Biodiversity Assessment - Warren
Warren
Introduction
The region comprises dissected undulating country of the Leeuwin Complex, Southern Perth Basin (Blackwood Plateau), South West intrusions of the Yilgarn Craton and western parts of the Albany Orogen. Loamy soils support Karri forest, laterites support Jarrah-Marri forest, leached sandy soils in depressions and as plains support low Jarrah woodlands and paperbark/sedge swamps, and Holocene marine dunes support Agonis flexuosa thickets, Banksia woodlands and heaths. The climate is Moderate Mediterranean.
Summary of overall condition and trend
Although the Warren bioregion is continental landscape stress class 5 as assessed by the Landscape Health report (1 is most stressed, 6 is least stressed), the original data used to obtain this ranking is incorrect and the region should have a stress class of 3. The wetlands and river systems are generally in 'fair' or 'good' condition, though the trend is for these areas to decline. There are quite high numbers of ecosystems and species at risk from a wide variety of threatening processes. The trends at both the ecosystem and species levels are either to remain 'static' or 'decline'.
Summary of conservation priorities
The bioregion contains quite a high number of relatively small reserves and parks, but there is little opportunity to expand existing CALM estate as nearly all of the unreserved land has been cleared. Reserve management is generally quite good, with biodiversity issues being addressed, however a large number of constraints still exist. NRM policies are being implemented and achieving some biodiversity outcomes.
Natural values
The dominant land-uses are grazing, irrigated horticulture and conservation, with significant lesser areas of forestry.
The high rainfall and low evapotranspiration of the region allow growth of high forests and wetlands at a scale unique in WA. The regions' vascular flora and invertebrate fauna include many endemic components, especially in plant groups such as myrtaceae, rutaceae, proteaceae, papillionaceae, restionaceae and sterculeaceae. In terms of vascular plant species, the region is a biodiversity hot spot with hundreds of taxa per square kilometre. It is a refugia, with relict taxa from a wetter milder era, evidenced by groups and species of vascular and cryptic flora and invertebrates normally associated with the rainforests/Nothofagus forests of SE Australia, and now exitnct elsewhere in the State. Tingle forest provides refugia for relictual invertebrates, and peat/organic wetlands support relictual populations of aquatic invertebrates. Karst features support an endemic invertebrate fauna. It is the State's richest area for bryophytes normally associated with rainforests. Notable values include the tall forests (Karri, Jarrah and the Tingles), the limestone systems with their cave faunas, and the mound-forming microbial associations in the west of the region. Its Gondwanan arachnid fauna includes the tingle Moggridgea and Torndirrup's Austrarchaea mainae as well as other Gondwanan relics such as Dardarus sp. millipedes, Cynotelopus notabilis and velvet worms. A number of notable Critical Weight Range vertebrates also persist in the region, including Isodoon obesulus, Dasyurus geoffroii and Phascogale tapoatafa. Rare birds include the Western Whipbird and several cocatoos and parrots.
Click here to link to a table of natural values within each subregion
Wetlands
There are eight wetlands of national significance, including the lower reaches of the Blackwood River, Cape Leeuwin System, Dogerup Creek System, Gingilup-Jasper Wetland System, Broke Inlet System, Maringup Lake System, Mt Soho Swamps and the Owingup Swamp System. The condition of wetlands ranges from fair in some areas to near pristine in others, with most ranked as good and near pristine. The trend also ranges from declining rapidly to static within the individual wetlands with no discernable overall trend. Threatening processes include broad-scale vegetation clearing (now controlled but impacts still surfacing), feral animals (foxes, pigs, deer, horses, cats and rabbits), exotic weeds (Watsonia, east coast wattles, exotic grasses, blue gums, clovers and allies), changed fire regimes, pathogens (Phytophthora dieback in adjacent forests and heaths), changed hydrology (salinity and water levels), pollution from herbacides and fertilizers (agricultural and plantation), plantation harvesting (and subsequent return to traditional agriculture on several significant holdings), illegal Ti-Tree cutting (bean sticks, cray pots and brush fencing) and mining (could affect a lake and groundwater).
A further eight wetland areas are significant at a subregional level, including Scott River Wetland System, Bolghinup Lake Swamp (Black Point), Lake Charley-Donnelly Estuary Wetland System, Lower Warren River System, Deep River/Walpole River/Lower Frankland River/Walpole Nornalup Inlet Wetland System, Bow River-Irwin Inlet Wetland System, Kordabup River/Parry Inlet Wetland System and the Denmak River /Wilson Inlet Wetland System. Conditions vary widely from degraded (Scott River Wetland System) to good-near pristine (Bolghinup Lake Swamp (Black Point) and Lake Charley-Donnelly Estuary Wetland System). Others, such as the Kordabup River/Parry Inlet Wetland System change in condition from near pristine at the source and become progressively worse until they are degraded at the mouth or in agricultural areas. Trends for all the wetlands are static except Scott River Wetland System which is declining. The threatening processes that affect wetlands of subregional significance are the same as those affecting the wetlands of national significance (as above).
