Counting Gayfeather Stems Out Of Scientific Curiosity – Year 2

Science doesn’t have to be complicated or difficult.  In fact, the essence of science is really just a way to satisfy our curiosity about the world.

There is great value in rigorous science, with sufficient replication and statistical power to merit publication in peer-reviewed journals.  That kind of science moves us forward as a scientific community, and provides checks and balances to make sure we don’t go too far down the wrong path.  At the other end of the spectrum, however, is the kind of science that any naturalist or land manager can use to answer basic questions about how the world works.  An observation triggers a question, and more observations help answer that question.

I photographed this dotted gayfeather at our family prairie the other night. When I noticed it flowering, I knew it was time to revisit my project from last year.

Exactly one year ago, I posted the results of about a half hour’s worth of data collection on dotted gayfeather (Liatris punctata) plants.  I had noticed that plants in one part of one of our restored Platte River Prairies seemed to have a lot more flowering stems than in another part of the same prairie.  It was pretty easy to walk around and count enough stems in both patches and see if my observation could be confirmed by data.  It was.  Gayfeather plants growing in the half that had been burned and grazed intensively during the previous year had many more flowering stems than those growing in the half that hadn’t been burned and was only lightly grazed.

This photo was taken back in 2017, and shows a huge dotted gayfeather plant in an area where the previous year’s burning/grazing had reduced grass competition.  You can also see an abundance of yarrow and stiff goldenrod that seemed to respond positively to the less competition.

At the time, I speculated that perhaps the reduced competition from grazed/stressed grasses had allowed the dotted gayfeather plants an opportunity to produce a lot more flowering stems.  You can read last year’s post for more details on my hypothesis, if you like, but in that post I’d promised to revisit the site again in future years to see if patterns of stem abundance fit my guess.

Well, I kept my promise yesterday, and the results are very interesting!

The number of stems per plant in the east half of the prairie didn’t really change between 2017 and 2018.  That half was has been largely ungrazed for the last couple years but was burned this spring and is currently being grazed pretty intensively.  The west half is where I noticed many more stems per plant in 2017 (the year after it was burned and grazed).  However, in 2018, the number of stems/plant in the west half came way down to match that in the east.  My initial hypothesis is supported!  (The error bars here represent 95% confidence intervals, for those of you who care about that sort of thing.)

The above graph shows averages based on counts of 58 and 63 plants from the east half of the prairie in 2017 and 2018, respectively.  In the west half, I counted 53 plants in 2017 and 43 in 2018 – it was harder to find flowering plants in 2018, making me wonder if some didn’t bloom or if they were just hidden in the dense grass (or both).

The west half of the prairie, was burned/grazed in 2016 and had very high numbers of  gayfeather stems/plant in 2017.  It was completely rested from grazing last year and is only getting very light grazing pressure in 2018.  As a result, grasses have recovered very well, and now grow pretty thickly around the dotted gayfeather plants.  My prediction was that as grasses recovered, the number of gayfeather stems would decrease.  They did.  In 2017, I was finding a lot of plants with stem numbers in the 20’s and 30’s, and one gigantic plant had 51 stems!  In the same area a year later, I found one plant with 21 stems and all the rest had 10 or fewer (most had 3 or fewer).

In the west half of the prairie, grasses have recovered after two years of near complete rest, and dotted gayfeather plants now have a lot more competition for light and space.  Most plants had only a few flowering stems, and based on how hard I had to look to find them, I wonder if many didn’t even flower this year.

Meanwhile, the east half was burned this spring and has been getting pretty intensive grazing all season long.  Cattle have been mainly focusing on grasses like big bluestem and Indiangrass.  It’s pretty similar to the way the west half was grazed in 2016, though this year’s high rainfall has let some grasses grow faster than the cattle can eat them.  As a result, the overall grazing intensity – and the stress on grass plants – won’t be quite as strong as it was when the west half was grazed in 2016, but I’m hoping it will be enough that grasses will be much less competitive in 2019.  If so, and if my hypothesis is right, I should see gayfeather stem numbers go way up in 2019 in this area.

In the east half of the prairie, this year’s burn has led cattle to graze grasses fairly intensively.  Those grasses should be much less competitive next year, and I expect to see gayfeather plants produce a lot more stems per plant.  We’ll see if I’m right in about a year.

So far, I’ve invested about 2 hours worth of time on this project.  That includes about 30 minutes of data collection each year (walking around and counting stems on all the plants I encountered) and about the same amount of time entering the data and creating a graph.  Despite that, I’m gaining confidence that my initial hypothesis about grass competition and gayfeather stem numbers was on the right track.  A year from now, if gayfeather stem numbers increase dramatically in the east half (burned and grazed this year) and stay about the same in the west, I’ll be pretty confident in my answer.

Now, my results aren’t going to cure cancer or likely change the world in any measurable way.  I probably won’t submit my results to a peer-reviewed journal (although I might actually submit a “note” if the results warrant it).  On the other hand, I’m learning a lot, and what I’m observing is a small clue to a larger puzzle.  I’ve got years of much more rigorous data showing that short-lived wildflowers respond very positively after grazing reduces the vigor of competing grasses.  That wildflower response, however, has mostly been from the germination of new plants that fill in while grasses are weak and then die out again as grasses retake their previous territory.

My observations of dotted gayfeather are giving me some intriguing insight into how long-lived perennial plants might respond to the same reduction of grass competition.  It appears likely that at least some long-lived plants are able to take advantage of that lighter competition by producing many more stems, leaves, and flowers.  That increase must certainly benefit pollinators, and maybe other organisms that feed on gayfeather.  Is it also important to the long-term survival of the plants?  Good question!  The plants sure create a lot more seeds when they make more flowers.  It would be really interesting to know if the plants also produce a bonanza of new buds at their bases (those buds are what allow them to grow new stems in the future).

