Burning land: part two
Burning land: part two
Australia's forests can recover from fire, but how quickly will this happen?
In the weeks before my trip to Australia for Christmas in 2019, I took a careful look at exactly where the fires in northern New South Wales were located. I was monitoring the main highway north from Sydney to the Gold Coast, the route I planned to drive, to see whether it was safe. At times, I saw, there were diversions from the main highway, as fires burned through the area. But there was no advice to avoid driving that route, so I decided to go ahead with my planned trip.
I kept an eye out for burned areas as I drove. Sure enough I saw areas of bush where the ground was burned bare and eucalypt trunks were blackened. In a few cases, one side of the road was burned and the other still grey-green, where the road had acted as a firebreak.
But there was something else, and it confused me. Many of the eucalypt trunks had soft green shoots growing out of them. Some of the sprouts were as much as a foot long. If the fires had just been through that summer, within the last month or two, surely the eucalypts wouldn’t be sprouting already? But there was no other sign of life in the burned areas, and if it had been the previous summer, surely there would have been more regrowth than just the eucalypt trunks?
I have been fascinated by eucalyptus trees for a long time. When I was a child, there were several growing in our garden, each so different from the others that I didn’t fully appreciate that they were closely related. One was tall and graceful, with pink flowers in the winter, and it always attracted a tui or two when it flowered. Another had bark which could be peeled off the trunk and lower branches. Another had thick, rough, resinous bark and leathery grey-green leaves. One was enormous, overhanging the house, and, when it began to split and fall, had to be cut down with the help of a cherry-picker.
As an adult, I’ve come to appreciate the way that eucalypts are both instantly recognisable as members of the group, yet also highly diverse. There are at least 800 species of eucalypt, and they grow from one end of Australia to the other, from the tropical north to Tasmania, from the coasts to the central desert. Apart from a few species which grow on islands to the north, as far afield as the Philippines, the vast majority of species are found only in Australia.
Distribution of eucalypts in Australia (some of the records which appear to be in the sea are actually on islands, but some are data errors).
Like the banksias I talked about in my last article, eucalypts are adapted to environments where fires occur frequently. Although the banksias and eucalypts are unrelated, similar traits occur in species from both groups – traits like hard, woody seed capsules, underground tubers, thick bark and the ability to resprout new shoots directly from the trunk when leaves and branches have been destroyed by fire.
The sight which confused me when I drove through the recently burned areas on the road north of Sydney was the new shoots resprouting from the trunk. What I didn’t know when I drove through was the speed at which they appear – these shoots can appear within a few weeks of a fire. Even when the trees are killed, there is still rapid recovery. Eucalypts retain seed on the tree, protected in woody capsules, and after a fire that seed is released, to grow, free from competition, on the ash-fertilised ground.
But the fires of last summer were some of Australia’s worst. As I mentioned in my previous article, they are among the most extensive recorded in the last two centuries. Given the way indigenous Australians managed the landscape to prevent out-of-control fires, we can also assume that they are among the worst in the last 50,000 years. Given this extent of fire, how well are species recovering?
So far, it seems as if it’s hard to tell. Yes, forests are showing recovery, as you’d expect from fire-adapted ecosystems. But it’s variable, depending on the severity of the fires. For many threatened plants, it’s too soon to tell, but there are worrying signs. More than 300 threatened species had more than 10% of their range burned. Many plant species – dozens, if not hundreds – had more than 80% of their range burned. This level of population loss threatens even species not considered at risk of extinction. It’s going to take more than a year to see just how well these species recover.
Like Australia’s plants, its native animals also have some ability to survive fire. Some animals burrow underground and some move fast – flying, leaping or running from danger. In a low-intensity fire, such as the frequent grass fires lit by indigenous Australians to clear the undergrowth and promote fresh grass, the canopy of the trees was often untouched, meaning that species such as koalas high in the tree tops could survive.
There are even some species of Australian animal which benefit from, and even promote, fire. Predators such as the goanna, a type of lizard, have been observed emerging from their burrows following fire and preying on injured animals. Birds of prey are often observed catching prey escaping from fire. In fact, some species have even been observed to spread fire by picking up burning twigs and dropping them in unburned areas, presumably so that they can then catch escaping prey.
The problem with last summer’s fire, though, was the same as for the plants – the fires were much more extensive and intense than usual. This has meant that huge numbers of individual animals were affected, often a significant proportion of their populations. A study from WWF estimated that around three billion land vertebrates – mammals, birds, reptiles and frogs – were affected. Koalas give one example of how devastating the fires were, in proportion to the whole population. There were reported to be anywhere from 5000 to well over 10,000 koalas killed by the bushfires, and more than 60,000 were affected in some way – killed, injured or affected by loss of habitat. It’s hard to get a clear indication of just how many koalas there are – the Australian Koala Foundation, which is a lobby group, estimated that there were fewer than 80,000 in 2019, although published estimates from 2016 suggested that the number was more like 300,000. Either way, that is a substantial loss to occur in a single season. For the areas worst-affected by the fires, the impacts are worse – up to a third of the koala population in New South Wales is thought to have died last summer.
One of the most disturbing aspects of last summer’s bushfires was that they affected areas usually untouched by fire. In Australia’s wettest areas, rainforest grows. Rainforest rarely burns, and when it does, it’s usually a sign of human influence. Because fire is an infrequent part of their environment, the species which occur there are mostly not fire-adapted. They usually lack protective bark, woody seed capsules and seed which germinates best when exposed to chemicals in smoke, and they have a limited ability to resprout from the trunk or underground tubers. This is not to say that they can’t recover – if a fire is of low intensity the forest can regrow from seed buried in the soil, just as it does from other kinds of disturbance. If the fire only affects a small area, seed can be carried into the area on the wind or by animals.
But in last summer’s devastating bushfire season, more than a third of rainforest in New South Wales and more than half of the rainforest in the Gondwana Rainforest World Heritage Area was burned. It’s far too soon to know what lasting impact these losses will have, but it’s hard to escape the conclusion that the areas will be affected for many years to come.
But the fires of last summer burned much more than forest – they also destroyed more than 2000 homes in New South Wales alone and killed 33 people. Australia’s ecosystems might be fire-adapted, but human infrastructure is not. And, more than any other animal, we have a complex and troubled relationship with fire. The impacts on people are what I will look at for my next article.
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