In Defense of Erosion

The Nebraska Sandhills region consists of about 12 million acres of sand dunes with a thin layer of vegetation draped across them.  That vegetation has come and gone over the last several thousand years, as long-term climatic patterns have shifted from wet to dry and back.  We are in a relatively wet period (geologically speaking) today, and grassland is clinging to the hills.  For now.

Except where it can’t.  Here and there, throughout the sandhills, particularly on steep hills, sand breaks through.  Most of the time, blowouts are triggered by a combination of topography and some kind of physical disturbance.  A two track road or cattle trail up a steep slope, for example, or a favorite hangout of livestock.  Just as with frayed fabric, once a small hole in the vegetation starts, it tends to spread.  Most Sandhills ranchers see blowouts as a great risk to their livelihood and work hard to prevent them, or to heal them once they start.  Those ranchers are encouraged in that view by watchful neighbors and a long history of agencies and university extension staff warning of the dire impacts of wind-induced soil erosion.

Sandh

Small blowouts dot the steeper hills in the background and a couple larger ones appear in the foreground.  Overall, these make up a tiny percentage of the landscape, but many ranchers see them almost as badges of shame.

big

A very large blowout like this can cause not only a loss of forage for a rancher’s livestock, but also a huge challenge for fence maintenance.

The Sandhills is ranch country, and all but a tiny fraction is privately-owned and managed for livestock production.  Most ranchers are conservative with livestock numbers and grazing strategies, trying to preserve that thin fabric of grass that feeds their livestock, and thus their families.

While there are certainly places that are prone to wind erosion and practices that can accelerate it, the risk of blowout creation and spread has also become a kind of mythology.  In much of the Sandhills, blowouts are actually difficult to create (we’ve tried) and the percentage of a ranch that could potentially be covered by blowouts is very small.

wet

Sometimes, wind erosion digs a blowout deep enough that it intersects groundwater, creating wetlands.

While conservative grazing has helped maintain healthy prairies in the Sandhills, it has also led to a loss of open sand habitat for a group of plant and animal species that depend upon blowouts and similar areas.  Those species are important, but asking a rancher to allow, let alone encourage a blowout, is much like asking a business man to go to work wearing Bermuda shorts with his sport coat.  The peer pressure and social norms associated with blowouts can be more influential than any potential loss of livestock forage they might cause.  Just as farmers judge their neighbors by the weeds in their fields, Sandhills ranchers judge their neighbors by the blowouts in their pastures.

blow

Blowout grass (Redfieldia flexuosa) is one of a select group of plants that can colonize a blowout and begin to stabilize the sand.

penstemon

Blowout penstemon (Penstemon haydenii) is a federally listed endangered plant that is found exclusively in blowout habitats.  This one is in a blowout that is healing and might not support penstemon populations much longer.

tiger beetle

Many species of tiger beetles can be found in Sandhills blowouts, including several of conservation concern.  These impressive predators hunt small insects in patches of open sand.

lesser earless lizard

Lizards, including this lesser earless lizard and other species, are often seen in and around blowouts, where they can forage in open areas but retreat quickly to cover to escape predation.

Regardless of the social or economic ramifications of blowouts for ranchers, bare sand patches really are important habitats for many prairie species.  The discussions I’ve had with ranchers about the ecological values of blowouts have always been polite, but I can’t say they’ve been met with great enthusiasm.  I understand that, but that doesn’t change the need to continue having those discussions.

spider

Spiderwort (Tradescantia occidentalis) grows on the edge of a large blowout, surrounded by bare sand and a cast of other plants struggling to survive in the shifting substrate.

It may be that changing climate will render moot our discussions about whether or not to allow or encourage blowouts in the Sandhills.  Eventually, we will experience enough consecutive years of hot dry weather that even the most conservative grazing won’t prevent widespread blowing sand once again.  We can’t predict whether those conditions will arrive in the next few years, or not for many decades.  When they do arrive, both the ecological and human communities of the Sandhills will be glad to have species that are well adapted to open sand.  Plants like blowout penstemon and blowout grass, for example, can help restabilize areas of bare sand, and they also provide food for both livestock and wildlife.

