The Wimmera is a biodiversity hotspot. The region is the geographical and biological transition between temperate and arid Australia. The Great Dividing Range that defines so much of Australia’s climate and biodiversity concludes at Dyurrite (Mount Arapiles) and with it, the distribution of numerous ‘temperate’ species, like the smoky mouse (Pseudomys fumeus), southern brown bandicoot (Isoodon obesulus) and long-nosed potoroo (Potorous tridactylus).\
At the foothills of Gariwerd (Grampians National Park) the temperate montane forest and woodlands give way to the Wimmera plains to the north and the grassy woodlands and wetlands of the south-west. Formerly dominated by grassy woodlands, these areas are famed for their agricultural productivity but also support important biodiversity assets like the Wimmera grasslands, internationally significant wetlands and habitat for the critically endangered south- eastern red-tailed black cockatoo (Calyptorhynchus banksii graptogyne).
First Nations people moved across these landscapes seasonally, accessing plants and animals for food, fibre and medicine and employing cultural burning and other techniques to keep a mosaic of vegetation cover.
Where Dyurrite (Mount Arapiles) signifies the end of the mountains, the Little Desert National Park represents the start of Australia’s arid interior. The Little Desert region supports a vast array of biodiversity: 670 or 24% of all Victoria’s vascular plant species, more than 220 bird species and 80 nationally threatened fauna and flora species.(34)
The Little Desert National Park is the largest contiguous patch of remnant native habitat in the Wimmera, protecting just over 130,000 hectares. Across the landscape there are several medium-sized remnants, such as the northern slopes of Gariwerd (Grampians National Park) and Burrunj (Black Range State Park), Dyurrite (Mount Arapiles) along with the Tooan State Park block, Jilpanger Nature Conservation Reserve, Tallageira Nature Conservation Reserve, Gurru (Lake Hindmarsh) and Ngalpakatia/Ngelpagutya (Lake Albacutya).
Between these medium and large parks and reserves, agricultural land dominates the Wimmera landscape. Importantly, a mosaic of small stands of native vegetation and habitat patches, strips and features remain interspersed within the agricultural matrix, such as:
- Small public land reserves and wetlands,
- Roadside, waterway and railway corridors, and
- Remnant vegetation, coarse woody debris, rocks, and scattered paddock trees.
These small patches of habitat are extremely important in supporting and maintaining biodiversity across the Wimmera region. Not only do they provide habitat for some biodiversity, but they also act as steppingstones and pathways for biodiversity to move through the landscape between patches of suitable habitat.
At a finer scale, the biological diversity of the Wimmera is demonstrated by the sheer number (618) and diversity of Ecological Vegetation Classes (EVC). In the upper catchment there are alpine and cool temperate rainforest vegetation communities, such as Montane Rocky Shrubland and Wet Forest, respectively. The lower catchment contains the inverse, Semi-arid Chenopod Woodland and Heathy Mallee, characteristic of the Mallee vegetation communities.
There have been 3,974 species recorded within the Wimmera region, including 3,169 plants, 61 invertebrates and 744 species of vertebrate fauna.(35) Of these species, 766 are introduced, 124 are endemic to the Wimmera and 232 have more than 75% of their modelled habitat distribution within the catchment.(36) Twelve species are officially listed as extinct or regionally extinct in the Wimmera. This figure may be higher as there are no complete records of the Wimmera’s biodiversity prior to European colonisation. A further 600 species (14%) are listed as rare or threatened with extinction(35) under Victoria’s Flora and Fauna Guarantee Act 1988 (FFG Act) new Threatened List.(35) (37) Additionally, 95 Wimmera species are identified as threatened under the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). Appendix 2 available on the Wimmera Catchment Management Authority (CMA) website provides a full list of the Wimmera’s threatened species.
