Biodiversity Assessment - Swan Coastal Plain
Swan Coastal Plain
Introduction
The Swan Coastal Plain Bioregion comprises the Dandaragan Plateau (SWA1) and Perth Coastal Plain (SWA2). Its climate is classified as Warm Mediterranean and rainfall ranges between 1000 and 600mm annually. It includes urban developments associated with the city of Perth, and is dominated by woodlands of Banksia and Tuart on sandy soils, sheoak on outwash plains, and paperbark in swampy areas. The colluvial and aeolian sand areas represent three phases of Quaternary marine sand dune development (which provide relief), and include a complex series of seasonal fresh water wetlands, alluvial river flats, coastal limestones and several off-shore islands. Younger sandy areas and limestones are dominated by heath and/or Tuart woodlands, while Banksia and Jarrah-Banksia woodlands are found on the older dune systems. Fine-textured outwash plains at the foot of the Darling Escarpment are extensive only in the south , and were once dominated by A. obesa-marri woodlands and Melaleuca shrublands. In the north-east especially, the plain rises to duricrusted Mesozoic sediments dominated by Jarrah woodland. The Dandaragan Plateau is the region's north-eastern corner, and is composed of cretaceous marine sediments mantled by sands and laterites. The plateau is characterised by Banksia low woodland, Jarrah - Marri woodland, Marri woodland, and by scrub-heaths on laterite pavement and gravelly sandplains.
Summary of overall condition and trend
The Swan Coastal Plain subregion has been subjected to almost every type of environmental disturbance. SWA1 is continental landscape stress class 2, while the very much larger SWA2 is mistakenly 3 as assessed by the Landscape Health report (1 is most stressed, 6 is least stressed). SWA2's stress class value should be between 1 and 2. The overall condition of dryland (and wetland) areas in the subregion is classed as 'degraded' with this trend likely to continue.
Summary of priority management/consevation priorities
The 25 threatened ecosystems in the Swan Coastal Plain are associated with fertile soils of localised extent and occurrence, especially if the occur in southern parts of the region (welands, clays and other alluvials and coluvials). These are almost entirely cleared. Twenty-four (16 endangered and 9 vulnerable) are in SWA2, while one endangered ecosystem is in SWA1. Of the 53 vegetation associations that occurred in SWA2 subregion in pre-european times, 18 are centred on SWA2 and, as well, have less than 10% of their original area in conservation lands. Eight high- and medium-priority ecosystems in SWA1 are not represented in conservation lands.
The reserve management standard throughout the Swan Coastal Plain is listed as poor-to-good for CALM managed reserves. Most of the larger reserves, national parks or conservation parks tend to be relatively well managed and most now have specific management plans. Smaller reserved areas are usually associated with protection of coastal plain wetlands or a small vegetated remnants surrounded by urban and semi-rural land uses. There are a number of processes that threatened the ecological health of CALM managed lands, including increasing soil salinity (particularly in the northern part of the bioregion), bushfire control, feral animal control, disturbance by urban development, agricultural activities, root-fungus (Phythopthera), weed invasions, limited diversity of vegetation communities within reserves/parks, a lack of formalised biodiversity monitoring programs, and the costs associated with acquiring land for new reserves and ongoing management.
The Dandaragan Plateau and Perth subregions are both listed as belonging to reservation class 4 (10 to 15% of area is reserved for conservation, any tenure), however the system is strongly biassed and threats are numerous and pervasive.
Natural values
A variety of plants, including Tuart are endemic to the region.
Click here to link to a table of natural values within each subregion
Wetlands
There are 26 wetlands of national significance are listed, with only one of these on the Dandaragan plateau. In overall condition they are fair-to-good, requiring minimum-to-signifiant management for recovery. Their condition is static, with a declining trend forecast for only one wetland. While many threatening processes affect these wetlands, all relate to urbanisation. Eutrophication needs to be addressed, along with invasion of weed species (particularly grasses from urban gardens), increased or decreased flow to the wetland, construction of canals, presence of feral animals, shoreline development and recreational activities.
