Choosing Your Destination Before You Choose Your Mode of Transport

Last week, I attended a science and stewardship conference of The Nature Conservancy in Madison, Wisconsin.  It was an inspiring and thought-provoking week.  There were a lot of topics that will provide fodder for future blog posts, but I wanted to start with an issue that came up in several sessions.  The topic had to do with setting appropriate objectives for conservation strategies, and for land management in particular.  In short, it’s really important to make sure we’re not setting objectives that are focused on strategies rather than outcomes.

This mixed-grass prairie is managed with both prescribed fire and grazing.  However,  neither fire nor grazing is the objective, they are tools that are strategically employed to create desired outcomes.  Gjerloff Prairie – Prairie Plains Resource Institute

Here’s an illustration of what I mean.  If I was planning a vacation for next summer, I probably wouldn’t start with the following question: “What mode of transportation should I take on my vacation next year?”

Clearly, it’s tough to answer that question without knowing more about the ultimate objectives of the vacation.  Where do I want to go?  What time of year am I going?  How many people are going with me?  If I’m planning to travel from Nebraska to Ireland, I probably won’t be able to do that by bus.  I could conceivably travel by motorcycle (if I had one) to the Rocky Mountains, but probably not if I was going during the winter or planning to take little kids with me.

It seems silly to start by thinking about how to get somewhere before deciding where to go, but as land managers, it’s easy to fall into exactly that mindset.  We sometimes set objectives about using fire or grazing, for example, instead of first defining the outcome we want and then thinking about what tools and strategies might get us there (which may or may not include fire or grazing).  In this post, I’ve provided examples of how this trap can present itself, both to managers of conservation land and private landowners, and some thoughts about how to avoid the trap.

Significant research has helped us understand the kinds of fire and grazing patterns under which North American prairies developed.  For example, in many places, we have a pretty good idea how often a particular site burned, on average, before European settlement.  We also have reasonably good information on the presence, abundance, and behavior of historic grazers.  Based on that information, a land manager could decide that the best management for their prairie would be to reinstate, as closely as possible, the timing and intensity of historic fire and grazing that site likely evolved under. 

Historically, prairies in this region probably burned on an average of every 4-5 years.  However, within that average range, there would have been wide variation.  More importantly, this prairie sits within a very different landscape today, with challenges not faced by those historic prairies.

Patch-burn grazing is often described, for example, as “mimicking historic fire and grazing patterns.”  Mob grazing advocates trumpet (though I’m skeptical) that their system replicates the way bison moved across a landscape.  Some in the Upper Midwest region of North America point to research showing high populations of indigenous people and scarce evidence of abundant bison and argue that their prairies should be managed only with fire.  We can argue about all three of those examples – and many more – but the bigger point is that none of those arguments should determine our management strategies.  Again, we shouldn’t be setting objectives about the strategy we want to use without first identifying the outcome we want.

To make a clunky return to my vacation travel analogy, it would be silly of me to choose horseback as my preferred mode of transportation across the Great Plains to the Rocky Mountains just because it’s what worked several hundred years ago.  Today’s landscape is broken up into countless fenced off private land parcels, which would make cross-country horse travel difficult, to say the least.  In addition, there is a pretty nice set of modern opportunities (roads and vehicles) I can take advantage of nowadays.

Likewise, our prairies exist within a different world today, with a new set of challenges and opportunities.  Mimicking historic disturbance regimes won’t necessarily keep prairies in good shape in a world with habitat fragmentation, massive invasive species pressure, climate change, nitrogen deposition, and other factors.  And speaking of good shape, our first and primary concern should really be to define what “good shape” is, right?  Are we managing for plant diversity or a few rare plants?  Are we trying to sustain diverse bird populations?  Habitat heterogeneity? Is ecological resilience the goal?  If so, what are the factors driving resilience, and how to we sustain those?  There are countless reasonable goals for land managers to choose from, many dependent upon scale, but those goals should be based on the outcome we want.

This annually-hayed prairie maintains high plant diversity but provides only one type of habitat structure for nesting birds and other wildlife species.  Depending upon the objectives for the site, that could be fine, but it very much depends upon what the manager wants to accomplish.

