Burning land
The bushfires in Australia last summer were devastating, but fire is nothing new in this parched landscape.
Before Covid-19 curtailed our ability to travel, I spent Christmas 2019 in Sydney. Early on Christmas morning, when most sensible people were probably enjoying a sleep-in, I went for a walk. I walked through the streets of Darlinghurst, then down Bourke Street, breathing hot, still air and scuffing tinder-dry leaves under my feet. When I reached the wharf at Woolloomooloo, I walked up a steep track beside the harbour.
I was heading to my favourite place in Sydney, the Royal Botanical Gardens. The gardens are an oasis of green lawns, shady groves, and plants with name tags on them. There are plants of all kinds, from all around the world, although my favourites are the locals – Australian natives such as graceful eucalypts, colourful kangaroo’s paw and the wondrous Wollemi pine. I can lose myself for hours there.
At the time, New South Wales was in the grip of the worst bushfires in years. When I’d arrived two days previously, I had flown in through pale brown clouds, with the smell of smoke filling the plane. The wind had shifted the day before, giving Sydney residents respite from the smell of burning forest, but everything was still parched – except for the botanical gardens. There it was possible, for a few moments, to forget just how unforgiving the Australian landscape can be.
But in one patch of the gardens I came across a reminder that fire is not the exception in this landscape, but the rule. The reminder was a banksia tree – named after Joseph Banks, who collected specimens and took them back to Britain. This particular species was Banksia serrata – with serrated leaves. It’s fairly common and widespread, growing from southern Queensland to Victoria, with a small patch in Tasmania, so it’s not surprising that it was the first of the banksia species to be named by European botanists.
To a New Zealander, Banksia serrata looks distinctly odd. The most obvious feature is the trunk, which is as wrinkled and knobbly as an elephant’s trunk. It almost looks as if the tree stopped growing and the bark didn’t. It’s hard to describe in words, so I’ve included a photograph so that you can see what I mean. And if you think my simile is far fetched, take a look at the image of an elephant’s trunk on this page.
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Trunk of Banksia serrata in the Royal Botanical Gardens.
The strange appearance of the banksia makes sense if you consider that the most delicate part of a tree trunk, the tissue which transports food and water around the tree, is directly under the bark. The bark protects this delicate tissue, but the thin layer of bark typical of most New Zealand trees isn’t much help in a bushfire. Trees with thin bark are killed easily by fire. The thick bark of the banksia, however, provides protection from all but the fiercest flames. Although the foliage may be burned away, new shoots sprout from the trunk, where they survived the fire protected by the thick bark.
But not all banksias use this particular strategy to survive fire. Some species have more conventional bark, and have woody, underground tubers from which the plant can resprout, after the above-ground parts of the plant are burned beyond recovery. Some banksia trees and shrubs don’t survive burning at all, relying on new plants growing from seed.
To consider a plant fire-tolerant, it simply has to have adaptions which allow it to recover more easily after fire. But banksias are more than just tolerant of fires – they depend on fire for their long-term survival. Although a banksia plant will grow perfectly happily in a garden, the majority require fire to open their hard, woody seed capsules, and chemicals found in smoke to trigger seed germination. Remarkably, experimental studies have shown that the seed capsules of Banksia serrata keep the seed temperature below 80oC during fires, even when the external temperature exceeds 500oC.
Seed capsules of Banksia serrata in the Royal Botanical Gardens.
Banksias are far from alone in the Australian flora in their ability to survive and even thrive after fire. From ground orchids to giant eucalypts, Australian plants cope with the reality that fire has been part of the landscape for millions of years. But the arrival of people complicated the relationship between Australia’s flora and fauna, and fire.
