Burning (for) biodiversity: what is a patch burn mosaic?

Great_Sandy_Desert Framed

Like patch mosaic burning? I bet you know someone who does. The concept – like corridors and connectivity – is popular with land managers and the public, and often adopted with ‘mucho gusto’.

The theory that underpins patch mosaic burning is simple. We light patchy burns or burn small areas to create a mosaic of zones, each with a different fire history. The mosaic of burnt and unburnt patches will, the argument goes, increase species diversity (or the abundance of some species) across a landscape, reserve or remnant.

Intuitively, this makes sense. At one level, it’s a simple strategy to spread risk; it says ‘don’t put all your eggs in one basket’.

Evidence, what evidence?

Unfortunately, the scientific evidence that mosaic burning promotes biodiversity is – to put it politely – equivocal and contested. Indeed, a recent global review of how vertebrates responded to fire mosaics found ‘little support for the patch mosaic burn theory’ at all.

This gulf between evidence and acceptance makes patch mosaic burning a great topic for a series of blog posts. In coming months, we’ll explore in more detail the tantalizing idea that ‘pyrodiversity begets biodiversity’.

A warning for future posts. If you view fire management in black and white, good versus bad, terms, I suggest you tune out now. There are no simple solutions to the complex issues surrounding burning and biodiversity. Consequently, the posts can’t and won’t present definitive statements about how ecosystems should (or should not) be burnt. The goal is to explore concepts, not prescribe outcomes.

What is a mosaic?

One of the challenges to patch mosaic burning is – to quote one reviewAll fires create mosaics of some kind. This makes it difficult to ‘operationalize’ mosaic burning. What size, shape and number of patches should we burn? How should burns be arranged over space and time? At any even simpler level, how do we tell if something is or isn’t a patch burn mosaic?

Let’s kick off the series with an animation. I’m happy to call the video below a comic, but you may recognize it as a comical Socratic dialogue. It asks a deceptively simple question: what is a patch burn mosaic (or a ‘PBM’ for short)?

The animation is a gif file which loops over and over. You can open a larger, sharper version in a separate web page by clicking on the image. To re-start it from the beginning, just refresh your web page.

Jane Ben Fire Mosaics 32

Want to re-read the final messages without watching the whole video again? Watch this version. The animation is also available as a YouTube video (instead of an animated gif file), which can be started, stopped and paused at will.

A mighty mosaic

The animation includes photos of patch mosaic burning in the Great Sandy Desert region, in north-west Australia. You can explore these striking fire patterns by zooming and panning inside the Google Map below.

If you can’t see the embedded Google Map on your browser or device, you can visit the area by clicking this link. Enjoy.

Acknowledgements

The original version of the top photo of fire scars in the Great Sandy Desert is from Wikimedia Commons. Many thanks to Dr Simon Watson for fact-checking this week’s story and animation.

Related posts

Further reading

The following papers provide a great introduction to the complexities of managing fire mosaics for biodiversity.

Don't miss this year's APCC conference. Click on image for more details.

Don’t miss the 10th APCC conference. This year’s keynote speaker is me. Click on image for details.

Clarke MF (2008) Catering for the needs of fauna in fire management: science or just wishful thinking? Wildlife Research 35, 385-394. [Full text article available for free here].

Driscoll DA & colleagues (2010) Fire management for biodiversity conservation: Key research questions and our capacity to answer them. Biological Conservation 143, 1928-1939. [Full text article available for free here].

Parr CL & Andersen AN (2006) Patch mosaic burning for biodiversity conservation: a critique of the pyrodiversity paradigm. Conservation Biology 20, 1610-1619. [Full text article available for free here].

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26 thoughts on “Burning (for) biodiversity: what is a patch burn mosaic?

  1. Great work Ian. I look forward to following the series. You have certainly raised the issues which keep cropping up and prove ilusive and/or divisive across this great land. I find the issues of where and when and for how long should I as a manager keep doing it are in the too hard basket. It is so much easier to create a mechanistic formula/plan get a 3-5 budget and set it running. The issues of broader long term consequences are rarely raised or raised seriously e.g. soil biology, increaser and decreaser species, impacts on community structure, compoistion and function.

