Last week, while working remotely, I saw a story pop up on the home page of Google.com. It was an article on Sciencex.com, a site where researchers can write popular media articles about their own research. The title of the article was very provocative: “No home where the buffalo roam? Birds decline after bison return to conservation grasslands.”
The article, which you can read here, was written by two of the authors of a peer-reviewed journal publication on the same research project. Because I was short on time, I skimmed through the article and was immediately bothered by the way the authors seemed to be interpreting and extrapolating their results and made a note to read the full journal article later. When I had the time to focus, I re-read the article on ScienceX, as well as the original journal article, which you can find here.
Because the authors were writing about topics I’m well-informed on (grassland birds, bison, grazing, and prairies), I had a number of concerns about how they portrayed their results. To keep this relatively short, I’m only going to present a few of those concerns here:
- The basic finding of their research was that high intensity (as judged by the researchers) year-round grazing by bison was correlated with reduced numbers of both adult and juvenile bobolinks within that management unit. Those bird numbers came from years of sampling bird populations (before and after bison were introduced to the site) by using mist nets to capture/release them.
- While their research focused on the response of a single bird species (bobolink) to bison grazing at a single site, the headline of the article in ScienceX is written such that a casual viewer would understandably assume the research documented declines of multiple grassland bird species across a range of bison grazed grasslands. To be fair to the authors, headlines are often written by the publication, not the authors, but it’s a bad start. Many people don’t read beyond the headline of articles like this, so headlines matter.
- In the ‘Conclusion and Recommendations’ section of their journal article, the authors make some pretty big extrapolations about their results. Those include this statement: “grasslands with high bison densities are not compatible with the objective of managing grassland for bird species of conservation concern such as Bobolinks.” In the ScienceX article, the authors consistently framed the description of their research in ways that suggested implications far beyond the very limited scope of their results.
- In both the scientific and popular articles, the authors cited two other studies that purportedly identified declines in grassland bird species following bison reintroductions. I’m familiar with both of those studies. One showed mixed results over a four year period and concluded “bison did not negatively impact nest success of grassland nesting birds immediately following their reintroduction (<5 y)” at a site in Illinois. The other showed bison grazing in a Kansas prairie decreased numbers of Henslow’s sparrows and dickcissels but increased numbers of upland sandpipers and grasshopper sparrows (all four species are of conservation concern).
- At the end of the ScienceX article, the authors did grant that bobolinks can do well in rotationally-grazed cattle pastures and that if the bison grazing at this site was managed to provide periodic rest periods from grazing, bobolinks would likely respond more positively. They then strongly implied that bison management of that type ‘may be beyond the capacities’ of organizations/sites outside of places like Yellowstone National Park.
So. Bobolinks, which prefer habitat with a relatively high amount of vegetation cover, declined in number within a grazing system that provided less cover than they prefer. That is not a shocking result. We don’t know how other grassland bird species did within this particular study area because the research either didn’t measure or report that. There is a tremendous amount of other research, though, that links bird species presence and abundance to habitat structure. Some birds like their habitat short/sparse, some like it tall/dense, and others like something in the middle. Anyone who has a reasonable amount of experience with grassland birds can walk into a prairie and tell you what bird species are likely to be present, just based on the height and density of the vegetation.
However, these scientists, while being careful to make accurate statements about their own research, consistently slanted their overall discussion of their study to imply that grassland bird conservation is not compatible with bison grazing – outside of huge landscapes such as Yellowstone National Park. They implied this based on their study of a single bird species in a single situation at a single site. They also presented incomplete, if not biased, portrayals of other research to back themselves up.
Bison grazing, like any grazing, is something that can be managed in many different ways, including at scales much smaller than the Greater Yellowstone Ecosystem. It’s silly to say it’s not possible to manage the timing or density of bison in smaller locations. That’s done all the time, including at sites I’m very familiar with.
On the other hand, it’s completely fair to look critically at how a particular site is being managed. We should always be evaluating the way species and communities are responding to prairie management treatments and adapt as we learn. However, that evaluation has to be conducted and applied sensibly. it wouldn’t make sense to broadly advocate against prescribed fire just because it is being used in a way that negatively impacts one bird (or butterfly, or whatever) species in one location. The same should apply to bison grazing or any other management strategy. The effectiveness of management strategies should be evaluated across a wide range of sites and assess a broad spectrum of implementation approaches.
People often get frustrated with scientists for being ‘wishy-washy’ in the way they talk about their results and how they can be applied, but there’s an important reason for that. Science is an iterative process. One study doesn’t tell us much – it’s the aggregation of evidence across many studies that starts to show us what’s really happening. Rarely does a single research project provide enough evidence to justify making strong statements about its implications, and when it happens, it’s usually an expansive study that examines a topic both broadly and deeply. As a result, scientists are wary of overstating the implications of a research project because they know it’s just one piece of a very complicated puzzle.
There is incentive, however, for scientists to make bold or controversial statements about their research – it’s a great way to get attention. That is displayed in this case, in which a very limited study of a single bird species at a single site has generated a lot of interest. I’ve seen the ScienceX article pop up several times in various feeds and conversations, which is why I decided I needed to write about it.
Most scientists resist the urge to strongly promote the implications of any single study because they recognize the danger in applying too much significance to or inappropriately extrapolating the results of any one project. They also work hard to collect and present their data with as little bias as possible and let their results be interpreted in the context of other similar work. In this case, I think the authors of the study and the publishers of both the journal article and the popular article gave in to temptation in a way that isn’t helpful – either to conservation or to the overall and growing distrust of science and scientists these days.