Tag Archives: adaptive capacity

The Show Must Go On

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Almost a decade ago, I wrote about two competing metaphors for prairie restoration. I suggested we view prairie restoration like the reconstruction of a city after a disaster rather than like the restoration of an historic building.  We need to concentrate on the roles and functions of prairie ecosystems rather than how closely a restored patch of prairie resembled what it used to be in the past.

Today, I’m hoping to stimulate conversation about the difficult decisions we face as we try to conserve prairies in the face of rapid climate change.  One conservation planning approach is to focus on conserving the stage, not the actors.  It advocates prioritization of sites with geophysical diversity because those abiotic conditions influence habitat heterogeneity, which supports biodiversity.  The hope is that we might be able to conserve “an abiotically diverse ‘stage’ upon which evolution will play out and support many actors (biodiversity).”

The varied topography and the habitat size and connectivity found in Flint Hills of Kansas makes it a ‘stage’ that can potentially sustain biodiversity – but only with thoughtful, persistent, and adaptive management.

I think the ‘conserve the stage’ approach has merit, but it’s just a first step, especially for prairie conservation.  We don’t just want to save the stage; we want to make sure the show goes on.  Thus, I present to you a long (and potentially ridiculous) metaphor for prairie conservation that builds upon the ‘conserve the stage’ approach.

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Every actor in a theatrical production plays a role that helps tell a story.  Likewise, every species in a prairie plays a role that contributes to the overall functioning of the ecosystem.  In a healthy and resilient prairie, all the key roles in are filled. 

Fortunately, there is a lot of redundancy built into prairie communities.  We have lots of species that provide pollination, seed dispersal, nutrient cycling, and all the other essential functions that keep prairies going.  We have a big cast, or maybe a big actors’ union.

Today’s prairie ‘show’ already looks different than it did in the past.  Prairie landscapes are fragmented, invasive species have joined the cast, and the climate is changing.  Those and other factors mean that some actors who played key roles in the past are no longer part of the show, at least at some venues.  Other actors remain in the cast but don’t play their roles as effectively as they used to.  Despite those changes, there are still really good versions of the prairie show being presented on various stages, though the versions vary quite a bit from place to place.

To keep the show going, we, as producers and directors, have to be creative and adaptable.  We face really difficult decisions, especially when it comes to actors who aren’t well suited for their roles anymore.  Continuing to direct the show with those actors as the main focus can weaken the performance of others and drag the whole production down. 

Making changes to the cast of a show comes with a lot of risk, however.  We don’t have a lot of experience with that process and we’re likely to make mistakes. Fortunately, in most cases, there are existing cast members that have the potential to adapt their roles and take on new challenges.  With some guidance, those actors will find new ways to collaborate with each other and put on a show that might not be exactly the same as we’re used to but will still have a plot we can follow and enjoy.

More frequent and severe flooding is occurring as a result of climate change. That increased flooding will likely affect which plant and animal species will persist in low-lying prairies like this one. Can we predict those changes and help guide them in ways that don’t lead to reduced biodiversity?

If more drastic actions are needed, we might recognize that some actors are on their way out and start training understudies who can gradually take over roles as needed.  If necessary, we might decide to recruit actors that are playing diminished roles on other stages and bring them in to rejuvenate their careers in a more suitable situation.  Similarly, we might help some of our own long-term stars find new opportunities elsewhere, rather than just watching them slowly fade away. 

In some cases, the world around us might force major a rewriting of the show itself.  We might find ourselves directing a shrubland or woodland production rather than a prairie show.  That doesn’t mean the show will stop or become less important, but it will require a different approach, a significantly altered cast, and a lot of adaptation by all involved.  However, if we stick with the mantra of ‘The Show Must Go On’, we’ll need to figure out how to adjust on the fly and sustain as much biodiversity and ecological function as we can.

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Ok, I have to break away from this tedious metaphor.  The real point here is that we can’t afford to be so invested in current or past versions of our prairies that we don’t allow them to adapt to changing conditions.  At the risk of sliding back into my metaphor, there are lots of old movies and plays that don’t hold up well today.  Jokes that used to be funny 20 or 30 years ago aren’t funny today.  Old references don’t land with new audiences.  In most cases, the basic stories themselves are still solid – they just need to be adapted for today’s world.  Prairies and their species also exist in a different world than they used to, and that world continues to change (very quickly) around them.

