Burning for Brolgas

..and some grazing, too

by Elinor Scambler

Part 1 of ‘Burning for Brolgas’ looked at the past high dry season population of Brolgas on the Townsville Town Common Conservation Park, and the major decline in numbers from 1980 when grazing was removed and invasive Para Grass (Urochloa mutica) spread across the wetlands.

By 2000 it was clear herbicide treatments had failed to check the weed. Now in Part 2, Ozcranes looks at experimental grazing trials from 2002, later combined with burning to compare the effects of different treatments on Para Grass survival and recovery. Programs were run by Queensland Parks and Wildlife Service, CSIRO Sustainable Systems, and NQ Dry Tropics NRM. A wide range of stakeholders was involved, including TRBOC (now BirdLife Townsville), who conducted bird counts.

Ozcranes is grateful to Dr Tony Grice of CSIRO Sustainable Ecosystems, for use of images showing project work at the Town Common. Note: The Reference List can be found at the end of ‘Burning for Brolgas’ Part 1.


Grazing

The task seemed daunting, with 100s of hectares overrun with 20 tonnes per ha of Para Grass. But grazing trials were a legal option, because in Queensland a Conservation Park (as distinct from a National Park) can be grazed in the interests of biodiversity. In October 2002, 37 cattle were placed in a 58 ha paddock including 7 ha of Para Grass (Williams et al. 2005). Six permanent plots were chosen to cover a mixture of Para with native grasses, fenced with mesh to prevent cattle grazing into the next plot. Another 40 ha was opened to cattle in June 2003.

Results Grazing significantly reduced Para Grass. Native grasses were comparatively unaffected, though a ‘watch’ was placed on Common Reed due to some decline in seed production. However, grazing did not reduce the thick ground-level thatch built up by successive generations of Para Grass. Species richness did not increase: native plant seeds could probably not germinate in the heavy mulch. A further trial to test fire as well as grazing was planned.

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Testing fire

L: Research vehicle overwhelmed by Para Grass on Townsville Town Common

R: Plot 12 before burning in August 2004. Dense Para Grass, with Townsville city and hinterland in background. Images courtesy (CSIRO Sustainable Systems)

Vehicle and para grass Vehicle and para grass

The new trials, 2004-2008

In the Dry season August 2004, the project team marked and fenced 12 x 6 ha Para grass plots. Images of the different treatments are in the right sidebar →

Cattle were removed before the first major rains, to avoid disturbing breeding Magpie Geese. Vegetation, birds and mammals were identified and measured/counted at every stage.

Results

The trial was a success. Burning and grazing both had major effects.

L: 2004 burning program (burnt area, & smoke on horizon)

R: Aerial view of plots. Images courtesy (CSIRO Sustainable Systems)

Burning program Aerial view of plots

Compared with the ‘do nothing’ plots, fire (although patchy) reduced both Para Grass biomass and the ground layer of thatch, and killed some individual Para Grass plants. Grazing only, without fire, reduced Para Grass but left some trampled thatch covering the ground (Grice et al. 2006). The best result was from Treatment 4, burning combined with grazing, which reducecd Para Grass biomass from an average of 77% to 4%. Frequency of native sedges and grasses increased, as did plant species diversity. It's still too early to know if the program (if continued) will increase Brolga numbers but areas of open water suitable for native wetland plants, are returning.

Complications Although some areas returned to fresh water wetland, Para Grass is still the dominant plant species and returns without repeated treatments. A number of issues affect future success of the program and need to be factored into future research and Management Plans (Grice et al. 2008):

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The future

Para Grass map

← Para grass is already a problem and is likely to spread further across regions important for northern Brolgas and all Australian Sarus Cranes (Map: CSIRO Sustainable Systems)

New fire trials continued from 2009, with reports and fact sheets available at RIRDC. It is hoped the work, including stakeholder communications and other achievements, can be applied more generally across the north where invasive Para Grass chokes wetlands (see map).

Para is also a significant problem in the Northern Territory and more resources can be found at the Northern Land Manager site.

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About the author Elinor Scambler (aka cranesnorth) studies cranes and also birds in rainforest revegetation projects. She began studying Sarus Cranes in north Queensland after surveying bird recruitment to a waterside revegetation site. A related species, Signal Grass Urochloa decumbens, overtook unplanted areas and the changed habitat excluded Sarus Cranes from one of the first roost and feeding sites identified on the Atherton Tablelands. She is the northern Australia representative for the Australian Crane Network and a member of the Crane Specialist Group».


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