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)
A nomination was received for Complex Notophyll Vine Forest: type 5b (Tracey & Webb, 1975; Tracey, 1982). This ecological community is known locally as "Mabi Forest", and has been identified by the Queensland Environment Protection Agency as Regional Ecosystem 7.8.3 (Goosem et al., 1999). Due to the localised representation of this ecological community in the landscape, it is recommended that the name of this ecological community reflect the strong local identity: "Mabi Forest (Complex Notophyll Vine Forest 5b)".
2. National Context
Vine forests are a feature of the tropical and sub-tropical regions of the eastern Queensland. However, given the complex interactions between abiotic characteristics at the different areas (such as soil composition, rainfall, and elevation), the structure and floristic composition of these forests vary widely across their range (Webb and Tracey, 1994).
The vegetation surveys conducted by Tracey (1982) in the humid tropical region of north Queensland (the Wet Tropics Bioregion), identified two similar forms of complex notophyll vine forest: types 5a and 5b. These two vine forest types are highly restricted to soils derived primarily from basalt. Further surveys of Queensland (Sattler and Williams, 1999) have identified notophyll vine forests in other areas of eastern Queensland. However, due to the differing complexities of structure and floristics between those complex notophyll vine forests on basalt in the Wet Tropics Bioregion and other notophyll vine forests in the State, Complex Notophyll Vine Forests 5a and 5b should be considered to be separate ecological communities.
Experts have further suggested that Mabi Forest (Complex Notophyll Vine Forest 5b) should be kept distinct from Complex Notophyll Vine Forest 5a due to differences in the abiotic variables (for example, rainfall and elevation) which are subsequently reflected in the differing floristics and structure between these two ecological communities. The most easily distinguished differences between Mabi Forest (Complex Notophyll Vine Forest 5b) and Complex Notophyll Vine Forest 5a are general location and structure.
Complex Notophyll Vine Forest 5a occurs on cool wet (cloudy) uplands and highlands, and structurally tends to appear as a forest with two layers. The top layer is dense and forms between approximately 30-36 m above ground, while the lower layer is sparse, and occurs between 10-20 m (Tracey, 1982). In this ecological community, epiphytes (plants that grow on other trees) are common throughout the forest layers.
Mabi Forest (Complex Notophyll Vine Forest 5b) occurs on moist lowlands, foothills and uplands. The drier nature of this ecological community compared to Complex Notophyll Vine Forest 5a, can be seen in the lack of epiphytes throughout the different layers of the forest. In Mabi Forest (Complex Notophyll Vine Forest 5b), epiphytes are generally found only in the upper branches of the canopy.
The ecological community, Mabi Forest (Complex Notophyll Vine Forest 5b), is restricted to those mapped areas of Regional Ecosystem 7.8.3, and other patches identified as Complex Notophyll Vine Forest 5b (Tracey and Webb, 1975; Tracey, 1982) in the Wet Tropics bioregion of Queensland.
Mabi Forest (Complex Notophyll Vine Forest 5b) is found on highly fertile basalt-derived soils, in the moist lowlands, foothills and uplands on the Atherton Tablelands in the Wet Tropics Bioregion of northern Queensland. A remnant patch is also located at Shiptons Flat, near Cooktown (Goosem et al., 1999). Annual rainfall in this area varies between 1300 and 1600 mm. The ecological community is heterogeneous within and between remnant patches, due to the influence of position in the landscape, local topography, and drainage.
Mabi Forest (Complex Notophyll Vine Forest 5b) is characterised by an uneven canopy (25-45m) with many tree layers. Most trees have a deep crown, often extending down to between the top-third and top-half of the trunk. As a result of the greater depth of crown, Mabi Forest (Complex Notophyll Vine Forest 5b) is distinctly different from nearby simple notophyll vine forests that only have shallow crowns with few layers (Tracey, 1982).
The description of the ecological community is based on leaf size of the component vegetation: notophylls are plants with leaf size between 20.25-45 cm2, microphyllic plants have leaf sizes between 2.25-20.25 cm2, while mesophyllic plants have leaf sizes between 45-180 cm2.
Notophylls (with some microphylls), are most common in the canopy of Mabi Forest (Complex Notophyll Vine Forest 5b), with mesophylls frequently found in the lower layers. These notophylls are commonly semi-evergreen, and undergo heavy leaf fall during times of moisture stress. The canopy also contains scattered deciduous trees. The trunks of trees in this ecological community are uneven in size, and plank buttresses are a common feature. Woody vines are generally conspicuous. Epiphytes are rare, but where they do occur, they are high in the branches, with only scattered epiphytes being found lower down. A prominent medium to dense shrub and scrambling vine understorey occurs beneath the tall canopy, and is a unique and distinguishing feature of this forest type (Tracey 1982). The shrub/vine layer is generally only 1-3 metres high. A list of characteristic plant species is at Table 1.