The resilience and function of prairies is highly dependent upon biodiversity, which depends upon habitat size and heterogeneity, along with other factors.  Maintaining high biodiversity in prairies that exist in fragmented landscapes comes with huge challenges, which are compounded by a rapidly changing climate.  Plant and animal communities aren’t the same as they were in the past and they’ll continue to change over the next few decades and beyond.  In fragmented landscapes, unless we take an active role, those alterations will largely take place in isolation, with limited opportunities for species to travel between one prairie fragment and another.  Even in landscapes with large contiguous grasslands, we’ll need to be very thoughtful about how we shepherd those prairie communities through the coming years.

These tent caterpillars probably aren’t causing serious impacts to this patch of wild plum, despite appearances. How will climate change, habitat fragmentation, and increased woody encroachment affect this insect species and its impacts on other species in the future? (This is just a random example – I’m not saying tent caterpillars are going to become a major problem!)

It’s really hard to look at the prairies we know best and imagine them with a different composition of species.  We’re used to measuring stewardship success by our ability to sustain the status quo.  Watching the population of a species diminish in size – or disappear entirely – feels like a major failure.  Most of us have also looked skeptically at any new species that show up in a prairie, worrying about potential negative impacts of that species on the existing community. 

I don’t have a lot of answers to the big questions we face.  I’m certainly not ready to lay out a plan or advocate for a particular approach to managing these changing prairies.  As I did in another recent post, I’m mainly trying to get some conversation going on this topic. 

The best I can do right now is offer a few ideas for discussion.  For example, I think we might be smart to reevaluate the way we look at our objectives for prairie management.  Instead of trying to maintain the current composition of plants and animals, maybe we should focus more on biodiversity and less on which particular species are present or abundant within those communities.  (That doesn’t mean we welcome invasive species, by the way.  Any species – plant, animal, or otherwise – that acts to reduce biodiversity is still a problem.)  

I also think we need more serious conversation about when to resist ‘state changes’ like the transition from grassland to shrubland and when to facilitate those transformations, while trying to preserve as much biodiversity and productivity as we can.  Again, I have little to offer in terms of specifics, but it seems clear that we’re not going to be able to stave off those state changes forever in at least some places.  Let’s start thinking about contingencies instead of just waiting for those sites to collapse.

There’s a lot of woody encroachment in this prairie. The number of trees in the surrounding landscape and a changing climate are both spurring that invasion. At what point does the fight against this kind of encroachment become fruitless? What do we do then?

Finally, it’s never been more important to find opportunities to enlarge and reconnect prairie fragments through prairie restoration.  The chances are slim that a small, isolated prairie fragment is going to adapt well to a rapidly changing world.  Growing the size of those fragments by restoring adjacent patches should be a top priority.  Can we find new approaches for creating those restoration opportunities in strategic locations? As we do that restoration work, we should also continue to test and discuss seed sourcing strategies, including the regional admixture approach, to see if we can further bolster the adaptive capacity of those small sites.

We’ll be figuring this out as we go, and we’ll surely screw some things up, but we can’t afford to just continue reacting.  At the very least, we need to be thinking ahead about the changes that are taking place and how those will affect prairies.  In some cases, we should probably be ‘acting ahead’ to guide state transitions, migration of species, or simply changes in species composition within individual prairie sites. 

What we can’t afford to do is live in the past.  We’re hurtling into the future whether we like it or not.  Let’s make sure we bring prairies along with us.

Ecological Resilience in Prairies: Part 2

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This is Part 2 of a two part series on ecological resilience in prairies.  In Part 1, I interviewed Dr. Craig Allen about the basic definition of ecological resilience and then wrote about the relevance and application or resilience to prairie ecosystems.  In Part 2, I explore how ecological resilience can influence the way we restore and manage prairies, and about how much we still have to learn about how to do that.

 

Influencing Resilience through Restoration and Management

Understanding ecological resilience should help us better design restoration and management strategies that build and maintain resilience in prairies.  Using the components of resilience discussed in Part 1, it seems apparent that when restoring (reconstructing) prairies, it’s important to maximize species diversity in seed mixtures.  More importantly, prairie restoration that adds to the size and connectivity of existing prairie remnants should make the entire complex of restored/remnant prairie more resilient (see earlier post on this subject).  Finally, selecting and altering restoration sites, when possible, to include topographic and other habitat type variation – and multiple examples of each type – can also help ensure the resilience of the resulting restored prairie. 

Designing management strategies for prairies that sustains ecological resilience is trickier because we still have much to learn.  We’re far from fully understanding the various stable states prairies may exist in, or flip to, let alone where the thresholds are between those states.  In addition, the level of plasticity, or range of adaptive capacity, of prairies is a subject of great debate right now among prairie ecologists – although the discussion is not usually framed in those terms.  The real question is – How much can prairies change their plant and animal species composition and still remain “in the bowl”? 

