Flaming the debate

Eastern redcedar encroaching loess hilltop prairie, a critically imperiled natural community in Missouri.

ResearchBlogging.orgAs my interest in prairie insects has increased over the past few years, so has my interest in their conservation. Many insects are restricted to prairies through dependence upon prairie plants or their unique physical and trophic characteristics. Thus, preservation of not only prairie plants but their insect associates as well is a major goal of conservationists.  The task is daunting – for example only ~1% of tallgrass prairie remains in the central U.S., the rest long ago converted to agriculture or otherwise irreparably altered.  Prairies are dynamic natural communities that rely upon disturbance – this need to “disturb to preserve” creates an oxymoronic conundrum for restoration ecologists that is made even more difficult by the fragmented nature of today’s prairie landscape.  The situation here in Missouri is even more difficult, as nearly all of our grassland preserves (tallgrass prairie, sand prairie, loess hilltop prairie and glades) are exceedingly small and highly disjunct relicts not connected as parts of larger systems.

In recent years, prescribed burning has become the management tactic of choice for restoring and maintaining grassland preserves.  There are good reasons for this – not only are increased floral diversity and reversal of woody encroachment well-documented responses to fire, but burning is also highly cost-effective (a critical consideration in today’s climate of shrinking public budgets).  As the use of prescribed burning on grassland preserves has become widely adopted, however, concerns about the impacts of fire on invertebrate populations have been raised.  The subject is now an area of intense research, but studies are hampered by the limited availability of large, long-unburned tracts of native prairie, and no scientific consensus has yet emerged.  Regrettably, the debate has polarized into “pro-” and “anti-fire” camps that seem unable to communicate with each other constructively.  This is unfortunate, since both ends of the spectrum offer ideas that could be used to achieve the goal of preserving prairie remnants while mitigating concerns about invertebrate impacts.  I have previously expressed my own views on the subject, a position that I suspect some might mistakenly characterize as “anti-fire.”  While I do support the use of prescribed burning, I do not support its use with no consideration of other prairie management strategies such as haying and light grazing (not to be confused with the heavy, abusive, unmanaged kind of grazing that has degraded so much of our landscape).  All of these tools (as well as parcels that receive no management at all) have potential value in prairie management and should be considered.

Those interested in potential fire impacts on prairie invertebrates will be interested in this latest salvo by Scott Swengel and colleagues, who used metadata analysis to correlate declines of prairie butterflies in the Midwest with the widespread adoption of prescribed burning as a management tactic.  The authors present convincing evidence that tallgrass prairie butterfly populations are not co-evolved with fire regimes currently used for prairie management, although their conclusions will no doubt be challenged.  Nevertheless, until a firmer scientific consensus can be achieved, prudence should dictate some measure of caution in the use of fire as an exclusive prairie management tactic.

Dear Colleagues:

We are pleased to announce a new article by Scott Swengel, Dennis Schlicht, Frank Olsen, and Ann Swengel, based on long-term data that has just been published online,  Declines of prairie butterflies in the midwestern USA.  This paper is available free from Springer Open Choice at http://www.springerlink.com/content/l732444592662434/fulltext.pdf or by going to the Journal of  Insect Conservation Online First section and scanning through the articles in ascending number order until getting to articles posted 13 August 2010.

The trends of tallgrass prairie skippers shown here, although disastrous, underestimate the decline in Iowa and Minnesota for several reasons:

  1. In statistical testing we only include sites with adequate data for testing, which eliminates many sites from inclusion that had 100% declines of a specialist we know about.
  2. Nearly all sites with long time series were the top sites to begin with, which are likely to take a longer time to show large declines than medium or low-quality sites.
  3. Recent government sponsored surveys not included here show another round of huge declines for Poweshiek Skipperling in Iowa and Minnesota.
  4. Some species went undetectable by the late 1980s and early 1990s, so didn’t register as a presence when the study began.  Hence, they cannot show a decline since then.

Some good news is that conservation based on existing knowledge of specialists’ management responses gets far better results (as shown by Regal Fritillaries and Karner Blues in Wisconsin than typical management.  So declines like this are not inevitable.

The Ecological Interpretations and Conservation Conclusion section of Discussion contain some of our new insights explaining the observed about land-use effects on prairies and butterflies.

Scott Swengel

My thanks to Scott Swengel for giving me permission to reprint his introduction.