Functional biodiversity and ecosystems of the Wimmera are of fundamental importance to the region. Functioning habitats and ecosystems provide significant tourism opportunities. For example, tourism in the Grampians region generates an estimated $295 million in direct economic output for the five surrounding local government areas.(38) Agriculture is the dominant land use in the Wimmera and plays an important role in Victoria’s economy and Australia’s food security. The Wimmera needs healthy biodiversity and ecosystems to support these critical economic and social industries.
Assessment of current condition and trends
Lake Lascelles ruby saltbush (Enchylaena tomentosa)
The remaining biodiversity within the Wimmera has been extraordinarily resilient with a large part of it cleared and modified for agriculture following European colonisation (Figure 13). Since 2000, the Wimmera has experienced a decade long drought, catchment-wide floods and fires that have impacted large areas of the national parks and reserves system. Despite these challenges, the Wimmera continues to support a vast array of regionally and nationally significant flora, fauna and ecological communities.
The extent and quality of habitat is a defining factor in the condition and trend of biodiversity and ecosystems. Habitat can be classified and described in a variety of ways. In general terms, thirty-one per cent of the Wimmera’s 2.3 million hectares is covered by natural habitat. Fifty-one per cent of this remaining natural habitat is public land protected within the National Reserves System, leaving 49% of the Wimmera’s native vegetation occurring on private land.(39) (40)
In Victoria, Bioregions and Ecological Vegetation Classes (EVCs) are the standard unit for classifying habitats and vegetation types at larger scales.(41) The bioregions and EVCs that support arable soils have been highly modified. For example, the Wimmera Bioregion covered 65% of the Wimmera region in 1770 compared to only 13% in 2005. There are 593 EVCs in the Wimmera and over half (55%) are listed as Endangered or Vulnerable under Victoria’s FFG Act. The FFG Act lists three Wimmera ecosystems as threatened and the Commonwealth EPBC Act identifies another six threatened ecological communities in the Wimmera. Appendix 3 lists these communities.
Natural ground cover, a measure of natural habitat, continues to decline in the Wimmera. The Victorian Land Cover Time Series(25) shows that between 1985 and 2019 natural ground covers declined by 162,000 hectares (6.9%). This includes a decline of 42,118 hectares (1.8%) in the last five-year time- period between 2015-2019.
The Wimmera has a long and successful history of protecting and managing habitat on private land, restoring habitat and connectivity though revegetation. Project Hindmarsh was well ahead of its time when in 1997 it set about connecting the Big Desert and Little Desert by revegetating on roadsides and private land. At a larger scale, Habitat 141 has been working across the Wimmera-Mallee region and beyond to restore habitat connectivity at a continental scale.
Since the establishment of on-title conservation covenants, Trust for Nature has permanently protected 16,355 hectares of native vegetation on private land.(43) This is one of the highest figures in Victoria and equates to about 5% of all native vegetation on private land in the Wimmera. From 2013 to 2020, 19,840 hectares of native vegetation on private land has been protected though 47 permanent and 1,047 long- term conservation management agreements.
At an individual species scale, habitat can have a more specific meaning. For example, an orchid’s habitat may be a soil type, aspect and light level. ‘Habitat complexity’ on the ground, such as coarse woody debris, rocks, grasses and shrubs, are important for terrestrial animals and small birds. Regardless of the scale, habitats and their quality are influenced by many factors, such as vegetation cover, land use, fire regimes, weeds and pest animals.
Critical fine scale habitat, such as large habitat trees and on-ground habitat complexity, continues to be lost across the landscape. The 2019 Environmental Report Card for the Wimmera(29) indicates woody vegetation or tree cover was down nearly 2% in the past two years. There are several reasons for this loss:
- Large habitat trees are generally old and subject to natural attrition, with live trees dying or dead ‘stag’ trees falling over.
- Wildfire and planned burning have a significant impact on large hollow trees and coarse woody debris on both public and private land by removing these critical habitat resources from the landscape.
