Does anyone else remember the old Atari game Missile Command? It came out in the early 1980’s – back when computer graphics consisted of pixels roughly the size of the keys on the keyboard I’m using to write this. For those unlucky people too young or too old to remember the game, here’s a quick summary…
In the game, the player’s job was to defend six cities (consisting of about 8 pixels each) from an increasing number of missiles coming out of the sky above. Those missiles were represented by long jagged lines that lengthened inexorably toward the cities below. To save the cities, the player had to place the cursor below the “missiles” and push the button on the joystick at just the right time to create an explosion (consisting of about 8 pixels) that would destroy the missile. There was limited ammunition available each round, so too many misses and the player had to watch helplessly while the remaining missiles destroyed his/her cities.
Each round of the game was increasingly difficult, with more and more missiles falling from the sky at higher and higher rates of speed. There was no winning the game (at least for me); the hope was to get through as many rounds as possible before the inevitable destruction of the poor cities below. It wasn’t the most enjoyable game I’ve ever played, but there weren’t a lot of other video game choices back then so I played it quite a bit.
Why am I writing about a 1980’s video game on a prairie blog? Well, I was reminded of the game the other day while listening to a conference presentation about tree encroachment in prairies. Dirac Twidwell, from the University of Nebraska-Lincoln was making the case that we should be directing conservation funding to prevent trees from becoming abundant in parts of Nebraska where they are still relatively scarce. Instead, we often focus on helping landowners clear trees from landscapes already full of trees in all directions. In those heavily infested places, the fight to prevent trees from invading prairies (or reinvading previously-cleared prairies) becomes really difficult. Hordes of seeds can come into those prairies from all directions and often overwhelm the most valiant efforts to stay ahead of them.
That’s when Missile Command popped into my head. It seemed a perfect (ok, pretty good) metaphor for the effort to prevent woody encroachment in prairies embedded within a landscape full of trees and shrubs. My mind wandered from what Dirac was saying (sorry Dirac!) and I decided to see how far I could take that video game metaphor. This blog post is the result.
There are three points I’d like to make about Missile Command and prairie conservation (that’s a sentence I never thought I’d write). The first is that I agree with Dirac’s main point. We need to be focusing much more effort on landscapes where tree encroachment has not yet become extreme. In those areas, the number of missiles (new trees or shrubs) coming at us is still manageable, and we can make it even more manageable by working to reduce the number of seed sources.
Eastern red cedar expansion is a big problem in Nebraska, and is exacerbated by the fact that we still plant cedar trees for windbreaks and shelterbelts, providing bases from which bird-dispersed seeds (missiles) can spread into the surrounding countryside. It would be great if we could stop planting cedars, of course, but if we are going to continue planting them, we should at least get more serious about killing off their progeny while they’re still small and relatively easy to destroy. The longer we wait, the more it becomes like later rounds in Missile Command, trying to catch more and more new trees with limited capacity.
There are landscapes in Nebraska and other prairie states where the scenario already resembles the latter rounds of Missile Command. There are numerous trees and shrubs in all directions, including eastern red cedar, but also many others like Siberian elm, honey locust, Russian and autumn olives, sumac, dogwood, and more. Keeping a quarter section of prairie free of trees is an intensely difficult job because missiles constantly bombard the area from all directions. In that situation, we have to stop trying to fight with the same strategies we used when trees were much less abundant. In video game parlance, we have to find a cheat code.
That’s my second point. When we’re in situations where tree and shrub invasion feels overwhelming, we need to change tactics. Trying to keep increasing the time we spend on old strategies isn’t sustainable.
For example, prescribed fire can be much more efficient at killing large numbers of eastern red cedar trees than cutting every individual tree with a pair of loppers, chainsaw, or skidsteer-mounted tree shear. Fire isn’t the easiest strategy to employ, but it sure can hit a lot of trees at once. If deciduous shrubs like sumac or dogwood are the problem, burning on a three or four year frequency (because we’ve decided that was the average historic frequency) probably isn’t going to be successful, at least here in Nebraska. More frequent and more intense fires might be needed, and/or herbicide application will need to be part of the equation.
