Terrestrial ecosystems

The dominant land use in the Gwydir subregion is agriculture based around a mixture of cropping and grazing (Figure 9).

The eastern half of the Border Rivers and Gwydir river basins comprises the ranges and foothills of the Great Dividing Range with elevations from 1500 m to 500 m. The western regions of these river basins comprise flat alluvial plains characterised by numerous anabranches and effluents where the elevation is less than 200 m. There are three distinct landform types across the former Border Rivers-Gwydir Catchment Management Authority area: the tablelands in the east, the slopes further inland and the plains in the western portion. The tablelands are mostly upstream of the Gwydir subregion. The climate grades from temperate (cooler and wetter) in the east of the river basins, to subtropical (hotter and drier) in the west.

The Gwydir – Border Rivers region includes four Interim Biogeographic Regionalisation of Australia (IBRA) regions (OEH, 2011): New England Tablelands, Brigalow Belt South, Nandewar and Darling Riverine Plains. The Gwydir subregion largely excludes the tablelands in the east and excludes all of the Queensland portion of the Border Rivers river basin. The focus of this report is the ecology of the slopes and plains. Table 16 provides a brief overview of the major landforms and biodiversity values across the three IBRA regions that are in the Gwydir subregion.

Table 16 Brief description of the Interim Biogeographic Regionalisation of Australia bioregions occurring in the Gwydir subregion

IBRA bioregion


Biodiversity values

Brigalow Belt South IBRA subregion

Landscapes derived from extensive basalt flow and quartz sandstones, variable soils and vegetation types.

Supports a variety of forests and woodlands including a number of threatened ecological communities, plant and animal species.

Darling Riverine Plains IBRA subregion

Occupies most of the upper catchment of the Darling and Barwon rivers in northern NSW and southern Queensland and includes the channels and floodplains of the lower reaches of these catchments.

River channels support red gum communities with coolibah and black box communities on floodplains. The bioregion contains 19 plant species and 63 animal species listed under state threatened species legislation.

Nandewar IBRA subregion

Formed on Paleozoic sedimentary rocks on the western edge of the New England Tablelands and includes the Tertiary basalts of Inverell and Kaputar.

The bioregion is characterised by box woodlands and includes 18 plant and 51 animals species listed under state threatened species legislation.

Source data: SEWPaC (2012)

The vegetation communities of the slopes are mostly fragmented remnants of forest grading into woodland further west. Species include white box (Eucalyptus albens), rough barked apple (Angophora floribunda), mugga ironbark (Eucalyptus sideroxylon), grey box (Eucalyptus microcarpa), forest red gum (Eucalyptus tereticornis) and kurrajong (Brachychiton spp.). Extensive areas of the plains region have been cleared for agriculture and the native remnant vegetation is influenced by floodplains and alluvial fans (Green et al., 2012; Green et al., 2011). The dominant native vegetation across the plains consists of floodplain woodlands of coolibah (Eucalyptus coolibah) with occasional myall (Acacia papyrocarpa) and belah (Casuarina cristata). The plains previously supported extensive areas of native grasslands of Mitchell grass and plains grass, and small fragments can still be found on the plains south-west of the township of Moree. Other communities occurring on the higher parts of the floodplain include poplar box woodlands (Eucalyptus populnea), wilga (Geijera parviflora), brigalow (Acacia harpophylla), white cypress (Calitris columellaris) and silver leaf ironbark (Eucalptus melanophloia) (Border Rivers-Gwydir CMA, 2007).

The western portions of the Border Rivers and Gwydir river basins contain approximately 1600 km2 of seasonal, semi-permanent and permanent wetlands and lagoons, some of which are internationally recognised under the Ramsar List of Wetlands of International Importance (Green et al., 2012; Green et al., 2011) (Figure 31). There are numerous protected areas covered by local and state reserve systems within the Gwydir subregion (Department of the Environment, 2010) and no national parks. Invasive species were recognised as the key problem in the Border Rivers-Gwydir river basin in a 2007 to 2008 survey. Invasive biota recognised as a major or moderate problem included environmental weeds, introduced animal pests, crop weeds and native pests (Marsh, 2010).