Regardless of whether more flowering stems has long-term benefits of the plant itself, the phenomenon sure provides an abundance of resources for bees, butterflies, and other pollinators.

Remember – this whole story started because I happened to notice a lot of flowers in one part of our prairies and took 30 minutes to count them.  That kind of cyclical curiosity and observation is the foundation of science, and is the reason we’ve learned what we have about the world around us.  Who knows – maybe my little gayfeather project will lead others to build upon my observations with a more rigorous project that will lead to greater understanding of plant communities, competition, and response to grazing and other stresses.  Whether it does or not, I’m already getting what I wanted out of the project – I’m having fun, learning something new, and stimulating my brain to come up with more questions about the prairies I love.

What are you seeing?  What kinds of questions are tickling your brain as a result?  Do you have a spare hour or two to explore a little further?  Think of what all of us could be learning with just a little bit of time and effort!

Measuring Our Influence as Conservation Scientists

I am a conservation scientist.  Like any other scientist, I develop and test hypotheses, trying to figure out how the world works.  Once I learn something, I publish my results in academic journals where other scientists can evaluate and build upon what I’ve learned.  Because I’m a conservation scientist, however, I also need make sure the people who directly impact prairie conservation (ranchers, land managers, policy makers, etc.) get my information and use it to improve the way grasslands are managed and restored.  If I fail to influence the actions of others in positive ways, I fail as a conservation scientist.

It doesn’t matter how much we learn about employing prescribed fire effectively if we’re not able to help others use the lessons we learn.

In science, keen observational skills and creativity often spark innovations, but rigorous collection of data is required to see whether a great idea actually makes sense or not.  While I’ve had some good ideas, I’ve also come up with plenty of grassland management and restoration strategies that turned out to be duds.  In each case, I learned a little more about prairie ecology and our land stewardship improved as a result.

I’m proud of the work I’ve done over the years to develop new and better ways of restoring and managing prairies.  I know those strategies are effective because I’ve spent a tremendous amount of time testing them, through both observation and rigorous data collection.  My computer is full of spreadsheets and graphs showing how prairie species and communities respond to various treatments.

I’m also proud of the work I’ve done to share what we’ve learned with others, but until recently, I’ve done very little to evaluate the effectiveness of that work.  I’m not alone – most of my colleagues in the world of conservation science do a great job of measuring the natural world and its responses to human activities, but do very little to evaluate whether their work is actually influencing conservation.  It’s fairly ridiculous when you think about it.  We would never think of devoting ourselves to a new invasive species control technique without testing its effectiveness, but for some reason we’re satisfied to rely on blind optimism that our outreach strategies are changing the world.

Come on, folks!  We’re scientists!  We love data, and we’re good at developing and testing ideas.  Why do we apply that passion and aptitude to only part of our work?  Why aren’t we testing whether our ideas are reaching the intended audience and influencing on-the-ground conservation work?  How can we adjust and improve our outreach strategies if we don’t have any data to work from?

To be fair, measuring outreach impacts requires a very different kind of scientific approach than most of us are comfortable with.  Instead of counting plants or observing behavior of birds, bees or bison, we have to assess the attitudes, motivations, and actions of people. Many of us took our career paths because we prefer the company of birds, bees and bison to people, but that doesn’t give us leave to just ignore people altogether – especially when the success or failure of our work hinges upon their actions.

Fortunately, we don’t have to work alone.  There are lots of scientists who are already good at studying people, and many of them are happy to work with us.  I’ve had very enthusiastic responses from those I’ve asked advice from, and their input has been very helpful.

We should probably take some of the energy we spend studying animals and put it towards studying the way people respond to our outreach efforts.

Whether you’re a scientist who actively shares your results with your target audience, or someone who relies on others to translate and transmit that information, there are some basic questions we should all be trying to address.  This is far from a comprehensive list, but it’s a start.

Defining Audience and Message

What lessons and messages from my work are most important?

Who is the audience for those?

What messengers/media will best reach the audiences?

What are the current attitudes/actions of my audience?  What are the main drivers of those those attitudes and actions?

Who are the credible voices my audience looks to for guidance?

How can I reach those credible voices?

Evaluating Success

Are my messages reaching my target audience?

How many people in that audience am I reaching?

Are my messages changing attitudes and/or actions?

At what scale, and to what degree am I making a difference?

Which messages, messengers, and media are most effective for reaching each of my audiences?

Many of us host field days, at which we can share what we’re learning with others.  How many of us are assessing the effectiveness of those field days and other outreach strategies?

I’ve spent a lot of time thinking about audiences and messages, and it’s really helped me focus both my research and outreach more effectively.  Recently, I’ve also started trying to answer some of the questions in the above “Evaluating Success” category.  I’m making some progress, but I need to do much more.

I can tell you how many presentations I’ve given over the last two years (40) and how many people were in those audiences (3,447).  I’ve also been keeping track of calls and emails asking for advice on prairie restoration and management.  Unfortunately, while I have a lot of numbers, I can’t easily translate them into acres of improved management or enhanced habitat quality.

I have, however, made at least some progress toward measuring conservation impact on the ground.  Much of that success came from survey work by one of our first Hubbard Fellows, Eliza Perry.  Eliza conducted interviews with some land managers and private lands biologists who had attended field days at our Platte River Prairies.  Among her many findings were that almost all respondents said what they learned from us had influenced their work, and they conservatively estimated that over 330,000 acres of land had been restored or managed differently because of that influence.  Beyond that, Eliza was able to identify key factors that led to our success and suggest ways to improve our effectiveness.

In addition, Eliza surveyed readers of The Prairie Ecologist Blog and I conducted a follow-up survey three years later.  Those surveys helped quantify the demographics of readers (e.g., about 2/3 of respondents have direct influence on prairie management).  The surveys also measured the degree of influence the blog has on readers’ understanding of prairies and approach to managing or restoring prairies (when applicable).  We even got a rough estimate of the number of acres on which management had been influenced by the blog (over 300,000).