Several species of plants found in Mabi Forest (Complex Notophyll Vine Forest 5b) are listed as Endangered under the Environment Protection and Biodiversity Conservation Act 1999, and others are listed as Vulnerable under the Queensland Nature Conservation Act 1992 or are identified as being restricted.
The dense shrub layer which largely distinguishes this ecological community is a reflection of the seasonal nature of rainfall patterns. This shrub layer is partially responsible for the extensive range of bird species, up to 114 species, which use Mabi Forest (Complex Notophyll Vine Forest 5b) for either foraging, nesting or as their main habitat.
4. How judged by TSSC in relation to the EPBC Act criteria
The TSSC judges Mabi Forest (Complex Notophyll Vine Forest 5b) to be eligible for listing as critically endangered under the EPBC Act. The justification against the criteria is as follows:
Criterion 1 - Decline in geographic distribution
Prior to European settlement, Mabi Forest (Complex Notophyll Vine Forest 5b) occurred as a continuous forest, in an area extending from the north through to the west of Malanda on the Atherton Tablelands. The ecological communities on the Atherton Tablelands were initially considered sources for high quality timber trees, such as Toona australis (Red Cedar), to the extent that by 1900 T. australis accounted for up to 75% of Queensland's total export earnings (Anon, 2000). Once the large timber trees were removed, the Atherton Tableland was progressively cleared for agriculture. The extent of clearing, to date, has been estimated as being between 90-98% (Anon, 2000; Goosem et al., 1999; Vegetation Management Regulations 2000).
Given the lack of explicit data on the extent of the decline in geographic extent of Complex Notophyll Vine Forest, for example estimations of pre-clearing area of extent, it is difficult to give an exact proportion of the extent remaining. However, based on the consensus between reports by the State government and experts, it is acknowledged that at least 90% of the original extent of Mabi Forest (Complex Notophyll Vine Forest 5b) has been cleared. Therefore, the ecological community is eligible for listing as endangered under this criterion.
Criterion 2 - Small geographic distribution coupled with demonstrable threat
Mabi Forest (Complex Notophyll Vine Forest 5b) now only persists as a series of small patches, with a geographic distribution of approximately 1050 ha. Over half of this remnant area is found within State Forests or Timber Reserves (approx 600 ha, of which 303 ha is in a World Heritage Area), while 5 ha is found in a National Park. The remaining 440 ha is primarily freehold (369 ha) with approximately 70 ha in Shire road or recreation reserves.
The low level of reservation of this ecological community in protected areas (World Heritage listing 25%; National Park 0.4%; freehold 9%), suggests that a further 65% of the remnant Mabi Forest (Complex Notophyll Vine Forest 5b) may, at some stage, be lost through clearing for timber or agriculture. The remnants of this ecological community on freehold land are gradually being cleared. Where this is not the case, the remnants are used by stock for grazing and as shelter. These uses of the forest for stock maintenance causes a reduction or prevention of recruitment of seedlings into the forest through trampling, grazing and soil compaction.
Patch sizes of remnant Mabi Forest (Complex Notophyll Vine Forest 5b) are small, with only two patches being greater than 100 ha in size, three between 20-100 ha, three between 10-20 ha, eight between 1-10 ha, and the remaining three are 1 ha or less.
This ecological community is highly fragmented, and much of the remnant patches are being invaded by exotic smothering vines such as Turbina corymbosa (Turbine Vine). Other threats to the ecological community, such as lack of genetic diversity in the remnant forest, invasion by feral and domestic animals, invasion by weeds, and increased effect of wind damage on the remnants, are typical of small remnants which are surrounded by land which is being used for agricultural purposes.
The small geographic distribution of Mabi Forest (Complex Notophyll Vine Forest 5b), in association with demonstrable threats, identifies this ecological community as being eligible for listing as critically endangered under this criterion.
Criterion 3 - Loss or decline of functionally important species
Many of the bird species present in this ecological community play key roles in pollination and seed dispersal. One species, Casuarius casuarius johnsonii (Southern Cassowary), has been identified as playing a critical role in seed dispersal in rainforests of northern Australia. Fragmentation and reduction in patch size of remnant Mabi Forest (Complex Notophyll Vine Forest 5b) has lead to the local extinction of the Southern Cassowary. Hypsiprymnodon moschatus (Musky Rat Kangaroo), is another key species that has been identified as playing a key role in the dispersal of large fruits (> 30 mm) from rainforest trees. This marsupial has also become locally extinct in this ecological community. The loss of these large seed dispersal vectors has serious implications for the regeneration of this ecosystem, with the potential to favour dispersal of small-seeded plants, thereby disrupting future ecological processes and structure of this ecological community.