- The conversion from grazing to dryland cropping introduce new threats to scattered paddock trees from stubble burning and spray drift and contribute to the decline in coarse woody debris.
- Both legal and illegal native vegetation removal and firewood harvesting contributes significantly to the loss of large habitat trees and coarse woody debris on both private and public land. Much of this illegal clearing and firewood harvesting goes unreported. In the Grampians region for example, illegal firewood removal has increased significantly where it appears to be highly organised and coordinated, including the felling and removal of large old habitat trees within the public land estate(37)
Two coordinated, large-scale, cross-tenure fox control programs are being delivered in the Gariwerd (Grampians National Park) and Little Desert regions. Collectively, they deliver fox baiting across nearly 380,000 hectares, conduct targeted fox trapping programs and both have commenced small-scale targeted cat control programs. Monitoring programs have demonstrated that foxes and cats remain widespread and readily detected at nearly all monitoring sites.(44) (45)
Feral and over-abundant native herbivores are having a significant impact on biodiversity and habitat in the region. Rabbits (Oryctolagus cuniculus) and brown hare (Lepus europaeus) are a perennial threat to ground flora. There has been an increase in deer populations across Victoria(46), with a similar trend seen in the Wimmera with red deer (Cervus elaphus) and fallow deer (Dama dama) populations appearing to expand across the region. Goats (Capra hircus) and pigs (Sus scrofa) are also an issue in some places.
Through the Victorian Government’s Biodiversity Response Planning process, Parks Victoria has implemented significant programs controlling deer and goats, implementing both aerial and ground control techniques in Gariwerd (Grampians National Park) and Burrunj (Black Range State Park). The program has removed 344, 287 and 133 animals over the past three years and appears to have had some level of success however, these species have not been eradicated and ongoing funding is required to maintain biodiversity benefits. There is also concern about the deliberate release of some species for recreational hunting, for example pigs and goats.
The impact of overabundant native herbivores (kangaroos and wallabies) is now being identified as a significant risk to biodiversity.(47) This is evident at the interface of public reserves and agricultural land where pasture and artificial water sources sustain higher than natural macropod populations. During 2020, Department of Environment, Land, Water and Planning (DELWP) undertook aerial surveys for kangaroos across Victoria. For the local government areas that make up the Wimmera catchment the eastern (Macropus giganteus) and western grey kangaroo (Macropus fuliginosus) population were estimated at between 126,100 and 387,800 individuals. In the upper catchment eastern kangaroo densities are high, estimated at 12.9 individuals per square kilometre.(48) Currently DELWP sets a cap on kangaroo harvesting at 10% of the estimated population.(49)
Weed control is conducted sporadically across the catchment with land managers implementing relatively conservative annual weed control programs. The extent and focus of significant weed control efforts is largely driven by short-term funding availability. For instance, Parks Victoria was funded for 3 years (2018-21) via the Victorian Government’s Biodiversity Response Planning process to deliver sallow wattle (Acacia longifolia) control in the north of the Gariwerd (Grampians National Park) region. Likewise, DELWP regionally was funded for 2020-21 to target boneseed (Chrysanthemoides monilifera subsp. Monilifera) in the region. Ongoing funding is required to continue this good work and maintain the biodiversity benefit achieved by this work.
Fire is an important ecological process in the Australian environment. Fire shapes habitat, ecosystems and the biodiversity that lives within them. Over the past 20 years the Wimmera has had many significant wildfires resulting in large parts of the National Parks and Reserve system being burnt. In the Little Desert National Park for example, there is a lot of recently burnt vegetation and not much old growth vegetation. This lack of variation in vegetation age class is not ideal for ecosystem health, many species require a diversity of vegetation ages to provide the habitat and food resources they require.