Being able to quantify outreach impact, even when the numbers are fuzzy and incomplete, has been really helpful.  It helps me justify my job, for one thing, and assures both me and my supervisor that the time I spend writing, giving presentations, and consulting with others has value.  Most importantly, it helps me assess what is and isn’t working and adjust accordingly.

While it’s still not fully within my comfort zone, I’m trying hard to make sure I’m measuring the effectiveness of our outreach efforts, just as I do our prairie management and restoration work.  I would love to hear from people who are trying to do the same thing, especially if you’ve found effective evaluation strategies.  As more of us focus on measuring the success of our outreach work, we’ll be able to learn from each other and establish some common metrics.  Hopefully, we’ll also become more effective at translating what we’re learning into large scale and meaningful conservation impact!

How Science Works and Why It Matters

As a scientist and science writer, I’m concerned about the way science is perceived by the public.  I think some big misunderstandings about how science works are creating distrust and dismissal of important scientific findings.  That’s a huge problem, and I’d like to try to help fix it.

Let’s start with this: Science is a process that helps us understand and explain the world around us.  That process relies on repeated observations and experiments that continuously change our understanding of how things work.

Scientists often come up with results that conflict with those of other scientists.  That doesn’t indicate that something is wrong; it’s exactly how science is supposed to work.  When scientists disagree about something, more scientists get involved and keep testing ideas until a consensus starts to emerge.  Even at that point, ideas continue to be tested, and either gain more acceptance (because of more supporting evidence) or weaken (because conflicting results are found).

There is no endpoint in science.  Instead, ideas move through various steps of acceptance, depending upon how much evidence is collected to support them.  You can read much more about how the process works here.

We are lucky to have easy access to immense amounts of information today.  However, it can be be very difficult to know which statements are supported by good science and which are just opinions amplified by people with an agenda and a prominent platform.  Today’s world, for example, still includes people who earnestly believe the earth is flat, despite overwhelming evidence to the contrary.

Media coverage of science often increases confusion.  How many times have you heard or read a media story about how a particular substance either cures or causes cancer?  In most cases, the scientist being interviewed tries to explain that their work is just one step in a long process of evidence gathering and doesn’t prove anything by itself.  That scientist might as well be talking to an empty void.  The headline has already told the story and pundits are shaking their heads and complaining about how scientists can’t ever agree.  (Please see paragraph three above.)

Unfortunately, confusion about how science works means the public often doesn’t pay attention when scientists actually do agree on things.  Loud voices can easily sway public opinion on important topics because it’s hard to know who to believe.  Often, we believe those who say things we want to be true.

Let me ask you three questions:

Do you believe that childhood immunizations are safe and effective?

Do you believe that rapid climate change is occurring as a result of human activity?

Do you believe that food derived from products containing Genetically Modified Organisms (GMOs) is safe for human consumption?

The scientific community has clearly and strongly stated that the answer to all three of these questions should be yes.  Despite that, many people will answer yes to one or two of these questions, but not all three.  If you’re one of those people, I have another question for you.

If you trust the scientific community and the scientific process on one or two of these topics, why not on all of them?

This post is not about vaccines, global warming or GMOs.  I’m not trying to tell you what to think. Instead, I’m inviting you TO think.

If you’re a scientist, are you spending enough time thinking about how to talk to a public that is skeptical of science?  Being right isn’t enough when there are louder voices shouting that you’re wrong.  How do you expect the public to find the real story when your results are hidden in subscription-only journals and written in technical jargon-filled language?  What can you, personally, do to help others understand what science is, why it’s important, and what it can tell us?

If you’re someone who believes the science on some topics, but not others, are you comfortable with the reasons behind that?  Do you think science has been polluted by money and agendas, or do you think money and agendas are trying to discredit science?  Have you spent enough time reading articles that contradict your position and evaluating the credentials of those on each side?  Is it possible that long-held beliefs are preventing you from looking at evidence with clear eyes?

While individual scientists may have biases, the scientific process has no agenda other than discovery.  Scientists are strongly incentivized to go against the grain – both employers and journal publishers get most excited by research that contradicts mainstream ideas.  Because of that, ideas that gain overwhelming scientific consensus should be given extra credibility because they have withstood an onslaught of researchers trying to tear them down.

Can scientists be wrong?  Yes, of course – scientists are wrong all the time, and they argue back and forth in pursuit of knowledge.  That’s a good thing.  Saying that science is untrustworthy because not all scientists agree is like saying that we shouldn’t eat fruit because some of it isn’t ripe.

We desperately need credible science in order to survive and thrive on this earth.  Sustaining that credibility is the responsibility of both scientists and the public.  Scientists must provide accessible and clear information about what they’re learning, but the public also needs to be a receptive and discerning audience.

There is a torrent of news and data coming at us every day.  As you process that information, think like a scientist.  Question everything, including your own assumptions.  Form an opinion and then test it by looking for information that might disprove it.  Most importantly, even when you’re confident in your viewpoint, keep your mind open to new evidence and alternate perspectives.

Finally, remember that science is a continual and cumulative process.  Conflicting research results don’t indicate weakness, they drive scientists to keep looking for answers.  Science shouldn’t lose your trust when scientists disagree.  Instead, science should earn your trust when scientists reach consensus.

 

Special thanks to Anna Helzer for helpful feedback on this piece.

