A Milestone for Prairie Restoration

Because conservation work can sometimes seem like blowing into the wind, it’s important to pause periodically to celebrate progress.  For example, I am really excited about what has been accomplished in the field of prairie restoration.  We’ve known for a while that we can convert cropland to prairie vegetation with a high diversity of plant species (150 or more species per planting), and that we can do that on a scale of thousands of acres.  The Nature Conservancy has large projects in states like Indiana, Illinois, and Minnesota where restored prairie landscapes now range from about 5,000 to 20,000 acres in size.  The U.S. Forest Service is transforming an old U.S. Army Arsenal into 20,000 acres of prairie in Illinois.  Prairie Plains Resource Institute, the organization that pioneered restoration techniques in Nebraska, is planting up to 1000 acres a year now and has established well over 10,000 acres total across the state.

Our staff celebrates a successful year of seed harvest back in 2015.

Our staff celebrates a successful year of seed harvest back in 2015.

Here in our Platte River Prairies, we’ve restored more than 1,500 acres of cropland to prairie.  That’s not insignificant, but more importantly, we’ve been testing the idea that those restored prairies can help defragment the ecological landscape around them.  Habitat fragmentation is one of the largest threats to today’s prairies because it shrinks and isolates populations of species, making them vulnerable to becoming locally extinct without the chance of recolonization from nearby sites.  The real promise of prairie restoration is that it can enlarge and reconnect scattered remnants of native prairie, providing populations of animals and plants a much better opportunity to survive and thrive.  It’s not feasible or desirable to convert the majority of cropland in the central North America back to prairie, but there are particular sites where strategic restoration work could make a huge difference in the potential survival of prairie species and ecological services.

In order for prairie restoration to help defragment landscapes, restored prairies have to provide suitable habitat for the species living in small isolated prairies.  Many bees and other insects specialize on certain plant species, for example, and other animals rely upon an abundance of prey, a diversity of seeds, or other particular food or habitat conditions.  Satisfying the individual needs of all those prairie animals is a critical measure of success if prairie restoration is going to successfully stitch isolated prairies back together.

Over the last several years, we’ve been collecting data to see whether the species of bees, small mammals, grasshoppers, and ants in our unplowed prairie remnants have moved into adjacent restored habitat.  The results have been very positive.  While not every species of animal living in our remnant prairies has been found in nearby restored habitat, we’ve found the vast majority of those we’ve looked for.  We suspect that most of the remaining species are also present but that our limited sampling effort just hasn’t yet picked them up.  We’ll keep trying.

Dillon Blankenship, a Hubbard Fellow, compared grasshopper, katydid, and tree cricket communities on three pairs of remnant/restored prairies back in 2014. Almost all species were present in both restored and remnant habitats. In the three species that weren't, only one or a very few individuals were found, so it's likely just a sample size issue.

Dillon Blankenship, a Hubbard Fellow, sampled grasshopper, katydid, and tree cricket communities on three pairs of remnant/restored prairies back in 2014. Almost all species were present in both restored and remnant habitats. In the three species that weren’t, only one or a very few individuals were found, so it’s likely just a sample size issue.

Data from James Trager and Kristine Nemec has helped us compare ant species composition in restored versus restored prairies along the Platte River. So far, we've documented 30 species and only one has been found exclusively in remnant prairie (and, again, it's likely to be a sample size issue).

Data from James Trager and Kristine Nemec has helped us compare ant species composition in restored versus restored prairies along the Platte River. So far, we’ve documented 30 species and only one has been found exclusively in remnant prairie (and, again, it’s likely to be a sample size issue).

Master Naturalist Mike Schrad and Hubbard Fellow Jasmine Cutter have both helped us compare small mammal populations between restored and remnant prairies. This table shows some of Jasmine's data from one site. In general, we're finding that the same species are in both restored and remnant prairies, but the relative abundance of those species is often different - with some apparently favoring remnant habitat and others favoring restored areas.

Master Naturalist Mike Schrad and Hubbard Fellow Jasmine Cutter have both helped us compare small mammal populations between restored and remnant prairies. This table is from Jasmine’s data from one site, showing the number of trapsites in which each mammal species was caught back in 2014. In general, we’re finding that the same species are in both restored and remnant prairies, but the relative abundance of those species is often different – with some apparently favoring remnant habitat and others favoring restored areas.  We’re now looking at how our management affects presence and abundance of each species through time.