With tens of thousands of years of experience of Australia, the indigenous people understood that the bush needs to burn. But not all fires are the same, and exactly when and how the bush needed to burn depended on many factors. A commonly quoted example of an indigenous burning regime is the method of regularly burning small areas, early in the season, resulting in “cool fires” that burned mostly grass. This regime improved access through the bush, and promoted fresh grass growth, which attracted kangaroos and wallabies. But that’s far from the only burning method that Australia’s indigenous people developed to maintain the Australian landscape. Glen Kelly, an environmental scientist from the Noongar people of south-western Australia, described a range of land management practices involving fire. Burning was used for many different purposes, including maintaining wildlife habitat, encouraging seed germination and improving the palatability of root crops. What the management practices had in common was that they all avoided large, infrequent, uncontrollable fires.
But the arrival of colonists rapidly disrupted the well-established fire management regimes. Used to the very different environments of Britain and Europe, and with no regard for 50,000 years of careful observation, European settlers struggled to make sense of the landscape. Eric Rolls, the author of “A million wild acres”, a history of European settlement of the Piliga Forests in New South Wales, described the relationship succinctly when he said, “Not even the elementary question 'If a fire starts do we put it out?' can be answered definitely."
In 1851, less than 20 years after the first permanent European settlement of Victoria, one quarter of the state – five million hectares – was burned in what was to be the first of many terrifying fire seasons for the colonists. But the extent of this fire is dwarfed by some of the more recent events. In the 2002/03 fire season, 38 million hectares burned, mostly in the Northern Territory. In 1969/70, 45 million hectares burned, and in the 1974/75 fire season a truly staggering 117 million hectares burned.
These fires, though, occurred largely in more remote parts of Australia, in the centre and north, and don’t rank among the most deadly fires in Australian history. The fires with the greatest number of fatalities have mostly been in the state of Victoria – 171 people died over two days in the 2009 bushfires there, 71 people died in 1939 and 60 in 1926. Victoria and South Australia were both affected by bushfires which killed 75 people in 1983, while Tasmania was the scene of fires which killed 62 people in 1967.
These past fires help to put the 2019/20 bushfire season into context. With 33 people killed, it was the sixth deadliest overall. In terms of extent, it ranks even higher, as the worst in southern or eastern Australia and the third worst overall. A total of around 17 million hectares burned, in the Northern Territory (7 million hectares), New South Wales (5.7 million hectares), Western Australia (2 million hectares) and Victoria (1.6 million hectares). No other fire season combined that number of deaths with such extensive damage.
What made the 2019/20 season so bad? At first glance, there’s one very obvious answer – 2019 was both the warmest and driest year on record for Australia. But a bad bushfire season doesn’t come as a result of one bad year. Winter rainfall was low for three successive years, 2017, 2018, 2019 (as seen in the graph from the Australian Bureau of Meteorology). And the whole preceding decade was unusually warm.
With patterns like this, it’s hard to ignore the role of climate change. But there’s more to it than that. Australia is affected by large-scale climate drivers such as El Niño and its Indian Ocean equivalent, the Indian Ocean dipole. The two years leading up to the 2019/20 fire season were, at most, only mild El Niño seasons, but 2019 was an extreme year for the Indian Ocean dipole, which contributed to the drought conditions.
Land management almost certainly played a role too. In Australia’s polarised climate change discussions, it can be difficult to separate genuine concerns about land management from attempts to dismiss climate change, the statements from farmers about the lack of hazard-reduction burns ring true. These kinds of comments are consistent with the views of Glen Kelly, whom I mentioned earlier in this article. As well as highlighting some of the different methods the Noongar people used to manage the landscape with fire, he raised concerns about a lack of burning in recent decades.
But something was different in the 2019/20 season, and it strengthens the case for the role of climate change over land management. In areas along Australia’s east coast where rainfall is typically high, you don’t see fire-adapted species like banksias and eucalypts, but rainforest. These areas of rainforest rarely burn, but in 2019/20 some did, including a third of the rainforest in New South Wales.
It’s been a year since the devastating bushfires – an eventful year which has made record-breaking bushfires and trips to Australia seem part of the distant past. But I can’t quite put those fires out of my mind, and so, in my next article, I will look at how Australia has recovered. Have the adaptations of species like banksia allowed them to bounce back? Or were these fires too severe even for them?
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