The 10-year period from the 2000s on saw unprecedented wildfires across the region. Approximately 90% of the Grampians National Park was burnt and a large extent of the Little Desert National Park. Subsequently, there has been a reprieve in large wildfires allowing DELWP and Forest Fire Management Victoria to implement their planned burning program. A key component of which is to introduce fire into the large fire scars to break up the large patches of single age classes, provide variety across the landscape and implement fire breaks to help prevent future large fires.
Fire and land managers in the Wimmera are increasingly using alternative burning techniques to improve biodiversity and cultural outcomes. For example, cool burns are being implemented in south-eastern red-tailed black cockatoo (Calyptorhynchus banksii graptogyne) habitat to reduce negative impacts of fire on the cockatoo’s food resources. Similarly, Traditional Owners led by Barengi Gadjin Land Council Aboriginal Corporation (BGLC) have conducted cool mosaic burns to help improve habitat quality and provide an alternative to hotter and more uniform fuel reduction burning.
There are various flora and fauna monitoring programs in the Wimmera collecting data, for a variety of purposes, that can be used to provide an indication of species, habitat and ecosystem trend and condition. These monitoring programs are providing evidence to inform the management of some Wimmera species and ecosystems:
- South-eastern red-tailed black cockatoo (Calyptorhynchus banksii graptogyne) annual flock counts. Bird numbers remain relatively stable however recruitment of new individuals into the population is relatively low compared with historical data.(50)
- Malleefowl (Leipoa ocellata) mound activity monitoring indicates the Malleefowl population is relatively stable and ‘varies up to +/- 50% per year’.(51)
- Platypus (Ornithorhynchus anatinus) live trapping and environmental DNA surveys have shown a slight increase in the range of platypus in the MacKenzie River. Genetic analysis shows the population is very small and has extremely low genetic diversity.(52)
- Gariwerd (Grampians National Park) long-term small mammal surveys have shown significant swings in species richness and abundance that appears to be driven by rainfall(53). In 2019, long-nosed potoroo (Potorous tridactylus) were not detected in one of their last know refuges(54), with the last know detection occurring in 2014.
- Small mammals and reptiles surveys in the Little Desert have shown higher abundance of species inside a predator-proof fence indicating invasive predators are having an impact on local biodiversity.(55)
Major threats and drivers of change
Biodiversity and ecosystems are dynamic by nature however there are several major threats that could drive significant changes in the biodiversity of the Wimmera. The continued pressure of long-term threats (habitat loss, fragmentation and pest plants and animals) and the emergence of new threats (a changing climate, high-intensity bushfires, increasing grazing pressure) collectively mean the biodiversity of the Wimmera faces a challenging future.
Rainfall averages and soil moisture are declining, and the number of hot days is increasing(5). These changes can threaten Wimmera habitats and ecosystems by driving shifts in vegetation composition and structure.(56)
Declining average rainfall and soil moisture is enabling large-scale land use change, primarily a shift from grazing to dryland cropping. The area used for dryland cropping has increased by over 44,000 hectares since 2015.(25) The conversion of native and introduced pastures to dryland cropping removes fine scale habitat from paddocks and exacerbates fragmentation. Generally, there is a diversity of fine scale habitat within a paddock used for grazing including paddock trees, shrubs, coarse woody debris, rocks, a diversity of ground flora, depressions and wet areas that enable wildlife to either live within or move through a paddock. Therefore, when land traditionally used for grazing get converted to dry land cropping, most fine scale habitat features are lost.
More hot days and declining rainfall averages and soil moisture are facilitating more frequent and more intense bushfires. Following the Millennium Drought there were multiple, large-scale, high intensity wildfires in Gariwerd (Grampians National Park) and the Little Desert National Park that have driven significant changes in vegetation structure and composition. The World Weather Attribution investigates the link between bushfire risk and climate change in Australia and found there is, at minimum, a 30% increase in the chance of severe fire conditions because of climate change in Australia.(57)
Both planned and unplanned fire can drive significant changes in important habitat values. Large hollow trees and coarse woody debris, critical to the ecology of many native species, are very susceptible to wildfire and planned burns on both public and private land. Extreme weather events such as storms and floods can also impact on biodiversity and habitat.
