Summary - City of Gosnells

Methods 29The pattern of vegetation distribution that is present in many palusplains on the SCP presents some specificdifficulties in wetland management category evaluation and in wetland management. Palusplains are laterallyextensive, and on the SCP they are largely cleared of native vegetation and often accommodate a plethora ofpoorly-planned and poorly-managed land uses. The MKSEA is not an exception in being a patchwork ofsmall native vegetation remnants, paddocks, vacant derelict dwellings, dams and drains, areas of dumped fill,roads, houses, factories, poultry sheds, truck yards, mechanical workshops, warehouses, quarries and privaterefuse dumps. If the vegetation of a ‘patchwork’ palusplain is evaluated over its entire area, the vegetationcondition is, effectively, averaged over the large area involved. This method of evaluation would be likely toresult in a MUW or REW category, regardless of the high conservation significance of remnants ofvegetation that may be present. The alternative method of evaluation, which is more commonly used, is toevaluate parts of an extensive palusplain as several, separate entities (after defining the boundaries that are tobe used in the assessment). In this case, the evaluation is likely to result in a MUW or REW category for theunvegetated units and CCW for the small vegetated units.Although the process of splitting an extensive wetland into several management units may be the mostobjective way of recognising small areas of high conservation value vegetation, it serves to reinforce thefragmentation of ecological units that are already critically small. Such splitting up of a palusplain intoseveral management units does little to recognise that ecological functions and processes, such asgroundwater flow, unify parts of a palusplain into a single unit and help to maintain areas of valuablevegetation. It also prompts the further loss of scarce palusplain habitat on the SCP. Palusplains that areclassed as ‘degraded’ or ‘completely degraded’ in terms of native vegetation often retain their geomorphicintegrity, soils or other attributes. Some can be restored and replanted, and can also be recolonised by nativeflora and fauna from adjacent native vegetation. If managed appropriately, such areas can provide additionalhabitat suitable for the reintroduction of flora that is currently threatened because its former range hascontracted to a small fraction of its previous size due to development.The approach taken in the current evaluations of wetlands in the MKSEA was to initially split extensiveareas of palusplain/floodplain into separate units based on vegetation condition. The wetland managementcategories of these wetlands were then evaluated separately via two questionnaire methods (VCSRG, 1998and EPA, 1993) and according to vegetation condition. Subsequently, the opportunities for maintenance andenhancement of conservation values and ecological functions were considered in the discussion of linkage ofareas with high conservation values via buffer zones and ecological corridors.3.4 Survey LimitationsEPA Guidance Statement for Terrestrial Flora and Vegetation Surveys for Environmental ImpactAssessment in Western Australia (EPA, 2004b) identify the main factors that can limit and constrain suchsurveys. The current project was evaluated against these factors (Table 3.4) and several significantlimitations were found to be present. These constraints are addressed below.1. Completeness and intensity of the surveyAn appropriate level of survey was used for the high conservation value flora and vegetation of the areain accordance with EPA recommendations. The only aspect of this survey that was not completed wasthe investigation of several blocks that clearly had remnant vegetation but to which landownerswithdrew or did not grant access (see below).Some investigations into the stratigraphy and hydrology of a sample of sites were made during thecurrent field survey and hydrological features of high conservation significance were found that werenot known previously in the MKSEA or in the Greater Brixton Street Wetlands. However, the currentsurvey of the MKSEA was primarily a biological survey, not a detailed hydrological study. Theintensity of the hydrological study was below that required to characterise the essential features of thehydrological cycle in the MKSEA and the hydrological interactions between the MKSEA and theGreater Brixton Street Wetlands. The hydrogeology of the Greater Brixton Street Wetlands is relativelywell-known thanks to a detailed, fine-scale hydrological field study by the V & C Semeniuk ResearchGroup (2001). The results of this study and the ongoing monitoring of the bores after 2001 by the V &Tauss, C. and Weston, A.S. (2010). The flora, vegetation and wetlands of the Maddington-Kenwick Strategic Employment Area.A survey of the rural lands in the vicinity of the Greater Brixton Street Wetlands. Report to the City of Gosnells, W.A. Version 18.04.10