We've had several research projects look at native bees in our prairies. Mike Arduser, Anne Stine (Hubbard Fellow), Bethany Teeter, and Shelly Wiggam Rickets have all helped us compare restored and remnant prairies. So far, we've found over 72 species and the vast majority have been in both remnant and restored prairie.

We’ve had several research projects look at native bees in our prairies. Mike Arduser, Anne Stine (Hubbard Fellow), Bethany Teeters, and Shelly Wiggam Rickets have all helped us compare restored and remnant prairies. So far, we’ve found over 72 species and the vast majority have been in both remnant and restored prairie.

I've collected more than 15 years of data showing that plant diversity and the frequency of occurrence of prairie plant species has remained stable through time. These four graphs show four species in one restored prairie where we're comparing fire/grazing management to fire only management.

I’ve collected more than 15 years of data showing that plant diversity and the frequency of occurrence of prairie plant species has remained stable through time. These four graphs show four species in one restored prairie where we’re comparing fire/grazing management to fire only management.  The long-term persistence of prairie plants and diverse plant communities is critically important for plant communities, but also for the success of efforts to defragment habitat for animals.

These results mean that where prairie landscapes have been largely converted to row crops, we don’t have to just watch while insect or small mammal populations careen toward local extinction in tiny isolated prairies.  We’ve shown that we can make those prairies larger and more connected, and that animal populations can grow and use new restored habitat and diverse plant communities.  We’ve also shown that restored prairies can sustain their biological diversity for decades, even through periods of intensive grazing and drought.  While there are still plenty of questions and potential improvements we can make, we’re now at the point where society needs to decide whether and where to do this kind of restoration.

I don’t know about you, but I think that’s pretty exciting!

Nebraska and other states in central North America have large swaths of productive and important cropland.  As I said earlier, I’m not advocating that we convert most of that back to prairie.  However, there are specific sites where row crop agriculture is marginally productive/profitable and the long-term interests of both society and local landowners might be best served by putting land back into diverse and productive grassland.  Agricultural policies and subsidy programs will obviously play a huge role in this kind of strategic large-scale restoration, and getting the policies in place to facilitate this kind of common sense restoration will be plenty difficult.  That’s nothing new, however.  What’s new is our confidence that if we can implement targeted restoration work, it can make a real difference to prairie conservation.

Restoring the viability of prairies in fragmented landscapes is critically important to prairie conservation success.  The challenges of conserving species in small isolated prairies are immense, and many of those prairies will continue to see declines in biological diversity and ecological function over time unless we can make them bigger and more connected with other prairies.  Helping to document our ability to do that – at least for many prairie species – has been one of the most satisfying things I’ve done during my career.

 

Important footnote:  Restored prairies are not the same as remnant unplowed prairies.  Soil organic matter levels, for example, can take many decades to recover from tillage, and relationships between plant and microbial communities may take just as long to become reestablished.  Our success in prairie restoration should definitely not be used as justification for plowing up remnant prairie!  However, it’s equally true that prairie restoration efforts aren’t failures just because they can’t create an exact replica of prairie as it existed before it was converted to farmland.  If defragmenting prairie landscapes is the primary goal of restoration, we just need to create restored prairies that complement – not copy – remnant prairies. 

 

Saving Pollinators One Thistle at a Time

Pollinator populations are in trouble for a lot of reasons.  Loss and degradation of habitat, pesticides, and diseases are all major contributors.  However, at least in the Central United States, much of the pollinator decline can be tied to spiny pink/purple-flowered plants and the way humans react to them.

Tall thistle, a native annual wildflower, is a big favorite among pollinator insects.

Tall thistle, a native annual wildflower, is a big favorite among pollinator insects.  However, it is seen by many people as a weed that needs to be eliminated from the earth.

On the face of it, thistles seem like they’d be pretty well-liked.  Thistle seeds are a major food source for birds and other wildlife, as well as for a variety of invertebrates. The abundant nectar and pollen found in thistle flowers make them one of the most popular plants among both pollinator and non-pollinator invertebrates.  As if that wasn’t enough, most thistles have large and/or abundant blossoms, which you’d think would make them very attractive to people.  Sure, they’ve got spines, but so do cacti, yucca, and many other plants gardeners love to landscape with.  So why do we hate thistles so much?

