND GREEN SPACE

Due to habitat loss, fragmentation and disruption to natural systems, a significant loss of biodiversity has occurred in urban areas. Since European settlement, Greater Adelaide’s vegetation has been subject to broad-scale clearance and disturbance. Today, only 13 per cent of the region retains native vegetation cover. Building on the direction set by The 30-Year Plan for Greater Adelaide, transport planning and investment will shift towards supporting a change in the nature of Adelaide’s urban form - focused on containing the growth of the wider metropolitan area, encouraging higher density development in the central city, and creating a network of well-connected major suburban centres (Government of South Australia 2015). Over time the new urban form will result in a significant increase in residential densities in designated areas, especially around transport hubs (Department of Planning and Local Government 2010).

Urban landscapes will be more ecologically sustainable where key habitat structures (e.g. trees, shrubs and woody debris) are maintained. The loss of habitat structures from modified landscapes is of increasing concern because of the negative consequences for both biodiversity and underpinning ecological processes such as nutrient cycling and carbon sequestration (Reduced availability of habitat structures in urban landscapes: Implications for policy and practice, Le Roux, Ikin et al 2014). Strategically located, well designed and linked open spaces, greenways, tree-lined and landscaped residential streets and commercial areas will be essential to a future healthy urban ecology (Department of Planning and Local Government 2010).

In addition to public greenspace, it has also been argued that suburban gardens, and backyards, also provide significant ecological and aesthetic benefits to the community. The interconnecting area of soft landscaping created by adjoining backyards can host a high degree of biodiversity, and can play a role in the conservation of a range of species. In addition to benefits to biodiversity, private greenspace can serve to create a favourable microclimate - planted areas can mitigate the 'heat island' effect that buildings and paving in urban areas can create, and trees can provide shade and prevent the absorption of heat (The life and death of the Australian backyard, Hall 2010). Other benefits include reducing stormwater runoff, and sequestration of carbon and other pollutants (Hall 2010).

Although not a direct measure of loss of private greenspace, the data presented here shows a clear trend towards larger house to block size ratios. With plans to create a more efficient urban form by building up to 70% of all new housing within existing urban areas, monitoring the loss of greenspace, and following through with targets to enhance the urban biodiversity of metropolitan Adelaide by supporting the development of urban forests, restoring watercourses, establishing linked networks of open space and encouraging the use of local indigenous species, will be important (Department of Planning and Local Government 2010).