The Much Maligned Coyote

Here in Nebraska, we’ve lost most of our largest predators.  Bears and wolves are gone (excepting rare long-distance wanderers).  Mountain lions are making a slow comeback in the northern and western parts of Nebraska, but the agricultural character and fragmented nature of our state makes it difficult to imagine a much stronger presence of large predators than we have right now.  That’s not a critique – it’s just reality.  It’s difficult to know what effect the absence of those predators has on our wildlife and natural landscapes, but based on what we know from research elsewhere, it’s surely significant.  Throughout the world, and across a wide range of habitat types, major predators stimulate complex cascades of impacts far beyond simply suppressing the populations of their favored prey species.  In fact, the diversity and abundance of many plant, invertebrate, and wildlife species have been shown to decline dramatically when dominant predators disappear.

Illustration by Kim Tri
Coyote illustration by Kim Tri, one of our Hubbard Fellows and, obviously, a talented artist.

Today, in the absence of wolves and bears, coyotes have stepped into the role of top mammalian predator across much of Nebraska.  It’s hard to know if they are as effective as their larger counterparts at maintaining ecosystem function, but there is strong scientific evidence for the strong and positive impacts coyotes have on a number of other grassland species.  Much of the research on this topic was published 15-20 years ago, but few people seem to be familiar with it.  In fact, rather than being celebrated for their importance, coyotes are widely reviled, and often shot on sight, by many (most?) rural citizens across much of prairie regions of North America.

There is much unfortunate irony in the vilification of coyotes.  One common coyote narrative is that coyotes are hard on nesting birds, especially game species like pheasants, quail, turkeys, grouse, and ducks.  In reality, coyotes feed mainly on rodents, and the major predators of birds and their nests tend to be smaller animals, including foxes, raccoons, and cats (especially feral house cats).  Coyotes are large and aggressive enough to intimidate or kill those “mesopredators”, keeping their numbers low and driving them into areas where coyotes spend the least time, such as wooded draws, farmsteads, and even surburbia.  In fact, numerous studies have documented detrimental impacts to bird populations ranging from songbirds to ducks and grouse when coyote numbers are suppressed and mesopredator populations swell.

One of the most dramatic studies of coyote impacts on the structure and function of ecological communities took place on 20,000 hectares of west Texas land back in the 1990’s.  Researchers halved the number of coyotes in one portion of the study area and left the population alone elsewhere.  Within a year of coyote control, the area with fewer coyotes experienced higher populations of bobcats, badgers, and gray foxes.  Perhaps as a result, 11 of the 12 rodent species in that area disappeared, leaving only a skyrocketing population of kangaroo rats.  Jackrabbits also tripled their numbers in the coyote control area, much to the chagrin of ranchers, since jackrabbits compete with livestock for forage.

Another great coyote illustration by Kim Tri.
Another great coyote illustration by Kim Tri.

Speaking of ranchers, many tend not to be coyote fans, in large part because coyotes are sometimes hard on livestock.  Sheep ranchers can suffer big losses to coyotes if they don’t actively protect sheep with dogs, overnight enclosures, and other strategies.  Cattle ranchers can also have trouble with coyotes killing livestock, especially just-born calves.  Coyotes are very good at killing young deer fawns – a great reason for prairie enthusiasts to be coyote fans, by the way – but some transfer that skill to calves as well.  While any self-respecting cow can protect her calf from coyotes under most circumstances, even the toughest mother is weakened enough by the process of giving birth that she is vulnerable to a quick sneak attack.

Unfortunately, the response to livestock losses is often the indiscriminate killing of whatever coyotes ranchers can find.  Research has shown that kind of “coyote control” to be largely ineffective, in part because it usually fails to kill the individuals actually causing problems.  For example, a fourteen year study showed that almost every sheep killed by coyotes was taken by the “alpha pair” in the pack’s social structure.  Those alpha animals are also the wiliest and most difficult to kill.  Furthermore, of course, in the unlikely event that coyote control efforts succeed at suppressing the population in an area, the results might not turn out in favor of the rancher.  Higher numbers of raccoons and foxes, not to mention jackrabbits, along with fewer ducks, grouse, and quail, might take the thrill out of the temporary victory.

Even if coyotes gain wider recognition for their positive effects on natural systems, however, the relationship between coyote and human is bound to be complicated.  As we continue to alter their habitat, coyotes will continue to adapt and survive as best they can.  At times, that will bring them into conflict with us.  It is understandable, for example, that a rancher needs to address livestock losses, and sometimes that could mean tracking down and killing the individual coyote(s) responsible.  However, that kind of careful, targeted response is much different (and more effective) than current broad, indiscriminate campaigns against an animal whose bad reputation is largely based on innuendo and misinformation.

Ideally, seeing coyote tracks on their property would be a positive experience for landowners.
Ideally, seeing coyote tracks on a property would be a positive experience for landowners.

Coyotes and other predators play critically important roles in grassland ecosystems.  It’s easy to understand how they directly suppress populations of their primary prey species.  However, as we continue to study predators, we find more and more of the kind of indirect impacts that ripple through ecological systems in ways that are difficult to predict.  While it seems unlikely that wolves and bears will ever return to prominence in Nebraska or most other prairie regions of North America, coyotes may be able to cover at least some of the ecological roles those larger predators once played.

But only if we let them.

 

How big do prairies need to be?

There is an awful lot we still don’t understand about prairies (and the rest of the natural world, for that matter).  First and foremost, we haven’t even come close to discovering all the species that live in prairies.  We have probably identified all of the birds, and most of the other vertebrates, but there are still many prairie invertebrates no one has yet described.  The world of microorganisms is beginning to open up to us, but that is still, by far, the biggest pool of unknown species.  How can we manage a natural system when we don’t even know what’s there – especially when those inhabitants have a tremendous impact on ecosystem function?

It's still possible that we'll find more snake species in North American prairies, but we've surely discovered nearly all of them. This one is a juvenile eastern racer (Coluber constrictor) in TNC's Platte River Prairies, Nebraska.
It’s possible that we’ll find more snake species in North American prairies, but we’ve surely discovered nearly all of them. This one is a juvenile eastern racer (Coluber constrictor) in TNC’s Platte River Prairies, Nebraska.