At heavily infested sites, it might be time to switch from carefully applying herbicide to individual trees to broadcasting chemicals across entire patches of woody plants. In some cases, deploying bigger equipment (dozers, excavators, etc.) to remove patches of big trees can be a lot faster than trying to eliminate them with hand tools. Sure, there’s going to be more collateral damage with these approaches, but as in cancer treatment (because why not bring in a new metaphor?), sometimes something drastic like chemotherapy is needed to deal with the problem before it kills the patient.
Most importantly, we need to stop working on the control of trees (and other invasives) on a site by site basis when those prairies are embedded within a landscape full of invaders. Trying to protect one city from an ever-increasing barrage of missiles isn’t sustainable. Trust me, I tried it many times when I was a kid.
Success will only come if we can start building partnerships with surrounding landowners and taking a neighborhood approach to woody plant control. By working collaboratively on eradicating trees and shrubs from sections, townships, and even larger areas, we can greatly reduce the invasive pressure in the interior portions of those control zones. That means all the partners can then work together to defend and expand the outer boundaries of those zones. It’s not the way most of us have worked in the past, but look at where that’s gotten us.
My third point is one I don’t really want to make, but it’s one I’ve been thinking more and more about. The world is quickly changing around us – including continual habitat fragmentation, increasing dominance of woody plants and other invaders within grassland landscapes, and increasing nitrogen deposition, just to name a few examples. When you add the rapidly changing climate to that mix, it gets pretty difficult to see how we’re going to hold the line in every prairie that stands in the way of those changes. It’s probably time that we start talking about how we can preserve as much biological diversity and ecological function as possible within selected sites that are inexorably transitioning from prairies to shrublands or other community types.
If you haven’t had this conversation with yourself or others, I’d encourage you to broach the topic. It’s not one I’m going to explore here at the end of an already-too-long blog post, but it is one I’ll return to in the future. I’d be curious to hear from others who are already ruminating on the subject and have helpful thoughts.
To wrap this up, however, let’s return to my youth. I often found myself staring blearily at the screen as the last of my 8 pixel cities was destroyed. Either my ammunition had run out or I just couldn’t keep up with the overwhelming barrage. I can remember those feeling of helplessness and frustration very clearly, and they are similar to the feelings I sometimes get today when I think about the threats to prairies.
When I was a kid, I didn’t have any way to reprogram the Missile Command game on my computer and give myself a better chance of success. There’s no such limitation on us as prairie conservationists, however. Just because some of our current approaches are becoming inadequate as trees and other invaders increasingly press in on us doesn’t mean we have to lose the game. With some creativity and teamwork, we’ve still got a chance to create our own cheat codes and win at least some of the time.
Hi. Chris Thanks I love all your posts Just for fun you might as well get the spelling of the “enemy” correct. Redcedar one word because it is not a true cedar. Leaned this recently using iNaturalist. Cheers
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I have problems with woody species here in North Dakota. But when i tell my department that we need to do do some controlling by either burning or cut and treat them, i always get a hard no. They love trees and rather see them then the grasslands and prairies. Its always big disappointment seeing fragments get smaller and smaller.
“When we’re in situations where tree and shrub invasion feels overwhelming, we need to change tactics. Trying to keep increasing the time we spend on old strategies isn’t sustainable. ”
My new favorite mantra and life philosophy. Posting this one on my Inspiration board.
As an Ohio prairie expert (yes, Ohio had and has “natural,” pre-settlement tallgrass prairies), I find it extremely interesting that, of all places, more-arid Nebraska has to worry about the loss of prairies to woodies; trees and shrubs.
Here in the Buckeye State (buckeye is tree) prairies have been invaded by and often lost to woodies since massive settlement in the first half of the 19th century. Good historical and ecological work (a bit of it mine, in my Firelands Prairie area in northern Ohio) has very accurately determined the locations and borders of our tallgrass prairies before settlement. Today, except for a very few unplowed remnants of the original prairies (<1000 acres, at just two or three local sites), Ohio prairies have been plowed and converted to row-crop fields, or cities.