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
There are 13 riparian systems in Warren. However, only six (Scott River, Gardner River/Cantebury River, Shannon River, Inlet River, Deep River/Weld River, Walpole River) have their main catchments within the bioregion and seven (Margaret River, Blackwood River, Donnolley River/Barlee Brook/Beedalup Brook, Warren River, Frankland River, Bow River, Kent River/Styx River) have only the lower reaches in the bioregion. Most riparian systems are in degraded or fair condition, while Shannon River, Inlet River and Deep River/Weld River are in good-near pristine condition. The trend for all river systems is declining or static. Threatening processes that affect riparian systems include: broad scale vegetation clearing within agricultural zone, increasing fragmentation, exotic weeds (Blackberry, Arum Lilly, Victorian Ti-Tree, pasture species), changed fire regimes, changed water levels, salinity, pollution, water damming and diversion, eutrification, mining, feral animals (pigs, horses, deer), and recreational use.
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
Four Threatened Ecological Communities (all Aquatic Root Mat Communities of Caves of the Leeuwin Naturaliste Ridge) have been declared as critically endangered and three as endangered ('extant marine shoreline stromatolitic community', Scott River ironstone heaths and Mount Lindesay vegetation complex) by WA. A futher 17 are listed as ecosystems at risk. The condition of ecosystems at risk varies considerably from 'near pristine' for Aquatic Root Mat Communities to 'degraded' for Spagnum communities of the Tingle Forest, with most classed as 'fair' or 'good'. All ecosystems at risk are either declining or static with the shoreline stromatolitic community 'declining rapidly'. Threatening processes include changed fire regimes, salinity, ground water nutrient loads, weeds (arum, kikyru, pasture grass), vegetation clearing and fragmentation, pathogens, roadside disturbance, mining activities, climate change, urban development, feral animals (pigs), human recreation and tourism, and pollution from agricultural activities.
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
Three plant species have been declared as Critically Endangered, 11 plants, one mammal (Parantechinus apicalis), one bird (Calyptorhynchus latirostris) and one amphibian (Geocrinia alba) as Endangered, while 10 plants, three mammals (Dasyurus geoffroii; Pseudocheirus occidentalis; Setonix brachyurus), three birds (Leipoa ocellata; Botaurus poiciloptilus; Calyptorhynchus baudinii), one amphibian (Spicospina flammocaerulea) and two invertebrates (Austroassiminea letha and Austrarchaea mainae) are classed as Vulnerable under WA state legislation. A further 55 plants and 16 animals (mostly invertebrates) are considered species at risk. Most species are currently in 'fair' or 'good' condition, though there are significant number of 'degraded' populations. The trend is for species to remain 'static' or 'decline', but in many cases (such as rare flora and invertebrates) current condition and future trends are not known due to lack of information on the species.
A wide variety of threatening processes affect species at risk: small population size, restricted distribution, changed fire regimes, pathogens, vegetation clearing and fragmentation, feral animals (rabbits, pigs, foxes, cats), weeds (pasture grass, watsonia, marrum grass), roadside disturbance and roadworks, grazing pressure, salinity, timber harvesting (and poor logging practices), altered water levels, recreation activities, urban development, climate change, and lack of recruitment.
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
This largely wooded bioregion supports populations of many species that are confined to southwestern Australia, including several threatened taxa, but is too small to be of major significance for any of them. There are few exotic taxa, the most prominent being the Laughing Kookaburra. The major guilds that declined in reporting rate between the two Atlas periods were associated with the coast, possibly because observations in the second Atlas were concentrated on land. Granivores increased in reporting rate, probably reflecting shifts in land use from grazing to agriculture. Three bittern species were recorded in the first Atlas, there is a single record of an Australasian Bittern and none of Little or Black Bitterns in the second, possibly reflecting declines in water quality.
Status: Moderately diverse heathland and temperate woodland avifauna with distinctive southwestern elements.
Rare and threatened: No major populations.
Increasers: Laughing Turtle-Dove, Red-capped Parrot.
Indicators: Banded Lapwing, Baudin's Black-Cockatoo, Tawny-crowned Honeyeater, Scarlet Robin, Hooded Robin, Jacky Winter, Varied Sittella, Crested Shrike-tit, Restless Flycatcher.
Trend: Increase in some granivorous birds.
Scenario: Most species stable but some losses of woodland birds from agricultural areas.
Actions: Restore, expand and connect woodland fragments, concentrating on areas where declining woodland species persist. Maintain a range of fire ages within forest.
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 30 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 .567. (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 .2. (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 .29. (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 .65. (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 .73. (The maximum new endemism index value recorded in a bioregion is 0.93 and the minimum is 0.5).
