Making Smart Assumptions about Prairie Management

Some people say it’s dangerous to make assumptions.  I disagree.  In fact, assumptions are both necessary and empowering.  Land managers make assumptions all the time.  If we didn’t, we’d never get anything done.

Assumptions are only dangerous when they are either unrecognized or untested.  For example, it’s reasonable for me to assume that my car’s engine has an adequate amount of oil in it, but it would be irresponsible not to check the level now and then to be sure.  Without the assumption that I still had oil, I’d probably stop to check my oil every mile or so and I’d never get anywhere.  In order to move forward, I have to make reasonable assumptions, including that my engine hasn’t lost all of its oil since the last time I checked it.

As land managers, we have to take a similar approach.  Much of the time, we assume that species and ecological systems are reacting predictably and positively to our management, but we also do spot checks to reassure ourselves.  Often those evaluations involve nothing more than a walk through a prairie to see how things are looking, but in some cases might conduct more intensive data collection.

Sometimes rigorous data collection is used to test assumptions, but other times the process can be much more informal.

Sometimes rigorous data collection is used to test assumptions, but other times the process can be much more informal.

Land managers also make broader assumptions about how restoration or management projects will contribute to conservation objectives.  As we plan projects, we make educated guesses that help us design our work effectively.  Then we implement the project and see what happens.  If we didn’t make assumptions, we’d be paralyzed by indecision and never get anything done.

It is critically important, however to recognize what assumptions we’re making, and to test them when we have the chance.  Here are several examples of assumptions we make in our Platte River Prairies management, and some of the ways we’re testing them.

Assumption #1.  Prairie plants can survive periodic intensive grazing.

Grazing is an important part of our management.  Most commonly, we employ variations of patch-burn grazing, in which a portion of a prairie is grazed pretty intensively for most of one growing season and then allowed to recover for a couple years before it’s intensively grazed again.  We use grazing to manipulate plant competition, especially by suppressing the vigor of dominant grasses to produce more plant diversity.  It also is our primary tool for creating heterogeneous habitat structure, including important habitat conditions (such as short grass/tall forbs) that are difficult or impossible to create without grazing.

Selective grazing by cattle can have positive impacts on both plant diversity and wildlife habitat.  These cattle at Konza Prairie in Kansas are grazing on primarily grass and leaving plants such as leadplant and purple prairie clover ungrazed.

Selective grazing by cattle can have positive impacts on both plant diversity and wildlife habitat. These cattle at Konza Prairie in Kansas are grazing on primarily grass and leaving plants such as leadplant and purple prairie clover ungrazed.

Our data show that overall plant diversity is thriving under our management, and it’s easy to see the variety of habitat conditions we create each year.  However, we’re making the assumption that we’re not losing any plant species due to periodic intensive grazing.  It’s an informed assumption, based on experience and our understanding of history, including the kind of fire/grazing interactions that happened in these prairies over the last several thousand years.  Regardless, it’s an assumption, and one we need to test.

We collect annual data from some prairies and less frequent data from others that allow us to track individual plant species over time.  So far, we’ve not seen any indication of plant species that are disappearing under our management.  Even if we weren’t rigorously collecting data, we could still test our assumption by simply tracking the population size of species most likely to be impacted by grazing.  We could use techniques such as photopoints or walking transects, or we could just mark and watch individuals or patches of plants over time.


An example of the kind of data that helps us evaluate the impacts of repetitive grazing on plant species.  Data from one of our restored prairies shows plant species that have maintained populations through 13 years of patch-burn grazing.  The data represent the frequency of occurrence for each species within approximately 100 plots (1 square meter plots).  From top to bottom, the common names of the species shown are Stiff Sunflower, Maximilian Sunflower, Illinois Bundleflower, Purple Prairie Clover, and White Prairie Clover.

Assumption #2.  Some exotic/invasive species are not harmful enough to warrant eradication efforts.

We have more than enough invasive species to deal with on our sites, so we have to be selective about which to spend most of our time on.  We set priorities based on experience, and focus most on those species we think have the greatest potential to harm plant diversity or habitat quality.  However, we recognize that our assumptions about impacts could be wrong, so we test them – both through general observation and data collection.  I’ve written before about data we’ve collected on both Kentucky bluegrass and sweetclover impacts, for example.

Assumption #3.  Restoring cropland adjacent to a small prairie will increase its conservation value.

The prairie restoration work we do is not focused on re-creating historic landscapes, but on trying to decrease the impacts of habitat fragmentation.  We assume that adding diverse prairie plantings around and between isolated prairie fragments will increase population size and connectivity for plants, insects, mammals, birds, reptiles, and more.  Bigger and more interconnected populations should be more viable than smaller and isolated populations.