We need to discover more species and understand the basics of their life histories, but there are some other really big prairie questions out there that need attention as well.  I thought I’d share a few of the ones I think are most important.  I’m hoping you’ll find them thought-provoking and join me in trying to chip away at them.  We’re not going to answer any of them in the near future, but more people thinking about them and making careful observations will speed us more quickly along the path.  Because each question takes some explaining, I’ll just deal with one here and cover the others in future posts.

Big Question #1:  How big and connected does a prairie landscape need to be to support the majority of prairie species and essential natural processes?

This one has bothered me for a long time because not knowing the answer prevents us from setting reasonable goals for landscape-scale conservation efforts.  As prairie landscapes get carved up by rowcrop agriculture (e.g., the Dakotas), how do we know how much fragmentation will be catastrophic to the ecosystem?  On the flip side, in landscapes that were carved up long ago, what size prairie restoration projects should we aim for to truly restore sustainable prairie ecosystems?

We know that some prairie species require large patches of habitat.  Based on quite a bit of research on birds, we can make reasonable guesses about the size of prairie landscape needed to maintain populations of most bird species.  I’m not completely up to date on this research topic, but I think it’s fair to say that if you had a couple thousand acres of prairie and managed it for a diversity of habitat structure, you’d see most of the grassland bird species in your region show up to nest.  To ensure that those populations were large enough to survive tough years, it’d be nice to have more like 5,000 or 10,000 acres.  Depending upon where you live, that might sound like an impossibly big number or a very manageable one (Illinois doesn’t even have 10,000 acres of remnant prairie in the state, while 10,000 acres is pretty small for a ranch in the 12 million acre Nebraska Sandhills).

Uplan
Upland sandpipers are found most often in larger prairies, especially those with relatively short vegetation.

Assuming that 10,000 acres is a comfortably large prairie for grassland birds, you might think we could just use that as a benchmark for other species as well.  Unfortunately, there are a number of problems with that assumption, many of which I laid out in an earlier post.  One big problem is that bird habitat (quantified largely by factors like vegetation structure and insect abundance) is not necessarily quality habitat for pollinators, ants, or many other species that rely on high plant diversity.  Each of those other species has particular needs, both for habitat size and habitat quality.

A few species (bison? prairie dogs? others?) might need considerably more than 10,000 acres to support a viable population.  However, many other species probably need considerably fewer.   In fact, 10,000 acres might seem like an entire universe to many invertebrate species – although the more we learn about insect migrations, the more complicated that picture becomes.  Is 10,000 acres enough to provide for the vast majority of prairie species?  Maybe.  We really don’t know.

Green darners, and many other dragonfly species, migrate long distances. So do a number of moths and butterflies. Other invertebrates can also travel long distances. Does that make them more or less reliant on large prairie blocks?
Green darners, and many other dragonfly species, migrate long distances. So do a number of moths and butterflies. Other invertebrates can also travel long distances. Does that make them more or less reliant on large prairie blocks?

Regardless of whether or not it’s big enough to sustain populations, we know that restoring and/or preserving a single 10,000 acre block of prairie somewhere in the central United States would not be sufficient to conserve all prairie species.  In order to preserve genetic health and allow populations to recover from catastrophic events, species need multiple habitats in multiple locations.  They also need connectivity between those habitats so that individuals can move between populations.  So, we will need multiple examples of large prairie blocks in every region of the country, with smaller prairies around and between them.  (Questions about what constitutes connectivity and how much connectivity each species needs are also big important questions, but before we address those, we first need to know how large individual habitat blocks need to be.)

Why is this so important?  I’ll give you two real world examples.  First, think about a prairie landscape that has been relatively intact for thousands of years, but is now becoming fragmented by a rapid increase in new rowcrop agriculture.  This is a situation all too familiar to conservationists in the Dakotas, where millions of acres of prairie have been converted to rowcrops over the last couple of decades.  As those conservationists struggle to protect remaining prairie through conservation easements and other strategies, they are doing so with limited time and money.  Knowing what size a prairie block needs to be to sustain species and ecosystem processes would be tremendously helpful.

Let’s say an organization obtains a conservation easement that prevents 5,000 acres from being farmed.  Should they prioritize obtaining an additional easement next to it so that if everything else in the county gets farmed up, there will still be a 10,000 acre block of prairie remaining?  What if they have to pay double the price to obtain that second easement?  Is it worthwhile?  Or should they spend the same amount of money on two more 5,000 acre easements in other locations?  Not knowing the answer to what seems a pretty basic question makes it really difficult to know how to proceed.

My second example is at the other end of the spectrum.  There are a number of large scale prairie restoration efforts going on around North America, where thousands of acres of cropland are being restored to high-diversity prairie communities.  The best of those start with a number of unplowed prairie fragments and enlarge and reconnect those through restoration. The complexes of interconnected remnant and restored grassland they build are many thousands of acres in size.  The Nature Conservancy’s Glacial Ridge project in Minnesota, Nachusa Grasslands in Illinois, and Kankakee Sands project in Indiana are all great examples of this, as is the US Forest Service’s Midewin Tallgrass Prairie in Illinois.

We have proven that we can rebuild prairie landscapes of 10,000 acres and larger.  The sites look good, with beautiful plant communities and abundant wildlife, but are they big enough to sustain that biological diversity?  Should those sites be spending $15,000 per acre to buy high-priced cropland around their borders and increase the size of their restoration projects? Or should they invest those funds in invasive species control and other management needs to protect the investment they’ve already made?