A number of the understorey shrubs are locally extinct from the small (< 1 ha) remnants. Loss of these shrubs diminishes the diversity of the ecological community, both through reduced plant diversity, and also reduced animal diversity.
The reduction in size and connectivity between remnant patches, and the loss of understorey shrub species, have played important parts in the local extinction of the functionally important large-seed dispersing animals. Without these fauna, the natural restoration of Mabi Forest (Complex Notophyll Vine Forest 5b) is unlikely in the immediate future. Therefore, the ecological community is eligible for listing as critically endangered under this criterion.
Criterion 4 - Reduction in community integrity
Clearing and fragmentation result in severe edge effects in the remnant patches of the ecological community. These edge effects cause changes to the persistence of native plant and animal species (biotic components of the ecological community). These changes may include, but are not limited to, alterations in: predator-prey relationships, competition between species, and seed predation. Changes to the non-living (abiotic) aspects of the ecological community are also caused by edge effects, and include increased light penetration, more extreme temperature fluctuations, and decreased soil moisture. The interaction of biotic and abiotic changes lead to increased weed invasion, higher rates of wind-throw and canopy damage, and changes to the rate of water transport through the vegetation. The overall effect of these changes is a significant alteration to the structure of the forest understorey and canopy.
Invasion by weeds is having a significant impact on the persistence of native species. For example, Rivina humilis (Coral Berry), which is an invasive weed of the understorey of Mabi Forest (Complex Notophyll Vine Forest 5b), causes additional degradation of some small fragments by replacing native shrubs such as Hodgkinsonia frutescens and Sauropus macranthus. The latter species, Sauropus macranthus, is listed as vulnerable under the EPBC Act. The majority of rare and vulnerable species are now absent from most remnants.
Remnant patches suffer severe wind damage due to abrupt boundaries with cleared agricultural lands and high edge to area ratios. Wind-throw is common, resulting in continual decline of remnant size, loss of mature hollow bearing trees upon which many hollow dependant animals rely, and creation of disturbed areas providing further opportunity for weed invasion.
Many small remnants are currently grazed or used as shelter by stock. One impact of these uses are the trampling of understorey species and canopy species seedlings, preventing natural recruitment and regeneration processes.
Due to the loss of key fauna, the regeneration of the plant community is unlikely in the immediate future. Without extensive enlargement and linking of the remnants, the key fauna, which are essential for the functioning of this ecological community, will not return to this forest. Therefore, the ecological community is eligible for listing as critically endangered under this criterion.
Criterion 5 - Rate of continuing detrimental change
The nomination provides no information under this criterion.
Criterion 6 - Quantitative analysis showing probability of extinction
The nomination provides no information under this criterion.
The Mabi Forest (Complex Notophyll Vine Forest 5b) ecological community meets criterion 1 as endangered for having had a severe decline in geographic distribution of more than 90%; criterion 2 as critically endangered for having a very restricted total area of occupancy coupled with demonstrable threats; criterion 3 as critically endangered for having a loss and decline in functionally important species; and criterion 4 as critically endangered for having a severe reduction in community integrity.
TSSC recommends that the list referred to in section 181 of the EPBC Act be amended by including in the list in the critically endangered category:
- Mabi Forest (Complex Notophyll Vine Forest 5b)
Elaeocarpus grandisFicus virens
Ficus obliquaMelia azendarach var. australasica
Alangium villoxum subsp. polyosmoides
Cupaniopsis serrata var. tomentella
|Lianes (vines)||Cissus antarctica
Publications used to assess the nomination
Anon, 2000. Vanishing Vegetation of Far North Queensland. Mabi Forest Working Group.
Goosem, S., Morgan, G. and Kemp, J. E. 1999. Wet tropics. In: The Conservation Status of Queensland's Bioregional Ecosystems. Eds P. S. Sattler and R. D. Williams. Environment Protection Agency, Brisbane.
Sattler, P. S. and Williams, R. D. (eds). 1999. The Conservation Status of Queensland's Bioregional Ecosystems. Environment Protection Agency, Brisbane.
Tracey, J. G. 1982. The Vegetation of the Humid Tropical Region of North Queensland. CSIRO, Melbourne.
Tracey, J. G. and Webb, L. J. 1975. Vegetation of the Humid Tropical Region of North Queensland. 15 maps at 1:100 000 scale. CSIRO Long Pocket Labs, Indooroopilly.
Webb, L. J. and Tracey, J. G.. 1994. The rainforests of northern Australia. In: Australian Vegetation. Ed. R.H. Groves, pp 467-500. Cambridge University Press, Cambridge.