Our assumption seems reasonable, but it’s expensive to harvest and plant more than 200 plant species in a crop field, so we need to see if we’re actually achieving our objective.  More importantly, we need to be able to show policy makers that this kind of strategy produces substantial ecological impacts.  Unfortunately, this kind of assumption is logistically difficult to test.

We have a long way to go, but we’re starting to look at whether various species living in our unplowed prairies are also found in adjacent restored prairies.  If those species aren’t using the new habitat, our strategy isn’t helping them.  If they are, that’s good to know – though there are still more assumptions to test (e.g., do those new habitats facilitate successful breeding and/or migration and colonization?).  So far, some preliminary investigations indicate that most ant and bee species appear to use restored habitats, and we’re now looking at small mammals and grasshoppers as well.


Bees seem to readily use the restored prairie habitats we create around and between formerly-isolated prairies. However, we are still evaluating bees and many other species to see how effective our restoration work has been.


Assumption #4.  We can maintain healthy populations of all prairie species through our “shifting mosaic” approach to wildlife habitat management.

This is a big one, and is very difficult to test.  We assume that by creating a variety of habitat conditions each year – including tall/dense, short/sparse, and mixed-height vegetation – all of the species in our prairies (insects, mammals, birds, plants, etc.) can find what they need each year.  On top of that, we’re assuming that as we shift the location of habitat conditions between years, species can either move to appropriate habitat or hunker down until better conditions cycle back through.

As with our assumption about plants and grazing, historical context applies.  Prairie species evolved in grasslands that were subjected to fire, grazing, and drought, and preferred habitat conditions for any particular species would have shifted around the landscape from year to year.  However, much is different today, including the size and fragmentation of grasslands, the presence of invasive species, and much more.  Are today’s species able to survive significant variations in habitat conditions from year to year?  Can a species that needs thatchy cover successfully find more of that habitat after a fire burns through its current location?  If so, how far can it travel, and through what kinds of habitats?


How easily can a species such as the red-sided garter snake find new habitat after a fire or other management treatment makes its current habitat unsuitable?

We haven’t gotten as far in testing this assumption as we have with some others, but we think a lot about it.  We’ve been gleaning information on animal movement from the scientific literature, and will meet with university scientists next month to discuss potential collaborative research on this topic.  Most importantly, we recognize that we are making some big assumptions about our management strategies, and we keep those assumptions in mind as we make our annual plans.  For example, we try to think about factors such as travel distance between similar habitat types (tall/dense or short/sparse habitats, for example) and we try to leave unburned refuges within large burn units.  Hopefully, we’ll get more guidance soon, but in the meantime, we’re moving forward the best we can.

Just as I watch for signs that my car’s engine might be getting low on oil as I drive, I also watch for signs that our land management strategies are working as we want them to.  (More on that in an upcoming post.)  Recognizing the assumptions we’re making is a critical piece of successful management, but testing those assumptions is just as important.  Assumption testing doesn’t have to involve intensive data collection; it can be as simple as making some annual notes about whether or not a particular patch of wildflowers is still there, or keeping track of how invasive species respond to various management treatments.  If we know what we’re uncertain of, we’ll be more thoughtful about management decisions and more observant of their impacts.

What assumptions are you making?  Are you working to test them?

…oh, and don’t forget to check your oil now and then.




The Kind of Conferences I Learn Best From

Last week, Eliza wrote a nice post about the value of professional conferences, and how much she’s learned by attending several of them during her time as a Hubbard Fellow.  It’s great to know that she’s getting a lot out of the meetings she’s attended this year.  Coincidentally, at the time Eliza’s post came out, I was attending the 5th World Conference of the Society for Ecological Restoration (SER) in Madison, Wisconsin – along with about 1,200 other people from around the world.  The conference was big enough that there were thirteen (!) concurrent sessions going on at any one time.  Topics ranged from peat moss restoration in Alberta to tiger habitat restoration in Sumatra.

The SER conference was well organized and interesting, but very different from most of the conferences I attend – including those that Eliza referenced in her post.  I think the SER conference was probably really good for scientists who wanted to get a pulse on the research going on around the world and pick up ideas for future research of their own.  However, as someone who actually restored and manages land, my main objective was to find ideas I could bring home and apply to our sites.  Because of the size and breadth of the conference, I found it difficult to figure out which presentations to attend; most of the talks were from habitat types other than mine and it was hard to decipher which might have themes that would fit with our work.  I ended up spending quite a bit of time in the hallways, talking with other attendees with interests similar to mine – and learning a great deal from them.

Wandering around the huge conference center last week made me consider what I really appreciate about the smaller applied conferences and workshops I attend – and often help organize.  Here is a list of attributes that I find valuable at those kinds of events.  Some of these attributes are probably good for any conference, butI think they are particularly important for those of us directly involved in land management and restoration.