At NASA’s 6400-acre Plum Brook Station in northern Ohio, straddling the Firelands Prairie area, I’m wonderfully in the process of re-establishing about 3000 acres of the original prairie. This gigantic site (the size, perhaps, of a 10 sq mile ranch in western Nebraska) was a WWII TNT manufacturing facility; later converted to a NASA cryogenics and space environments facilities complex. NASA has invited me to advise on the restoration of both the original 3000 acres of native tallgrass prairie, but also about 500 acres of oak savanna. The NASA people are wonderfully receptive to all that I advise.
And, of course, frequent and ample use of prescribed fire is the primary restoration tool — one that at first was received with a bit of wariness. But now, after about a decade of annual spring fires, invading brush is being pushed back and suppressed wonderfully.
So much of the prairie management literature states that burns, at the most frequent, should be semi-annual, no more frequent than every other year. Triennial burn frequencies are purported to be even better. The claim is that continually annual burns favor grasses and suppress forbs, resulting in giant stands of just big bluestem. Forbs get burned out, it is claimed.
At Plum Brook Station, after a decade of burning, we’ve discovered that, simply, annual burns are most effective at retarding brush invasion. Areas with biennial or triennial burn frequencies simply have remnant brush sprouts from un-killed root crowns. There, woodies simply re-sprout after a single season’s fire. Root crowns are not killed. In two years, the re-sprouts are thick and cast shade on the prairie, thereby reducing the next burn season’s fuel loads. Except in areas completely free of woodies (after at least 5 consecutive years of spring burns), we burn every spring.
Simply, we haven’t had any of the tallgrasses (big bluestem, switchgrass) actually take over and suppress forbs to any objectionable degree.
I lay out all of this to the NASA people, so they can understand the necessity of consistently annual burns. They’ve now seen the results, both on areas burned annually, and others with less frequent burn schedules. Just as Native Americans did before settlement here (we have numerous historical records documenting annual burns, both in fall and spring), we are burning every year — with great success. Woodies, both native and invasive, are evermore absent in our best, most-often burned prairies.
Now, thanks to this article, I can mention that even in arid Nebraska, loss of native prairies to woodies is a real problem. Woodies HAVE to be controlled, both at the humid eastern end of the Prairie Peninsula (here in Ohio — my Firelands Prairie was the easternmost large landscape prairie in North America), and also at the western end, even in Nebraska.
Today, fire is essential for the maintenance of tallgrass prairies. They are not self-sustaining climax communities. Since the end of the Xerothermic Interval, 4000 yrs ago, they have been maintained by anthropogenic fire.
A missing, important factor in modern times is the absence (at the end of the Pleistocene, the Ice Age) of mammoths and mastodons, which significantly browsed woody plants (to the ground). Elk, too, were significant browsers, absent today from Midwestern tallgrass prairies.
Today, only three things keep tallgrass prairies from succeeding to woody brush and forest; chainsaws and brush mowers, herbicides, and most useful and import (and natural — Native Americans were natural), human-set fires.
Thanks for all of that John. Yes, Nebraska has plenty of woody encroachment pressure. It’s been a big issue in eastern Nebraska for a long time but is really ramping up in the western parts of the state as well.
Annual burning is a really interesting topic. I’ve certainly seen annually-burned prairies and savannas with impressive plant communities. I’ve also seen sites where frequent burning has pushed the community into grass-dominance. If we could understand what’s behind those differences, we’d be much further ahead in our understanding of prairie ecology! From what I’ve seen, there’s likely an east/west influence in those responses, but I’m sure it’s much more complex than that.
Another factor in annual burning (on my mind because I have a future blog post percolating) is the impact of frequent fires on invertebrates and other animals. Fire impacts on invertebrates has been pretty well documented by Ron Panzer in Illinois, and his work – and that of others – has been an important reminder to all of us that we need to be cognizant of potential ramifications of our fire work. Annual fire in woodlands worries me less than annual fire in prairies because of the inherent patchiness of most woodland fires and the more comprehensive consumption of fuels in most grassland fires. Whether during the dormant or growing season, uniform burning can have big impacts on inverts, especially in isolated sites.
