September 21, 2010

Gum Trees Thrive on Fire

Australian eucalyptus trees have been dying back for years. Scientists now claim that setting or allowing more frequent forest fires might be one way to help save them in their own natural environment.

The ubiquitous and sweetly smelling eucalyptus tree is considered an environmental scourge in many parts of the world, but its fast and straight growth has proven useful, particularly for house construction in countries where there’s a scarcity of available native trees. In the Andes, for example, it continues to out-compete local pines, partly through human choice but also because its unusually deep roots absorb ground water needed for other trees to thrive.

Nevertheless, in their own natural environment of the Australian bush, Eucalyptus, (or gum) trees have been dying off since the 1970’s; a potential disaster for a range of other plants and all the animals that depend on them. One cause was determined in 2004, which was a rising alkaline content in the soil due to lime used in road making which sometimes finds its way into nearby forests.

However, eucalyptus trees are dying way beyond the impact of roads. This is believed to be partly due to a symbiotic relationship between Bell Miner birds and sap sucking insects, which take advantage of semi-logged gum forests. Yet, Eucalyptus die-back has been noticed without the intervention of these creatures.

The latest theory from the University of Tasmania, initially expounded by them in 1968 but not taken seriously at the time, suggests that a medium level of forest fire occurrences is required to maintain a healthy Eucalyptus population. If there are too many fires, the land is likely to transform into grassland; too few fires, and the landscape will turn into dry rainforest, out competing the gum trees with other species.

Traditionally, naturally started fires and blazes set by indigenous aborigines to make it easier to move through forests and stimulate growth of other ground based plants, have maintained an eco-balance favourable to the gum tree. But with the introduction of modern fire prevention and control techniques alongside the diminishing use of indigenous methods, the Eucalyptus now appears to be suffering.

Not everyone agrees with the obvious answer – to allow more forest fires under certain conditions. It certainly poses an important decision for Australian policy makers.



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