Drought Returns to the Platte River Prairies

Here’s an aerial view of the Platte River and some of our prairies adjacent to it. Rainfall has been scarce upstream from us and river water levels have been dropping.

It’s been a while since our Platte River Prairies have seen drought. We had about six years of drought from late 1999 through 2006 and a one year extreme drought in 2012 that tapered off over the next year or so. We’ve had some dry periods since, but nothing severe or extended. The recent wet years have been productive, both from an agricultural and ecological standpoint, but here in the Great Plains, we know that drought can reappear at any time.

We started the 2020 growing season with flooding, but since mid-June, the Platte River Prairies have been drying out. The most recent drought maps show our sites right on the border between moderate and severe drought. To the east of us, much of the central tallgrass prairie region is in the same boat (which is maybe not the best metaphor when talking about drought).

Current drought map from the University of Nebraska-Lincoln Drought Mitigation Center.
Photographed a couple weeks ago, this purple prairie clover was maintaining its vibrant green color, but most of its neighbors had given up on the year and gone dormant because of the dry conditions.
This aerial photo shows how alluvial soil patterns really pop during drought. The soil beneath most of our prairies was laid down by ancient river flows. The browner strips in the above photo are where soil is characterized by especially shallow organic matter layers over sand. The greener areas have somewhat more organic matter, which helps hold and make moisture available to plants when rain becomes scarce. The patterns are particularly strong in formerly cropped areas (such as in the bottom right of the photo) where topsoil was depleted by farming before the site was restored to prairie vegetation.
In this photo, you can see vegetation response to alluvial soil patterns on the ground. Plants have gone dormant in less productive soils but are still green where there is a thicker layer of topsoil above the sand.

Drought makes life hard for people who rely on the vegetative production of prairies for their livelihood. Savvy ranchers have to incorporate drought into their ranch management plans, often including ‘trigger points’ that help them decide when to start cutting herd numbers in response to rainfall amounts by certain dates on the calendar. Economic survival relies on the ability to bank both money and prairie plant vigor during years of abundant rainfall in order to stay afloat (see, there I go again) during dry years. Inexperienced ranchers can get into trouble by ‘utilizing’ all the available grass in a wet year and then having no root reserves beneath the prairie when drought hits.

The economic impacts of drought are real and important, and they affect prairies as well as people. Across most of the Great Plains, most of the grasslands that still exist have survived (haven’t been turned to row crops or other human uses) because they can produce enough forage to support a ranching operation. More than 97 percent of Nebraska is privately owned, and most of those owners need income from the land so they can pay taxes and put food on the table. In landscapes like the Nebraska Sandhills, the survival of prairies and the survival of ranchers are inextricably linked.

As the soil dries, it becomes quickly apparent which plant species are well adapted to those conditions. Here, entire-leaf rosinweed (Silphium integrifolium) blooms while surrounded by dormant grasses and other brown vegetation.

From a purely ecological perspective, however, drought is not a serious threat to prairies. In fact, drought is one of the three main factors (the others are fire and grazing) that created and maintain prairie. Any prairie plant or animal species that has persisted for thousands of years has done so because of adaptations to drought. Those species can respond by changing their behavior, growth and reproductive rates, and other strategies. Populations of some species will decrease during droughts, but others thrive – often because of the lower competition from waning species.

This restored cropfield (former cropland) has green/brown patterns formed by alluvial soil patterns. However, the greenest strips are where we restored wetland/wet meadow habitat by re-excavating old swales before planting prairie vegetation. By digging those areas down closer to groundwater, we helped ensure that even during drought, there will be green vegetation and moist soil available for the species that rely on them. (The yellow in the photo is from Maximilian and sawtooth sunflowers.)

As a result, prairie communities look very different under drought conditions than when rainfall is plentiful. Plant species that were uncommon become abundant and others fade from dominance. Invertebrates and other animals respond accordingly. The populations of some animals decrease as their food source diminishes or habitat conditions become less favorable. Others simply change their diets to match the altered abundance of the prey or forage species available to them.

While prairies can look very different during drought, the resilience of prairies means the basic ecological functions and services are sustained. Plant production still feeds herbivores and those herbivores are available for the predators that consume them. Pollination still occurs, seeds are produced and dispersed, and carbon is pulled from the atmosphere. Life goes on.

