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.

Photo of the Week – January 23, 2015

There are a few subjects I can’t seem to keep from photographing.  Milkweed seeds, for example.  Patterns of ice on frozen wetlands.  Dew-covered insects.  And sunflowers.

What flower is more distinctive?  Their bright yellow color and big round flowers stand out, even in the most showy of flowery prairies.  Insects seem to find stiff sunflower attractive too, based on the number of insects I’ve found and photographed on them.

Plains sunflower (Helianthus petiolaris) in restored sand prairie.  The Nature Conservancy's Platte River Prairies, Nebraska.

Plains sunflower (Helianthus petiolaris) in restored sand prairie. The Nature Conservancy’s Platte River Prairies, Nebraska.

We’re fortunate to have seven different species of sunflower in our Platte River Prairies, five of which are perennials.  The above photo is of one of the two annuals, plains sunflower, which inhabits the drier sandy uplands of our sites and is very abundant in the Nebraska Sandhills to our north.

I have plenty of sunflower photos I like, but this is one of my favorites from last year.  I like the overall composition, but I also like that the sunflower in the foreground is atypical.  Something has prevented the petals (ray florets, for you botanists) from developing completely.  It’s interesting (and not unattractive), and also stimulates questions about what happened, and why.

I like mysteries…