Tag Archives: fire frequency

Is Prairie Stewardship Hampered By Our History Goggles?

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I often think one of the biggest issues we face in grassland restoration and management is that we’re a little too stuck in the past.  This expresses itself in various ways, but I think it’s a nearly universal issue with everyone involved in prairie ecology and stewardship.  To one degree or another, we’re all looking backward.  Let me explain.

We’ve all stood on a hill and stared into the distance, trying to envision what that view would have been a few hundred years ago.

An obvious example of what I’m talking about appears in prairie restoration (reconstruction) when someone’s goal for a prairie planting project is to create a prairie that looks like it used to look a few hundred years ago.  I hear this a lot less than I used to, which is good, given the numerous problems with that goal.  However, even those of us who claim to be focused on more practical objectives can slip up sometimes.  It just feels good to recreate something from the past, especially when the past must have been so great!

The same romanticism for the old days affects our management, too.  Regardless of what our plan says (you’ve all got a clear, written management plan, right?), most of us can’t resist glancing around and wondering what a particular site must have looked like “back in the day”.  It’s real easy to for the resulting mental pictures to start influencing the way we evaluate the condition of a prairie and the direction we try to push things through stewardship actions.  We don’t really think we can get back to what it used to be, and yet…

I see the impact of those “history goggles” all the time, both in my own head and during conversations with other prairie people.  One of the more frequent appearances comes during thinking or talking about plant community composition.  “Oh,” someone will say, “that wildflower used to be much more common before European settlement.” Or, similarly, “Those grass species never used to be as prominent when these prairies were surveyed in the 1920’s”.

Don’t get me wrong – historic plant community composition can be helpful.  It’s nice to know how things have changed because it helps us understand why, or at least helps us ask the right questions.  Answers to those questions can guide us as we devise management strategies.  Where we get into trouble is when we use past conditions as explicit targets for today’s stewardship. 

Our prairies live in a different world than prairies of old.  Habitat fragmentation, rising atmospheric CO2 rates and nitrogen deposition, climate change, and invasive species are just some of the major factors that have changed within last century or two.  We should expect prairies to adapt to those drastic changes.  After all, adaptation is one of their best features!  

Invasive species such as crown vetch (Securigera varia) and many others have drastically changed the competitive environment within prairie plant communities.

History goggles also come into play when we think about prairie management tools and tactics.  How many discussions have you been in that center on the historic frequency and/or season of fire in prairies?  As with plant composition, understanding when and how fires burned in the past can be helpful, but yesterday’s fire frequency shouldn’t automatically be today’s fire frequency.  See above for some of the major differences between historic and present-day prairies.

People who apply grazing to grasslands often wear very thick history goggles.  If I had a nickel for every time someone’s tell me their particular grazing strategy mimics what bison used to do, I’d be swimming in nickels.  I don’t want to swim in nickels.  Even if your approach somehow perfectly mirrors what bison used to do (and it doesn’t), why would that be the best approach for today’s prairies, which aren’t what they used to be?  That applies, by the way, to whatever grazing animal you’re working with – including bison. 

There are lots of great reasons to put bison in prairies, cultural, ecological, and otherwise.  Expecting them to eradicate smooth brome and reverse climate change, though, is going to lead to some big disappointment.  That doesn’t mean bison (or cattle, for that matter) can’t play important roles in today’s prairies.  In many grasslands, especially larger ones, they can manipulate habitat structure, combat the dominance of grasses, and create lots of wonderful messiness.  They can’t (or won’t), however, turn back the clock. 

Bison or other large grazers can play important roles in some prairies, but they can’t suppress rising atmospheric carbon dioxide.

We’ve got to cast off our history goggles and look forward if prairie conservation is going to succeed.  Restoration and management strategies need to be built on creating future prairies, not past ones.  That’s an uncomfortable, even scary, prospect though, isn’t it?  We don’t have any reference points in the future, after all.  It’s easier to look back (or guess) at what used to be and try to aim there.

I don’t have the answers to this dilemma.  I do have ideas.

Prairie communities really are good at adaptation.  Because of that, I think we should be looking for ways to facilitate and guide prairies as they adjust to new conditions.  One way to do that is to help them maintain the resilience they need to adapt.  We do know something about how to do that.  (Remember, ecological resilience doesn’t mean natural communities don’t change.  Instead, it’s a measure of their capacity to adapt.) 