This and the other aerial photos in this post were taken last week. The big green band through the middle of this photo is a riparian area where we converted a sandpit lake (from a sand and gravel mining operation) to a stream with adjacent wetlands. Through all the droughts over the last 20 years, this stream has continued to flow, providing important refuge for aquatic species and terrestrial animals that need access to water.

As this drought ramps up, there’s no way to know how long it will hang around. I feel for the ranchers and farmers who are going to have to dip into their reserves (financial and ecological) for a while. I hope they can make it through this drought, not only for their own sake, but also for the sake of the prairies they protect and care for. I don’t worry too much about the wildflowers, insects, birds, or other species living in the prairies, however, especially those living in relatively large and/or interconnected grasslands with diverse plant and animal communities. They’ve been through this before. You might say they’ve had thousands of years to either sink or swim (ok, that time I did it on purpose) during periods of drought.

If you’re interested in learning more about the resilience of prairies and the way they can respond to drought, here are links to a couple posts I’ve written previously.

The ‘Bench Strength’ of prairies in relation to climate change.

How to build and maintain the ecological resilience of prairies.

Prairie plants have deep roots, but not for the reasons we’ve always thought.

This entry was posted in Uncategorized by Chris Helzer. Bookmark the permalink.

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.

19 thoughts on “Drought Returns to the Platte River Prairies

  1. As an Ohio prairie expert, who first saw real prairies along the Niobrara River in Nebraska, on a college (Bowling Green State University) summer ecology study course in 1971, I noted with appropriate interest in this story that three ecological factors maintain the prairies in the region: grazing (originally by bison, elk, etc.), fire (both lightning-induced and anthropogenic), and drought.

    I work in prairies at the eastern edge of the Prairie Peninsula (now, the Corn Belt), in north central Ohio. Wonderfully, I’m restoring up to 3000 acres of native tallgrass prairie at NASA’s Plum Brook Station in Erie County, near Sandusky, Ohio. NASA fully supports this long-term, on-going project. About half the area of this 10 sq mile facility, a major aerospace test facility, a former WWII ordnance works, was originally a part of the Firelands Prairie. But most of it became overgrown with both woody brush and deciduous forest.

    How, then, to restore the original native tallgrass prairie? Only one method could work: prescribed fire. Fortunately, the NASA people learned, understood, and applied the principals of fire ecology in tallgrass prairies. I got hired by NASA because I am an Ohio Certified Prescribed Fire Manager, authorized by the state to conduct prescribed fires. NASA Plum Brook Station prairies are now reappearing. Several thought to be lost species have regrown.

    Nonetheless, I’m still called into account by outsiders for “those destructive fires” I set. In most cases, after they learn that prairie fires are natural, essential mechanisms for their maintenance, all is well.

    Now, to the point. Out here in humid Ohio, it’s been hard to explain why tallgrass prairies should persist here (40″ of annual precipitation). On the High Plains, as noted in this article, drought plays an important role in suppressing woodies and selecting for drought-adapted herbaceous plants. But here, drought is never a vegetation-controlling factor on our woist prairies. In presettlement times, we had deer and elk which grazed the prairies and browsed the woodies. But our prairies persisted only because Native Americans deliberately and intelligently burned them each year; to herd game to effective killing points (“flame hunting”) and to keep the landscape open for easy ambulation (not possible through 6-ft woody brush).

    So, here, drought was never a prairie-controlling factor. I have to keep reminding locals of that. They think the prescribed fires are “unnatural,” shouldn’t be allowed — until they see the resulting high-quality prairies that result.

    Drought as a prairie factor in Ohio? Nope. Just fire.

    • Thanks for the response, John. It’s interesting, isn’t it, to talk to people about whether ecosystems are ‘natural’ when they are a product of hundreds or thousands of years of human management? Regardless, I take your point about the eastern edge of the prairie being very different than Great Plains prairies in terms of the influence of drought. The UNL drought mitigation center maps currently show drought extending through most of the eastern tallgrass prairie, including portions of Ohio. Do you think those droughts really had zero influence or just a reduced degree of influence compared to fire in those eastern sites? It seems like the two could have been connected in terms of droughts (even mild ones) and their impact on fire intensity? Thanks again for the thoughtful comment.

      • I must be careful. Yes, the eastern Corn Belt (Prairie Peninsula), in this regard in Indiana and Ohio, certainly has summer droughts. And they do, to small degree affect upland plant communities, both forests and prairies.

