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FIGURE 11: White Gum Wet Forest
FIGURE 11: White Gum Wet Forest
Five EPBC-listed threatened ecological communities occur in the Region: Subtropical and Temperate Coastal Saltmarsh, Lowland Native Grasslands of Tasmania, Alpine Sphagnum Bogs and Associated Fens, Black and Brookers Gum Forests and Woodlands, and Tasmanian White Gum Wet Forest.
Tasmanian Lowland Native Grasslands (Figure 8) are made up of two TasVeg mapping types – Lowland Poa Labillardierei grassland (GPL) and Lowland Themeda triandra grassland (GTL). There are extremely limited occurrences of GPL and GTL in the Region (130 ha total, which is 0.6 % of the Tasmanian mapped extent). All of the GTL community in the region is protected in the Arthur Pieman Conservation Area. These factors contributed to the low score that Lowland Native Grasslands was given in the MCA, but because of some of the species that may rely upon grassland ecosystems, such as threatened orchids (CCA Priority BS9) and the two listed butterfly species (CCA Priority BS8), there may still be opportunities to direct future management actions towards reducing threats to remnant patches of Lowland Native Grasslands.
The Alpine Sphagnum Bogs and Fens TEC (equivalent to the TasVeg Threatened Vegetation Community, Sphagnum peatland; Figure 7) is almost completely contained in state reserves and the TWWHA, and so protected from most human-induced threats. It is acknowledged that climate change could pose a threat to this TEC, particularly through altering hydrological regimes (causing drying of peatlands) and increasing the risk of fire (which has destroyed large areas of Alpine Sphagnum Bogs in the Australian Alps). Weeds may also pose a threat. Although this community didn’t score highly enough in the MCA to become a CCA Priority, an Action is planned in the Priority BI1: Tasmanian Wilderness World Heritage Area, to: “Assess the weed, fire and drought threat to patches of the EPBC-listed Threatened Ecological Community, Alpine Sphagnum Bogs and Associated Fens, and work with PWS to manage these threats if there is an opportunity to do so.” An extensive and important listed ecological community in the Region is Coastal Saltmarsh (Figure 9). Its high score in the Threatened and important ecological communities MCA (based on the extent, importance and risk in the Region) resulted in this TEC being noted as CCA Priority BC1. The Atlas of Coastal Saltmarsh Wetlands in the Cradle Coast Region (Prahalad 2016) documents and maps twelve discrete wetland complexes in the Region. The largest and most diverse of these saltmarsh communities occurs in coastal areas between East Inlet and Woolnorth Point in the far northwest of the region. Covering more than 1700 ha, this community is most extensive in the Duck Bay, Robbins Passage and Boullanger Bay area, known in our Strategy as the Robbins Passage - Boullanger Bay wetland (Priority WW2).
From a global perspective, the Robbins Passage coastline provides critical feeding habitat for migratory shorebirds at the southern reach of the East Asian Australasian Flyway; some 11,000 birds migrate to this coastline each year. The Coastal Saltmarsh ecological community here is highly productive as a food source for resident and migratory birds, but it is threatened by the invasive weed Spartina anglica (Rice Grass), by landholder use of tidal barriers or levees to reclaim saltmarsh for pasture, by grazing and trampling, by marine debris impacts, by eutrophication from upstream land uses, and by sea level rise.
The Black Gum (E. ovata) – Brookers Gum (E. brookeriana) forest/woodland TEC (Figure 10) is associated with lowland landscapes, often with poorly draining soils and sites that are wet or seasonally waterlogged such as the margins of swampy flats, but also in well-drained gullies. Most known remnants of the E. ovata-dominated component occur east of Burnie, with minor occurrences scattered along the north-west coast, west coast including the TWWHA and King Island. The E. brookeriana component is most prevalent in the far north-west and King Island.
The Tasmanian White Gum (E. viminalis) Wet Forest TEC (Figure 11) occurs mainly on fertile, well-drained sites in lowland areas in the central to eastern part of the region that receive high average annual rainfall (more than 1000 mm). Some of the largest stands occur on the flats and lower slopes of the major river valleys. Both threatened eucalypt forest ecological communities have been heavily cleared historically and are now fragmented and many remnants are small, isolated, and in a modified condition. Any remnants that remain largely intact (in terms of structure and/or diversity of characteristic species), retain mature/old growth trees, or are connected to other native vegetation and form a large patch, have the best chance for longer-term survival and are a high priority for protection and management. Very small, isolated and/or degraded patches (e.g. those subject to permanent or ongoing high disturbance) are less likely to have the structure, composition and function of the associated ecological community. CCA plans to implement Actions to protect remnants of the threatened Eucalypt forests through Priority BC3: Threatened Eucalypt Forests and Woodlands.
Local threats and challenges to EPBC-listed Threatened Ecological Communities
Rice Grass has the potential to spread readily across the saltmarsh communities and coastal wetland in this area, and will remain the focus of restoration efforts in the 2030 Strategy. Thanks to the concerted efforts of Landcare volunteers in the Circular Head area, the weed is close to containment there. The potential to locally eradicate a highly invasive weed and to restore areas of endangered saltmarsh community along the East Inlet to Woolnorth Point coastline represents a real and achievable outcome for RLP investment in the Cradle Coast Region, with good community support. Similar weed control activities are planned in other saltmarsh remnants under Priority BC1. The practice of building tidal control structures (levees) has been used by some beef and dairy farmers along the Robbins Passage-Boullanger Bay coastline. This practice has resulted in the conversion of Coastal Saltmarsh to pasture, and is another threat that can be addressed through NRM Actions in the next Strategy period. The Eucalypt forest TECs share similar threats and some common approaches in management response. Threats from clearing due to forestry and agricultural activities have been a significant cause of historic decline in extent. Agriculture and plantation forestry still pose a threat to E. viminalis forests due to their location on fertile soils on flats and lower slopes. Irrigation development is an ongoing threat, as is residential and commercial development particularly around Burnie, Ulverstone, Devonport and Wynyard. Incremental damage from tree removal, lopping or removal of understorey vegetation is also an issue. Invasion by weeds leads to ongoing loss of species diversity and ecological function in remaining patches. Undisturbed patches are generally resistant to weed invasion but disturbed and fragmented forests or forest edges are susceptible to invasion by species such as blackberry and gorse. The faunal component of the Eucalypt TECs is threatened by invasive species such as deer, cats and sugar gliders. Agricultural land management practices have a range of impacts on both threatened forest communities. Threats include grazing pressure in remnants not excluded from stock, chemical drift from pesticides and herbicides applied to crops and pasture, altered hydrology from excessive groundwater extraction and water quality decline due to nutrient runoff. Plantation forestry in proximity to remnants also presents a risk of hybridisation with non-Tasmanian plantation eucalypts, particularly E. nitens. Climate change is the most significant emerging threat with related impacts including altered flooding and fire regimes, prolonged drought and heat stress, increased competition from invasive species and poor regeneration and recruitment of native species.