The ecological resilience of prairies relies heavily on two factors: habitat size/connectivity and biological diversity.  The first helps the second persist and the second provides the redundancy of function that means there are species to fill crucial roles no matter what’s a prairie has thrown at it.  Making prairies bigger and better connected comes through restoration (reconstruction) efforts that build new grassland habitat adjacent to and between existing habitats.  We have lots of evidence that prairie species respond well to that kind of restoration.

There are lots of thoughts about how to manage for biological diversity in prairies, many of which seem to work well.  There isn’t a single best way to do it, and the effectiveness of practices and approaches can vary by geography, soil type, prairie size, and many other factors.  The key is to focus on the diversity of the plant community, as well as the more difficult to measure communities of animals, fungi, bacteria, and others. 

The diversity of plant and animal communities (and other taxonomic groups) is a key to the ability of prairie communities to adapt to change.

This is where I think it’s most important to push past our reliance on history.  It’s tempting to judge plant species, for example, by whether we think they used to be part of the plant community at a particular site, or how abundant they might have been.  We’re getting to the point where that may not be very relevant anymore.  That includes non-native plants, by the way. 

Now we’re getting into really uncomfortable territory for some folks but let me be clear that I’m not proposing we stop preventing the appearance or spread of all non-native plants in prairies.  What I am proposing, however, is that the native or non-native status of plants might not be the best metric to apply.  Many of us have already started down this path by looking at natives like Canada goldenrod, for example, as a species that can be problematic if it’s allowed to run rampant.  Why do we care?  Because in some places, it can become dominant enough that it suppresses the diversity of the plant community.  That’s a bad thing for ecological resilience.

Non-native plants that have the same potential to suppress diversity need to be targets for management action.  However, some non-native plants don’t suppress the diversity around them – they add to it.  I think that’s ok.  The immigration of new species into prairie communities is inevitable, so fighting it seems fruitless. 

Yellow salsify, aka goat’s beard (Tragopogon dubius) is an example of a non-native plant that seems to have joined plant communities I’m familiar with in an innocuous, if not helpful, way.

In many places, woody plants – native and non-native – are becoming more abundant in prairies.  Their success is driven largely by rising CO2 levels, which prairie managers have no control over.  That means that in some cases, we’re just going to have to figure out how to manage for biodiversity in shrubby prairies.  We don’t know enough about how to do that yet.  Instead of pouring all our limited resources into resistance, we’d be smart to start learning about how to manage the height and density of shrubs and see how plant and other communities respond.

I could go on, but I think the key point is that focusing on ecological resilience, and thus biological diversity, gives us a target to aim for as we look forward.  We can evaluate the success of our management strategies by whether they lead to increased or decreased plant and animal diversity.  If our prairies are maintaining their diversity, they should have a good chance at adapting to whatever is thrown at them. 

It’s hard to turn away from history as our reference point for success.  You know what else is hard?  Failure.  It’s frustrating to try and try to restrain prairies from moving away from what they used to be.  Why are we subjecting ourselves to that frustration?  Let’s see if we can learn how to support our favorite ecological communities as they flex their adaptation muscles and find ways to thrive in this new world.

What’s the Best Burn Schedule for Prairies?

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Fire has been part of prairie ecosystems for as long as prairies have existed.  In many parts of North America, prairies both came into existence and then persisted because of intentional and thoughtful application of fire by Native peoples.  Forces such as drought and lightning, intertwined with human management, have helped maintain prairie habitat for millennia.  Fire, people, and prairies are inextricably linked.

Great!  So how often should I burn my prairie?  And what time of year should I burn it?

Ok, hang on. 

While those questions are reasonable in the right context, they’re almost useless on their own.  You’d never ask an experienced baker, “hey – how much flour should I use and when do I add it?”  The obvious response would be, “I don’t know, what are you trying to make?”

Prairie burns should be conducted for specific reasons, not just because the calendar says it’s time to burn.

There is no set recipe for good prairie management.  If prairies are anything, they are dynamic.  That dynamism necessitates an adaptive approach to management.  Burning, like all other management treatments, should be part of that approach.  Every fire should be planned and conducted on its own merits, not as part of a pre-planned schedule.

Weather fluctuations, alone, can strongly influence the growth and flowering of plants.  Insect populations are directly tied to weather as well, but also linked to what happens to plants.  Because so many other species eat, or are eaten by insects, anything that affects them ripples through the entire ecosystem. 

The fickleness of the weather can make a prairie act very differently from one year to another.  On top of that, the behaviors of invasive species, disease organisms, herbivores, pollinators, predators, and other members of prairie communities are also driven by complex, interconnected, and unpredictable forces.  It’s a big, glorious mess.