For now, the Sandhills provides a vibrant grassland that supports both humans and wildlife.  That will likely change at some point in the future.  Hopefully, blowout-dependent species will find enough habitat to maintain their populations until we really need them.

…and hopefully no one will feel like they have to wear Bermuda shorts in order to make that happen.

Advertisements

About Chris Helzer

Chris Helzer is the Director of Science for The Nature Conservancy in Nebraska. His main role is to evaluate and capture lessons from the Conservancy’s land management and restoration work and then share those lessons with other landowners – both private and public. In addition, Chris works to raise awareness about the importance of prairies and their conservation through his writing, photography, and presentations to various groups. Chris is also the author of "The Ecology and Management of Prairies in the Central United States", published by the University of Iowa Press. He lives in Aurora, Nebraska with his wife Kim and their children.
This entry was posted in Prairie Management, Prairie Natural History, Prairie Photography and tagged , , , , , , , , , , . Bookmark the permalink.

10 Responses to In Defense of Erosion

  1. marknupen says:

    I am curious if subtle chemical changes in the sand can diminish vegetation or regeneration instead of a wind blowout explanation. Not sure why chemical changes can occur but have been curious if wind alone is the answer for these “blowouts”, which occasionaly see here in the Northwestern Wisconsin Barrens Sands

    • Chris Helzer says:

      Hi Mark, I can’t think of any chemical changes that might happen and that would influence erosion. That doesn’t mean there isn’t something I don’t know about, though.

    • James McGee says:

      The Chinese have been battling desertification for a long time. As Chris mentions, wind is an important factor and much of the effort to reverse desertification is put toward blocking wind so vegetation can get established. The wind not only causes the sand to move, but it also dries the sand out much faster. The chemical changes Mark asks about would probably be most applicable when considering the loss of water retaining organic matter. An interesting thought regarding the creation of blowouts is grazers may gather at these naturally windy locations on hot days because the wind helps cool them. I will leave it to Chris’ readers to determine if there is any fact to my speculation. I know masses of people have caused damage to dunes while traveling to cool off in the waters of Lake Michigan.

  2. Paul says:

    Chris, do you think high severity and LARGE fires in the past may have had a positive role in creating some sandy habitat diversity? My initial guess would be not – – if you have tried to create such areas and failed. I am curious about your thoughts.

    • Chris Helzer says:

      Hi Paul, I’m sure fire was a factor, but I really think long-term severe drought was the biggest factor that drove open sand at a large scale. The combination of drought stress/mortality on plants and hoof action from large animal herds probably opened up holes in the vegetation pretty well at times. And steep hills were probably the first to open up.

      • Paul says:

        Thank you Chris! That makes perfect sense, and times of extreme drought might have also been times or more extreme fire as well. We need time machines!!

      • James McGee says:

        Have you considered the possibility that the difficulty in forming blowouts is not due to a lack of enough grazing, but to the presence of the grazers themselves? “On the Biology of the Sand Areas of Illinois”, Volume 7, Issue 7, pp. 164 states, “In fields that have been pastured, there is frequently a black crust an inch or so deep formed over the surface, probably by the decay of grass and leaves trampled into the sand by cattle. In dry weather this crust is quite hard and effectually checks the shifting of the sand.” However, this publication then goes on to state, “It is also said that cattle may destroy vegetation, and that blowouts may be started in this way.” It seems possible that cattle trampling initiates the conditions which would allow a blowout to be created, but the processes in which cattle return organic matter to the soil prevents blowouts from actually forming in all but the least used areas.

  3. Ann Horsman says:

    Your photos are wonderful, Chris. Thanks for your blog, it is very interesting and well written.

  4. Louise says:

    Yes, this is so interesting and you write about in such a friendly way. Thanks!

  5. Pingback: That Predator Just Killed My Predator! | The Prairie Ecologist

PLEASE COMMENT ON THIS POST!

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s