1. Comfortable group size.  I like meetings at which I have a decent chance of meeting a majority of participants, or at least knowing something about who they are and what they do.  That helps me find people I might want to talk to and learn from, and also makes group discussions possible and effective.  I think meetings of 80 people or less are ideal.

This year's Grassland Restoration Network workshop was hosted by the Missouri Department of Conservation.  The attendance was strong, but still small enough that it was possible to meet and talk with a majority of them during the workshop.

This year’s Grassland Restoration Network workshop was hosted by the Missouri Department of Conservation. The attendance was strong, but the group small enough that it was possible to meet and talk with a majority of them during the workshop.

2. Narrow Focus.  It’s nice to know that a high percentage of presentations I listen to are going to be relevant to my work.  Two of my favorite gatherings each year are those of the Grassland Restoration Network and the Patch-Burn Grazing Working Group because both are focused on activities I’m very involved in.  While their ranges of subject matter are relatively narrow, both of those meetings include participants from across a large geographic area, with a wide variety of perspectives and experiences I can learn from.

3. Lots of discussion time.  At many conferences, presentations are typically limited to 15-20 minute time slots and although presenters are encouraged to leave time for questions at the end, they rarely do.  Even when there is time, it’s not discussion time, but rather a couple of quick clarification questions.  I like sessions in which there is a short presentation (or two) of thought-provoking ideas or examples, followed by a well-facilitated group discussion that brings out innovative thoughts and questions from audience and presenters alike.  Many times, those kinds of discussions generate ideas far different – and more interesting – than what the presenters started talking about.

4. Effective field trips.  I learn best when I can see what someone’s site really looks like, and evaluate the impacts of their work firsthand.  The best field trips are those during which the trip host takes us not just to places where their work has been very successful, but also where things have not turned out at as they’d hoped.  Seeing both the good and the bad, and having honest thoughtful discussions (in the field) about those is incredibly useful, and generates ideas I can bring back home and use.  I also appreciate field trips that allow participants to wander away from the vehicles a little and explore, instead of just loading us into vehicles as soon as the host is done talking.


Participants of this year’s Patch-Burn Grazing Working Group meeting walk across The Nature Conservancy’s 7-mile Fen in western South Dakota.  This was one of two half-day field trips we went on during the conference, and the hosts did a great job of showing us results of their efforts, but also giving us time to explore and evaluate the site ourselves.

5. Plenty of time and space for informal networking.  Conferences and workshops I help organize typically schedule plenty of time to just sit around and talk informally.  It’s really frustrating to go to a conference that is scheduled from dawn to dusk with events and presentations, leaving no time for getting to know other participants.  Much of what I learn from group meetings comes from side discussions during which I can really get to know someone and learn about their experiences.  The benefits of that informal time extend beyond the conference as well because I come home with a list of people I can call in the future when I have a question or idea on a particular topic.

Informal discussion time, whether in the field or indoors, is often the most valuable part of any conference.  This conversation - during the 2013 Grassland Restoration Network - occurred during some free time on a field trip.

Informal discussion time, whether in the field or indoors, is often the most valuable part of any conference. This conversation – during the 2013 Grassland Restoration Network – occurred during some free time on a field trip.

6. Presentations that focus on a lesson or message rather than statistical methods.  In graduate school, students are usually taught to give presentations that follow the format of a scientific journal article: introduction, methods, results, discussion.  When giving a thesis defense presentation to get your degree, that’s probably appropriate.  However, at a conference with others who want to learn about your project, spending most of your allotted time talking about how you set up your project and analyzed your data is worse than useless.  The most useful presentations focus on the results and how they fit into the larger context of a topic.  If I want to know what statistics you used to analyze your data, I’ll ask you at another time or read the publication you’ll eventually write.  Tell me what you learned and why it’s interesting and important.

7. An accessible price.  When I help organize workshops and conferences, keeping the cost of attendance down is a top priority.  Most of the attendees at our meetings are land managers or scientists that work for state agencies or non-profit conservation organizations, and both money and time are tight.  It’s hard enough to convince people to leave their sites and task lists for a couple days.  Making them pay high registration fees in addition to hotel and travel costs is an unnecessary barrier to their attendance.  We can’t do anything about travel costs to get to the meeting, but we work hard to find conference centers and lodging options that are low cost.  Often, those lower cost meeting locations tend to facilitate better informal interactions anyway.

This is the kind of conference venue I like best...

This is the kind of conference venue I like best…

I was grateful for the opportunity to attend the SER conference in Madison last week, and I got the chance to meet some new friends and catch up with some old ones.  However, the conference also gave me a chance to compare and contrast meeting styles and think about what attributes are important to me.  I’m curious to hear what you think on this topic.


P.S. I have one request to anyone who talks about ecological restoration.  Can we please agree to stop using the phrase “If you build it, they will come”?

Seriously.  Thank you.