I feel it’s important to say this here:  I am a big proponent of both fire and grazing as management tools – you can find myriad examples of that by searching through my previous blog posts.  However, while I think combining fire and grazing can create some fantastic results, those strategies/results don’t fit all objectives.  More importantly, your particular site may or may not respond well to those kinds of fire and grazing combinations.

Let’s say your primary objective is to provide habitat for as many species of grassland birds as possible.  First, you’ll need a pretty big swath of land – many bird species have minimum habitat size requirements.  Assuming you’ve got sufficient land, the major factor grassland nesting birds respond to is habitat structure.  Some birds prefer tall thatchy structure, others like short/sparse vegetation, and others want something in-between.  A reasonable outcome-based objective might be that you want to provide all three of those habitat types across your prairie each year (and you’ll want to make sure the habitat are being successfully used by a diverse bird community).  Perfect.  Now, how will you create those habitat types?

 Grasshopper sparrows tend to nest in prairies with relatively short structure, but with some thatch (which they use to build nests) along the ground.  Some of the highest abundances of grasshopper sparrows around here are found in relatively heavily-grazed prairie.

Fall or spring fires can create short habitat structure that some birds really like to nest in.  However, some bird species (e.g., grasshopper sparrows) usually like short habitat with a little more thatch in the ground layer than is usually found in recently burned prairies.  Also, while burned areas are short and unburned areas are tall, it’s difficult to create in-between height/density habitats using only fire.  This is where other tools such as mowing and grazing might be helpful.  Mowing can reduce the height of tall vegetation and create short or mid-height structure that grasshopper sparrows, meadowlarks, and other species prefer.  Grazing can do the same and can have the advantage that cattle or bison are selective grazers, eating some plants and leaving others.  This can create structure with both tall and short vegetation mixed together and can also help suppress grasses and allow for greater expression of forbs (broadleaf plants) – something birds such as dickcissels often prefer.

Upland sandpipers prefer to nest where vegetation structure is short, but often move to sites with strong forb cover and a little patchier structure when their chicks become active.

If we’re trying to create optimal bird habitat, then, fire, mowing and grazing might all be useful tools to consider.  It’s important to understand how each tool can be used to affect habitat structure, as well as the potential risks of using each (fire can sometimes kill aboveground animals and stimulate invasive plants, grazers can sometimes target vulnerable plants and create issues via trampling).  With all of that information, you can start putting together strategies that employ the right tools, and then test those strategies against the OUTCOMES you desire.  Notice that the process I’ve just described is independent of the kinds of historic fire returns for your area or whether or not you think grazing was a significant factor in the evolution of regional plant communities.  Define your objective by the outcomes you want and test/adapt strategies based on that objective.

Other examples: At my family prairie, we aren’t using prescribed fire because we’ve been able to use grazing to meet our objectives of habitat heterogeneity and increasing plant diversity, and we use loppers/herbicide to successfully control woody invasion.  In small prairies where preserving particular plant species is the objective, a strategy using only fire or mowing could be most appropriate.  If that small prairie has rare insects or reptiles that are especially vulnerable to fire, maybe mowing is the best tool.  Regardless, the right tools and strategies depend upon the outcome-based objective.

This photo was taken in the burned patch of a patch-burn grazed prairie at Konza prairie, near Manhattan, Kansas.  The grazing created varied habitat structure because of the selective grazing by cattle.  Leadplant and other ungrazed forbs contrast with surrounding short grasses.

For ranchers and farmers who manage prairies, this same objective setting process should apply, but of course those prairies also have to help provide sufficient income to keep a family or business thriving.  Even in those cases, however, it’s still important to start with outcome-based objectives.  Those objectives can include a certain amount of needed income but should also include specific habitat or other ecological objectives.  Once you’ve decided, for example, that you really want to manage in a way that provides a certain amount of quail habitat or provides consistent pollinator resources through the season, you can look for ways to accomplish that while still providing the needed income.  When a conflict between income and habitat objectives arises, you can make the decisions that make sense to you, but at least you’re making those decisions with all the information needed to fully consider the options.