Over a quarter of SWA2's land area (from Wedge Island to Dunsborough) is wetland. Some 4700 basin and flat wetlands are listed, most of which would warrant inclusion as wetlands of regional significance. Clearly, it is impractical to include them all here and the reader is refered to the atlas (Hill et al. 1996a). No wetlands of sub-regional significance are listed in the Dandaragan subregion (SWA1).
Nationally important wetlands
Map: IBRA map showing DIWA locations, towns, subregions, major roads and reserves and most common threatening processes.
Click here to link to a table of Australia's Important Wetlands (Directory of Important Wetlands of Australia): their type, condition, trend and threatening processes within each subregion.
Regionally important wetlands
Click here to link to a table of provisional identification of wetlands of regional significance: their type and special values within each subregion. The reliability of the overall subregional assessment is indicated.
Click here to link to a table of provisional identification of wetlands of regional significance: their condition, trend and threatening processes within each subregion.
Riparian Zones
Moore River/Gingin Brook, Hill River, Swan River, Serpentine River, Murray River, Harvey River; Collie River and Preston River flow through the Swan Coastal Plain. Most have their catchment areas in bioregions to the east. Vegetations associated with these rivers and catchments are in fair-to-poor condion, with a decline in vegetation quality expected. Threatening processes affecting the region's riparian vegetation include broadscale vegetation clearing, increasing fragmentation/loss of remnants/lack or recruitment, changes in hydrology due to salinity and altered flow regimes, grazing pressure, exotic weeds and feral animals.
Map: Riparian threatening processes.
Click here to link to a table of riparian zones: their average condition, trend and threatening processes for each subregion. The reliability of this overall assessment is indicated.
Ecosystems at risk
Ten Threatened Ecological Communities have been declared as Critically Endangered, 6 as Endangered, and 9 as Vulnerable, by WA in the Swan Coastal Plain bioregion. Overall, 48 ecosystems (vegatation-units) have substantially reduced area on the Swan Coastal Plain. The list includes a high number of associations that are either eucalypt woodlands with shrubby understorey (NVIS 8) and other shrublands (NVIS 32) which includes wetlands. The wetland environments on the Swan Coastal Plain are under particular threat from altered surface flow regimes and groundwater levels as well as invasion of weed species, disturbance by people, vehicles, and feral animals. Eucalypt woodlands have been adversely affected by vegetation clearing and fragmentation, weed invasion, feral animals and changed fire regimes. Banksia woodlands appear to be under the same pressures as eucalypt woodlands, and several are listed as threatened. Only 2 of the 48 ecosystems are showing signs of improvement, the rest are rapidly declining (2), declining (13), static (14) or unknown (17). Forty-one of the contracted vegetation-units in SWA2 each covered more than 0.1% (ie 1 334 ha) of the subregion in pre-European times. Seven have less than 10% (av = 3.5%) of their original area remaining, and so could be considered at risk. Few are adequately represented in reserves, at best less than 3.4% of original area is reserved. 18 have between 10% and 30% of the original area remaining and ' of these, only 4 have greater than 10% of the sub-region pre-European area in CALM reserves.
Map: IBRA map showing frequency of threatening processes for ecosystems.
Click here to link to a table of provisional list of threatened ecosystems in Australia: their broad vegetation type (National Vegetation Information System - Major Vegetation Subgroup), recommended status, current legislative protection as a threatened ecosystem, trend and bioregional distribution. These ecosystems are arranged in the bioregion of their principal occurrence. The reliability of the recommended status is indicated.
Click here to link to a table of provisional list of threatened ecosystems in each subregion: their threatening processes.
Click here to link to a table of provisional list of threatened ecosystems in each subregion: their recommended recovery actions
Species at risk
Sixteen plant, 1 reptile and 1 invertebrate species have been declared as Critically Endangered, 19 plants, 1 mammal and 1 bird as Endangered and 18 plants, 4 mammals, 1 bird, and 2 reptiles as Vulnerable under WA state legislation. One species Dasyornis broadbenti litoralis (Rufous Bristlebird - western subspecies) is extinct in the subregion. Species are equally divided among two trend categories, either static or delining to declining rapidly. There are many threatening processes that affect these species, including broadcale vegetation clearing, increased fragmentation/loss of remnants/lack of recruitment, grazing pressure, feral animals (rabbits), exotic weeds, changed fire regimes, pathogens, changed hydrology (due to both salinity and altered flow regimes), and recreational use of areas by people.