Figure 31

Figure 31 Major river systems, Interim Biogeographic Regionalisation of Australia regions, and nationally and internationally recognised wetlands in the Gwydir subregion

Source data: Department of the Environment (2013b) ©Commonwealth of Australia 2013 Matters of state, national and international environmental significance

There are many state and nationally listed threatened species found in the subregion listed under the New South Wales Threatened Species Conservation Act 1995, and the Commonwealth’s Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act). The state listed species include amphibians (one species), mammals (19 species), reptiles (five species), birds (37 species), fish (four species) and plants (28 species). The six species listed as endangered under the EPBC Act include the regent honeyeater (Xanthomyza phyrgia), Australian painted snipe (Rostratula australis), spot-tailed quoll (Dasyurus masculatus asculatiusm (s lat.)), Lake Keepit hakea (Hakea pulvinifera) and Tylophora linearis. An additional 23 species are listed as vulnerable under the EPBC Act. Table 17 documents the ten threatened ecological communities of the Gwydir subregion under the New South Wales Threatened Species Conservation Act 1995, the majority of which are also listed under the Commonwealth’s EPBC Act. Current threats to the existing extent and condition of these communities include land clearing, effects from weeds and feral animals, grazing by domestic livestock and the effects of fertiliser. Details on nationally and internationally significant aquatic ecosystems are described in the next section.

Table 17 Threatened ecological communities of the Gwydir subregion listed under the NSW Threatened Species Conservation Act 1995 and/or the Commonwealth’s Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act)


Commonwealth status


Brigalow within the Brigalow Belt South bioregion


Low woodland or forest community dominated by brigalow (Acacia harpophylla), with pockets of belah (Casuarina cristata) and poplar box (Eucalyptus populnea subsp. bimbil).

Coolibah - Black Box Woodland


Semi-arid to humid subtropical woodland where coolibah (Eucalyptus coolibah subsp. coolibah) and/or black box (Eucalyptus largiflorens) are the dominant canopy species and where the understorey tends to be grassy. The ecological community is associated with the floodplains and drainage areas.

Cadellia pentastylis (Ooline) community in the Nandewar and Brigalow Belt South Bioregions

Not listed

An unusual and distinctive forest community with the canopy dominated by the tree Ooline (Cadellia pentastylis). Other canopy species include White Box (Eucalyptus albens), Ironbarks (E. beyeriana and E. melanophloia), Dirty Gum (E. chloroclada), Narrow-leaved Grey Box (E. pilligaensis), Green Mallee (E. viridis) and White Cypress Pine (Callitris glaucophylla). The understorey is made up of a range of shrubs, such as Wattles (Acacia spp.), and grasses.

Carbeen Open Forest Community in the Darling Riverine Plains and Brigalow Belt South Bioregions

Not listed

Exists as woodland or as remnant trees. Characteristic tree species are Carbeen (Corymbia tessellaris) and White Cypress Pine (Callitris glaucophylla). Associated trees include Corymbia dolichocarpa, Eucalyptus populnea, E. camaldulensis, Casuarina cristata and Allocasuarina leuhmannii.

Inland Grey Box (Eucalyptus microcarpa) woodland

Not listed

Woodlands in which the most characteristic tree species, inland grey box (Eucalyptus microcarpa), is often found in association with bimble or poplar box (Eucalyptus populnea subsp. bimbil), white cypress pine (Callitris glaucophylla), kurrajong (Brachychiton populneus), bulloak (Allocasuarina luehmannii) or yellow box (Eucalyptus melliodora), and sometimes with white box (Eucalyptus albens).

Marsh club-rush sedgeland

Not listed

Dense stands of marsh club-rush (Bolboschoenus fluviatilis) up to 2 m tall. Understorey species include tussock sedge (Carex appressa), ribbed spike rush (Eleocharis plana), blown grass (Lachnagrostis filiformis), water couch (Paspalum distichum) and swamp buttercup (Ranunculus undosus).

Natural grasslands on basalt and fine-textured alluvial plains of northern NSW and southern Queensland

Critically endangered

Temperate grasslands are typically dominated by tussock grasses in the genera Austrodanthonia, Austrostipa, Bothriochloa, Chloris, Enteropogon, or Themeda. Representatives of these genera, as well as temperate grassland forbs, are present to some extent throughout the ecological community.

Semi-evergreen Vine Thicket in the Brigalow Belt South and Nandewar Bioregions


A low, dense form of dry rainforest generally less than 10 m high, made up of vines and rainforest trees as well as some shrubs.

Weeping Myall woodland


Low woodland and low open woodland to low sparse woodland or open shrubland. The tree layer grows up to a height of about 10 m and invariably includes weeping myall or boree (Acacia pendula) as one of the dominant or only tree species present.

White Box-Yellow Box-Blakely's Red Gum Grassy Woodland and Derived Native Grassland

Critically endangered

Dominance of white box (Eucalyptus albens), yellow box (Eucalyptus melliodora) or Blakely’s red gum (Eucalyptus blakelyi) trees and a species-rich understorey of native tussock grasses, herbs and scattered shrubs.

Source data: NSW Department of Environment and Heritage (2013a) and Department of the Environment (2013a)

Last updated:
5 January 2018