Arboriculture & Urban Forestry 39(3): May 2013 are discrete: it is unlawful to drain stormwater into the efflu- ent disposal system (Government of South Australia 1929). While some local council innovations treat the resource in a more holistic manner, urban-wide and watershed-wide integrated management is in its early development stages. Most solutions to date center around demand management through regulation and pricing, the installation of rain wa- ter tanks plumbed directly into the household grey-water system, and the watering of parks and gardens using treated effluent rather than potable water (Laurenson et al, 2010). Figure 1 illustrates national arrangements for water governance. At the state level, three tiers of governance are involved (Figure 2). The convoluted nature of these interfaces generates haphazard institutional arrangements. Many of the or- ganizational structures result in a silo approach to their perceived areas of responsibility, engendering uncer- tainty and greatly complicating resource management. 105 For example, substituting treated effluent for the potable water previously used to irrigate the city’s parks and gar- dens, especially within the constraints of what was seen as a drought situation, has public appeal. Adelaide has three main sewerage treatment plants. The northern plant’s effluent is used for irrigated agriculture, the southern plant provides grey water for some of the State’s premier vineyards, and the central effluent treatment plant discharges the majority of its treated output directly into Gulf St. Vincent. With water restrictions, the Federal and State governments constructed a pipeline to convey treated effluent to the city’s parks and gardens. The project proceeded despite warnings by scientists and arborists concerning the long-term viability of the project: the treat- ed effluent has elevated sodium levels and many of the soil profiles to which it will be applied are sodic (Meyer 2008). To better integrate urban greenspaces with the environ- ment in which the city is situated, some research argues for planting species indigenous to the area (Mibus and Shepherd 2004). In making their arguments, the authors of these studies often ignore the built forms as a major and inescapable factor of the urban environment. Especially in periods such as the recent PDP, calls are made for plant- ings of water efficient, indigenous, desert region tree species. The aggressive nature of their root systems, with the consequent threat to pavements, road surfaces, and adjacent buildings, is often not considered. Indeed, in some cases, urban environments may be so anthropogenically affected that native plants may be inappropriate as urban habitat. Most Australian native flora are non-deciduous. Con- sequently, understory litter problems are continual, and especially where such trees are planted adjacent to roads and walkways, management demands in respect to understory maintenance are higher than for deciduous species. Addition- ally, many writers suggest that the most beneficial remediation of the urban heat island effect can be most efficiently achieved through the planting of deciduous species, allowing maxi- mum solar warming of buildings in the winter while shield- ing them from summer radiation (Correy 1992; Brindal and Stringer 2009; Fisher 2009; Gómez-Muñoz et al. 2010). Lost opportunities notwithstanding, a number of sci- Figure 2. South Australian (state) arrangements for water gover- nance (2010). Diagram courtesy of the National Water Commis- sion Archive. Seeking and Implementing Science Based Information While the relationship between science and public policy is symbi- otic, in Adelaide, when necessity dictates, such as with the introduc- tion of policies that which might prove unpopular to constituents (e.g., water restrictions), science is invoked selectively to justify the policy and to seek solutions that lessen negative public reaction. Short-term political expediency too often ignores good science. entific innovations with potential importance to urban foresters have been validated by the climatic condi- tions of the last decade. An example are projects to col- lect stormwater runoff directly from buildings or ad- jacent paved areas, channeling it either into aquifer storage for subsequent irrigation use or dispersing it directly into soil profiles, thus making it avail- able to local trees. The system in one of these projects, Brompton Parfitt Square, is illustrated in Figure 3. Mortality of trees that have access to these projects was, during the decade under examination, zero. Interestingly, as urban run-off increases, existing infrastructure constraints can provide an unexpected opportunity for innovative urban greenspace design. One residential suburb (Northgate) was recently devel- oped on land that had previously been used for agricul- tural research purposes. However, because the storm- water infrastructure that carried the water westward to the gulf could not carry the additional capacity, the suburb had to incorporate a series of greenspaces and ©2013 International Society of Arboriculture
May 2013
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