Map: IBRA map showing frequency of threatening processes for species.
Click here to link to a table of species at risk in each subregion: their status, trend and subregional distribution. The reliability of the assessment of trend is indicated and whether recovery plans have been prepared.
Click here to link to a table of species at risk in each subregion: their threatening processes.
Table: Australia's Important Wetlands (Directory of Important Wetlands of Australia): their type, condition, trend and threatening processes within each subregion.
There is no data available for this table within the bioregion.
Birds
Many of the species confined to the south-west have been recorded in the Swan Coastal Plain, but the bioregion contains a major proportion of the population of none of them. Nevertheless, given their rarity and rapidly declining abundance, the bioregion's populations of Vulnerable Australasian Bittern and Carnaby's Black-Cockatoo are important for conservation. Turtle-Doves make up the bulk of the exotic bird population, but there is also a higher proportion of records of native species introduced from eastern Australia than in any other bioregion. Most of these introductions are aviary escapes and four (Laughing Kookaburra, Sulphur-crested Cockatoo, Long-billed Corella and Rainbow Lorikeet) were recorded at much greater rates during the second than the first Atlas period, the Rainbow Lorikeet having newly arrived. Except for the Chestnut-breasted Mannikin, which was recorded during both Atlas periods, it is possible that other introduced species recorded have not established wild populations. There was a decline on the reporting rate of ground-feeding insectivores, but freshwater bird reporting rates failed to replicate a national decline. This is possibly a consequence of the wetter conditions in the second Atlas period.
Status: Much altered bioregion with moderately diverse avifauna including distinctive southwestern elements; moderate load of native introduced species.
Rare and threatened: No major populations.
Increasers: Laughing Kookaburra, Sulphur-crested Cockatoo, Long-billed Corella, Rainbow Lorikeet.
Indicators: Australian Shelduck, Banded Lapwing, Carnaby's Black-Cockatoo, Tawny-crowned Honeyeater, Scarlet Robin, Hooded Robin, Varied Sittella, Crested Bellbird, Crested Shrike-tit, Restless Flycatcher.
Trend: Decline among some ground-feeding insectivores.
Scenario: Introduced eastern species may increase in urban and suburban areas.
Actions: Restore, expand and connect woodland fragments, particularly those containing declining woodland species.
Click hereto download a summary report including the physical characteristics of the bioregion, a species list, and summary statistics [Excel file]. The file may open on your screen. To save it to your system 'Save as' under the File menu.
Mammals
Number of species and status
There are 40 mammal species within this bioregion. (The maximum number of species recorded in a bioregion is 86 and the minimum is 25).
Click here to link to a table of number of species in each status class for this bioregion.
Click here to link to a list of mammal species and their status for this bioregion.
Critical weight range
The critical weight range (35 - 5500 g) of mammals is the size range of Australian mammals that have been most affected by environmental changes following European settlement. In this bioregion, the proportion of mammal fauna within the critical weight range is .55. (The maximum proportion of fauna within the critical weight range recorded in a bioregion is 0.632 and the minimum is 0.222).
Faunal Attrition Index
Faunal attrition is a measure of contraction or loss of species richness with a region. A high index value means many species have declined or are extinct in the bioregion. The index can be used to compare the status of mammal fauna to regional attributes such as changes since European settlement and average annual rainfall. The Faunal Attrition Index for mammals in this bioregion is .35. (The maximum faunal attrition index value recorded in a bioregion is 0.66 and the minimum is 0).
Click here to link to a table of Faunal Attrition Index for groups of mammals shows the contributions of each group to overall patterns of faunal decline.
Faunal Contraction Index
A range contraction index is a measure of the extent to which the range inhabited by a particular species has contracted. A high index value means that many of the species comprising the region's original mammal fauna have contracted from a high proportion of the regions they originally occurred in. The faunal contraction index for the mammal fauna in this bioregion is .34. (The maximum faunal contraction index value recorded in a bioregion is 0.51 and the minimum is 0.07).
