Daly Basin
Bioregional Description
The Daly Basin bioregion comprises gently undulating plains and scattered low plateau remnants on Palaeozoic sandstones, siltstones and limestones; and neutral loamy and sandy red earths. The most extensive vegetation type is open forest dominated by Darwin Stringybark Eucalyptus tetrodonta and Darwin Woollybutt E.miniata with perennial and annual grass understory. The Daly Basin includes no subregions.
Special values
This bioregion comprises much of the catchment of the Daly River, one of the largest river systems in northern Australia. Some special values are associated directly with that river system, such as the unusually high diversity of freshwater turtles (with 8 species, the richest in Australia) and the exceptionally extensive and well developed riparian rainforest network. The bioregion also contains 11 species listed as threatened at Territory or national levels. The endangered gouldian finch Erythrura gouldiae has a major stronghold in this bioregion. There area also contains some extensive cave systems with distinctive biota.
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Summary of overall condition and trend
Condition is generally good across much of the bioregion, reflected in a continental stress class score of 5. However, as one of the most fertile areas in northern Australia, and because of its proximity to Darwin and Katherine, the bioregion is one of the most developed in the Northern Territory. About 8% of the region has been cleared for horticultural production or intensive grazing, and more extensive development is being proposed. Much of the uncleared lowland area has been relatively heavily grazed by livestock, often in conjunction with the development of exotic pasture grasses. Mining and urban development have had some localised impacts in the bioregion. More extensively, the condition of the entire bioregion is being destabilised by the spread of weeds, feral animals (principally pigs) and altered fire regimes. -
Summary of priority management/conservation priorities
A conservation plan for this bioregion has recently been completed. It recommends a series of additional reserves to enhance the comprehensiveness of the existing reserve network, and to partly offset conservation losses due to proposed major horticultural developments. It also proposes a series of off-reserve conservation management actions, including retention of riparian corridors and bushland remnants on horticultural properties. Another priority is improvement in the integration across tenures of the management of weeds, feral animals and fire. -
Wetlands
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Nationally important wetlands
Much of the lower Daly River is recognised as a nationally significant wetland (NT001 Daly River middle reaches: wetland types B1 and B6). It provides the largest annual discharge of any river in northern Australia, possesses important breeding sites for colonially-nesting waterfowl, supports much of the Australian population of the pig-nosed turtle Carettochelys insculpta, areas of distinctive limestone tufas, significant riparian vegetation, and the occurrence of two threatened fish (freshwater sawfish Pristis microdon and speartooth shark Glyphis sp A).
- Other wetlands of subregional significance
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Nationally important wetlands
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Riparian zones
This bioregion is centred on the Daly River and includes at least parts of its important tributaries, the Katherine, Flora, Douglas, Fergusson and Fish Rivers. The riparian zones in this bioregion have been unusually well documented. Most are in reasonably good condition, although many sites have been detrimentally affected by heavy infestations of weeds and by feral animals and livestock. In some cases, frequent hot fires have also degraded riparian vegetation, and large stretches have been disturbed by recent. -
Species at risk
The Daly Basin contains 11 threatened species. Of these, the bioregion is probably particularly significant for gouldian finch (for which the bioregion holds the largest known population), and the orchid Nervilia plicata, whose total known range consists of two sites in this bioregion.
Number of taxa in the Daly Basin bioregion listed as threatened at national and/or NT level (nb this table includes only species definitely recorded from the bioregion (rather than putative occurrences based on modelling) and presumed to be still extant in the bioregion).
| taxa | National | Northern Territory | ||
|---|---|---|---|---|
| endangered | vulnerable | endangered | vulnerable | |
| plants | 0 | 0 | 2 | 2 |
| fish | 0 | 2 | 0 | 0 |
| birds | 1 | 3 | 1 | 2 |
| mammals | 0 | 1 | 0 | 0 |
There is also some evidence that there is broad scale decline affecting at least some groups of mammals and birds in this bioregion, in addition to those species currently listed as threatened.
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Other flora values for eucalypts and acacias
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Endemism
This bioregion contains no endemic eucalypts and one endemic acacia - Acacia douglasica (=A.. sp. Douglas River). This species may be affected by increased incidence of land clearing, and intensification of grazing practices; but there are no data on current trends or population size.
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Richness
This bioregion has moderately high richness for Acacia (49 species) and Eucalyptus (45 species).
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Endemism
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Birds
Some bird species and guilds exhibited changes in abundance over the period between the two bird Atlases. However, these changes may be artefactual: "decreases in some guilds may be the result of changes in birdwatcher behaviour rather than real trends in abundance" (Garnett & Crowley). -
Mammals
The mammal fauna of this region has proven relatively resilient. Of 51 species recorded, 1 has become regionally extinct, 1 has declined and 49 species are stable.
Management Responses
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Reserve consolidation
The Daly Basin bioregion includes a portion of the large Litchfield National Park, and several smaller reserves. The conservation plan for the Daly Basin proposes three additional conservation reserves in order to achieve a CAR system for this bioregion. These reserves will also ensure the retention of adequate samples of those environments most likely to be cleared for horticultural development. The realisation of these proposed additional reserves will depend upon the provision of specific acquisition finances and availability of resources for ongoing management. -
Off park conservation for species and ecosystem recovery
The recovery plan for gouldian finch provides some management guidelines for this species. There is also some existing management action associated with the Northern Territory Strategy for conservation of biological diversity of wetlands. The conservation plan for the Daly Basin provides specific recommendations for the maintenance of the rainforest patch network, for riparian areas and for wetlands.
A water allocation plan is in preparation for the Daly River system. -
Integrated NRM
The Daly Basin conservation plan provides a firm basis for integrated natural resource management across this bioregion, with specific consideration of protection of significant habitats and sites, regional- and property-scale management priorities for threatening processes, and the establishment of a monitoring program.
As with other bioregions in northern and central Australia, biodiversity conservation will require landscape-scale integration of management of weeds, feral animals and fire regimes. While there are many commonalities in this management across tenures, there is also a marked disjunction in this bioregion between "remote" poorly-resourced Aboriginal lands and more accessible, leasehold or freehold lands supporting intensive horticulture or pastoralism. The conservation priorities in the former lands are to provide resources and capacity building to Aboriginal owners in order to encourage and allow them to manage their lands better. The priorities in the more developed lands are to ensure retention of viable remnants and linkages, and to prevent, limit or mitigate erosion, pollution and other detrimental consequences of increased development.
Further Information and Gaps
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Major data gaps and research priorities for bioregion
Although some information is now available about the hydrological requirements of the aquatic biota of the Daly system, information is still limited, such that there is some uncertainty about the impacts of greatly increased water use associated with horticultural development and about the quantity and timing of minimum required environmental flows. Management would benefit from more detailed environmental mapping, in particular vegetation mapping at the scale of 1:100,000 or better.
There is also some priority to establish a bioregional monitoring program, especially relating to the occurrence of threats, their impacts and the consequences of their management. - Other information