Bushfire and our environment
A brief introduction to fire in our environment
Fire has been a major influence in shaping the Australian environment. Over millions of years, the continent has moved northwards and progressively
dried out. The inland seas and rainforests have dried up, and the dry climate experts have thrived, evolving into the array of eucalypts, wattles and
heath species that are so familiar to us today.
Australian plants have evolved with drought and fire. Other than a few of the cold (alpine) and wet (rainforest) plant communities, our flora is largely
dependent on fire for its long-term survival.
Burn too often, and the colourful wildflowers that we enjoy in Spring, give way to the faster growing grasses. Exclude fire for too long and we lose
the variety in the shrub layer, which often develops into dense thickets of a single species. Next time you are in the bush, look carefully at the plants
around you and see if you can work out how they have adapted to a fire-prone environment.
Adaptations to fire:
♦ Plants that have heavy, thick protective pods or capsules release their seed after fire - banksias, eucalypts, hakeas.
♦ Trees and shrubs that resprout from underground lignotubers and epicormic shoots - eucalypts, banksias, teatrees.
♦ Plants that flower after fire - Christmas bells, ground orchids, grass trees.
♦ Trees, shrubs and herbs that have hard seeds that germinate after fire - Acacias, pea flowers.
Hakea seed capsule releases seed after fire
Eucalypt resprouting after fire
Christmas Bells flower after fire
Banksia cone releases seed after fire
Our animals are dependent on the plant communities they live in, and must adapt to fire too. An ecosystem may look as though it has recovered after a fire,
with the trees and shrubs covered in fresh new growth, and wildflowers in profusion, but have the animals returned? You may see many of the larger
marsupials such as kangaroos and wallabies eating the fresh new grass. However, small animals that live on the ground, such as skinks, snakes and
marsupial mice (Antechinus sp.) need enough leaf litter to hide and forage for food. The larger predators including owls and hawks need habitat supporting
the ground-dwelling animals they feed on, and large trees with hollows to nest in.
The behaviour of fire in the Australian bush has been extensively studied and described. This is only a brief summary of some of the main factors that
influence how a fire will behave.
Vegetation type - the types of plants will influence how intense a fire is. Find a fresh eucalypt leaf and hold it up to the light. You will be able to see that
it is covered in tiny dots which are the oil glands. Crush it in your hand and smell it - there will be a strong smell of
eucalypt oil. Many Australian plants have volatile oils in their leaves - the eucalypts, boronias, teatrees (Melaleuca spp. & Leptospermum spp). You will
also notice that the leaves are often quite hard and feel dry (sclerophyllous). A fire in a heathland or scrubby eucalypt forest will be much more intense
due to the volatile oils and dry, flammable leaves. The humidity, and large, soft, high moisture level leaves of wet communities such as rainforests,
are generally resistant to fire in all but the worst fire weather conditions.
Slope - fire will travel much faster up a slope than along flat land or downhill. This means that houses and other infrastructure at the top of slopes
is at higher risk from bushfire.
Aspect - the aspect (direction that the land is facing) will also influence the intensity of a fire. Slopes that face north and west are hotter and drier
than those that face south and east. This means that they will tend to have drier and more flammable vegetation growing on them.
Temperature & humidity - the ambient temperature and humidity will determine how intense a fire is. Bushfires are uncommon on cold winter days,
and are easier to control on humid days. A hot, dry day (anything over 28 degrees celsius) means that a bushfire can be difficult to control.
Gosford City Council manages over 250 bushland reserves - from dunes to hill tops - these natural areas provide habitat for some of our best-loved flora and fauna. Since the mid-1970s, Council has been aware of the importance of Gosford's green backdrop, to conserve nature and to preserve the striking visual landscapes of the Central Coast. The Coastal Open Space System (COSS) reserves are carefully chosen for their natural beauty, habitat values, linkages to other bushland and flora and fauna species.
Bushland reserves that contain a range of habitats, including rainforested creek lines, shrubby eucalypt hillsides and dry sandstone ridgelines, are the best environments for animals such as yellow-bellied gliders, squirrel gliders and forest owls.Fire management in our bushland reserves is one aspect of management for long term conservation of flora and fauna.
Photo: Rick Worthy