Unfortunately, the answers to these fairly simple questions are not going to be simple to obtain.  We and others have taken a few baby steps by comparing the diversity and abundance of invertebrate species among prairie fragments of varying sizes and degrees of isolation, but we’re just getting started.  I think a better approach would be a large collaborative project that focuses on some of our largest, most intact prairie landscapes such as the Sandhills of Nebraska and the Flint Hills of Kansas and Oklahoma.  Studying how populations and ecosystem processes differ between core areas of those landscapes and the fragmented edges would be an excellent start.  We could learn which species might be most vulnerable to the negative impacts of fragmentation, and then focus on those species through additional research looking at how they are doing in prairies of varying sizes across their ranges.

We can learn a lot by studying how species do in the core versus the ragged edges of huge intact prairie landscapes like the Nebraska Sandhills.
We can learn a lot by studying how species do in the core versus the ragged edges of huge intact prairie landscapes like the Nebraska Sandhills.

I’ve planted this idea with quite a few people, but nothing has really taken off yet.  I’m not giving up.  This is too important.  Does anyone have a couple million dollars to spend answering one of the most pressing conservation questions of our time?

Here are a couple other examples of big research questions I think about.  I’ll address them in more detail in future posts.

1. How effective is prairie restoration (converting cropfield to high-diversity prairie plant communities) at defragmenting prairie landscapes?  Do populations of plants, insects, and wildlife in small prairie fragments grow larger and more interconnected when surrounding cropland is converted to prairie?  What are the key ecosystem components that need to be restored in order for that to happen?

2. How do prairie species respond to fire and grazing management patches, and how should that affect the scale and frequency of those management treatments?  What happens to a vole or other creature living in the unburned patch of a prairie when that patch burns?  Can it travel to other suitable habitat?  How does it know where to go?  What kinds of habitat can it cross and how far can it travel?

3. How does plant diversity influence the productivity and sustainability of grasslands, especially in ways that directly influence agricultural production?  Why should a rancher care about the plant diversity of his/her pasture?  Are there demonstrable increases in soil health, pollination services, forage productivity, forage selection, etc., and are those strong enough that a rancher would trade slightly lower annual income for them?

 

Pretty but Powerful

Because they can’t run away, plants may seem helpless against the many large and small herbivores that like to eat them.  Nothing could be further from the truth.

This caterpillar may appear to be chewing on a helpless plant, but most plants are not as helpless as they seem.
The plant this caterpillar is chewing on may not be as helpless as it appears.

Many plants have physical defenses such as thorns or stiff hairs to deter animals from eating them.  Grasses contain varying levels of silica, which can increase the abrasiveness of their leaves and help make them more difficult to eat and digest.  In addition, the chemical makeup of many plants helps make unpalatable or toxic to potential herbivores.  While herbivory is certainly a major threat, plants also have a variety of defenses against pathogens (diseases).  If you’re interested in more background on this topic, here is a really nice overview of plant defenses against both diseases and herbivores.

A the stiff hairs on plants such as black-eyed susan (Rudbeckia hirta) can make them more difficult for some herbivores to eat.
A the stiff hairs on plants such as black-eyed susan (Rudbeckia hirta) can make them more difficult for some herbivores to eat.

Within the last couple of years, there have been a couple of published studies that highlight some fantastic strategies plants use to defend themselves.   In the first of those, German scientists studied a wild tobacco plant and found that when it is attacked by a caterpillar the plant releases a chemical that, in turn, attracts a predatory bug to eat the caterpillar.  The production of the bug-attractant is triggered by the caterpillar’s saliva.  Essentially, then, the caterpillar sets off an alarm that calls in predators to eat it.  How cool is that?

A second study, done at the University of Missouri-Columbia, found that a species of mustard plant could detect the vibration signature of a caterpillar chewing on one of its leaves.  When the plant identified that signal, it increased production of chemicals that make its leaves taste bad to herbivores.  Researchers were able to replicate and reproduce the vibrations and trigger the response in the lab.  They also showed that other kinds of vibrations did not cause the plants to defend themselves, so the chemical production appeared to be a direct response to herbivory.

Cattle and other large herbivores have to deal with a number of plant defenses, from silica and other compounds that make plants difficult to eat and digest to chemicals that make them bad tasting or toxic.
Cattle and other large herbivores have to deal with a number of plant defenses, from silica and other compounds that make plants difficult to eat and/or digest to chemicals that make them bad tasting or toxic.

These and other research projects help show that plants are not at all defenseless.  Not only do they have strategies to make themselves more difficult to eat (toxins, spines, etc.), they can also respond when they are attacked.  In prairies, there are numerous examples of plants defending themselves in interesting ways, including sunflowers that produce sweet stuff to attract predatory ants and grasses that increase their silica content under intensive grazing pressure.

Of course, herbivores have evolved their own tricks to counter all those plant defenses. Several insect species, for example, have developed ways to deal with the toxins produced by milkweed plants and happily munch away on leaves that would kill other insects.  Now its the milkweed’s turn to (through natural selection and over many years) come up with a response to that response.  The world is pretty fascinating, isn’t it?

So, the next time you’re walking through peaceful-looking prairie on a pleasant morning, remember that those little plants you’re crushing beneath your feet may not be as helpless as they appear.  Sure, those plants are mostly fighting back against animals trying to eat them, but you may still find yourself an accidental victim of their defense strategies.  Experienced hikers are well acquainted with the abrasive edges of grass leaves and the sharp spines on species such as roses and cacti.  At one time or another, most of us have blundered into a patch of nettles or poison ivy.

No, plants are certainly not helpless.  Let’s just be thankful they haven’t (yet) figured out how to chase us down.

Concerns about EARTH A New Wild’s Messages About Grassland Conservation

I know that many of you watched the first two episodes of EARTH A New Wild last week on Public Television, including Episode 2: Plains.  I watched as well, and while I was glad for the attention paid to grasslands, I also had some concerns about the content of the Plains episode.  If you didn’t see it, you can watch it here.

