Kathryn Teare Ada Lambert
Contd from previous issue
Since the recent bushfire in woodland near Moonbi in New South Wales, numerous bird species have returned. On a visit over this past weekend, I observed currawongs landing in the canopy, saw fairy wrens darting in and out of foliage sprouting from the ground, and heard peep wrens in tufts of foliage on bark and high branches. Honeyeaters moved between burnt and intact trees on the edge of the blackened forest and butterflies visited new plants flowering after recent rain.
Weeds can help
Weeds usually benefit when fire opens up the tree canopy and lets in light. While this has a downside – preventing native plants from regenerating – weeds can also provide cover for native animal species. A study I co-authored in 2018 found highly invasive Lantana camara provided habitat for small mammals such as the brown rat in some forests. Mammal numbers in areas where lantana was present were greater than where it was absent.
Lantana often grows quickly after fire due to the increase in light and its ability to suppress other plant growth.
Hope for threatened species?
Generalist species – those that thrive in a variety of environments – can adapt to burnt forest. But specialist species need particular features of an ecosystem to survive, and are far less resilient. The critically endangered Leadbeater’s possum lives only in small pockets of forest in Victoria.
It requires large fires to create a specific habitat: big dead trees provide hollows for shelter and nesting, and insects feeding on burnt wood and carcasses provide a food source.
But for the Leadbeater’s possum to benefit from the fire regime, bushfires should be infrequent – perhaps every 75 years – allowing time for the forest to grow back. If fires are too frequent, larger trees will not have time to establish and hollows will not be created, causing the species’ numbers to decline.
Similarly in NSW, at least 50% and up to 80% of the habitat of threatened species such as the vulnerable rufous scrub-bird was burnt in the recent fires, an environmental department analysis found.
Only time will tell whether biodiversity in these areas is forever damaged, or will return to its former state. Large fires may benefit some native species but they also provide food and shelter for predatory species, such as feral cats and foxes. The newly-open forest leaves many native mammals exposed, changing the foodweb, or feeding relationships, in an ecosystem.
This means we may see a change in the types of birds, reptiles and mammals found in forests after the fires. And if these areas don’t eventually return to their pre-fire state, these environments may be changed forever – and extinctions will be imminent.
Kathryn Teare Ada Lambert, Adjunct Lecturer/ Ecologist, University of New England.
This article first appeared on The Conversation.