Biodiversity Assessment - Northern Kimberley
Northern Kimberley
Introduction
Dissected plateau of Kimberley Basin. Savannah woodland of Woollybutt and Darwin Stringy bark over high Sorghum grasses and Plectrachne schinzii hummock grasses on shallow sandy soils on outcropping Proterozoic siliceous sandstone strata. Savannah woodlands on Eucalyptus tectifica - E. grandifolia alliance over high Sorghum grasses on red and yellow earths mantling basic Proterozoic volcanics. Riparian closed forests of paperbark trees and Pandanus occur along drainage lines. Extensive mangals occur in estuaries and sheltered embayments. Numerous small patches of monsoon rainforest are scattered through the district. Dry, hot, tropical, sub-humid climate with summer rainfall. The Mitchell subregion has a diverse array of exposed basement strata dissected by rivers, and a rugged sunken coastline, deeply embayed. Skeletal sandy soils incompletely mantle sandstone boulder country, significant areas of volcanic and dolerite surfaces as well as lateritised upland with open forests, and alluvial floors along major river valleys. The Berkeley subregion is less dissected than the Mitchell, and is dominated by an upland of mainly Pentecost sandstones more continuously mantled by (sandy) soils supporting an open savanna woodland with few vine thickets.
Summary of overall condition and trend
Continental landscape stress class is 6 as assessed by the Landscape Health report (1 is most stressed, 6 is least stressed). This should be reviewed in the light of the threatening processes that are operating at the landscape scale (fire, grazing). Indications are that there is a continuing general deterioration in the condition of the bioregion mainly due to fire and grazing.
Summary of conservation priorities
Current fire management practices, pastoral practices and feral animal control need to be improved. An investigation of the current status of individual species and ecosystems is urgent, along with research to build a better understanding of the impact of threatening processes. A range of vegatation associations and 'at risk' ecosystems need to be reserved.
Natural values
Special values: A sunken coastline with extensive coastal archipelagos (e.g. Buccaneer, bonaparte, Osborne Is, Eclipse Is and Sir Graham Moore Is) that form a microcosm of the NK1 subregion and present an opportunity to protect intact ecosystems. There is tropical laterite flora with a palm-dominated landscape (Livistona eastonii) unique in Western Australia. The flora and fauna of north-western margin is still intact. The Cape Bougainville rainforest on laterite and volcanics has no hoofed feral animals and is the largest single patch of rainforest in the Kimberley. An intact fauna persists in this bioregion, including threatened and endemic species such as the golden bandicoot (Isoodon auratus), scaly-tailed possum (Wyulda squamicaudata), monjon (Petrogale burbidgei), nabarlek (Peradorcas concinna) golden-backed tree-rat (Mesembriomys macrurus), Kimberley rock-rat (Zyzomys woodwardi), rough-scaled python (Morelia carinata), black grasswren (Amytornis housei). The subregion is fox and rabbit free and essentially uninhabited. There is a wide range of endemic vertebrates and land snail species. The declared rare flora species Eucalyptus ceracea is endemic.
Main land-uses are grazing of native pastures, Aboriginal reserves, UCL and Crown reserves, and Conservation.
Click here to link to a table of natural values within each subregion
Wetlands
Four nationally important wetlands of which three are river systems and one a series of wetlands. Two of these are in good condition and two are considered to be near pristine. Two are declining in condition but the trend for the two that are near pristine is unknown. The primary threatening processes for all these wetlands are changed fire regimes and grazing pressure. Three wetlands within the Mitchell subregion have been identified as being of regional significance. Further work is required for the Berkeley subregion. The wetlands are a riverine floodplain, a freshwater swamp forest and a permanent freshwater lake. One is significant for the maintenance of ecological processes and the other two are valuable as breeding and feeding grounds for a diversity of taxa. The threatening process for one is unknown and grazing pressure is the main threat for the other two.
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
The condition of riparian zones within the bioregion is generally good but is declining. Threatening processes include changed fire regimes, grazing pressure from feral herbivores and changed hydrology.
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
Three Threatened Ecological Communities are declared Vulnerable by WA: Walcott Inlet and Roe River Rainforest Swamps and Theda Soak Rainforest. Fifteen other ecosystems have been identified as being 'at risk'. They include as tropical and sub-tropical rainforest (NVIS 2), tropical forests and woodlands (NVIS 10, 11), paperbark forests and woodlands (NVIS 15) and herbland, sedgeland and rushland (NVIS 38). A number are unclassified at the NVIS scale of resolution. Most are in fair condition, and declining or static. The main threatening processes are grazing pressure and changed fire regimes. There is no data on threatened ecosystems in the Berkeley subregion; its rainforests, for example, are subject to the same pressures as their counterparts in the Mitchell subregion.
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
Under WA State legislation, 2 plant species, 3 mammals, 2 birds and 5 reptiles are declared as vulnerable, 1 bird and 1 reptile are declared as endangered, 42 plants are listed as either priority one or priority two, and 1 plant and 2 mammals are declared rare. The Commonwealth lists 2 birds and 2 turtles as endangered, and 3 birds, 4 turtles and 3 mammals as vulnerable. The threatening processes for most plants and terrestrial vertebrate are mainly changed fire regimes operating at the landscape scale. To a lesser extent grazing pressure and predation have been identified for vertebrates.