    • Thanks Richard, I’m glad you enjoyed it. I’m confident that I won’t be able to deal with most of the issues you raise (budgets etc), but hopefully the posts will be informative and useful nonetheless. Best wishes Ian

  2. Hi Ian
    Great animation and I also enjoyed the pace – I felt like Pavlovs dog – Ha!
    Indeed PBM has been bandied about as a “safer” option to try burning regimes.
    By pointing out the complexities attached to a land management regime I was prompted to wonder how much of our flora evolved sclerophyllous or adapted that way. Provenance raising its ugly head again.
    The real issue for me however was, Is blanket burning an area any more effective toward prescriptive land management than PBM? A Claytons fire – The fire you have, without truly burning.
    I really look forward to the series
    Cheers
    Runar

    • Hello Runar, thanks for writing in. I’m glad you enjoyed the (Pavlovian) video. I won’t be able to address many of your questions in the blogs, but hopefully they’ll still be enjoyable & interesting. As an aside, sclerophylly (hard thick leaves) is usually interpreted as an adaptation to stresses such as low soil nutrient or water stress, and not as an adaptation to fire. That’s perhaps an interesting topic for another blog in the future. Best wishes Ian

  3. Hi Ian,
    After talking with some indigenous rangers near Arnhem Land a couple of weeks ago about their burning regimes I contemplate a few things, like what were the triggers used for burning the Western Plains Grasslands pre European settlement? Up in the north the indigenous culture has somehow prevailed enough to retain this knowledge, but has this information been completely lost in SE Australia? The attitudes to burning up there seem blaze compared to the guesswork (involving much agonised thought) I see here in Victoria. They also have the advantage of enormous tracts of land to manage using burning compared to the small highly fragmented, degraded but precious landscapes we have been left with. Your animation poses many complex questions about a practice that was possibly managed using a few simple laws, and unfortunately it seems we now need to find the answers the hard way. I’m also looking forward to your next blog posts, even if they don’t answer my questions.
    Cheers
    Chris.

    • Hi Chis, thanks for writing in. Great question. Unfortunately traditional indigenous knowledge of fire practices was greatly disrupted in SE Australia, and has little input to most fire management here nowadays. Also, as you point out, our challenges are very different nowadays, with small remnants, threatened species, introduced exotics, plus lots more complications for fire managers with our built infrastructure (houses, properties etc). The practice of indigenous burning doesn’t fit well with the process of submitting annual burn plans a year in advance, as agencies do nowadays. I think you’re right – we do have to find the answers the hard way, as you put it – but we also seek answers to questions and issues that weren’t posed before – which makes it more challenging. I hope you enjoy the next blogs, best wishes Ian

  4. A good discussion to have. I am sure some patch burning is good for some spp, see the work of Dr Sarah Legge on granivorous birds in the Kimberleys, among many other works. I am sure it is thought to be good for humans too as I recall Dr Andrew Burbidge many years ago recording the casual firelighting patch burning of Indigenous people he was working with on mammal surveys in WA and clearly it is a well-ingrained cultural activity. Most such activities have a basis in common sense and clearly this encourages food spp for humans living off bush resources. I think perhaps the corollary might be easier to get one’s head around, is patch burning BAD for spp and if so where and how?

    • Hello Max, great to hear from you again. Thanks again for your comments. I think (hope?) I’ll address your query (when is patch burning bad for species?) in the next blog, or perhaps the one after that. Stay tuned – now I just have a small task ahead to write them 🙂

  5. What great discussion this is generating Ian. Something that has always disturbed me with the PB concept is, are we always burning the same patches? In a complex landscape, different fuels become available at different times. eg: where there is heathland interspersed with Stringybark forests and Melaleuca swamps it’s relatively easy to set prescriptions that will enable burning of the Heathlands only. In a geographic sense it can look like we have achieved a wonderful “patch” burn but in ecological terms we have burnt an entire EVC. In my mind that is not patch burning.