Prescribed fire can be a great tool for accomplishing some objectives, but it can also be difficult to implement for some managers.  While it is an important ecological process in prairies, employing prescribed fire should still be seen as a tool/strategy, rather than as an objective in and of itself.

There are plenty of reasonable prairie management objectives to choose from, but they should be based on outcomes rather than on tools and strategies.  Employing more frequent prescribed fire is not a good objective.  However, using more frequent prescribed fire might be a great strategy to reach a particular outcome.  (It could also be a terrible strategy, depending upon your objective.)  Don’t fall into the trap of choosing your transportation method before you know where you want to go. 

P.S. I’m sure some of you are thinking it, so let me address what might appear to be a weakness of my vacation transportation analogy.  Yes, it’s perfectly fine to start vacation planning by deciding that you want to take a cruise ship or motorcycle if the OUTCOME you really want is to ride on a ship or motorcycle.  If you don’t care where you go, the destination isn’t the outcome, it’s just a by-product of your mode of travel.  Fine.  But I think you understand what I was trying to say, right?  Sure, you could argue that conducting prescribed fires could be your objective if all you want is a legal way to light things on fire and watch them burn.  If that’s your objective, though, you’re not managing prairies, you’re lighting things on fire – and there’s a big difference.  Ok?  Ok.

Trying to Create Something Different in the Nebraska Sandhills

At our Niobrara Valley Preserve (NVP), we’re experimenting with prairie management techniques to see if we can create a wider range of habitat conditions than is found throughout much of the Nebraska Sandhills.  On many Sandhills ranches, pastures look fairly similar to each other in terms of vegetation structure.  That’s because Sandhills ranchers tend to be careful in their grazing management to avoid wind erosion that can cause “blowouts” of bare sand.  As a result, pastures are rarely grazed intensively enough to create wide expanses of bare ground.  If intensive grazing does happen, it’s usually on a small scale and/or for short periods of time, which allows for quick recovery of grasses.

The Nebraska Sandhills have tremendous innate heterogeneity.  Just in this photo, you can see areas of bare sand created by pocket gophers and/or other animals, habitat structure created by various kinds of plants, including grasses, wildflowers, yucca, and shrubs.  Vegetation height varies greatly across small areas.

Overall, the ecology of the Nebraska Sandhills seems very healthy.  It’s a huge and mostly intact grassland landscape, and because of the dry sandy soils, topography and diversity of vegetation, there is quite a bit of habitat heterogeneity that is independent of management.  As you walk across most Sandhills pastures, you will move through both short/sparse vegetation and taller/dense vegetation, and occasionally come across other structural components like yucca plants or plum thickets.  Wildlife and insect species can often find the habitat structure they need somewhere in that pasture, though it might be in a small patch surrounded by other habitat types.  That seems to be true even for many bird species, which have relatively large breeding territories.  As an example, in pastures with fairly tall vegetation, we often see and hear horned larks that are (apparently) nesting in a few small and scattered patches of the short vegetation structure they prefer.  Those patches of short habitat often occur in gravelly flat areas or in favorite feeding areas for cattle, where grass growth is weak because of frequent grazing.

This late July photo shows a portion of our west bison pasture that was burned this spring and has been grazed intensively by bison all year. Because bison are in the pasture year round, they had immediate access to the burned area and started grazing regrowth as soon as it was available.

We’re trying to figure out more about how management with patch-burn grazing or other similar grazing systems affects Sandhills ecology.  Patch-burn grazing has part of the management of our bison pastures at NVP since the early 1990’s.  Because of that, we know Sandhills vegetation can recover from fires that are followed immediately by season-long intensive grazing.  However, we still don’t know much about how many animal species might respond – positively or negatively – to the kind of large patch heterogeneity created by this kind of management.  Instead of pastures with interspersed small areas of tall and short vegetation, we’re trying to create large patches (500-1000 acre patches within 10,000-12,000 acre pastures) of each habitat type and then shift the location of those patches between years.

Plains sunflower (an annual) often becomes very abundant after fires because it germinates well in exposed soil and then thrives in the absence of strong competition from perennial grasses.  This is the current year’s burn patch in our east bison pasture, where plains sunflower tall and blooming, surrounded by short-cropped grasses.

