Threatened Species and threatened ecological communities
Advice to the Minister for the Environment and Heritage from the Threatened Species Scientific Committee (TSSC) on amendments to the List of Ecological Communities under the Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act)
18 April 2005
A nomination was received for the Melaleuca tamariscina ssp. irbyana Low Open Forest, locally known as the Swamp Tea-tree Forest. This ecological community is recognised under the Queensland Vegetation Management Act 1999 as two endangered Regional Ecosystems 12.3.3c and 12.9-10.11 Melaleuca irbyana Low Open Forest. Additional advice from taxonomists supports the recognition of M. t. irbyana as a full species. It is recommended that the name of the ecological community be changed to Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland to reflect its local name, recent taxonomic revision and geographic distribution.
The species, Melaleuca irbyana, has a very limited distribution in north-eastern New South Wales (NSW) and south-eastern Queensland. It occurs only in a small number of restricted sites within each of these regions. The species is listed as endangered in NSW but is not listed as a threatened species in Queensland or nationally. However, Melaleuca irbyana is identified as forming a distinct ecological community in Queensland. It comprises Regional Ecosystem 12.9-10.11, where it occurs on land zone 9-10, and Regional Ecosystem 12.3.3c, where it occurs on land zone 3. Both Regional Ecosystems are identified as endangered under the Vegetation Management Act 1999 in Queensland.
In Queensland, Melaleuca irbyana forms a thicket that is almost entirely composed of M. irbyana in the upper to mid layers. However, in NSW, M. irbyana only occurs in mixed melaleuca forests with two other species, M. nodosa and M. sieberi. The difference between these single species thickets in Queensland and the mixed melaleuca stands in NSW is due to differences in soil type. According to the NSW National Parks and Wildlife Service, the Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland does not occur in NSW. Therefore, ecological communities in NSW containing M. irbyana are not included as part of the Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland ecological community.
The Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland is confined to a small section of the Moreton basin in the South-east Queensland bioregion. The occurrence of this ecological community has been identified and mapped by the Queensland Herbarium, as Regional Ecosystems 12.3.3c and 12.9-10.11. Local councils have also mapped it. The local council mapping has identified additional patches of the ecological community (not part of these Regional Ecosystems). Additional patches that are at least 5 hectares in size are included as part of the Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland.
The Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland occurs primarily to the south of Ipswich City, within the local government areas of Beaudesert, Boonah, Esk, Ipswich, Laidley and Logan.
The Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland is a low open forest dominated by a dense thicket of Melaleuca irbyana with or without an emergent tree layer of eucalypts. Melaleuca irbyana forms a canopy 8-12m high. Common tree species that penetrate above the canopy of M. irbyana are Eucalyptus crebra, Eucalyptus melanophloia, Eucalyptus moluccana and Eucalyptus tereticornis (Boulton et al., 1998; Porche, 2002).
The understorey flora beneath thickets of M. irbyana includes very few shrubs or vines due to the low penetration of light and heavy clay soils. Instead, the understorey comprises a range of native forbs, twiners, grasses and sedges (Ipswich City Council, 1998: Bean et. al., 1998 Cooper et. al., 1995). One plant species from this ecological community, Slender Milkvine (Marsdenia coronata), is listed under the EPBC Act as vulnerable.
The areas where the Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland occurs are characterised by seasonally inundated alluvial plains with seasonally cracking, grey clay soils known as Tea Tree Clays (Harms, 1996). These soils are heavy, coarse, low in nutrients and form localised, small depressions and mounds. The subsoils are highly erosive, saline, acidic and dominated by magnesium. Since the soils are heavy in texture, they have poor drainage and become waterlogged after heavy rainfall, sometimes for prolonged periods (Noble, 1993). This soil type is locally common south of Ipswich and does not occur elsewhere in the state (Noble, 1993). The Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland provides habitat for a range of native vertebrate fauna. Thickets of M. irbyana provide shelter and nesting sites for forest-dwelling bird species (Boulton et. al., 1998); the abundance of fallen logs in the ecological community provides favourable habitat for ground-dwelling reptiles (Porche, 2002); and frog populations are evident during wet seasons when temporary pools form on the waterlogged soil. No nationally threatened animal species are known to occur in the Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland.
Patches of Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland can be considered to be in good condition if all components of the vegetation structure are well represented. This includes: a thicket of Swamp Tea-tree as a middle canopy, emergent eucalypts above the Swamp Tea-tree canopy and understorey herbs and vines beneath the Swamp Tea-tree canopy.