As an example, I manage a sand prairie that was hayed annually in the mid-summer for about 20 years before The Nature Conservancy purchased it in 2000.  Over that 20 year period, the plant community in that prairie adjusted to that annual haying regime.  Species such as stiff sunflower, leadplant, and sand cherry became restricted to a few steep slopes where hay equipment couldn’t go.  Early summer grass and forb species became very abundant, but later season flowering plants were less so because they were mowed off around their flowering time each year.  The prairie was a nice quality mixed-grass prairie, with good plant diversity, but definitely had the “look” of an annually-hayed prairie. 

Stiff sunflower has increased in abundance since annual haying ceased.

When we took over the management in 2000, we let the site rest for about 5 years and burned portions of it each year during that time.  Then, we began introducing some combined fire and grazing treatments at different intensities and at varying times of the season.  As a result, the prairie looks fairly different now.  Stiff sunflower and leadplant have spread considerably through the site, re-taking lower slopes where hay equipment had earlier eliminated them.  Cool-season grasses (native and non-native) change in abundance from year to year, but warm-season native grasses are certainly more dominant than they previously were.  Overall forb diversity is about the same as it was, but the relative abundance of many forbs has changed, and those abundances now vary from year to year, rather than remaining fairly stable.

In the context of plasticity, or adaptive capacity, this prairie has demonstrated that the 20 years of haying was not enough to move the plant community into a new stable state from which recovery, if that’s the right word, was not possible.  The community was altered by that haying regime, but upon alteration of that regime, the community composition morphed to match changing conditions – without losing plant diversity.  In other words, assuming that the prairie hasn’t lost anything critical during the 11 years of our management, both the haying regime and our current management have kept the prairie “in the bowl”, though it changed appearance fairly dramatically.  Its adaptive capacity is broad enough to include the “hayed” look and the “crazy Nature Conservancy management” look.  The real test of this, of course, would be to reintroduce haying for another 20 years and see if the plant community reverted back to something very similar to the condition it was in when we purchased it. 

This sand prairie has changed species composition substantially since we switched management from annual haying to a mixture of prescribed fire and grazing.

Here’s another example from my own experience.  We have a 45 acre restored prairie (prairie reconstruction) that was seeded in 1995 by Prairie Plains Resource Institute adjacent to a degraded remnant prairie.  The seed mixture included approximately 150 species of mesic prairie plants, most of which established successfully.  We managed the prairie with periodic spring fire for its first seven years, and then incorporated it into our experimental patch-burn grazing system (light stocking rate).  During nine years of patch-burn grazing management, (6 of which were during a severe drought) the plant species composition in any one place has bounced around quite a bit due to the fire/intense grazing/rest cycles imposed by the patch-burn grazing management system.  Overall, however, the prairie has maintained its mean floristic quality within 95% statistical confidence intervals (I collect annual data which entails calculating floristic quality within 100 1m2 plots and averaging the values across those plots).   Read more about our patch-burn grazing work and results at this restored prairie and others here.

That’s not to say the prairie hasn’t changed – it has.  Some plant species have increased in frequency among my annual data collection plots, some vary in frequency from year to year, and others stay fairly stable.  However, no species has dramatically declined over the time period.  (I wish I had data on other species, particularly insects, but I don’t.)  Perhaps the most interesting, and somewhat concerning, phenomenon has been an increase in the frequency of Kentucky bluegrass in my plot data.  The increase has been fairly steady over the nine years of patch-burn grazing and data collection, and bluegrass is now in about 75% of my 100 1m2 plots, though it rarely looks dominant where it occurs.  To this point, that increasing frequency doesn’t seem to be impacting the overall diversity or floristic quality of the plant community, but that doesn’t mean it won’t at some point.  Two possibilities are: 1) Our management is allowing bluegrass to enter the plant community but remain a minor component, or 2) Kentucky bluegrass is on a steady march of increasing dominance and will eventually turn my restored prairie into the same kind of low-diversity degraded prairie that exists in the adjacent remnant prairie.  I won’t be completely shocked by either scenario, but I have hope that #2 won’t happen because of the way bluegrass is acting in the community to this point.  It’s way too early to know for sure.

