These plants and animals are now flourishing as life creeps back after bushfires

The influx of insects

This summer's fires left a mass of decaying animal carcasses, logs and tree trunks in their wake. While such a loss can be devastating for many species, especially those that were already vulnerable, many insects thrive under these conditions.

For example, flies lay eggs in animal carcasses; when maggots hatch, the decaying flesh provides an abundant source of food. This process helps to break down the animal's body - reducing bacteria, disease and bad odours. Flies are important decomposers and their increasing numbers also provide food for birds, reptiles and other species.

Similarly, beetles such as the gray chafer, whose larvae feed on decaying logs and tree trunks, add nutrients to the soil when they defecate, helping plants to grow back.

The insects also take advantage of the mass of new leaves on trunks and branches. For example, native psyllids - an insect similar to aphids - feed on the sap of the leaves and thus grow on the new shoot.

Then come the birds

Once the insects begin to return to an area from neighbouring forest areas, the birds that eat them follow them.

An increase in the number of psyllids encourages honey eaters, such as bell miners and noisy miners, to return. These birds are considered pests.

A CSIRO study carried out after bush fires in Victoria's East Gippsland in 1983 revealed that several native bird species - the fire and scarlet robin, the buff-rumped scissorbill and the beautiful wren - increased rapidly to levels above pre-flame levels. As the shrubs in the undergrowth grow back, other species will move in, slowly increasing biodiversity.

Since the recent bush fire in the woods near Moonbi in New South Wales, many bird species have returned. On a visit last weekend, I observed currawongs landing in the canopy, saw fairy wrens bursting through the foliage and out of the ground, and heard wrens chirping in the tufts of foliage on the bark and tall branches.

Honey eaters were moving between the burned and untouched trees at the edge of the blackened forest and butterflies were visiting the new plants that were blooming after the recent rains.

Weeds can help

Weeds usually take advantage of the fact that fire opens the canopy of the tree and lets light in. While this has a downside - preventing native plants from regenerating - weeds can also provide shelter for native animal species.

A study I co-authored in 2018 found that the highly invasive Lantana camara provided habitat for small mammals such as brown rats in some forests. The number of mammals in areas where the lantana was present was greater than where it was absent.

Lantana often grows quickly after a fire because of the increased light and its ability to suppress the growth of other plants.

Is there hope for endangered species?

Generalist species - those that thrive in a variety of environments - can adapt to burned forest. But specialized species need the special characteristics of an ecosystem to survive, and are much less resilient.

The Leadbeater's opossum, a critically endangered species, lives only in small pockets of forest in Victoria.

It needs large fires to create specific habitat: large dead trees provide hollows for shelter and nesting, and insects feeding on burnt wood and carcasses provide a source of food.

But for the Leadbeater's possum to benefit from the fire regime, bush fires would have to be infrequent - perhaps every 75 years - giving the forest time to regrow. If fires are too frequent, large trees will not have time to establish themselves and hollows will not be created, resulting in a decrease in the number of species.

Similarly in New South Wales, an analysis by the Department of Environment has shown that at least 50% and up to 80% of the habitat of threatened species such as the vulnerable red coypu has been burned in recent fires.

Looking ahead

Only time will tell whether the biodiversity in these areas is forever damaged or whether it will return to its former state.

Large fires can benefit some native species, but they also provide food and shelter for predatory species such as cats and foxes. The newly opened forest leaves many native mammals exposed, altering the food chain, or food relationships, in an ecosystem.

This means that we can see a change in the types of birds, reptiles and mammals found in forests after fires. And if these areas do not return to their pre-fire state, these environments may be changed forever and extinctions will be imminent.