Creating large patches of various habitat types could bring both advantages and disadvantages to different species.  As an example, large patches could create an abundance of resources that support larger and more viable populations of some animal species. On the other hand, a vole who likes thatchy habitat could wake up in the middle of a 1000 acre burn, and it would have to make a long dangerous trip to find a more suitable place to live.  Trying to evaluate those potential costs and benefits is a big challenge for us.

This landscape shot shows the abundance of plains sunflower across the entire burned patch.

One possible advantage of the kind of shifting mosaic of habitat approach we’re trying is that it helps avoid risks that come from having the same habitat conditions in the same place year after year.  Just as crop rotation can help avoid buildups of pests and pathogens, shifting habitat types from place to place could have important benefits.  For example varying the location of habitat types from year to year could limit disease outbreaks and help prevent predators or herbivores from building up large and potentially destabilizing populations.

Showy evening primrose, aka fourpoint evening primrose (Oenothera rhombipetala) where the prairie was burned in 2015 and grazed intensively in both 2015 and 2016.  This opportunistic biennial is taking advantage of a long period where grasses are weakened by prior intensive grazing and haven’t yet recovered.

The most intriguing part of our experimentation for me, though, is the idea that we could create large ‘recovery patches’ where grasses have been weakened by a full season of intensive grazing and the plant community is temporarily dominated by opportunistic, mostly short-lived plant species.  That combination of short grasses and tall ‘weedy’ wildflowers can provide excellent brood-rearing habitat for some birds and important structure for reptiles and invertebrates that need to regulate their body temperature by moving quickly from sun to shade as needed.  Studies in other landscapes have shown that this kind of recovery patch habitat creates pulses of high insect biomass, which could have numerous impacts – including the provision of an awful lot of food for wildlife.  In addition, if an abundance of opportunistic plants include species beneficial to pollinators, that could provide quite a bonanza of resources for bees, butterflies, and other insects.

Zoomed out

In most of the Sandhills, patches of  ‘weedy’ habitat tend to be in small, static and widely scattered locations such as around windmills or other places where cattle or bison frequently congregate.  We’re wondering what might happen if we created big patches of the same habitat type and shifted their location from year to year.  In our Platte River Prairies, patch-burn grazing (and similar strategies) has sustained prairie plant diversity over many years, but we haven’t looked closely for similar responses in the Sandhills.  In addition, we know a little about how birds respond to patch-burn grazing in the Sandhills, but not much about impacts on other species like lizards, pollinators, small mammals, or invertebrates.  Now we’re trying to collect data on the responses from all those different organisms.

The lesser earless lizard is often found in and around sand blowouts or other habitat patches with abundant bare sand.  Will they respond positively to much larger patches of sparse vegetation?  Can they successfully shift their population locations as we burn/graze new sites?

Will pollinators such as this plasterer bee (Colletes sp) benefit from higher abundances of flowering plants in big patches of Sandhills prairie that are recovering from season-long intensive grazing?

This is part of our east bison pasture that hasn’t burned since 2012, and has been only lightly grazed during that time period.  It should support a different array of wildlife and allow different plant species to thrive than more recently-grazed areas.  Providing a wide range of habitat types across the prairie seems beneficial for biological diversity, but we still need to test that idea in the Sandhills.

I’ve really enjoyed digging into all the questions we have about our attempts to create more habitat heterogeneity in the Sandhills.  We haven’t had time to answer many questions yet, but we feel like we’re at least creating something different than what exists throughout most of the Sandhills landscape.  A few years from now, we might conclude that the heterogeneity we created didn’t really result in any significant positive or negative impacts compared to what exists elsewhere.  If that’s the conclusion, we’ll move forward with that in mind.  On the other hand, we might find that there are some important positive (and/or negative) impacts of the shifting mosaic approach we’re testing.  In the meantime, it’s exciting to have the opportunity to try something different and watch what happens.  Stay tuned…

If nothing else, huge populations of Plains sunflower like this one in our west bison pasture provide a different (and I think beautiful) look to parts of the Sandhills landscape at the Niobrara Valley Preserve.