Thursday, September 21, 2017

Correlation Does Not Equal Causation: Lawsuits, Pirates, Forest Fire, and Global Warming

Yesterday, The Washington Post published an op-ed piece written by Montana Republican Senator Steve Daines about the awful wildfire season we’ve been experiencing here in Montana and the West. It is good to bring attention to an issue that has gotten lost in the coverage of the widespread devastation hitting Texas, Florida, and now Puerto Rico during an unusually intense start to the hurricane season.

It is troubling, however, how Senator Daines takes a very complicated issue—the causes and consequences of wildfire—and lays blame squarely on the shoulders of “radical environmentalists” and their lawsuits, which he purports prevent efforts to clear and thin trees by forest managers.  If these lawsuits would only cease, writes Daines, wildfires would be less intensive, less pervasive, and produce fewer damaging greenhouse gases. And, perhaps as importantly, Montanans would have more jobs as there would be more timber for mills to process into lumber. Stop the lawsuits, and everyone would benefit!

Senator Daines was a champion debater in high school, and like a skilled orator, he does his best to frame the facts to best advance his core thesis. In so doing, he intentionally obscures or downplays the biggest drivers of fire: temperature and climate. At best, that’s disingenuous. At worst, it gives us false hope for the power of forest management in stemming the effects of wildfire in the West.

Let’s unpack just one point Senator Daines makes in his article: the association between acres burned and declining timber harvests. Daines tells us that “If you look at the decline in timber harvests on National Forest land since 1990, you can’t miss the correlation between harvesting and wildfire. Harvests drastically declined and, combined with the legal obstacles preventing the removal of fire fuel, wildfires grew larger and more severe. We have effectively increased the risk of wildfire by allowing cluttered forest floors to build up with more material that can burn.”

The logic seems crystal clear: Declining timber harvests have increased fuel loads, which lead to more and more intensive forest fires. The reason? Lawsuits from the aforementioned radical environmentalists. And Senator Daines links to a study conducted by The Nature Conservancy and the U.S. Forest Service in support of his claim that “an abundance of science shows that a properly managed forest would reduce the size and severity of wildfires.” Stop the lawsuits, and we’ll have better managed forests with smaller and less severe wildfires, he argues.

If only it were so simple. This Sunday morning, MTN is airing a Face the State devoted to the problem of fire in the West. I encourage you to tune in. In preparing for the show, it was immediately apparent to me how complicated the issue of fire is in the American West even if I am not a fire ecologist—or any kind of ecologist.

But there’s one thing I do know as a social scientist—and it’s something that Senator Daines surely knows, too, as an engineer: Correlation does not equal causation. Senator Daines makes a causal claim when he asks us to look at the correlation between timber harvests and forest fire intensity. But simple bivariate relationships are not evidence that X generates Y; indeed, these simple associations are often misleading without having undergone a rigorous statistical analysis. (For a bit of fun, check out this website (LINK) devoted to correlations which are not causally related, such as the decline of pirates and rising global temperatures or people falling and drowning in pools and the release of Nicolas Cage movies). If I were to draw a causal conclusion from these relationships, we should be able to fix global warming by issuing more letters of marque or keeping Nicolas Cage away from the box office. Clearly, that’s absurd! And it is just as absurd to make forest policy based upon two trends moving together without a deeper analysis controlling for other factors.
Clearly, to address global warming, we need...Pirates!

Most troubling is that Senator Daines conspicuously ignores two key factors in his opinion piece: climate and temperature. According to fire ecologists and foresters, those are the key drivers of fire intensity and growth—and forest management or lack thereof plays a much smaller role (this recent example). You would hardly know that, however, from reading the Senator’s article.  You also would not know that fire is an essential part of a healthy Western forest which requires its regenerative powers to remain in balance and even to allow certain species to propagate (such as the ubiquitous lodge pole pine).

Finally, an abundance of science clearly demonstrates that carbon emissions by humans is a critical factor responsible for climate change which is leading to hotter and drier summers in the West. To reduce the likelihood of the West burning, we should pursue policies that would reduce those emissions. Senator Daines claims that thinning our forests would reduce the release of dangerous greenhouse gases, but has refused to acknowledge in this piece and elsewhere that carbonemissions from the burning of fossil fuels is responsible for precisely the conditions most directly responsible for leaving our forests in cinders.

I could go on, as Dr. Diana Six of UM, a leading expert on pine beetles, has argued that thinning itself by pine beetles helps our forests adapt to the new realities of a warming world and that thinning by cuts might stymie an important natural process. Declining timber yields in Montana have less to do with lawsuits and more to do with the free market (lumber companies moving south where trees grow faster and wages are lower) and unfair trade practices (government subsidies for timber in Canada)—here’s an extensive report on the issue published in 2005.

Bottom line: There are no silver bullets when it comes to fire in the West, and we need our elected officials to start leading an honest discussion instead of providing us with false hope and convenient scape goats for a problem that is much larger and messier than Senator Daines suggests.