Ecology And Environment

How Forest Fires help Ecosystems and Forests



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Ecosystems are interdependent cycles of life. Forests support many ecosystems sensitive to extremes of heat, cold, drought and rain. Forest fires would seem to be a destructive force that violently disrupts the harmony of forest life. But forest fires may, in fact, refresh and revitalise ecosystems and forests.

Forest fires often demonstrate the frightening process of large scale environmental destruction. And yet, in dry Australia, (often referred to as "the land of fire"), in the midst of such mayhem, there can be regeneration. In Australia, eucalyptus are well known for new growth from burnt trunks or from lignotubers storing dormant buds that develop into suckers when fire destroys the top growth. Further, forest fires may open the soil seed bank stimulating seeds dormant for an average of 10-15 years. K.W. Dixon, S. Roche and J.S.Pate reported in 1995 that some native Western Australian seeds responded to smoke from burnt vegetation. Studies by the Bushfire Research and Development Group based at The University of Melbourne, Australia suggest that the biodiversity in ecosystems and forests may be enriched by fires, but far more data needs to be collected.

Even though Australia expects annual summer fires, satellite imagery is showing that regular fires are not diminishing but indeed strengthening the biodiversity in forest areas. In many ways, Australian forests need fires.

At first glance, Australia's forests appear endangered, only appearing in selected areas. "Australia has 149 million hectares of forest. Of this, 147 million hectares is native forest, dominated by eucalyptus (79%) and acacia (7%) forest types, and 1.82 million hectares is plantations." In comparison with the rest of the world, "Australia has the world's sixth-largest forest estate and the fourth-largest area of forest in nature conservation reserves." The largest area of forest in Australia is to be found in Queensland. (http://adl.brs.gov.au/forestsaustralia/facts/type.html - Department of Agriculture, Fisheries and Forests).

Yet these perceived endangered pockets of fires could benefit from fires. A chain of 50 separate reserves of sub tropical rainforest from Newcastle in NSW to Brisbane in Queensland are known collectively as Gondwana Rainforests of Australia and have a World Heritage listing. Interestingly, this area is Australia's closest link to the evolution of her flora and fauna and survives within close proximity of fire prone grassland and woodland zones. Why? Do fires diminish competition of species and domination of one species? Is fire a leveller? Studies are still continuing for answers.

Some studies suggest that controlled fire reduces the build-up of fuel on a forest floor which, if left too long, increases the risk of more destructive fire. A controlled fire will protect the ecosystem and forest. But other studies by Dr Marianne Horak at the CSIRO in Canberra suggest that fire is a natural feature of the Australian forest ecosystem and meanwhile, caterpillars are the natural "secret weapon" to reduce forest litter. In other words, natural forest fires naturally protect forest ecosystems.

Some plants need fire to singe or break their hard seed coats. The short lived, fast growing acacias and the Australian Mountain Ash are two examples.

Forest fires remove competing plants, open up the canopy to more sunlight and ash from burnt plants enriches the soil. Some plants are well-prepared for fire. In Australia, banksias and hakeas have woody fruits and cones which protect the seeds during fire.

The focus in most forest fire studies is on the survival of flora. But what of fauna in the forest area? They are an integral part of the forest ecosystem. So far, it is known wombats are able to go underground in times of fire and it is surmised that other surviving animals move and adapt to a new community. Koala communities in the south of Sydney NSW are known to do this, But detailed studies of their movement and change in living patterns are not well documented. However, it could be guessed that adapting means developing new skills and eating patterns and maybe establishing new relationships with other fauna. Surely fires have contributed to enhancing survival strengths.

While there is some evidence that forest fires help ecosystems and forests, the initial visual of bare, scorched earth creates some doubt. I had doubts when vicious fires in the early 1990's ravaged Mount Tomah Botanical Gardens in the Blue Mountains, west of Sydney. They were cool climate gardens. I thought they were safe. Hesitantly, I returned two years later. The garden looked vibrant with new growth, stubbornly withstanding the heat of a summer's day. My observations as I wandered the gardens told me that the plants looked stronger than they were before the fires.

And then there is the case of the Wollemi Pine. It was discovered in those same, fire prone Blue Mountains in 1994. This conifer can grow to 40 metres in height and its trunk can be 1 metre in diameter. "The Wollemi Pine is one of the world's oldest and rarest tree species belonging to a 200 million-year-old plant family. It was known from fossil records and presumed extinct until it was discovered in 1994 by a bushwalker in the Wollemi National Park just outside Australia's largest city, Sydney. Dubbed the botanical find of the century, the Wollemi Pine is now the focus of extensive research to conserve this ancient species." (http://www.wollemipine.com/faq.php#where)

Forest fires COULD help ecosystems and forests. If only we knew more detail about "the how" and protected that process.

Bibliography K.W. Dixon, S. Roche and J.S.Pate - Article entitled "The promotive effect of smoke derived from burnt native vegetation on seed germination of Western Australian plants" in journal "Oecologia" Vol.101, 1995 cited in http://cat.inist.fr/?aModele=afficheN&cpsidt=3520388

Bushfire Research and Development Group - http://www.forestscience.unimelb.edu.au/research/bushfire/index.html

Gondwana Rainforests of Australia - http://www.environment.gov.au/heritage/places/world/gondwana/index.html

Dr Marianne Horak - http://www.csiro.au/multimedia/LifeOfMoths.html

 

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