Faunal Endemism Index
Endemic species are those restricted to certain regions. Regions containing endemic species are considered to have high biodiversity conservation values because opportunities to conserve those species do not exist elsewhere. A high index value means that the species comprising the original mammal fauna typically occurred in few bioregions. The faunal endemism index value for the mammal fauna in this bioregion is .67. (The maximum faunal endemism index value recorded in a bioregion is 0.79 and the minimum is 0.52).
New Endemism Index
Extant (still surviving) species that have undergone major range contractions can be considered 'new endemics'. Bioregions that contain new endemic species are often important refugia for threatened species. The new endemism index for the mammal fauna in this bioregion is .75. (The maximum new endemism index value recorded in a bioregion is 0.93 and the minimum is 0.5).
Click here to link to a list translocated species that has/have been successfully translocated into this bioregion.
Exotic Mammals
The number of introduced exotic mammal species that occur within this bioregion is 14. (The maximum number of introduced exotic mammal species in a bioregion is 16 and the minimum is 5).
Click here to link to a list of introduced exotic mammal species for this bioregion.
Extinct mammal species
The number of extinct mammal species that previously occurred within this bioregion is 10. (The maximum number of extinct mammal species in a bioregion is 29 and the minimum is 0).
Click here to link to a list of extinct mammal species for this bioregion.
Management responses
Reserve consolidation
In SWA2 there are 65 nature reserves, 8 national parks and 2 conservation parks. Only one nature reserve is listed for SWA1.
Approximately half of the nature reserves in this subregion are small (<100 ha), with 10 reserves < 10ha and only 8 exceeding 1000ha. In the southern and central zones of the subregion, the areas highly disturbed by urban development and intensive agricultural activities, nature reserves are frequently associated with protection of coastal plain wetlands or a small vegetated remnants surrounded by urban and semi rural land uses. The largest reserves are found in the northern part of SWA2, with all but two being greater than 700 ha. These reserves contain coastal and northern sand plain communities grading to low eucalypt woodlands which in season are used by commerical apairists. There are no resident staff on nature reserves; management visitation varies greatly with urban wetland reserves often frequently visited and others restricted to a minimum of once per year. Few reserves have formal approved management plans or interim management guidelines. In the southern and central parts of the sub-region, because of their small size and position low in the landscape, most reserves have significant weed invasion (especially watsonia, arum, bridle creeper, kikuyu and other annual and perennial grasses). Feral animals (foxes, rabbits and increasingly in the south, pigs) in all but the largest reserves are not controlled. Significant problems impede the agencies ability to undertake control programs in urban and semi urban environments. Across all areas of the subregion, phytophthora disease is changing the species composition of reserves. Understorey species composition is often depauperate and in a degraded state in the smaller reserves, resulting from grass and other weed invasion, grazing impacts and too frequent fires. Fire regimes aimed at biodiversity conservation outcomes are generally absent, deliberately lit wildfires can and do occur frequently depending on the proximity of the reserve to urbanisation. Formalised biodiversity monitoring programs are absent.
Five of the eight national parks have management plans which are being implemented, although targeted ecological monitoring programs are either absent or inadequate. Park area ranges from 1059 ha to 26 965 ha, with 2 of the 8 parks primarily servicing the recreation and day visitor requirements of the Perth metropolitan area. Three parks have staff in residence. All but two are sited on or near the coast (Lesueur NP and Moore River NP), so the overall diversity of vegetation communities contained within these parks is limited. Feral animal control (fox, rabbit) is undertaken but is hampered by their close proximity to urbanisation. Salinity issues are generally not evident on the western side of the subregion but extensive use of ground and surface water resources may be impacting of the overall health of the vegetation in a number of these parks. Fungal disease (Phytophthora sp, Armillaria sp) are present in all of the parks and Tuart decline (Borer, Phorocantha spp) are currently impacting on much of Yalgorup, Neerabup and Yanchep NP's. The southern and central zone parks often have high weed loads esp. Arum, bridle creeper and pasture grass sp, often associated with riparian and moisture gaining sites. Fire regimes are often dominated by the requirement to protect adjoining land values. In most parks formalised biodiversity monitoring programs are absent.
