Are fires getting worse?

In which I go asking for trouble

Writing an opening paragraph of a scientific paper is hard. You need to find just the right scale at which to dive in. For people not intimately familiar with your research (this is a very large number, let’s face it), it’s nice to start off a bit broader than your topic, so you can give it context, explain its relevance and significance. This is a bit like laying the table ahead of a feast, or describing the scene before the characters appear and begin speaking. But starting off too broad runs the risk of confusing, boring or inducing vertigo in the reader as they zoom through multiple levels to finally arrive at the actual focus of the paper. This is a bit like having an overly long foreword to a book, which is admittedly only a problem for people incapable of skipping forewords, like me.

Cook stirring cauldron, Sgt Wooldridge (Source: Wikimedia Commons)

If you were to grab the first paragraph of every paper written on wildfire in the last ten years, dump them into a big cauldron and utter some kind of incantation (there is probably R code for this) that extracted the most common statements - the kind used to justify all the effort that went into the study - I bet that “fires are getting worse” would be in the top five (plus or minus one). This assertion is especially common in studies just slightly downstream from fire i.e. where fire may not be the focus, but is an important influence on whatever is. It probably also jibes with perceptions of wildfire among many in the broader community (whether influenced by the media, their own experience of fire, expectations about climate change impacts, or something else).

I’m sympathetic to the worsening wildfire meme because I agree with the general sentiment that fire regimes around the world are undergoing a wide range of changes, with an even wider range of impacts on people and planet, many of them very worrying, and that we had better think carefully about what the future of fire holds.

Where I will not allow my fingertips to sit idly by, is where these statements are shoddily expressed and unfurnished by citations. That’s right, I am having a pedantic whinge, because I say that words matter. I say that wildfire and its future are complex and that we can all handle a bit more nuance and a bit less superficiality in our discussions of it. How much more nuance? Not that much, actually. Instead of saying that wildfires are getting worse, let’s specify

1. the fire regime where change is happening,

2. the aspect of fire that’s changing,

3. the nature of the change and

4. how we know it’s changing.

A big paper that came out in the journal Nature Communications last year gives a really nice example of this. Led by Pep Canadell and colleagues at CSIRO and the Bureau of Meteorology (sorry, BoM), the paper looks at wildfire trends in Australia, drawing an important scientific line in the sand and at the same time doing a public service, by putting some hard numbers on a hitherto much speculated upon topic.

With regard to the four points above, they looked at

1. forest fires in Australia (there’s still a fair bit of diversity within this category, but it’s definitely a useful grouping),

2. the annual area burnt by wildfire and what time of year it burnt (very important measures, although fire intensity and severity were not included - more on them another time),

3. finding an increase in burnt area in all seasons between 1988 and 2019 using linear regression (among various other changes, the paper is well worth a read),

4. based on two different remote sensing datasets (agency records also contribute to some of the analyses).

We can now tap our friendly scientist on the shoulder and gently suggest they rephrase ‘fires are worsening’ to ‘annual area burnt by forest fires in Australia increased by about 15,000 square km between 1988 and 2019 based on satellite records (Canadell et al. 2021)’, or something like that. They might even like to chuck in a reference to a few other papers that have come out recently, looking at slightly different aspects of Australia’s changing forest fire regimes, just to see where they agree and where they differ.

Of course, they may not have been thinking of Australian forests / burnt area / the last 30 years / satellite data at all when they wrote ‘fires are worsening’, which is all the more reason to be precise in the first place!