At the landscape scale, scattered paddock trees provide connectivity for animals and genetic connectivity for tree populations. At the local scale they provide a distinct microclimate, increased soil nutrients, plant species richness and structural complexity, and provide habitat for many animals.(58) Scattered trees help maintain biodiversity throughout largely cleared parts of the landscape.(59) Large, scattered trees are being lost for several reasons including natural attrition, stubble burning, spray drift, legal and illegal clearing.
In a highly fragmented landscape like the Wimmera the density and distribution of small patches of remnant native vegetation between the larger more intact reserves are critically important to maintaining functional ecosystems. They provide habitat for a vast array of species and enabling mobile species to migrate between the larger patches. This provides gene flow and re-colonisation opportunities that is critical to maintain viable populations in fragmented landscapes. Consequently, the loss of scattered paddock trees, vegetation on roadside reserves and other small patches of habitat are likely to be a major threat to biodiversity conservation in the Wimmera.
The introduced red fox (Vulpes vulpes) and feral cat (Felis catus) have long been implicated in the decline of many of Australia’s native fauna species and extinction of at least 34 mammal species.(60) (61) In the Wimmera, introduced pests are implicated in the ongoing decline of species like the Mitchell’s hopping mouse (Notomys mitchellii), southern brown bandicoot (Isoodon obesulus obesulus) and plains wanderer (Pedionomus torquatus). They are also contributed to the regional extinction of species like the white-footed rabbit-rat (Conilurus albipes), western quoll (Dasyurus viverrinus) and western barred bandicoot (Parameles notina).
Within the region there are two well-funded, best practice, large-scale, cross-tenure fox control programs centred around Gariwerd (Grampians National Park) and Little Desert National Park. The former has been running since 1996 and despite this effort, ‘foxes and cat occupancy remains very high across the sites surveyed, indicating that they are present at most, if not all of the sites sampled for at least part of the year’(62) Introduced predators will continue to be a significant driver of the trend and condition of fauna populations in the Wimmera until an effective management strategy can be established.
Introduced and native herbivores can directly threaten biodiversity by direct browsing pressures, driving changes in floristic and structural composition, and contributing to erosion and weed dispersal.
DELWP has designed a new modelling tool called Strategic Management Prospects (SMP) to help land managers consider and compare the most effective management actions to protect biodiversity. SMP is a modelling tool that compares the cost and benefit to local biodiversity of implementing different management actions.(63)
In the Wimmera, SMP has suggested 89 actions across 236,039 hectares to best protect the Wimmera’s biodiversity. Fifty-five of these management actions recommend controlling introduced and overabundant-native herbivores across 225,935 hectares or 95.7% of the total proposed works. Thirteen management actions recommend weed control across 8,668 hectares or 3.7% of the proposed works.
Pest plant and animals work aimed at improving habitat quality constitutes 99.9% of the total area of proposed works. This suggests that over-abundant herbivores and invasive weeds are the major threat and driver to the Wimmera’s habitats, ecosystems and species. Interestingly, in the SMP analysis, invasive predator management does not rank amongst the top 3% of priority actions and only constitutes a small proportion of the top 10% priority actions – 17% of actions and 7% of area.(63)
Invasive plants threaten the region’s biodiversity primarily by outcompeting and displacing native species. Many invasive plants are well-established in the region and ongoing management is required to keep them contained.
Over recent years there has been new and emerging species of concern to the region’s biodiversity. Invasive grasses including Chilean needle grass (Nassella neesiana) and serrated tussock (Nassella trichotoma) continue their migration west. If they become established they pose a significant ecological threat and could negatively impact the local agricultural economy.
