DARLING RIVERINE PLAINS BIOREGION Background Report

16/08/02 Darling Riverine Plains Bioregion Background Report
populations of olive perchlet (Ambassis agassizii), and purple-spotted gudgeon (Mogurnda
adspersa) (FSC 2001c).
7.2.2 Potential Threatening Processes
Competition from honeybees (Apis mellifera) (preliminary determination)
The NSW Scientific Committee have made a preliminary determination to list competition
from honeybees as a key threatening process under the TSC Act. Breeding colonies of
honeybees compete with native hollow-dependant fauna for tree hollows. At least 20% of
bird species are hollow dependant (Saunders et al. 1982) and all native arboreal marsupials
depend on tree hollows except the koala (Lindenmayer et al. 1991). Threatened species likely
to be affected by competition from feral honeybees include the squirrel glider, Major
Mitchell’s cockatoo, glossy black-cockatoo and superb parrot (NPWS 2001a).
Honeybees, both feral and managed, often remove up to 80% of the floral resources produced
by plants, and this may result in the displacement of native fauna such as honeyeaters and
native bees which rely on these resources (Paton 1993, 1996, 2000; Sugden & Pyke 1991;
Sugden et al. 1996). Apiary has an unmeasured impact on biodiversity and some studies have
shown that where nectar and pollen resources are limited Apis mellifera may reduce the
degree of seed set in some plant species (Gibbs & Muirhead 1998; Paton 1996; Pyke &
Blazer 1985).
Alteration to the natural flow regimes of rivers and streams and their floodplains and
wetlands (preliminary determination)
The NSW Scientific Committee has made a preliminary determination to list ‘alteration to the
natural flow regimes of rivers and streams and their floodplains and wetlands’ as a key
threatening process under the TSC Act. The NSW Scientific Committee has found that this
process is recognised as a major factor contributing to loss of biological diversity and
ecological function in aquatic ecosystems, including floodplains (NPWS 2001a). The NSW
Scientific Committee describes alterations to natural flow regimes as either reducing or
increasing flows, altering seasonality of flows, reducing frequency, duration and magnitude
of flow events, altering water levels and increasing the rate of fall of water levels (Walker
1985; Cadwallader & Lawrence 1990; Gehrke et al. 1995; Kingsford 1995. Maheshwari et al.
1995; Robertson et al. 1999, 2001; NPWS 2001a).
A high proportion of flow alterations to the majority of streams across New South Wales have
had a major impact on the pattern of natural flows in these waterways. Alteration of flows
reduces habitat by changing the area, frequency and duration of flooding of floodplains and
terminal wetlands. Increasing flows causes more permanent flooding of wetlands, riparian
zone degradation, increased habitat for invasive species, and loss or disruption of ecological
function. Threatened species recorded within the DRP affected by this process include the
blue-billed duck, and freckled duck (NPWS 2001a).
Installation and operation of instream structures that modify flow (proposed
recommendation)
The Fisheries Scientific Committee has made a recommendation to list ‘Installation and
operation of instream structures that modify flow’ as a key threatening process under the
FMA, 1994. The Fisheries Scientific Committee identifies instream structures which modify
flow as including dams, weirs, navigation locks, floodgates, culverts, flow regulators, levee
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