The TSSC judges the ecological community to be eligible for listing as critically endangered under the EPBC Act. The justification against the criteria is as follows:
The present extent of the Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland is estimated at 644 hectares, based on mapping information supplied by the Queensland Environmental Protection Agency and local councils. This estimate comprises 234 ha of Regional Ecosystem 12.9-10.11, 68 hectares of Regional Ecosystem 12.3.3c, and 342 ha of additional patches identified by local council vegetation mapping.
The pre-European extent of the Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland, based on mapping information supplied by the Queensland Environmental Protection Agency, is estimated as 2,474 ha. This comprises 2,379 ha of Regional Ecosystem 12.9-10.11 plus 95 ha of Regional Ecosystem 12.3.3c.
An estimated pre-European extent of 2,474 ha and estimated present extent of 644 ha indicates that the Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland has undergone a decline in extent of 74%. Consequently, the Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland is eligible for listing as vulnerable under this criterion.
The Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland had a naturally restricted distribution within the Moreton basin that is linked to the presence of a particular soil type (Tea Tree Clays). The current area of occupancy for the ecological community is approximately 644 hectares. This indicates that the nominated ecological community currently has a very restricted geographic distribution.
Land tenure data for Regional Ecosystem 12.9-10.11 indicates that the majority (200 hectares) occurs on freehold land (Accad et al., 2003). The only known conservation site for the ecological community is Purga Nature Reserve near Ipswich (Ipswich City Council, 1998). Another patch at Mutdapilly Dairy Research Station, operated by the Queensland Department of Primary Industries, also is being actively managed for conservation, although it does not constitute a formal conservation reserve (Queensland Department of Primary Industries, 2001).
The Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland is subject to continued demonstrable threats, notably fragmentation, edge effects from surrounding pastoral and urban lands, clearing, grazing and invasion by weeds and feral animals. This ecological community occurs primarily as small patches. About 78% of patches identified as Regional Ecosystem 12.9-10.11 and 12.3.3c are less than 5 hectares in area. Only two patches exceed 20 hectares in size. Small patches are more likely to be threatened by edge effects and disturbances from surrounding agricultural and urban developments than are larger patches.
Weeds are a problem in disturbed sites of the Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland. More than 40 species of introduced plants are known to have established in the ecological community. Many of the weed species are tolerant of the understorey conditions or colonise the edges of patches. Weeds of particular concern include Lantana (Lantana camara) and Creeping Lantana (Lantana montevidensis).
Introduced animal species known to occur in the ecological community include the Common Mynah (Acridotheres tristis), Fox (Vulpes vulpes), Brown Hare (Lepus capensis) and Feral Dog (Canis familiaris). These species are suspected to be having an impact on the ecological community, but the impact is not quantified.
The Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland presently has a very restricted area of occupancy (estimated to be approximately 644 ha). The small size of most patches coupled with the large extent of this ecological community on freehold land indicates that it is susceptible to ongoing threats. Therefore, this ecological community is eligible for listing as critically endangered under this criterion.
The Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland has suffered a decline of at least 70% of its former range. This decline includes the loss of functionally important species through the partial removal of M. irbyana. The partial clearing of M. irbyana allows stock to access the ecological community and heavily graze the understorey. This, in turn, leads to a loss of native biodiversity and enhanced invasion by weeds.
Grazing pressure coupled with the fragmentation of patches also restricts the regeneration of M. irbyana in the ecological community. Melaleuca irbyana is recognised as being a long-lived species with a slow juvenile growth phase and, consequently, young plants are particularly susceptible to disturbance. Given its slow juvenile growth and the existence of continued threats, such as grazing and fragmentation, it is likely that regeneration of M. irbyana will continue to be adversely affected in the future. The rate of clearing of Regional Ecosystem 12.9-10.11 was estimated as 4.25 ha/yr between 1997 and 2001 (Accad et al., 2003). No further clearing of this Regional Ecosystem was noted between 1999 and 2001 although this may not be the case for patches not classified as a Regional Ecosystem.
There is, however, a lack of data about the restoration capacity of the Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland. For example, information about the extent of seed production on mature trees, the viability of propagules and the persistence of the soil seed bank are absent. Without such data, it is not possible to evaluate the rate at which this ecological community could regenerate. Therefore, this ecological community is not eligible for listing under this criterion.
One indicator for the reduction in integrity of an ecological community is the degree to which stands of the ecological community are fragmented. The majority (78%) of Regional Ecosystems 12.9-10.11 and 12.3.3c comprise very small (< 5 ha) fragments. As noted under Criterion 2, smaller patches are more likely to be disturbed by threatening processes than larger patches. This means they are more threatened than larger patches by disturbances from surrounding agricultural and urban developments. Continuing threats, such as clearing, grazing and exotic weed invasion, further hamper the integrity of existing patches, particularly by interfering with the naturally slow regeneration of M. irbyana.