The recent measles outbreaks in the United States have been the topic of much discussion lately.  While there is a great deal of finger pointing going on regarding vaccinations, I worry that a bigger issue is being ignored; in today’s noisy world, it is very difficult for the public to know what information is based on good science and what is not. The growth of the anti-vaccination movement is a good showcase of the issue, but the problem is much broader, spanning topics from climate change to dietary supplements.  It often seems that anyone with charisma and/or a loud voice can gain credibility and a following, especially if they are promoting a message that feeds people’s fears or tells them what they want to hear.  Cutthroat politics and a desire among media outlets for provocative stories both stoke the fire, and there is almost no way for the average citizen to sort truth from propaganda.

As a scientist who spends a lot of time and effort communicating about science, this is something I really struggle with.  I try really hard to present only the best information I can, and to distinguish between facts, assumptions, and opinions.  At the same time, I do have an agenda – I want to see prairies conserved, and I feel strongly that factors such as biodiversity, habitat heterogeneity, and ecological resilience are critically important.  While there is a lot of research that backs up those assumptions, I still have to acknowledge my biases, and I try to be careful not to pass off opinions as science.  It’s very difficult.

All of this is leads back to my main topic of this post; my disappointment in the Plains episode of EARTH A New Wild that aired on Public Television last week.  I was disappointed with the program because I thought it presented a very one-sided perspective on some ideas, and their promoter, Allan Savory, that are very complex and widely disputed. To be fair, the narrator of the series, M. Sanjayan, did mention that Savory and some of his theories are controversial, but not that numerous scientists and studies have actually contradicted those theories.  Instead, he appeared to endorse Savory’s ideas, and much of the episode explored how they could be applied in grasslands around the world.  I welcome any attention paid to prairie conservation issues, but I felt the Plains episode led people to believe that the strategies it advocated were better supported by science than they really are.

My intent with this blog post is not to discredit or disprove the theories and ideas promoted by Savory or the Plains episode.  Instead, I want to provide additional information that I hope will help round out some of the topics presented in the episode and facilitate a productive discussion among those who watched it.  The following are a few pieces of information I feel are important to be aware of as you consider the potential value and application of the ideas presented in last week’s show.

Controversy over Savory’s Big Ideas

  • Allan Savory gave a TED (Technology, Entertainment, Design) talk back in 2013 that gained a lot of attention because of its assertion that “planned grazing” was necessary to reverse desertification and climate change. In fact, he claimed that his method of intensive, concentrated grazing is the only viable solution to reverse those two processes.  The most specific rebuttal (among many) to that talk was published by five eminent grassland scientists in a Society for Range Management journal (Rangelands 35(5):72-74. 2013).  The rebuttal addresses each of the main claims made in the TED talk and refutes them.  Unfortunately, the article is not available online to those who don’t have a subscription allowing access to SRM publications.  A brief summary and links to some responses to the rebuttal are included at the end of this post if you’re interested.
  • There were many other critiques and rebuttals of Savory’s TED talk, including one by George Monbiot in The Guardian and another by James E. McWilliams in Slate.  Both echo many of the points made in the Rangelands rebuttal, and also provide links to other information, including numerous scientific studies that refute both Savory’s TED talk claims and the broader success of his Holistic Management grazing practices.  You can read a rebuttal to Monbiot on the website of the Savory Institute.
  • To be fair, it’s important to separate Savory’s “bolder” theories about desertification and climate change from his more moderate Holistic Management and planned grazing ideas, which have been incorporated by a segment of the ranching community across the world.  Among other things, Holistic Management encourages careful planning and monitoring, which is certainly positive, but its proponents also tend to promote the use of higher stocking rates than many rangeland scientists feel are sustainable.  The results of scientific studies evaluating the results of Holistic Management and planned grazing have been decidely mixed.  Some studies have supported Savory’s theories, but many others showed that planned grazing either didn’t deliver the promised benefits or performed less well than other grazing systems.   As is typical in the scientific process, more data needs to be collected and research projects need to be repeated to resolve the inconsistent findings so far.  In the meantime, however, it seems premature to conclude that Savory’s grazing strategies are obviously and significantly better than other options.
  • Allan Savory is vocal about his distaste for the use of fire for managing grasslands and excludes it from his land management recommendations. Coincidentally, there was no mention of fire in the entire Plains episode, despite it being one of the three major forces that control grassland ecosystems (along with grazing and drought).  An example of Savory’s thoughts on fire can be found in a quote from An Overview of Holistic Management and Holistic Decision Making from the Savory Institute’s website, which says that fire “pollutes the atmosphere and exposes soil contributing to desertification/climate change.”  Climate change and its contributing factors comprise a very complex web, and I sure can’t say that fire is not part of that web, but it’s also important to consider the way fire affects carbon in the atmosphere, a topic I covered in an earlier blog post.  Of course, fire can have both negative and positive consequences, as can any management tool, depending upon the way it is applied.  However, most people working in prairie conservation feel that prescribed fire is a very important tool, and there is abundant research that supports that view.  One synthesis of that research can be found here, and Chapter 4 (page 29) deals with central North America, in particular.

The Complex Issue of Prairie Dogs

  • During the segment on prairie dogs and black-footed ferrets, the Plains episode highlighted the ability of prairie dogs to increase the health of grasslands. They create habitat for other species by burrowing, and grazing/clipping of vegetation by prairie dogs can increase the forage quality of grassland areas.  All of that is true and important.  However, research also shows that prairie dogs can change the composition of a plant community in ways that lower forage quality and/or quantity available for livestock and other animals.  As a result, there is strong evidence that prairie dogs can compete with livestock for forage.
  • I was disappointed that the Plains episode focused only on the positive aspects of prairie dogs, especially because it also talked about (and showed) ranchers working to eradicate prairie dogs without really explaining why.  Balancing the ecological benefits of prairie dogs with the economic impacts they can have to ranchers is a key component of prairie conservation in North America.  It is a complex and multi-faceted issue that requires understanding and empathy on all sides if it is going to be resolved. Here are links to two recent research publications that highlight the complexities of the prairie dog issue.  The first is publicly accessible, but the second is only available to those who have journal access subscriptions.  Thank you to my friend Stephen Winter for providing these citations.