Interestingly, I have some large exclosures within this restored prairie that have never had grazing, only prescribed fire at a similar frequency to the grazed portion.  Those exclosures have very little Kentucky bluegrass in them – probably because of both the differing management and the fact that the exclosures are on the far side of the restoration from the neighboring bluegrass-dominated remnant prairie.  However, the exclosures also have much lower plant diversity and mean floristic quality than the grazed portion of the restored prairie.  Visually, they are dominated by warm-season grasses and a few large forbs (e.g., perennial sunflowers).  At this point, I prefer the grazed portion of the prairie because it seems to line up better with my management objectives of maintaining diverse and resilient plant communities (assuming it’s not slowly becoming a bluegrass wasteland). 

This photo was taken when the 1995 prairie seeding was nearing the end of its establishment period (fifth growing season). The prairie has maintained its mean floristic quality (and all of its plant species) through years of patch-burn grazing and drought.

To relate this example back to adaptive capacity, it appears likely that the grazed portion of the restored prairie has the adaptive capacity to retain its integrity as a prairie community through fairly wild fluctuations in species composition as a result of stresses from fire, grazing, and drought.  This is, again, remembering that I’m only evaluating the plant community and that the experiment is far from over.  On the other hand, it appears the exclosed portions of the prairie have lost plant diversity over time.  Whether the communities in those exclosures are still “in the bowl” or in a new stable state of lower diversity is a big question.  To address it, I’m going to open one of them to fire/grazing this coming year and exclude a portion of the currently-grazed prairie and see what happens.  If the two plant communities trade identities to match their new management regimes, I’ll know that both were still “in the bowl” and understand more about the adaptive capacity of our prairies.  If they don’t, that will be equally instructive!

The Upshot

Building and sustaining ecological resilience in prairies may be the most important component of prairie conservation in the coming decades.  Threats from invasive species, habitat fragmentation and detrimental land management practices, compounded by climate change, will make conservation extremely difficult.  Armoring prairies with ecological resilience gives us the best chance of success. 

In order to build that resilience, we first have to understand it better.  It is certainly more complex than the few simple examples I’ve provided.  There are numerous belowground processes and systems we still know relatively little about.  Even aboveground, there are many more questions than answers regarding the way species interact with each other and their environment – and what is required to maintain those interactions.  To gain a better understanding of these natural systems, we have to rely on experimentation and observation.  I think there are essentially two broad questions:

  1. What is the adaptive capacity of prairies, and where are the thresholds between the desired state and other, less desired, stable states?  This will certainly vary between tallgrass and mixed-grass prairies, and between sand prairies and black soil prairies, etc., but there will almost surely be some consistent themes. 
  2. How important is it to keep the ball moving within the bowl?  In other words, are prairies really like our human bodies, in that the more we stress and rest them, the better prepared they are for future stresses?  (Does the bowl shrink if we don’t keep pushing at the edges?)  Or do we just have to keep prairies from being stressed too far in any particular direction? 

 

We can work toward answering these questions with direct experimentation on prairies we manage (similar to my simple experiment with grazing and exclosures in the restored prairie example presented earlier).  In addition, though, we can learn much from prairies that “flip” to less desirable stable states (hopefully not the ones we’re managing!) by documenting as much as we can about what happens to them and why. 

Most importantly, I hope that thinking about ecological resilience with regard to prairies will make you look at the prairies you’re familiar with in a new way.  Seeing prairies as balls rolling around in a bowl makes watching and managing prairies a much different experience than seeing them as a stable “climax community.”  When we expect change, it’s easier for us to perceive change, and the more observant we are, the more we’ll learn.  And goodness knows we have plenty to learn.

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If you’re interested in learning more about ecological resilience, here are some relevant references that Craig Allen recommends (I’m pretty sure it’s just a coincidence that he’s a co-author on all of them).  The Gunderson et al. book reprints a lot of the classic / foundational papers on the subject.    

Sundstrom, S., C. R. Allen and C. Barichievy.  Biodiversity, resilience, and tipping points in ecosystems.   Conservation Biology: in review.

Gunderson, L., C. R. Allen, and C. S. Holling. 2010.  Foundations of Ecological Resilience.  Island Press, New York, NY.  466pp.  

Allen, C. R., L. Gunderson, and A. R. Johnson.  2005.  The use of discontinuities and functional groups to assess relative resilience in complex systems.  Ecosystems 8:958-966.

Forys, E. A., and C. R. Allen.  2002.  Functional group change within and across scales following invasions and extinctions in the Everglades ecosystem.  Ecosystems 5:339-347.

Peterson, G., C. R. Allen, and C. S. Holling.  1998.  Ecological resilience, biodiversity and scale. Ecosystems 1:6-18.