Mature trees of M. irbyana are essential for the process of recruitment because they are a supply of viable seeds. Selective clearing of these mature trees may impact upon the integrity of this ecological community because clearing could potentially disrupt recruitment and regeneration of the Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland. As noted in Criterion 3, however, essential data on restoration capability are lacking for both M. irbyana and this ecological community, making it difficult to evaluate the degree of human intervention necessary to restore and maintain the integrity of the ecological community. Therefore, this ecological community is not eligible for listing under this criterion.
The Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland occurs primarily on freehold land, where it is susceptible to incremental clearing. The extent of clearing of Regional Ecosystem 12.9-10.11 in the four years between 1997 and 2001 was 17 hectares, or a rate of 4.25 ha/year (Accad et al., 2003). This equates with a change of 17% over the decade 1991-2001, assuming a constant rate of clearing. However, the rate of decline for Regional Ecosystem 12.9-10.11 has not been constant, as no clearing was noted for 2000 and 2001.
It is not known to what extent clearing has continued for Regional Ecosystem 12.3.3c and for patches of the ecological community not classified as part of a Regional Ecosystem. A rate of decline of at least 30% over the immediate past or future is required for the ecological community to be eligible for listing. A recent rate of decline of 17% for Regional Ecosystem 12.9-10.11 and a lack of information about other components of the ecological community mean that this ecological community is not eligible for listing under this criterion.
The nomination provides no information under this criterion.
The Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland meets Criterion 1 as vulnerable as it has shown a substantial decline in geographic distribution; and Criterion 2 as critically endangered as it has a very restricted geographic distribution and is subject to demonstrable and ongoing threats.
TSSC recommends that:
Accad, A., Nelder, V.J., Wilson, B.A. and Neihus, R.E. (2003). Remnant Vegetation in Queensland: Analysis of Remnant Vegetation 1997-1999-2000-2001, including Regional Ecosystem Information. Brisbane: Queensland Herbarium, Environmental Protection Agency.
Bean, A.R., Sparshott, K.M., McDonald, W.J.F and Neldner, V.J., (Eds) (1998) Forest Ecosystem Mapping and Analysis of South-Eastern Queensland Biogeographic Region. A: Vegetation Survey and Mapping. Queensland Government, Queensland.
Boulton, S.C., Kingston, M.B., Turnbull, J.W., (1998) Bremer Basin Vegetation Study for Ipswich City Council. Ecograph.
Cooper, S., Walker, B., and Low, T., (1995) Conservation Survey, Status and Management of Melaleuca irbyana and Freshwater Wetland Communities. Report prepared for Ipswich City Council, Ipswich, Queensland.
Environmental Protection Agency, Queensland, (2004) Regional Ecosystem Description Database (REDD). Version 4.1. Updated August 2004.
Harms, B.P., (1996) Field Manual in Noble, K.E., (ed.) Understanding and Managing Soils in the Moreton Region. Queensland Department of Primary Industries Training Series QE96003, Queensland.
Ipswich City Council (1998) Purga Nature Reserve Fact Sheet, Ipswich City Council Department of Conservation, Parks and Sport, Ipswich, Queensland.
Noble, K.E., (1993) Understanding and Managing Soils in the Moreton Region. Resource Information. National Landcare Program. Queensland Department of Primary Industries, Queensland. Porche, D., (2002) Recovering an Endangered Ecosystem - Swamp Tea Tree. Beaudesert Shire Council, Queensland.
Queensland Department of Primary Industries, (2001) Swamp Tea Tree Protection at Mutdapilly Research Station. Queensland Department of Primary Industries News, Queensland.
The Swamp Tea-tree (Melaleuca irbyana) Forest of South-east Queensland comprises two Regional Ecosystems classified as Endangered in Queensland (RE 12.3.3c and 12.9-10.11), plus additional patches identified in local council vegetation mapping. It occurs south of Ipswich in Queensland and has a very restricted distribution of less than 1,000 hectares. The ecological community is highly fragmented with most patches occurring on freehold land.
The key threat to the survival of the ecological community is vegetation clearance, mainly due to urban and agricultural developments. Additional threats include fragmentation, weed invasion and grazing.
The priority recovery and threat abatement actions required for this ecological community are:
This list does not encompass all actions that may be of benefit to this ecological community, but highlights those that are considered to be of the highest priority at the time of listing.
The development of a recovery plan is considered to be of high priority.