    The other thread coming from this discussion is the loss of indigenous knowledge on burning and how do we re-learn what is lost? I wonder if it would be useful to set burning prescriptions that maximise food production? There is increasing evidence that Aboriginal burning was as much about increasing grains and tubers as it was about improving hunting. (Ref: Pascoe 2014. Dark Emu Black seed). It just makes sense to me that if I was relying on bush tucker for my survival & I noticed, (over a period of 40,000 years) that a particular type of fire produced good tucker for the following year I would want more of it. Just a thought that I think is worth exploring.

    • The people involved in Kosciusko to the Coast (K2C) have been working with several indigenous people from around the Canberra / Monaro region to recover/document/use indigenous knowledge of patch burning and I think this is only one of many projects along these lines. I know that a number of groups working in Arnhem Land, central Australia and the Kimberleys such as Australian Wildlife Conservancy, The Nature Conservancy and Bush Heritage Australia have also done extensive work on documenting traditional burning practices then there is the major monograph on traditional fire practices in Arnhem Land published by Jon Altman’s group at the ANU a few years back, well worth a read.

    • Hello Jim, thanks for writing. There’s probably a big difference between what gets called ‘patch mosaic burning’ in the ecology literature and what happens on the ground. In the literature, discussions of patch mosaic burning largely focus on how fires are arranged in ‘uniform’ vegetation types. Consequently, differences in vegetation (and other biota) between patches are due to the burn pattern only. Burning certain vegetation types and not burning others would not be called a ‘patch mosaic burn’ in that context. In practice, things aren’t that simple of course. One of the take home messages from the animation above is that, we call so many different things ‘patch burn mosaics’ that the term has become somewhat meaningless in practice. Unless we set more concrete goals then virtually everything can be called a ‘patch burn mosaic’ of some kind.

      In our highly altered ecosystems in SE Australia, I’m always really curious about the potential linkages and potential conflicts between attempting to burn to achieve ecological outcomes and the attempt to emulate past indigenous burning practices. I really like your suggestion of designing a fire regime solely to maximise food production outcomes somewhere. I think it’d be a fascinating experiment for seeing how consistent this goal might be with trying to ‘promote biodiversity’ more broadly, or to conserve specific threatened species. Thanks too for the reference to Bruce Pascoe’s book, I haven’t seen it. Best wishes Ian

    • Indeed, Jim. Beth Gott, Monash Uni, has researched Aboriginal burning in Victoria, saying ‘Aboriginal burning in selected areas aimed to maximise and preserve vegetable foods or other desirable species’. That is, they burnt carefully to encourage many useful plants, not just edible ones. She has a paper, ‘Indigenous burning and ecosystem biodiversity’ in Proceedings of the Royal Society of Vic, Vol 14, number 1, June 2012. And thanks, Ian, I look forward to increasing clarity on the often misapplied concept of mosaics.

  6. Hi Ian, I’m very much looking forward to the rest of this series of posts… Great topic! As an archaeologist currently undertaking PhD research on Aboriginal landscape manipulation/ecological engineering in SW Aus, I find the concept of ‘patch mosaic burning’ to be particularly interesting both in terms of biodiversity and the management of risk from uncontrolled fires. However I agree that we need to be cautious about our approaches – both in terms of operationalising the model and its history/utility across multiple regions. The ‘mosaic’ thing makes me wonder, too… at the right scale, everything becomes a mosaic!
    If you haven’t come across this short article previously, it’s an interesting little piece: http://rspb.royalsocietypublishing.org/cgi/content/long/280/1772/20132297

    • Hello Carly, thanks very much for writing in. I suspect I may have under-estimated the breadth of interest in patch mosaic burns from different readers – from indigenous burning practices to fuel reduction burning as well as biodiversity impacts. I’ll have to stick to my area of expertise, which is biodiversity rather than the other important facets of the topic. Hopefully the blog posts will still raise lots of interesting questions even within this more limited scope. Thanks very much for the fire reference, I haven’t read that paper and look forward to doing so. Best wishes for your PhD, Ian