As a result, the answer to how a prairie should be burned depends on lots of factors. What is your overall objective for your prairie management?  What has the weather been doing?  How did prairie communities respond to recent management treatments (fire or otherwise)?  What are the significant invasive species threats and what influences their ability to become dominant?

This site was burned to control eastern redcedar trees. The timing of the burn was aimed at creating enough localized heat to kill the target trees.

Even bakers don’t always follow a fixed recipe.  Based on how the dough is shaping up, they might add a little extra flour – or not.  Factors like humidity and altitude cause ingredients to act and interact differently and it’s not always possible to accurately predict those responses.  As a result, bakers are constantly testing, learning, and adapting. 

Prairie management has to be even more flexible and adaptive than baking.  Knowing what the average historic fire frequency was in your area is instructive, but it shouldn’t necessarily dictate how often you burn your prairie.  You should be burning when/if it will help you achieve your broader objectives, and if your recent observations show that it would be helpful.

Scientists and historians have estimated historic fire frequencies for most prairie regions.  That’s interesting information, but remember that those are based on long-term averages, which smooth over a lot of variation.  You can be sure the people setting fires centuries ago weren’t gridding out the landscape and deciding when to burn a patch based solely on a regimented schedule.  They burned when it made sense for their objectives, which means some areas surely burned more frequently than others.  Lightning fires, too, would have ignited on irregular schedules, driven by the capriciousness of forces like thunderstorms, drought cycles and grazing.

Historic fire frequencies are mathematic syntheses of irregular events, they’re not instruction manuals.  At their best, they can help us understand the kind of world prairies evolved in.  That’s definitely useful, but the world is significantly different than it used to be, so what might have been appropriate in the past might not always apply today.  Use history as context, not as a template to be blindly followed.

There is much discussion about how common summer fires were in historical prairies. That’s an interesting conversation, but it’s even more important to evaluate what the impacts of summer fires are today and how they might (or might not) achieve local objectives.

Similarly, the optimal seasonal timing for a burn should be based on what you want to accomplish with that particular treatment.  What timing will make the most sense for your objectives?  What are the potential negative consequences of that timing?  The predominant season of fires hundreds of years ago helped shape today’s prairies, but – just as with fire frequencies – that history shouldn’t be the only guide to what we do now. 

With regard to both the seasonal timing and frequency of fires, it can also be important not to get locked into a rigid pattern.  Every fire has both positive and negative consequences.  If you always burn at the same time of year, the same species will always be negatively impacted, and that will surely include some species you don’t want to suppress.  Mixing up the seasonality of burns now and then can help ensure you don’t drive any species to local extinction.

Burning on the same schedule over many years in a row can also cause problems.  Regardless of what frequency you choose, there will be some species that thrive in that regime and others that don’t.  If you don’t ever vary the pattern, you risk losing the species that aren’t suited to it.

Most importantly, be sure there are adequate unburned refuges available any time you burn so you don’t eradicate whole populations of animals (especially invertebrates).  Again, every fire has negative consequences, no matter the timing.  Populations of some species will likely be wiped out, or nearly so, within the burn footprint. 

This beetle was fortunate to find a mini refuge within this fire and will probably survive, but many of its peers might not have been so lucky.

In landscapes with lots of prairie, affected species can probably recolonize from nearby unburned areas – though that process may take more than a year or two.  That recolonization works much less well in fragmented landscapes.  If you burn the only 40 acres of prairie within miles, populations of animals that perish in the fire are unlikely to re-establish.  Even if there is other grassland habitat around, you might have invertebrates in your prairie that are tied to plant species not present in those neighboring habitats.  That will put those invertebrates at risk of local extinction if a burn snuffs out their entire population.

This summer burn covered only a portion of the management unit and there is a lot of other prairie habitat nearby to supply recolonizers from any species negatively impacted by the fire.

Prescribed fire is a powerful force in prairies.  Every fire has both positive and negative consequences, driven by the timing and frequency (as well as its intensity) of its application.  Prescribed burning should be used as part of an adaptive management approach.  Every management treatment (fire, grazing, mowing, herbicide application, etc.) should be applied when it will help achieve objectives and in response to observation and evaluation of what’s happening on site.  After all, smart bakers and prairie managers both know it’s risky to rely too much on a set recipe. 

You might say they both knead to be adaptable and roll with the punches. 

…Or you might not. You might not say that at all.

Hey!  Some of you might remember Evan Barrientos from when he was a Hubbard Fellow about six years ago.  Evan’s doing great work these days as a conservation photographer, videographer, and storyteller.  His latest personal project is called Fireforest.  It’s a terrific examination of the role of fire in Colorado forests – I encourage you to check it out!