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.
Click here to link to a table of species at risk in each subregion: their status recommended recovery actions.
Birds
The North Kimberley is the only bioregion that contains all the taxa endemic to the Kimberley bioregion. It is of major importance to the Chestnut Rail in the coastal mangroves and the endemic Black Grasswren. It has major populations of the Endangered Gouldian Finch and northern subspecies of Crested Shrike-tit and is the only bioregion in which the Vulnerable western subspecies of Partridge Pigeon was recorded. There are no introduced birds. The reporting rates of some ground-feeding insectivores and rainforest birds increased, the latter at least probably reflecting a focus on this habitat during the second Atlas.
Status: Diverse bioregion with a high level of local endemism.
Rare and threatened: Chestnut Rail in the mangroves, Black Grasswren in the old spinifex on sandstone, Partridge Pigeon, Crested Shrike-tit and Gouldian Finch in woodlands.
Increasers: None indicative of landscape health.
Indicators: Emu, Australian Bustard, Partridge Pigeon, Varied Lorikeet, Black-tailed Treecreeper, Black Grasswren, Purple-crowned Fairy-wren, Jacky Winter.
Trend: Generally stable.
Scenario: Possible long-term loss of fire sensitive species.
Actions: Reimpose mosaic burning, at least in representative habitats.
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 57 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 .474. (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 0. (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 .12. (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 .69. (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 .72. (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 7. (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 0. (The maximum number of extinct mammal species in a bioregion is 29 and the minimum is 0).
Table: Extinct Species
There is no data available for this table within the bioregion.
Management responses
Reserve consolidation
Regional conservation lands include one large Biosphere reserve (Prince Regent River Nature Reserve), one large national park (Drysdale River), two smaller national parks (Mitchell River and Lawley River) and two small conservation parks (Laterite and Camp Creek). These reserves comprise 13.2 % of the bioregion. Their management standard is poor to fair. Apart from a donkey control program, no feral animal control programs exist. There is limited strategic aerial prescribed burning and some opportunistic hand burns, the latter being confined to very small areas of the Mitchell subregion. The effect of threatening processes (fire, weeds, ferals) remains to be determined. Due to uncontrolled stock access, vegetation changes are overt within the region's reserves, particularly in valley systems.
Of the 31 vegetation associations mapped in the region, 16 are un-reserved and, along with nine unreserved 'at risk' ecosystems, have a high priority for acquisition. A further eight vegetation associations have a high priority for further acquisition, even though small areas are reserved. Acquisition priorities include grasslands with associated woodland, hummock grasslands with associated woodland, pindan shrublands, tropical woodlands and tropical forests including rainforests, mangroves and mudflats. The level of reservation of three of the ecosystems at risk is unknown. Although the region would be ranked as class 5 for reserve aquisition on the basis of area, the reserve system's strong bias indicates that a rank of 3 is more appropriate.
Constraints on reserve acquisition include include competing land-uses (such as pastoral production), cost of purchasing pastoral lands, and the lack of data on biodiversity patterns across the subregion's landscape - we cannot accurately define all acquisition priorities on the ground.
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
Recovery actions for mammal, bird, turtle and plant species 'at risk' require data on status, population trends and mechanisms of threatening processes, as well as locations of remaining populations. For 'at risk' ecosystems, frequent, broad scale, hot, late dry-season burning in savanna needs to be avoided, feral stock needs to be removed from conservation estate, stock on other lands need close-order management, and donkeys and pigs need to be eradicated. Savanna fire regimes and grazing are the main causes of decline in biodiversity values throughout the region, including its rainforests and riparian zones. To address this issue, coordination between Government agencies, the pastoral grazing industry, traditional owners and the broader community will need to be improved. A large off-park effort is needed and there are resource constraints and limited community capacity.
Integrated NRM
Existing NRM actions include legislation for pastoral lease condition inspections by the Department of Agriculture. Pastoralists are notified of any problems and, ultimately, the Commissioner for Soil Conservation can resume the lease. In practice, this process does not appear to be very effective. Other actions include threat abatement planning as part of NRM, co-ordinated efforts by the Department of Agriculture to control donkeys, Land Conservation District Committees that provide a venue for discussing conservation matters and integrating property and catchment planning. There are a range of opportunities for NRM. Duty-of-care for biodiversity on pastoral lands needs to be tightened. Environmental management systems for controlling weeds, fire and feral animals should be co-ordinated across a variety of land tenures through Land Conservation District Committees, supported by research into the mechanism and impacts of these threatening processes and cost/effective solutions. Shire planning should incorporate biodiversity objectives and acknowledge the worth of the natural environment to tourism and the cost of managing bioodiversity and making national parks accessible. Catchment and regional plans should developed collaboratively by all stakeholders. Constraints include financial resources, the small number of people available to implement strategies and that few people recognise biodiversity benefits.
Map: IBRA map showing frequency of recovery actions (species).
Map: IBRA map showing frequency of recovery actions (ecosystems).
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
There are no region-wide vegetation, soil and environmental geology maps at better than 1:250 000 scale for planning. No quadrat based fauna and flora survey of region for assessing species and ecosystem status, condition, trend and effects of threatening processes such as cats, cattle, donkeys, pigs, fire and weeds.
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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