SANDSTONE COUNTRY OF THE
WEST ARNHEM AND KAKADU REGION
As part of the West Arnhem and Kakadu project, TNRM is working with ranger groups to support fire management to improve the condition of sandstone country. The stone country incorporates the Arnhem Plateau Sandstone Shrubland Complex, a listed Threatened Ecological Community.
The sandstone country extends from Kakadu across into Arnhem Land and south to Katherine, occupying an area of around 20 000 km2. Comprised mainly of sandstone and landscapes derived from sandstone, it is known locally as warddewardde or stone ountry.
Blocks of sandstone country occur in Kakadu National Park, the Warddeken IPA, southern Djelk IPA, near Gunbalanya, and on Jawoyn country and Mimal country.
The major drainages of the East and South Alligator, Katherine River, Liverpool River and rivers that flow into the Roper River have their genesis in the upland sandstone country.
The main rock type of the Arnhem Land plateau is sandstone of the Kombolgie Formation. The escarpment is the most striking scenic feature of the region, being prominent in parts of Kakadu National Park. Outliers are remnant rock outcrops and mounts isolated from the main plateau.
The extent of the sandstone country can be seen in the Arnhem plateau shrubland complex map
The sandstone consists of a complex mosaic of habitats, with different vegetation types interwoven between the highly dissected rock formations.
The main habitats comprise:
escarpments and cliffs
rock platforms and boulders
drainages and upland wetlands (including paperbark swamps)
monsoon forest (including anbinik forests)
See if you can find the endemic Black Wallaroo in this photo
White-throated Grasswren, a threatened species
FLORA AND FAUNA
The stone country supports a high diversity of animal and plant species. The Arnhem Shrubland Complex includes a diverse array of shrubs and herbs in genera such as Acacia, Boronia, Calytrix, Goodenia, Grevillea, Hibbertia, Hibiscus, Jacksonia, Micraira, Pityrodia, Phyllanthus, Stylidium and Tephrosia.
The stone country supports a high number of endemic and threatened species. The endemic species are only known from the Arnhem Land plateau region. Two species of frogs, three geckos, six skinks, the Oenpelli Python, a freshwater turtle, four bird species and two mammals are endemic to the region.
Among the plants, anbinik Allosyncarpia ternata is a large myrtaceous rainforest tree endemic to the plateau. This is just one of around 40 plant species endemic to these environments.
The Arnhem Land plateau is of major significance for threatened species. This includes flora and fauna species listed in the Northern Territory and under Federal legislation.
The stone country provides vital habitat for threatened fauna such as the Arnhem Land skink Bellatorias obiri, White-throated Grasswren Amytornis woodwardi and Northern Quoll Dasyurus hallucatus.
FIRE AND ITS EFFECTS
The aim of fire management in the sandstone is to approximate traditional burning, in order to create a mosaic of burnt and unburnt patches. Extreme fires can burn large areas and are detrimental to biodiversity values.
Some plants of the Arnhem Shrubland Complex are fire sensitive, for example the cypress pine (Callitris intratropica). Monsoon forest patches within the sandstone can also be degraded by frequent fire – traditional burning protected these areas with small burns to retain important fruit trees and yams. There is also a high proportion of obligate seeders. These plants require long fire-free intervals to survive and reproduce.
Fire projects employ traditional owners to manage fire. Much of this fire management is done from helicopters using aerial incendiaries, however, some fire mitigation work is done on-ground.
More information about fire management projects across the region can be found on the ALFA website.
Burning spear grass in the dry season to create fire breaks
The main weed threats to the sandstone are the grassy weeds gamba grass and perennial mission grass. These grasses alter fire regimes and have resultant effects on the ecology of various habitats.
Populations of feral water buffalo are a major threat to the stone country springs, wetlands and monsoon forests. Buffalo have colonised many parts of the plateau and surrounds and cause considerable damage to sensitive riparian vegetation. Feral pigs also cause major disturbance, and feral cats feed on an array of native animals, as they do elsewhere across Australia.
FURTHER INFORMATION / RESOURCES
Arnhem plateau shrubland complex factsheet
Arnhem plateau shrubland complex map
Biodiversity and fire in the sandstone
Woinarski, J.C.Z., Russell-Smith, J., Andersen, A.N. and Brennan, K. 2009. Fire management and biodiversity of the western Arnhem Land plateau.