  7. A number of presenters at the Australian Mammal Society’s Predator Symposium this past Thursday spoke about research on predation of native mammals in fire affected areas.
    In one study where cats were tracked, it was quite surprising to see how far cats would travel out of their normal ranges to visit a well-burnt area. A different study reported cats and foxes moving into the burnt area.
    A study focusing more on a prey species – the pale field rat – found (somewhat less surprisingly) that their survival was much higher in areas that had been subjected to a long, slow overnight burn (leaving a mosaic effect) compared to a nearby area than had been burnt out quickly on a hot day. It was reported that none of the study animals died during the fire, or from starvation afterwards, but the fatalities were from decreased shelter leading to increased predation.
    We have a very rich diversity of small animal species who have evolved to survive fire and the immediate after-effects, but not yet had time to adapt to the effects of post European settlement.
    It’s not just plants that are affected by fire.

    • Hi Dayna, thanks very much for sharing the new findings from the mammal conference. Everything I heard about the conference sounded fantastic. The reports of high levels of predation by cats and foxes after fire are very worrying aren’t they. As you point out, they highlight how much the system has changed since Europeans arrived. Thanks again, is great to hear back from conferences that I (and many others) didnt get to. Best wishes Ian

    • When discussing mosaic burning we talk about the bits that are burnt & the bits that aren’t burnt. Has anyone given some thought to the “ecotone.” Species richness increases significantly on those edges where forests meet rivers or open woodland meets forests. At how fine a scale can those edges make a difference? Does the edge effect make any difference at all to biodiversity in a burnt/unburnt sceario?

      • Hi Jim, great question. I don’t know that there’s a lot of information to answer it though, unfortunately. I’d planned to discuss edges in fire mosaics in another post, but this will probably be at least two posts away, so stay tuned. Best wishes Ian

  8. Great post Ian, and entertaining .gif! I suspect we often over-think the necessity of coming up with the ‘appropriate’ fire regime, as we have witnessed in so much of grassland management. The result being that procrastination results in no fire at all. Despite all our planning and deliberations on what the desired fire regime might be, the implementation of such is another story altogether. I remember a fire-truck getting bogged (in pouring rain) while the relevant agency was implementing a ‘hot-burn’ on a western Victorian grasslands! Which reminds me of this you-tube clip http://t.co/oyLWaYu7S1 you might have mentioned previously, on how ‘prescribed ecological burns’ might not always be exactly ecological in outcomes. Thx again, look forward to more on this issue.

  9. Can science change as the environment changes? There cannot be fault, those who are right and those who are wrong – just ongoing discussion. The sources of observations of Indigenous people burning are varied. E.M.Curr is often quoted by botanists wrote of indigenous people managing the landscape with fire – but he was keen to portray them as primitive (fire was not then or now seen ‘legally’ as a form of agriculture and included no actual observations he made of Indigenous burning in his book ( I could find) – a book, written decades after the event, Recollections of Squatting in Victoria (or earlier the Port Phillip District). The context to the man and his family was researched and written by Simon Furphy http://press.anu.edu.au/publications/aboriginal-history-monographs/edward-m-curr-and-tide-history. Joel Wright, a Gunditjmara linguist, pulled together many and varied uses of fire by his people https://www.youtube.com/watch?v=kHZjyuE2qP8 which shows just how easily indigenous use of fire can be misinterpreted – confusing defensive and aggressive fire, smoke signals etc. Each of over 500 nations is different in a land twice the size of Europe and though almost lost to history many Indigenous Nations did live in villages and cultivate the land without fire see Gerritsen http://rupertgerritsen.tripod.com/pdf/published/Traditional_Settlement_in_SW_Vic.pdf. How can we revisit the assumptions regarding the use of fire by the more than 500 Indigenous Nations of people of what the English chose to call Australia?
    Kind Regards to all, always keen to be proved wrong, Bob Mac

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