Neither of the Conservation Parks have resident staff , although a management Plans is available for Leschenault Peninsula CP. Size ranges from 27 ha to approx 1000 ha. Weed invasion along riparian habitats and pasture grass invasion along the boundaries is of concern. Fox and rabbit control is undertaken. Fire regimes currently set at exclusion are yet to be optimised for biodiversity outcomes. Formalised biodiversity monitoring programs are absent but vegetation assessment plots were established during the Swan Coastal Plain Vegetation project and could form the basis of permanent monitoring program.
The Bioregion has been assigned a reservation class of 4 (11.8% of region's area is reserved), however reserve system bias and threatening processes are significant enough in the region to warrant a higher priority (Class 3). However, there are a number of factors which constrain the ability of CALM to aquire reserves. The priority issue is that the bioregion has many competing land-uses (such as agriculture, mining, urban area and grazing), and the cost purchasing land close to urban areas is very high. To a lesser extent, other issues such as difficulties in identifying biodiversity values in some areas due to lack of resolution of data also affect the ability of CALM to aquire new land for reservation.
Click here to link to a table of comprehensiveness, adequacy and representativeness (CAR) of the National Reserve System in terms of ecosystems and area sampled and a ranking of reserve management. The bioregional priority for consolidating the National Reserve System is based on this CAR analysis and threat.
Table: Bioregional and subregional priorities and ecosystem priorities to consolidate the National Reserve System and associated ecosystem constraints.
There is no data available for this table within the bioregion.
Off-park conservation for species and ecosystem recovery
The Diatomite Lakes of the Dandaragan Plateau and the Plant assemblages of the Wannamal Lake system are both highlighted as priority species for conservation in SWA1 as at present there are no recovery or action plans for the areas. Critical Weight Range mammals are also highlighted but a recovery plans exists for these. The majority of threatened flora species in SWA2 have most known populations located off-reserves and several of the threatened invertebrate species (bees and moth species) are also only known from non-reserved land in the highly cleared areas of the swan coastal plain (SWA2) subregion. Also highlighted in SWA2 as priorities for off-park recoverys were 1) Remnant vegetation complexes on the Abba Plains, including but not limited to the Busselton Ironstone TEC east of Busselton and subjected to extensive clearing for agriculture and 2) Agonis and/or tuart woodlands along coastal wetlands supporting populations of Western Ringtail Possum in the Busselton to Bunbury area threatened by urbanisation.
The only Recovery Plan that has already been written for SWA1 is for the Chuditch. Most species of flora have broad discussion of actions required to assist recovery detailed in the publication Declared rare and poorly known flora in the Moora District (CALM, 2001) which covers the northern zone of SWA1. The draft Swan Region Threatened Flora Management Plan provides recovery actions for all DRF flora within the Department of Conservation and Land Management's Swan Region (covering the southern zone of SWA1.). Recovery Plans or Interim Recovery Plans exist for all Critical ranked flora (state ranking), fauna species and TEC's and all Endangered and Vulnerable ranked mammal fauna and bird species (except the Australiasian Bittern - covered in the National Action Plan for Birds). However, no Recovery Plans or Interim Recovery Plans exist for any of the ranked invertebrate fauna.
Recovery actions for all species include habitat retention and protection on both Government managed land and privately owned land as the first priority. In addition to this, Recovery Plans for fauna include the control of feral animals, fire management, and reduction in habitat degradation through grazing pressure. The focus for Recovery Plans for flora generally include control of feral animals and weed invasion, research to gain a better understanding of life history requirements for all rare flora and protection from road maintenance activities and grazing.