        But, have those infrequent drought periods actually controlled the invasion of woody species (shrubs and trees) into these eastern prairies? I’ve studied all of the existing historical data (settlers’ accounts, survey records, etc.) and the extensive ecological work that has tried to account for the persistence of prairies here in the east. No evidence that in recent millennia drought has been a factor.

        Interestingly, Dr. Edgar Nelson Transeau, at Ohio State University first examined the evidence for a drought factor in the 1930s. He did find that precipitation in the Prairie Peninsula (from eastern Nebraska east to central Ohio) was indeed less than in areas to the north and to the south. https://esajournals.onlinelibrary.wiley.com/doi/10.2307/1930078

        But that big paper, for half a century, erroneously guided the management of Buckeye State prairies. Until the 1970s and 80s drought was thought to be the sole controlling agent here, and that fire in prairies was merely incidentally curious; certainly not “natural.”

        But I and my Ohio prairie colleagues were able to show conclusively that absent fire, virtually every Ohio prairie, even those on very sandy xeric sites, would eventually succeed to woody vegetation. Today, the Ohio EPA allows prescribed prairie fires, and across the state prairies are being pyrogenically restored.

        But, no, drought here, even in years like 1988, when we had a very severe, summer-long drought, does not much affect our prairie plants. They are better adapted to droughts than our woody plants. In 1988, when everything else was curling up into heated, dry oblivion, our prairies were virtually unaffected. A tiny reduction in biomass production, and reduced seed growth. But the prairies remained green throughout the summer and fall. Deep roots into ample subsurface moisture.

        So, no. Droughts in the eastern portions of the Prairie Peninsula have simply never been long enough or severe enough to suppress woody plant invasion and capture of our otherwise small prairie islands. Anthropogenic fire, for millennia (as revealed in archeological records) maintained the eastern prairies since the end of the Xerothermic Interval, about 8000 years ago. https://ohioplants.org/prairie/

        It should be noted that native prairies in Indiana, Illinois, and Iowa, too, get invaded and taken over by woody vegetation if left unfired for decades. It just takes longer. In Ohio, because of our ample precipitation, woodies begin to take over in just five years or so of fire absence.

        • The only situation where your argument seems to break down is when prairies are burned regularly, but still have brush encroaching on them. I completely agree fire is an important factor in maintaining prairies. However, moisture is important too. Some example of prairies that have persisted in otherwise forested landscapes include alvar, gravel kames, marl deposits, serpentine deposits, and along the Great Lakes shoreline. During a drought year, I have seen the waist high thicket of cottonwood saplings eliminated in dry-gravel areas leaving only the prairie plants and tenacious non-native invasive species, like Siberian elm. A change in precipitation and/or humidity can be enough to shift the community one way or another. Without days with low humidity fire could not occur.

          • “Without days with low humidity fire could not occur.”

            In fact, I’ve very successfully burned Ohio prairies in periods of nearly 100% humidity. Humidity is not the controlling factor; it’s fuel moisture content. That’s why we don’t burn during the growing season. Plant tissues are saturated with water, can’t support a fire. Most of our fires are in March or April, following two or three days of 50-degree weather. That sufficiently dries the stems and leaves of the prairie vegetation, allowing fires hot enough to consume it. It also allows the fires to burn hot enough to destroy the meristem (growth) tissues in seedling or small woody plants. Their above-ground tissues are killed. Consequent re-growth is weak and in the weakening shadow of the fast-growing prairie plants.

          • In the Chicago Area, they don’t even bother getting the volunteers together unless the humidity is 50 % or lower. Of course, temperature and wind are also big factors. When it gets colder and wind speeds are down the humidity has to be even lower. Even with these conditions, I’ve gone to burns and the fire would not carry. Some seasons we have been lucky to get even a few days of marginal burning. Other years, they burn for weeks straight until they need to take a day or two off to rest.

            I know that tall-warm-season grasses burn more easily. If those are being burned, then you can get away with fire conditions that are not as favorable. Still, I think getting fire to carry during “periods of nearly 100 % humidity” is a stretch.

            When humidity is very low, the previous year/s buildup of fuel can be burned during the growing season. However, they don’t do that intentionally in the Chicago Area because it hurts the conservative plants to the benefit of short-lived species and invaders. It does happen occasionally, but only because there are a lot of people now and many are careless with fire.

    • So, in fact, in north central Ohio prairies are only semi-natural and were probably created and certainly maintained by the Native American peoples. Interesting.

