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Fire in the Mitchell Grasslands

Fire and land use

The most significant land use in the Mitchell Grassland is cattle grazing and this is reflected in the approach to fire by land managers. Of particular concern is the effect of fire on native pastures. This relationship is still poorly understood, so many land managers are hesitant in their use of fire as a management tool.

This 1999 satellite photo, centred on the Mitchell Grasslands which run from the top left to the lower right of the image shows few fires occur in the region. Blue regions show fire from early in the year; red shows late fires—often accidental wildfires

In general, fire is excluded from Mitchell grasslands by pastoral management so as to maintain forage throughout the dry season. As a result this region of the tropical savannas probably has the lowest rate of intentional, and managed, fires of any of the regions. The majority of fires are accidental, often started by lightning strikes. These fires can cause serious damage, particularly after a series of good seasons when fuel loads are high.

Burning as a management tool

For those concerned with the overall health of the region, there is a consensus that greater controlled burning is required. There is evidence that a judicious use of fire can increase tiller production and therefore total grass yield as long as seasonal conditions are favourable. (Scanlan 1980) Burning also promotes seeding in Mitchell grass and, in the absence of grazing, may act to maintain the dominance of Mitchell grass and keep invading species at bay.

These positive outcomes of burning mitchell grass depend upon seasonal rainfall—if the rains fail, then burning can have distastrous results. Of all the savanna regions, the Mitchell grass country is the one most prone to unseasonal weather fluctuations. This translates into greater vulnerability overall for land managers; that is, slimmer margins for error in land-management decision-making. However, the ever-increasing invasion of woody weeds into much of this country may soon compel land managers to adopt fire as part of their pasture management regime.

At present the costs of burning for pastoralists, both in terms of spelling required to allow fuel levels to build up, as well as possible short term losses in animal production while grasses recover, remain unclear. These uncertainties, in addition to climatic variability, means that controlled burning is likely to remain uncommon in the region until research and extension has demonstrated that benefits outweigh costs.