The draft Swan Region Threatened Flora Management Plan provides recovery actions for all Declared Rare Flora within the Department of Conservation and Land Management's Swan Region (covering the central zone of SWA2) even though there are no specific recovery plans for critically endangered flora and TEC's of the Swan Coastal Plain. Other Recovery Plans which have a much wider application than the Swan Coastal Plain bioregion include the National Recovery Plan for Malleefowl, The Action Plan for Australian Birds 2001, Action Plan for Australian Marsupials and Monotremes and The Action Plan for Australian Reptiles
On average the Swan Coastal Plain requires significant off park effort to prevent the further degradation of ecosystems and species within the bioregion (rank of 2 on Off-Park Conservation scale).
Integrated NRM
Natural Resource Management Actions such as soil conservation, land clearing legislation, Bushcare, strategies for local government, and local conservation have been largely ineffective in SWA bioregion. Consequently, there are many opportunities for NRM activities to operate more effectively and suggestions include the following:
- incentives for conservation on private property, such as rate rebates, or additional subdivision rights.
- legislation including duty of care for leasehold and other lands - requires more rigorous control and needs to be concentrated on high disturbance areas such as rail and road reserves.
- Institutional reform e.g. rural reconstruction, industry reconstruction, new tenure and management arrangements.
- Tradeable rights - carbon credits would provide impetus to new revegetation efforts.
- Other planning opportunities including local government planning and National Action Plan for Water Quality and Salinity.
- Integration with property management planning, catchment planning and Landcare. Increasing the role of NRM in all agricultural activities.
- coordinated threat abatement planning
- improved local government planning
- increased/improved integration with property and catchment management planning
A number of impediments exist. The current role of Government Departments in NRM and policing of activities such as land clearing is fragmented and unclear. Departments whose have responsibility for resource exploitation may also have resource protection roles. Penalties for undertaking activities such as land clearing are comparatively minor and do not have the support of the greater rural community. Need to increase awareness of conservation values through education of various industries (mining, agricultural) and the public in general. There is also a high level of property speculation for assumed future urban or rural subdivision at inflated land prices, and a large part of this speculation is on bush blocks. Limited financial resources are also a major constraint. Both subregions are ranked as having major contraint problems to implement effective NRM actions due to the extent of past degradation, competing land uses, high property values, urbanisation pressures.
Click here to link to a table of contribution of integrated Natural Resource Management to the protection of biodiversity in each subregion: existing measures and effectiveness.
Table: The contribution of integrated Natural Resource Management to the protection of biodiversity in each subregion: feasible opportunities and comments.
There is no data available for this table within the bioregion.
Further Information & Gaps
Data gaps and research priorities
As yet there has been no regolith mapping in the Swan Coastal Plain and vegetation mapping is 1:250,000 at best. Most reserves do not have long term survey data for vertebrates and many of the invertebrate specimens have been yet to be sorted, identified or analysed, even though existing data suggests there may be significant species or groups of species withing the region. There is relatively little data available on the habitat requirements for virtually all invertebrates, persisting CWR mammal and uncommon vetebrate and plant species. There is no data to provide a regional context (including population trends) for most species, including introduced or pest species. Detaile floristic surveys have been carried out in the southern part of the Swan Coastal Plain which has provided valuable information, especially about Threatened Ecological Communities, however more survey work is required in the northern part of the region. At present there is no quantitative data on the effects of exotic predators, weed colonisation, fragmentation and farm clean up, fire or mineral extraction (on gypsum). To date there has been no monitoring of the effect of salinity on species composition of communities is in place, although 10 bench-mark quadrats have now been established.
References
Environment Australia 2000. Revision of the Interim Biogeographic Regionalisation of Australia (IBRA) and the Development of Version 5.1. - Summary Report. Department of Environment and Heritage, Canberra.
A complete list of references is available by clicking here.
Further information
View the Landscape Health in Australia report.
View the Terrestrial Biodiversity Assessment 2002 report.
Download the Terrestrial Biodiversity Assessment 2002 Database - Biodiversity Audit Data Entry System (BADES), and specifications
Click here to link to a table of some major data gaps in each subregion in terms of protecting biodiversity.
Before you download
Most publications are downloadable as PDF files. Adobe Acrobat Reader is required to view PDF files.
If you are unable to access a publication, please contact us to organise a suitable alternative format.
Key
Links to an another web site
Opens a pop-up window