      • I will contend that the tallgrass prairies of Ohio, which existed for several thousands of years after the end of the Xerothermic Interval (which was a hot, dry period that did allow prairies to originally establish in Ohio after the glaciers), are, and always were “natural.”

        Yes, those prairies absolutely depended upon the annual burns set deliberately by Native Americans. But those peoples were native and natural themselves, using their intelligence and fire to control vegetation. Without human-set fires, eastern prairies would not have survived, and most of our oak forests would have (as they are today) succeeded to red maple forests. Oaks in moist areas, like prairies, are fire-dependent. It’s taken a century for Ohio foresters in the forests of Appalachian Ohio (southeast) to understand that prohibition of fires in oak forests dooms them. Shade-tolerant red maple seedlings, in thirty years, begin to top out over the oaks and shade them. With that, the oaks weaken and fungal diseases and insects kill the oaks. Finally, prescribed fires are now being conducted in the hillside oak forests. Oaks can withstand the leaf fires along the ground. The red maple seedlings are killed. With prescribed fire (at least in certain areas to start), our oak forests are being restored.

        It’s utterly arrogant to presume or categorize Native Americans as “unnatural.” Like us prairie biologists today, for centuries they used fire intelligently and deliberately to maintain both prairies and oak forests; wonderfully. By understanding the ecological intelligence of Native Americans in presettlement times, there is nothing “unnatural” about prescribed, human-set prairie (or oak forest) fires. Smokey Bear, bless him, notwithstanding.

        • Just to be crystal clear, I certainly do not think of Native Americans living in presettlement times as “unnatural.” The lived on nature’s gifts.
          It was however a big mistake when humanity started thinking we can live outside of and rule the rest of nature; a mistake we’re now beginning to see the consequences of unfortunately.

  2. Very interesting post, Chris. Thanks for this info. You mentioned “excavating” a certain area before replanting prairie species in order to get the top of the soil “closer to the ground water”. How close to the water table does the surface have to be before that strategy is significantly helpful during a drought ?

    • Michelle, we were just measuring depth-to-groundwater the other day, coincidentally, and we were finding water about 2.5 to 3.5 feet below the ground – digging from the bottom of the wetland swales.

  3. Great post and dialogue. Your aerial photos put so much into perspective that isn’t as easily seen from the ground. Good thinking. I am also encouraged by Blakeman’s comments about the eastern prairie in Ohio. His remarks that Ohio foresters are finally recognizing the importance of managing forests with fire. And I thought even Neanderthals were more intelligent that foresters!

    • “I thought even Neanderthals were more intelligent tha[n] foresters!”

      Well, let me make this clear. Ohio forestry professionals determined some time ago, in the 60s and 70s, that the oak forests in Ohio’s Appalachian hills were in decline and being slowly overtaken by other, less valuable species such as red maple. They understood that the absence of fire for over a half-century had set in motion new ecological forces that would prevent the growth of oaks. Simply, the foresters were all for prescribed fires. The problems were with the general public, who, for that same half-century took to heart what Smokey proclaimed: “Only you can prevent forest fires!”

      Setting on fire a half square mile of mature oak forest, in the public mind, could be only destructive. Look it up. The Smokey Bear advertising has been amongst the most effective in modern history. All forest fires are BAD. Period. Such is the public’s perception.

      And now, watching many of the forests of California in utterly destructive conflagrations (caused by fuel accumulation in the absence of periodic fire, anthropogenic or lightning-caused) reinforces Smokey’s message. Slowly, forest owners, public and private, are learning that prescribed fire is restorative, not destructive. Our foresters know. Regulatory and landowning stakeholders need, now, to understand the matter. After seeing a burned-over forest floor, it’s not an easy lesson to teach. The public thinks in one-hour or one-minute time frames. For both prairie and forest management by prescribed fire, time frames must be decadal.

      • I can only agree that there’s nothing unnatural about forest- and grassland fires.
        The main problem is (in my eyes) that forest owners are worried that their profit from logging is going to decrease. And of course the cost of hiring people like you to carry out prescribed fires.
        But it certainly would be both wise and smart when done with proper planning.
        I hope you can go on to convince the people in power making the right future decisions.

          • Well, my thinking is simply that forest owners are worried that timber quality and/or quantity will be negatively affected by prescribed fires, resulting in loss of income.
            Money is the curse of this world.

  4. It would seem that throughout the development of English’s metaphorical usage, it has had more experience with watery environments than with droughty ones.
    Oh yeah, good essay on the resilience of prairies, too.

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