Mornington Sanctuary - Ecosystems /Plants
The Central Kimberley is one of the world’s ‘last true wilderness areas’ [Earth’s Last Wild Places (2002), Conservation International], and it is also one of the most biologically unexplored regions of Australia. Comprehensive surveys of the property are being undertaken so that the distribution of animals and vegetation communities on Mornington can be determined. Vegetation communities can be readily identified from aerial photographs. Using a complete set of aerial photographs taken by the Western Australian State Government in 1997, we are compiling a detailed vegetation and geology map. It is a lengthy process, as all vegetation types identified from the photographs must be visited on the ground (ground-truthed) to check the floristic details. When complete (by December 2006), this vegetation map will be the most accurate and detailed of its type in the Kimberley.
The Tropical Savanna Ecosystem
Mornington is a vast property, covered mainly with different types of tropical savanna. Tropical savannas dominate the northern third of the Australian continent, and constitute a significant proportion of Australia’s overall biodiversity. They are under threat across their range as a result of the impacts of cattle grazing and inappropriate burning. Managing and protecting the diversity of flora and fauna which rely upon a healthy savanna is a key management challenge for AWC.
Savannas come in many (often subtly) different forms – the density and species assemblages of trees, shrubs and grasses all vary depending on bioregion, climate and geology. Mornington contains a high diversity of different savanna types, most of which are not represented in any National Parks.
The vegetation of WA has been categorised by the National Land and Water Resources (NLWR) Audit into a large number of vegetation associations, based largely on a system developed by Beard in 1979 (Beard Vegetation Associations, or BVAs). Mornington contains at least 12 different savanna-type BVAs. Of these:
- 7 are not represented in any Government National Parks or Nature Reserves at the regional level, and
- 8 are unrepresented at the subregional level.
- The National Audit has identified each of these BVAs as high priority for inclusion in the national reserve system.
Several other types of ecosystem occur on Mornington, nestled within the savanna matrix, and they have all been identified by the NLWR Audit as being ecosystems ‘at risk’ and are also poorly represented in the national reserve system.
- Assemblages of permanent/ephemeral wetlands, damplands, and riparian habitat of the Kimberley region.
Livistona palm forests and fire sensitive vegetation (such as Pandanus, Terminalia spp., figs and other rainforest elements) are found in gullies and along some permanent creeks where they are protected from fires. These areas are disproportionately important nuclei for biodiversity. However, they are extremely vulnerable to degradation by stock through physical damage, overgrazing, and subsequent invasion by weeds.
- Savanna communities of which Callitris intratropica is a component
Callitris intratropica is distributed across the northern tropical woodlands, but has been declining in recent years because of an increase in the frequency of widespread, hot fires. This tree occurs in the northern part of Mornington.
- Herbfields of sandstone pavements
Mornington has extensive areas of savanna woodland on sandstone pavements, which support diverse plant communities that are adapted to cope with occasional fire, but are unable to survive too frequent fires.
- Plant assemblages of sand plain seepage areas between/near sandstone ridges.
Some of the sandstone ranges on Mornington have sandy strips at their base that are permanently moist because of seepage from the adjoining range. These areas support a diverse flora that is sensitive to inappropriate fire regimes.
- Flora and fauna assemblages of Gladstone Lake
Lake Gladstone is on a travelling stock route adjacent to the NW boundary of Mornington. It is the largest permanent wetland in the Kimberley, and is listed as wetland of national significance in the “Directory of Important Wetlands in Australia” (DIWA database). The area provides critical habitat for many species of plants and animals, including threatened species like the Red Goshawk and Gouldian Finch, and some migratory bird species (e.g. pratincoles, phalaropes, dotterels and sandpipers), all of which are protected under the Environment Protection of Biodiversity and Conservation Act 1999. Lake Gladstone is in the catchment of the Fitzroy River, one of the largest unregulated rivers in Australia and a hotspot for freshwater fish biodiversity.