The only trouble with living in paradise (apart from the long commute) is combustibility. Our gorgeous view – mile after mile of incendiary eucalypts. So the still, dry days and nights of autumn were thick with smoke, not from the big bad one we’re dreading, but hazard reduction burns in the bush all round the town.
Last time I went down to Bujwa Bay, it was the kind of cool and breathless day that must make the Rural Fire Service very very happy. Mist hovered over the water in a bright line of morning light. Forty minutes of silent paddling past the sleeping celebrities of Berowra Waters and I was round Oaky Corner and into the sunshine.
In the quiet there was a cryptic crunching noise. Eventually, I spotted the pair of glossy black-cockatoos hidden amongst at the shore-line casuarinas. My sense of being some kind of bird whisperer evaporated when, after fifteen minutes fooling around trying to get a decent shot of the cockies, I looked up to meet the eye of a bloody great big white-bellied sea eagle sitting directly above me. And then, just round the corner, his pal taking in the rays. They’re not stupid these birds, parked in the sunniest spot on the bay.
Having bonded with the local bird-life, when I heard about the burn-off, I was worried. What happens to it all when the bush goes up in smoke?
It’s not all bad news.
“Although fuel loads in the… heath and woodland were high, and flames soared above the tallest trees and shrubs, birds moved easily in front of and above the fire to appear minutes later on the blackened vegetation to feed on less fortunate insects and small lizards”.
It’s a nice idea to think that the burn-offs that protect the town are a boon for the local plants and animals too. And there’s a euphonious catchphrase that goes with that idea: “pyrodiversity begets biodiversity”. Fire incinerates the garden escapes and wakes the soilbank’s astounding store of dormant seeds. If we burn little and often, it’s been thought, we make a mosaic of habitats: patches of open space and newly germinating seeds; places burnt a few years back; and refuges long unburnt, full of craggy trees, hollow logs and dense undergrowth.
Pyrodiversity is popular amongst land management folks, and there’s some evidence that it works, at least in some places. But not everyone buys the story that the frequent fires that protect people and property suit other critters too. Out in the mallee, near where I grew up, a fire and biodiversity project run by Deakin and LaTrobe universities has been laboriously checking the idea out.
For all the mallee’s underground lignotubers, ready to reshoot after fire, other parts of the ecosystem – large stretches of spinifex grass, for one, that shelter dragons and legless lizards – can take fifty or more years to return after a burn. All of which makes me feel tremendously guilty about the swiftly abandoned spinifex-covered cubbies that my brother and sister and I used to make in the mallee scrub out the back of our house. We will never know how many now-extinct species we displaced.
Away from regrets about the trail of ecological devastation I left in childhood and back to burn-off related angst. The research in these arid areas suggests it’s not pyrodiversity that’s important for a species-rich environment but having enough country that’s reached the right stage of maturity since the last fire. As a person in mid-life, it pleases me to say that older vegetation often seems to sustain more species of birds, mammals and reptiles, including the rare ones. Even birds that like paddocks and open plains prefer unburnt land. Some reptiles favour recently fired landscapes, but plant communities that haven’t been burnt for a decade or two harbor the richest variety of lizards and snakes.
I tried and failed to find the experts on biodiversity and fire on Hawkesbury sandstone. But researchers studying both subtropical Queensland and foothill forests in Victoria said similar things. A varied landscape is important, but
the richness of frugivore, insectivore and canopy forager assemblages is driven by the presence of structurally complex vegetation and old-growth canopy trees, which are more likely to be present in areas that have not experienced fire for a prolonged period of time (Burgess 2016)
Paston and colleagues put their conclusion bluntly: “prescribed fire is of little utility for the broadscale conservation of biodiversity” (2011, 3238).
And it seems, for birds at least, smaller patches of unburnt country won’t really do – it’s larger areas that haven’t seen fire for a while that are rich in species. One bunch of researchers found that little islands of older habitat surrounded by new growth was grabbed by one or two aggressive predatory or colonial birds, rather than harbouring lots of different critters. One recent paper, written about arid areas, sum it up:
Our results suggest a shift in current fire management thinking… is needed, away from a focus on creating small, unburnt patches towards preserving large, intact, unburnt areas (Berry 2015 493)
What does all this mean for Bujwa Bay?
There was nothing moving in the incinerated trees on the ridgeline as I made my way up the creek at high tide, but then, it was early and damn chilly. Even the herons had given up on fishing and were huddled in the trees, keeping their feet dry.
But the damp fringes of the mangroves were alive with silvereyes and yellow-faced honeyeaters, and I heard the plunk of a sacred kingfisher diving for breakfast. Gullies are especially valuable habitats for birds at the best of times. If they’re protected from fire by burning on the slopes nearby they can be an even better retreat when that big one comes. The top of the creek was lush and green. I can only guess that the rangers and RFS know what they’re doing.
In the light of recent research, Taylor and his colleagues comment dryly “current fire management for avifaunal conservation may require substantial refinement” (Taylor, 2012, 525).
But let’s not fool ourselves. Around here at least, fire management is not for the avifauna. It’s for me, and people like me, who choose to live high on a hill, surrounded by the beautiful, burnable bush.
Additional references. Because the whole thing is really is quite complicated and you might want to check I didn’t get it totally wrong.
Berry, L. Lindenmeyer, D, Driscoll, D. (2015) “Large unburnt areas, not small unburnt patches, are needed to conserve avian diversity in fire-prone landscapes” Journal ofApplied Ecology Vol 52 Issue 2
, David B., , , , , , and Complex responses of birds to landscape-level fire extent, fire severity and environmental drivers” Diversity and Distributions 20, 467–477
Nimmo, D, Kelly, L., Spence-Bailey, L, Watson, S.J. Taylor, R.S., Clarke, M.F and Bennett, A.F. (2012) “Fire Mosaics and Reptile Conservation in a Fire-Prone Region” Conservation Biology 27 (12)
Pastro, Louise L., Christopher R. Dickman and Mike Letnic (2011) “Burning for biodiversity or burning biodiversity? Prescribed burn vs. wildfire impacts on plants, lizards and mammals” Ecological Applications Vol. 21, No. 8, pp. 3
Robinson, Natasha, Leonard, Steven, Bennett, Andrew, Clarke, Michael (2016) “Are forest gullies refuges for birds when burnt? The value of topographical heterogeneity to avian diversity in a fire-prone landscape” Biological Conservation 200, pp.1-7
Sitters, Holly , Di Stefano, Julian, Christie, Fiona, Swan, Matthew, York, Alan (2016) “Bird functional diversity decreases with time since disturbance” Ecological Applications, 26(1), pp. 115–127
Smith, Annabel, C.Michael Bull, Don Driscoll (2013) “Successional specialization in a reptile community cautions against widespread planned burning and complete fire suppression”Journal of Applied Ecology 2013, 50, 1178–118