This is not at all a criticism of the annual burning you’re doing in Ohio. Rather, it’s another good example of how tough decisions have to be made when overwhelming threats to prairies sometimes have to be dealt with in ways that have collateral damage. All of us have to make the best decisions we can. Unfortunately, it’s really hard to predict the impacts of reducing invertebrate (and probably vertebrate) diversity and abundance on overall ecosystem function. We’re not usually very good at evaluating and tracking changes to prairie communities outside of plants, let alone predicting how those changes might impact the plant community in the long-term.
Good luck with your restoration work!
Yes, fires burn up inverts; can very negatively disrupt insect and other invertebrate populations. This is a matter that should be attended to.
At our NASA Plum Brook Station facility, the 10 sq miles of the site are intersected by over 60 miles of fire-break road ways, breaking the entire area up into 65 separate road-bound burn units. Within each of those separate management areas are a diversity of soil types (sandy, xeric areas; clayey hydric areas), with varying prairie vegetation.
Therefore, even with continual annual spring burns, ample areas go unburned, both with herbaceous and woody vegetation. As in pre-settlement times, when Native Americans burned this area every fall and spring, there are large numbers of unburned spots which are refugia for inverts.
At Plum Brook Station (and at a nearby near-virgin prairie), a new species of moth was discovered. It was found to require Spartina pectinata, prairie cordgrass, for portions of its life cycle. Were we to burn off all of our cordgrass every spring the species would be extirpated. I watch this closely; know where all of our cordgrass stands are. In fact, it would be very difficult to burn all of them every year. The rare prairie moths continue to thrive at Plum Brook Station.
Externally, I design and specify Ohio prairie restorations. For each of these projects, I advise on required post-planting management. That’s a problem here in Ohio. “Well, we’re planting real prairie. We’ll let nature have it’s way; will let it grow without human interference.” No, the new prairie must be properly mowed or burned. If not, in five to ten years it will be a brush patch.
But what about the inverts that get sizzled by the recommended fires? That’s why my designs include at least five separated prairie islands (often separated by 8-ft curved, mowed walking lanes. With these islands, at least one area each year can be left unburned, allowing the bugs to live out their lives there. We simply rotate the burns, with adjacent unburned/burned geometries. Bugs have to move but 8 feet to get from an unburned area into the new growth in a burned area. The fire-mosaic concept. Important (well, for invertebrates, crucial).
Springs in Ohio can be wet. One of the historically wettest springs was last March and April. I had only two days where fuels were (barely) dry enough to burn, with low surface winds. So, even with a fire manager who wants to burn everything every spring, meteorology simply intervenes.
We know from historical accounts that the local Native Americans, the Delawares, burned every square foot of both forest floor (leaves) and all of the prairies. Early settlers were alarmed; couldn’t understand it. Just thought the locals to be ignorant. So wrong!
The massive burning of both forest and prairie landscapes was a smart human hygiene thing. Simply, frequently burned areas have marked-reduced populations of both ticks and chiggers. For us, today, ticks and chiggers are pretty much only an incidental nuisance; obviated by the dermal application of some modern chemical. For Native Americans, living in the vegetation of the local landscapes, ectoparasites were more than an infrequent, incidental annoyance. They transmitted diseases and made life otherwise most uncomfortable. The burning of forest duff and prairies each year significantly reduced the problem.
My question is “Why spring burns?” Why not fall right after hard frost?
Very good question. A burn, especially later in the autumn, as mid to late October, after insects will have gone into dormancy or buried themselves underground, would minimize their destruction by prescribed fires.