Both Savory and Sanjayan are charismatic speakers, and very effective salesmen.  The ideas presented in the Plains episode of EARTH A New Wild are attractive because they appeal to our romantic sense of balance in nature, and imply that we can play an important role in re-setting that balance.  I agree that large predators are key components of ecosystems, and that we should find ways to live with them when it’s possible, and attempt to replicate their role when it’s not.  However, I felt the Plains episode unnecessarily focused on a very narrow set of theories and proposals for grassland conservation; a set built upon widely and vigorously challenged assumptions.  I am very optimistic about our ability to conserve our grasslands and other ecosystems, but doing so will require robust and well-rounded conversations and a wide range of strategies.  As we continue those conversations, it will be imperative that we are upfront with each other about which strategic options are based on good science and which are not.

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Here are the main points from the rebuttal to Savory’s TED talk that was published in the journal Rangelands.  The rebuttal essentially focuses on Savory’s presentation piece by piece, including:

1) Pointing out the fallacy of Savory’s statements that all non-forested lands are degraded and that rangeland science fails to either understand the reasons for or to be able to mitigate that degradation;

2) Laying out the physical impossibilities of Savory’s claim that changing the way grasslands are managed could solve climate change;

3) Pointing out that photos were the primary evidence used to support Savory’s claims of restoring degraded grasslands and that several of the photos he used either had a different grazing history than Savory claimed or were from a completely different location than Savory stated.

4) Refuting Savory’s statements about the benefits of hoof action breaking up biological crusts in desert grasslands  to increase water infiltration by pointing to the well-studied ecological roles (protecting soil from wind erosion and carbon loss) played by those same crusts.

For those of you who do have access to the Rangelands journal, I hope you will read not only this rebuttal article, but also a response from Richard Teague and the subsequent response to that critique.  In addition to providing context around Savory’s climate change and desertification theories, the series of three short articles also provides an excellent synopsis of the many arguments among scientists trying to understand the complexities of grazing management.

 

 

Can Aphids Photosynthesize?

Well, no.  But recent research shows that at least some may be able to convert sunlight into energy in a process very similar to the way plants do it.

A study published in Nature magazine back in August looked at a species of aphid called Acyrthosiphon pisum, which changes color based on the air temperature around it.  At optimal temperatures, the aphid tends to be orange, but in cooler temperatures, the aphid is more often green.  Through a series of experiments, the scientists determined that – as in plants – the pigmentation of those aphids helped them generate energy, and that the green aphids made more of it than the orange ones.

Can aphids make their own energy?

As is usually the case, more research is needed to confirm exactly what’s going on, and to see if other aphid species have the same ability.  But these are pretty extraordinary results. The process of converting sunlight to energy is common in plants, of course, but insects and other animals don’t do that – or so we thought. 

What the aphids appear to be doing isn’t technically photosynthesis (no carbon dioxide is fixed and converted to organic compounds – I’m just telling you what I read…) but many of the essentials are there.  The scientists wonder if the ability helps the aphids survive when they don’t have quick access to food – such as when they’re traveling from one plant to another.

You can read a more complete description of the study here.

Evolution in Milkweed-Eating Insects

Not many insects can feed on milkweed.  Milkweed plants produce a toxin that disables a protein in animals – a protein that facilitates important functions such as muscle contraction.  Only a small number of insect species around the world have evolved ways to get around this challenge. 

A milkweed bug on swamp milkweed in the Platte River Prairies, Nebraska.

A new study published in the journal Science looked at 14 insect species that feed on milkweed and found that each had developed one of two ways to solve the milkweed toxin challenge.  Ten of the insect species had gone through a genetic mutation that changed the protein in a way that the prevented the toxin from being able to act on it.  The other four species had created a duplicate gene in the protein that allowed it to both carry out its normal function and alter itself to avoid being impacted by the toxin.  You can see a summary of the study and a link to the full article here.

What’s most fascinating is that while these insects are only very distantly related to each other (they spanned three different orders of insects) they ended up with the same solutions to the milkweed toxin issue.  It’s not like one insect species millions of years ago developed in a way that made it immune to milkweed toxin and then begat other species of insects that retained the same quality.  These insects each developed the immunity INDEPENDENTLY.  Fantastic.

The red milkweed beetle (left) and the monarch butterfly caterpillar (right) are not closely related insects. However, both have independently evolved the same ability to feed on milkweed plants without ill effects.

Now, I have to be careful when talking about evolution because it’s easy to give the impression that these insects did something purposeful to change their bodies – they didn’t.  They changed because natural selection favored individuals with certain genetic mutations that allowed them to eat milkweed without suffering changes to essential proteins.  Unfortunately, evolution can be a hot-button topic these days, and one of the biggest reasons is that many people have a fundamental misunderstanding of how evolution actually works.  If you’re interested, here is a link to website with a very brief but clear explanation of the process.

In the case of milkweed-eating insects, it’s easy to see that being able to eat a plant that competing herbivores can’t eat is a major advantage.  Somewhere in history, a few lucky individuals ended up with a random genetic mutation that allowed them to eat milkweed without ill effects.  Those individuals got a sudden leg up on their competition and, as a result, were more likely to survive and reproduce.  What’s crazy and fun in this case is that multiple unrelated species ended up with similar genetic mutations of their proteins.  They each accidentally “found” the same path to success.  It’s a great world we live in.