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.
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.
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.
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.
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.
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
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.
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.
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.
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.
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!!
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.
Your photos are wonderful, Chris. Thanks for your blog, it is very interesting and well written.
Yes, this is so interesting and you write about in such a friendly way. Thanks!
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Hey Chris, love the blog. I read it often. I’m researching sand dune restoration in oak savanna/prairie communities and the literature seems to lean heavily on coastal (fresh or salt water) dunes. You mentioned above that you’ve tried to restore sand dunes (though a bit unsuccessfully perhaps). Do you have any literature or resources you could share that you leaned on to guide this work?
Thanks Kris, we’ve had good success with restoring sand ridges in our cropland restoration work. We create wetlands with big scrapers, creating swales that intersect with groundwater. We turn the sandy spoil piles in to long ridges that mimic the alluvial topography in nearby remnants. We plant those with sandy habitat species and they establish well, especially if we bury the top soil at the bottom of those ridges, rather than topdressing them. We’ve also had excellent luck with a project in which we converted farmed sand dunes back into high diversity prairie. Shoot me an email if you have more questions. Not sure of any literature that would be of help to you. chelzer(AT)tnc.org
Hi Chris, I was reviewing this note and have a question about mosses and lichens that I notice extensively over the Namekagon Barrens Wildlife Area in northwestern Wisconsin. It seems odd to see moss on such sandy soil as the Northwest Sands of northwestern Wisconsin? It would seem you need more moisture to find the moss and lichens covering the bare soil between the other plants?
Therefore, does the presence of moss and lichens ? prevent the dunes from developing, ie dunes shaped by winds????
It just seems contradictory to have such extensive layer of moss and lichens on a ‘Barrens’ type habitat???
Hi Mark, I’ve seen moss growing in dry sandy prairies here too. I’m not even close to an expert on mosses and their various habitats, so I won’t try to guess much about them, but I’m sure that like flowering plants, mosses have a wide variety of habitat associations between species. Sedges are similar – people tend to associate them with wetlands, but our upland sandy habitats have a number of abundant and really important dry habitat sedges. I don’t have any idea whether moss and lichens play much role in dune development. I’d be surprised – I think belowground root biomass is the biggest factor that prevents vegetated dunes from blowing. That’s based on some excellent research at the University of Nebraska. https://digitalcommons.unl.edu/natresdiss/123/