Biology Reference
In-Depth Information
Box 6.2.
The biodiversity benefits of removing willows
On the Murrumbidgee River at Gundagai, New South Wales, the local anglers' club,
Bushcare group and the council have removed willows from large stretches of the
riverbank with assistance from the Murrumbidgee Catchment Management Author-
ity. Within six months of poisoning willows and excluding stock, native reeds and
rushes recolonised the area. The return of these habitats resulted in dramatic
increases in frogs, birds, insects and not only small fish but also large fish such as
Yellow Belly which take advantage of the bountiful supply of food now available in
this part of the river.
- often being used as foraging sites by such species as the Black-fronted Dotterel.
The mud from these areas is also used by the White-winged Chough, Magpie Lark
and Welcome Swallow for nest building.
As in the case of streams and natural drainage lines, there are some important
factors which strongly influence both the quality of the water in farms dams and
also their value as habitat for farm wildlife (see Figure 6.11). A key one is native
vegetation - around the edges of a farm dam, at the boundaries of the water line,
and in the water. Native vegetation that surrounds a farm dam shades the water,
reduces rates of evaporation, and lowers water temperatures, making algal blooms
less likely to occur. It also filters sediments and excess nutrients (e.g. from animal
dung), thereby contributing positively to water quality - both for livestock and
native animals and plants. The native vegetation surrounding a farm dam is used
Box 6.3.
Re-snagging waterways
The loss of large logs from streams has long been recognised as a key process
threatening the integrity of waterways in many parts of Australia. These losses can
occur in two ways - by deliberate removal, known as de-snagging, and by the
clearing of riparian vegetation which removes the source of logs and large branches.
Significant steps are being taken in some regions to address the problem of the lack
of logs in streams. For example, the New South Wales Roads and Traffic Authority,
in partnership with the Murray-Darling Basin Authority, has embarked on a major
project to re-snag many kilometres of the Murray River. The source of logs is the
large number of trees cut down as part of the expansion of the Hume Highway in
southern New South Wales. The aim of this substantial river restoration program is
to recreate native fish habitat and improve the overall ecology of the river. Snags are
critical habitat for native fish such as Murray Cod which use them for breeding,
sheltering and as foraging sites. Snags not only provide important habitats for a
diverse range of aquatic life, they also play an important role in shaping rivers and
creeks, creating variation in the depth and flow of a waterway, resulting in a diver-
sity of habitats for wildlife.
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