The Townsville Town Common Conservation Park is a seasonal
wetland of national significance for birds. Declared a Conservation
Park in the late 1970's, the wetland habitat has degraded
significantly over the past 50 years due to weed infestation,
dominated by para grass. The increase of para grass on the
Townsville Town Common has dramatically altered water bird habitat,
especially for brolgas and magpie geese.
Para grass is an exotic weed, capable of destroying ecosystem
structure and function. Introduced to Australia from Africa in the
late 1800's to increase pasture productivity, para grass has since
spread outside grazed areas where it monopolises large areas of
land by out-competing complex mosaics of native vegetation. In many
cases, the wetland vegetation becomes a virtual monoculture. Many
of the species depending on the diversity of wetland plant
communities decline as a result. For example, the brolgas are
reliant on the bulbs of sedges such as bulkuru, and the magpie
geese nest and feed in the wetlands.
This project commenced in 2004 and examined how various
combinations of fire and grazing by cattle can reduce the abundance
of para grass. Twelve 6 ha plots were established in an area of the
Townsville Town Common Conservation Park that was dominated by para
grass. Plots were allocated to one of four treatments:
- Unburned and ungrazed control plots
- Burned and ungrazed plots
- Unburned and grazed plots
- Burned and grazed plots
The project documented changes in wetland vegetation and
the animal communities dependent on it.
Fires occurred in August 2004, October 2005, and November 2006.
Sites were grazed soon after the fires and cattle were removed from
these sites before the on-set of the wet season.
Significant increases in para grass abundance were observed in
control plots which were ungrazed and unburnt. Patch 'burning' and
'burning plus grazing' treatments each year for three consecutive
years led to a marked decrease in para grass weed infestation.
Importantly, two food species (wild rice and bulkuru) important for
wetland birds have increased in the treated areas. With more food
and more free water, it is not surprising that more and more
bird species were surveyed in the burned plots, although bird
usage varies greatly between seasons regardless of treatment. We
have also been encouraged by the findings that the patch burning
treatment does not result in major problems for other faunal groups
(mammals, reptiles and amphibians).
The Environmental Protection Agency and Queensland Parks and
Wildlife Service used the results of the research to develop
management strategies to control para grass in the Town Common.
Developing and promoting methods for maintaining and restoring the
Town Common is of regional significance, as a model for
restoring para grass-infested seasonal wetlands throughout North
Queensland.