Sallow wattle (Acacia longifolia) has become well-established in Gariwerd (Grampians National Park) with its spread exacerbated by recent fire. This species has the capacity to drastically change ecosystems by outcompeting native plants. Significant resources are currently being invested in Gariwerd (Grampians National Park) to protect assets from the threat of sallow wattle and continued investment is required to maintain this good work.
The community has a strong desire to access public natural areas such as bushland, lake and stream reserves. This access has the potential to impact on biodiversity and needs to be managed so it does not reduce environmental condition or amenity.
Desired outcomes for the future
Outcomes to be achieved in 20+ years
- The biodiversity of the Wimmera is thriving because ecosystems are restored, habitat has been recreated and missing species have been returned.
- The knowledge and experience of First Nations people is informing biodiversity planning, management and delivery in the Wimmera.
Outcomes to be achieved in 6 years
- Ongoing collaboration and two way learning in biodiversity planning and management by supporting and strengthening partnerships with First Nations people.
- Increase the extent, quality and protection of habitat on private land in the Wimmera.
- Improve habitat quality on public land in the Wimmera.
- Ecosystems are being restored and species are being conserved by translocating locally extinct and vulnerable species within the Wimmera.
- A coordinated regional scale monitoring program is providing up-to-date data on habitat, ecosystem and species trend and condition.
- Vulnerable Wimmera vegetation communities and species have been identified and a strategic plan has been developed and management actions to mitigate threats are being implemented.
A coordinated and strategic regional approach to biodiversity conservation will be required if the Outcomes for biodiversity are to be achieved. Several organisations have developed strategic plans or prioritisation processes that encompass elements of the Wimmera’s landscape and biodiversity. There is no overarching document that takes a holistic view of the Wimmera, setting targets and priorities for biodiversity conservation and management. This gap will be filled by February 2022, with input from regional stakeholders, bringing together and consolidating existing regional planning work including Biodiversity Response Planning, Conservation Action Planning, and parts of the Carbon Ready Plan and Action Plan for the Regional Land Partnerships Program and describing how the Regional Catchment Strategy (RCS) will contribute to and report on the targets set out in Biodiversity 2037.
Protecting Victoria’s Environment – Biodiversity 2037
The state-wide Biodiversity 2037 strategy is Victoria’s plan to stop the decline of native plants and animals and improve the natural environment. The plan establishes a long-term vision and goals for biodiversity in Victoria. Specific targets have been developed to deliver on these goals. Through a Biodiversity Response Planning process, the Department of Environment, Land, Water and Planning are working with all relevant partners and stakeholders to identify and implement on-ground actions that will best contribute to the Plan’s targets. Actions taken to achieve the outcomes of this RCS will also contribute to the Plan’s targets.(66)
Wimmera Carbon Ready Plan
This action plan under the RCS details the actions required for the management of native vegetation, soils and other natural assets in the context of adapting to and mitigating the impacts of a changing climate.
Action Plan for the Regional Land Partnerships Program
This addendum to the RCS sets out how the Wimmera region will contribute to the Australian Government’s 5 year Outcomes and Investment Priorities under the Regional Land Partnerships Program.
Wimmera Invasive Plant and Animal Management Strategy
This action plan under the RCS outlines an approach to setting priorities for coordinated management of invasive plants and animals in the region.
Trust for Nature’s State-wide Conservation Plan
This Plan defines the Trust for Nature’s conservation priorities and priority areas. Taking a statewide perspective of the value of private land for healthy ecosystems, the Plan provides a baseline for achieving conservation targets across the state.(65)
Wimmera Parks Conservation Action Plan
The Conservation Action Plan for parks and reserves managed by Parks Victoria Wimmera focuses on the resilience of natural assets and maintaining ecosystem services.(34)
Habitat 141 is a long-term, collective response to habitat fragmentation and climate change along the 141st longitude. This biodiversity hotspot stretches from the coast of South Australia, along the Victorian border, and up to the rangelands of New South Wales.