The cultural dislike of thistles is not at all a new phenomenon; references to the unpopularity of thistles can be found at least as far back as the Book of Genesis in the Bible.  There, thistles are mentioned when God curses Adam after he eats the forbidden fruit. Genesis 3:17-18 – “Cursed is the ground because of you… Both thorns and thistles it shall grow for you…”  Clearly, if God includes thistles as part of His curse on all humanity, they are not a crowd favorite.

Regardless of why thistles are so widely disliked, our contempt for them causes serious problems for pollinators.  This happens in two ways: 1) direct destruction of an important floral resource for pollinators, and 2) major side effects associated with #1.

Because thistles are so important to pollinators, our compulsion to destroy them is a major problem.  Sure, some thistle species are invasive and can cause enough ecological damage that their control is warranted.  Most thistle species, however, are targeted for destruction purely because they are thistles.  Many of those are native wildflower species and are not at all aggressive or problematic.  Regardless, there are few places where thistles are tolerated, let alone encouraged.  The result is the loss of a big source of food for many pollinators.

Musk thistles and regal fritillaries (before we chopped them because they are designated as noxious weeds and we are legally obligated to eradicate them.) The Nature Conservancy's Platte River Prairies, Nebraska.

Musk thistles and regal fritillaries.  Musk thistles are designated as noxious weeds and we are legally obligated to eradicate them.) The Nature Conservancy’s Platte River Prairies, Nebraska.

While the loss of thistles themselves is a big problem for pollinators, the methods we use to eliminate them can have much bigger impacts.  If we were content to dig thistles out of the ground one by one, things wouldn’t be so bad.  Of course, that’s not always feasible – some perennial species such as Canada thistle are rhizomatous and can’t be killed by digging.  Herbicide use is the other available option.  Spot spraying individual plants or clumps can be relatively innocuous, but only if the person spraying is judicious and selective about what they spray.

However, working thistles one by one takes a lot of time, and just because we hate thistles doesn’t mean we want to spend a lot of time getting rid of them.  Broadcast herbicide spraying, by airplane or boom sprayer, can kill lots of thistles in very short order.  It’s a great way to get rid of all those unsightly pink flowers in one fell swoop…at least for that season.  Unfortunately, broadcast spraying also kills a wide array of other wildflowers, and most of those never recover (the ones that do are the ones we tend to like least – like ragweeds).

The grand irony is that because broadcast spraying kills so many non-target plant species, the spaces left open by those dead wildflowers are usually colonized by thistles.  Thus, while broadcast spraying is quick, it tends to perpetuate thistle populations by destroying their competitors.  (Also, most large thistle populations are there because of chronic overgrazing or some other major disturbance that weakens perennial vegetation and creates space for thistles to grow.  Broadcast spraying doesn’t address those underlying issues.)  Oh, and by the way, killing off all the wildflowers in a pasture or roadside also wipes out the pollinators that depend upon them for food.

Our cultural dislike of thistles leads us to kill off as many as we can each year.  Since thistles are a major food source for pollinators, that’s grave news for pollinator conservation.  Our desire for more “efficient” ways to kill thistles has led to even worse news, however – the loss of plant diversity across millions of acres.  Since plant diversity sustains pollinators by providing varied and consistent food through the season, losing that diversity at a large scale is devastating.  We can rebuild some of what we’ve lost through restoration, and we can save what’s left, but only if we change the way we think about thistles.  We’d better hurry; pollinator declines are not slowing down.

I think we need a thistle fan club.  Who’s with me??  Let’s do this thing.  I’ve come up with a basic logo and tag line (below) to get us started.  Click here to get an easily printable version you can hang on your office door or tape to your car window.  It’ll be a great conversation starter!  In fact, let’s have fun with this.  If you feel like it, take a picture of how you displayed the logo and put it on your favorite social media with the hashtag #thistlehelp.  Not a social media person?  Feel free to email me a photo – maybe I’ll collect some of them and use them in a future post.  If you email me, please keep the file size below 1 mb…   Use this email address: chelzer(at)tnc.org.

The bees and butterflies of the world are depending on you.  This is going to sweep the nation, you’ll see!

ThistleFanClub