Table: Translocated Species
There is no data available for this table within the bioregion.
Exotic Mammals
The number of introduced exotic mammal species that occur within this bioregion is 9. (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 6. (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
There are 25 nature reserves and 4 national parks within Warren. Nature Reserves vary in size from 12 ha to 4300 ha and the management standards rank is fair (biodiversity values and or management issues are poorly indentified, resource degradation is occurring though retievable). The majority of reserves (20) are small (<100 ha) and there is a noticeable absence of Nature Reserves in the central part of the subregion. No staff are resident on reserves and management visitation is generally limited to minimum of once per year. Very few reserves have formal approved management plans or interim management guidelines. Most reserves have significant weed invasion (e.g. pasture grasses and clovers) and feral animals (fox, rabbit and pig) problems. Phytophthora is infecting native vegetation communities in all parts of the region and this is compounded by seasonal inundation. Very small reserves often have depauperate understorey species composition and are often in a degraded state because of grazing impacts, extended fire frequencies and grass invasion from surrounding farmlands.
Waren contains 11 national parks in their entirety and the major portions of 3 others. The parks range in size from 50 ha to approximately 117 000 ha. Management plans exist for Leeuwin Naturaliste, Shannon, DeEntrecasteux and Walpole Nornalup National Parks. Staff are resident at 4 parks (Leeuwin Naturaliste, Walpole Nornalup, Torndirrup and William Bay) and other parks are serviced as needed from the nearest CALM office. The management standards rank is good for all parks except Scott, which is fair (result of Phytophthora and feral pig impacts). The factors impacting on conservation values are: linear design of Sir James Mitchell, Leeuwin Naturaliste and William Bay National Parks; semi rural land developments and an intensification of agricultural practices on adjoining lands impacting surface water; and routine feral animal (fox, some limited rabbit) control undertaken in all of the National Parks. Weeds are subjected to annual control programs in the most accessible areas, though the spread of some weeds (african thistle) is being exacerbated by high recreational visitor numbers. Fire regimes are strongly influenced by high visitation numbers and protection of adjoining land uses in parks close to urban and semi rural developments. The development and implementation of fire regimes consistent with biodiversity goals is absent from all of these parks.
Fifty of the region's 54 vegetation associations are well represented in conservation estate. However, two vegetation associations (Jarrah-Marri Medium Forest and Low Jarrah Forest Mosaic and Jarrah-Marri Low Forest) that only have small areas of their distributions in reserve and remain high priority. The overall reservation priority class is 5 because most vegetation types within the bioregion are reserved to the extent possible, and only minor additions to the system are feasible. Constraints to the acquisition of new reserves include: irreplacibility, limited opportunity to meet CAR requirements, economic contraints (price of land) and competing landuses such as mining and agricultural land.
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
No priority species or groups are identified for recovery in the bioregion, however salinity, changed water levels, fire, feral animals, disease, pollution and weed invasion are major threatening processes active across the region, at both species and ecosystem levels. The Off-Park recovery actions required are: restoration of hydrological systems (including adjacent bioregions); data gathering on individual plant life histories and development of fire regimes (frequency, timing, intensity) designed to maintain taxa and ecosystems; mapping of peat communities; maintaining and expanding existing baiting/control programs for foxes and developing better control techniques for cats, rabbits, and other feral animals; continuing to develop disease management systems (particularly in relation to Phytophthora), identifying assessment systems for ecosystems and taxa at risk and developing remedies; working with community and others to reverse impacts of agricultural fertalisers and pestacides/herbacideds on aquatic systems; and resourcing environmental weed control programs both on and off reserve.
Integrated NRM
Existing: threat abatement (e.g. Salinity Action Plan, Western Shield, and Weed Action Groups), industry codes of practise (Timber Industry regulation), Environmental Management Systems, planning with local governments and integration with property management planning, catchment planning and Landcare for land clearing controls. Feasible oportunities: institutional reform (e.g. finalize reservation actions for the Salinity Action Plan that have been pending for many years), environmental management systems (greater inclusion of tertiary institutions in research with student funding assistance), and further control over the process to prevent further land clearing. Main constraints are limited financial resources, lack of staff trained in conservation biology. Warren has an NRM rank of 4, indicating that NRM instruments are in place and achieving some biodiversity outcomes.
Map: IBRA map showing existing projects part of NRM.
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.
Click here to link to a table of contribution of integrated Natural Resource Management to the protection of biodiversity in each subregion: feasible opportunities and comments.
Further Information & Gaps
Data gaps and research priorities
The primary gaps are environmental mapping and biodiversity survey work. In particular, consistent vegetation mapping, longer term fauna, invertebrate and rare flora surveys, detailed studies of the habitat requirements of uncommon species and quatitative data on threatening processes, especially detailed Phytophthora mapping.
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.
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