Swengel, S. R., D. Schlicht, F. Olsen & A. B. Swengel. 2010. Declines of prairie butterflies in the midwestern USA Journal of Insect Conservation: DOI 10.1007/s10841-010-9323-1.

Copyright © Ted C. MacRae 2010

14 thoughts on “Flaming the debate

  1. It seems nearly impossible to question the use of fire in grassland management without being labeled anti-fire. Most Ohio sites are frequently burned and now, thanks to some Federal grants, the woods are even being burned. I believe we do too much burning, but I think the burning is causing another problem that has nothing to do with the biology of the sites. Land managers are sending the message that these sites can NOT be managed without the use of fire and the general public, at least those interested in such things, believe them.

    As a private landowner, fire is not a tool that is readily available to me. I can’t just go out and fling a match into the tall grass. Most other landowners are in the same situation and they believe that there is no way they can manage grassland on their properties, because they can’t burn. I have a lot of respect for the work being done by government agencies and private organizations, but I believe that successful preservation of these fragile habitats can only be achieved if sites on private property are also properly managed.

    My work takes me onto many private properties and I have found some wonderful grassland sites. Some of these are now being managed by the landowners and are developing into some excellent grassland habitat. Other sites have been bulldozed and planted to fescue, some because the owners were told by experts that fire was an essential management tool and there was no way to manage the site without it.

    My property hasn’t seen fire in the 25 years since I bought it and the previous landowner told me that he didn’t recall any fires in the 55 years he lived here. Without fire, the grassland area continues to expand and species diversity, both plant and invertebrate, is increasing. My management methods aren’t as easy or exciting as the use of fire, but they do work. It amuses me when a pro-fire manager acknowledges that my site looks really good and then goes on to add, “but, it really needs to be burned.”

    • Hi Steve, and thanks for your well-informed perspective. Your experience adds a lot to the discussion. Of course, the question of whether fire is needed at all is a separate issue – I’m just asking restoration ecologists to at least consider that impacts are real, not burn everything so frequently, and utilize less fatal management options whenever possible.

      Being branded as “anti-fire” for even voicing the concern is perhaps the most annoying part of this whole debate. It feels sort of like being branded as “not a patriot” for questioning war. As I said in a comment on another post, the concerns are neither trivial nor spurious and deserve proper consideration.

  2. I have thought that we should take a large portion of the Great Plains states (the declining towns or very low population areas), and make a large national park or preserve. Restore the bison, native vegetation, etc. I know this would place me in a largely hated position, but……

  3. Love to see this followup post and this article! I haven’t read it yet, but a lot of this was just discussed at this years Lepidopterists’ Society meeting in Washington. We have seen some really sad cases over the last few years and are working really hard to convince landowners to back off the burns – in the lep community at least this paper is welcome!

    • It’s a good read, and my impression is that the authors have been quite conservative through the use of generalist species as outgroups and elimination of sites in which specialists were already eliminated.

  4. Ted, thanks for bringing such a reasoned voice to the discussion. I agree that the debate has become too polarized. Many on the anti-fire side want to eliminate all prescribed burns, while many on the pro-fire side want to burn everything possible. My own view is that we are burning some parcels too frequently, however overall there is an insufficient application of fire.

    • Good point, Doug – there are far too many remnants that aren’t receiving any fire at all, while those that are are getting the heck burned out of them.

      Still, I’m not convinced that all grassland remnants need fire – loess hilltop prairies for example were xeric enough to maintain themselves as grasslands until settlement brought with it overgrazing and invasive exotic plants. Now, intervention is required to prevent them from being encroached, but it is more a result of human disturbance than suppression of fire that has caused this. While fire is certainly an effective remedy for encroachment, other, less fatal techniques may be more appropriate from a historical context.

      Other grasslands, such as more mesic tallgrass prairies, almost certainly relied historically on periodic burns to prevent conversion to woodland.

  5. This is a super important topic, Ted! I am in the process of preparing a review and commentary on studies of the topic to present at the Natural Areas Association conference in October. (Don’t ask — Not sure how I let myself get roped into that task!!!)

    @ Steve Wilson — I am really interested in discussing your experience more with you. Might you e-mail me at james dot trager at mobot dot org, from whence we can proceed?

    • I’ll be anxious to see your talk – I’ve got the dates penciled in my calendar.

      You got roped into that task because you are an entomologist with considerable hands-on experience with the use of fire for grassland restoration and management – that’s why. 🙂

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