DARLING RIVERINE PLAINS BIOREGION Background Report

temporally. Annual averages are of little value for understanding the responses of ecological
processes and requirements.
Major changes have been made to this natural environment since European occupation.
Extensive areas have been cleared of native vegetation, especially in the east, and in the west
the combination of drought and overgrazing by sheep and rabbits have led to extensive
denudation of the land. Agricultural enterprises have created changes including altered runoff
patterns, changes in turbidity and nutrient status of rivers and increased salinity in the
rives and in the soil. Stream regulation has changed flow and flooding patterns resulting in
change to riverine and wetland ecosystems. Land tenure varies from large areas of leasehold
land (50% of the bioregion) in the west, to predominantly freehold (40.5% of the bioregion)
in the east. Approximately 9.5% of the bioregion is Crown land. The large number of
administrative boundaries crossing this bioregion has resulted in inconsistent levels of
research being carried out.
No systematic plant or animal surveys have been conducted across the entire bioregion but
general descriptions of vegetation communities are broadly consistent, with several
woodland, shrubland, grassland and wetland communities having been described. Coolibah,
Black Box and River Red Gum communities are generally the most common associations.
More detailed mapping of these communities is needed. There are three communities,
Corymbia tessellaris (carbeen), Acacia loderi (nelia), and the artesian springs community
listed as threatened under the Threatened Species Conservation Act, 1995 (NSW) (TSC Act)
and the Acacia harpophylla (brigalow) community has a preliminary determination. The
brigalow and artesian springs communities are also listed under the Environment Protection
and Biodiversity Conservation Act, 1999 (Commonwealth of Australia) (EPBC Act) and
several other communities have been noted as of concern.
A total of 1 129 plant taxa are recorded on databases covering the Darling Riverine Plains
bioregion within NSW. Nineteen of these species are listed as vulnerable or endangered, five
as extinct under the TSC Act and twenty are on the national register of Rare or Threatened
Australian Plants (ROTAP) (Briggs & Leigh 1996). There are also 229 exotic species
recorded. These plant records are unevenly distributed across the bioregion and detailed
floristic surveys have been patchy with large areas never having been surveyed.
The distribution and abundance of terrestrial vertebrates is also based on few and scattered
surveys and incidental records and there are substantial gaps in the coverage of the
information. The most detailed information available is for waterbird fauna in the three major
wetlands, Macquarie Marshes, Narran Lakes and the Gwydir Wetlands and some detailed
analysis is possible. Five hundred and six terrestrial vertebrate species have been recorded
from the DRP. Of these, 65 are listed under the TSC Act, 9 as extinct, 11 endangered and 45
as vulnerable. Other threatened species are noted as being predicted to occur in the bioregion
or as of concern, either near threatened or in decline. Twenty-four species are listed under the
Japan Australia and China Australia Migratory Bird Agreements (JAMBA and CAMBA).
The information available for invertebrates and fish is more limited than that for the
terrestrial vertebrates. This needs to be rectified, not only to understand the biodiversity of the
bioregion but also because of their importance as food resources for vertebrate species both
within and outside the DRP and as indicators of ecosystem health. There are 30 fish species
known from the DRP and three of these have been listed as threatened by the Fisheries
Management Act, 1994 (NSW).
High fire frequency, anthropogenic climate change, clearing of native vegetation, predation
by feral cats, foxes and Gambusia, competition and land degradation by feral goats and