Actually, we’ve tried fall burns many times. But never with much success. Sure, we can burn the prairie duff, but even during all of the autumn, until cold wet November or December, our Ohio prairie vegetation simply never dries out completely. In-the-stem pith, in both grasses and forbs, stays moderately or very moist. Ohio is humid, with ample, consistent precipitation every month of the year. We’ve found that prairie vegetation does not dry out thoroughly until a few consecutive 50-degree days in March or April have adequately evaporated histological moisture in the plant tissues, primarily in stem piths.
This is because our soils, except on the very rare pure sand areas, simply never dry out. Soil moisture constantly wicks up into stem xylem vascular tissues throughout the fall. The prairies will burn, but flames are coolish, not high, and great amounts of white smoke is produced. The burning of thoroughly dry prairie vegetation produces minimal smoke, very hot, woody-killing flames, and minimal clouds of white smoke. Our fall burns are not the hottest, and dense clouds of white smoke are produced.
The prime reason we burn is top singe and destroy the meristem tissues of the woodies; thereby obviating their re-sprouting. For us, fall burns, with slightly moist stem tissues, produce cool flames that fail to adequately destroy the re-growth tissues, the meristems of the woodies. Lots of white smoke; but to little desired effect.
Same thing happens in spring, unless we take care to burn only after two or three days at 50 degrees or more. By spring, it appears that the column of moisture in grass and forb vascular tissues has been disrupted; not uninterrupted down into roots. With a bit of warmth (the two or three days of 50 degree dry weather), the stems internally do dry enough to allow hot, complete burns. They severely singe the still wet, live meristems of the woodies; thereby significantly inhibiting their re-sprouting.
This temperature/moisture regime is different in drier prairie areas to the west. Different prescribed fire outcomes. Each prairie is different. Prairie managers must learn the traits and behaviors of the local prairies they manage. For us, in northern Ohio, spring fires are the only ones that really work; suppress the brush, invigorate new prairie growth.
Annual burning doesn’t seem to ever push remnant communities to grass dominace in the eastern tallgrass. Here the most burned sites are the most diverse with the most representation of “conservative plants.” Reconstructed prairies might be another story though, and they aren’t an insignificant consideration. A lot of our oak ecosystems were also thought to have been burned annually. Faunal issues are real and can be addressed with refugia, but they also got by in the past…but a few did rely on metapopulation dynamics to recolonize after local extinctions, and we generally don’t have that luxury anymore. For those species, the choice is often risk them vs. doom the community they depend on, dooming them as well. Powashiek Skipperling was recovered on a site near me that was annual burned over about a decade. Then it was stopped. It’s now been 4 or 5 years with now skipperlings, despite annual surveys. I’m not surprised. The prairie dropseed is smothered by its own litter, and floral resources are much reduced. It wasn’t a winnable situation without a landscape prairie.
Annual burning doesn’t seem to ever push remnant communities to grass dominace in the eastern tallgrass. Here the most burned sites are the most diverse with the most representation of “conservative” plants. Reconstructed prairies might be another story though, and they aren’t an insignificant consideration. A lot of our oak ecosystems were also thought to have been burned annually. Faunal issues are real and can be addressed with refugia, but they also got by in the past…but a few did rely on metapopulation dynamics to recolonize after local extinctions, and we generally don’t have that luxury anymore. For those species, the choice is often risk them vs. doom the community they depend on, dooming them as well. Powashiek Skipperling was recovered on a site near me that was annual burned over about a decade. Then it was stopped. It’s now been 4 or 5 years with now skipperlings, despite annual surveys. I’m not surprised. The prairie dropseed is smothered by its own litter, and floral resources are much reduced. It wasn’t a winnable situation without a landscape prairie.
Just a quibble. It’s not necessarily helpful to see Native American land management practices as any more or less “natural” than our own. No question they were “useful” given their objectives, and smarter, and we’d be wise to make use of them. But maintaining a prairie ecosystem for the last 4000 years has been a conscious decision of humans to actively manage it for human objectives. Seeing Native Americans as somehow more “natural” romanticizes them, and simultaneously “de-naturalizes” us. We need to understand and describe ourselves as being as inextricably linked to the natural world as all those who have come before us, in order to up our game and make it clearer what’s really at stake here.
25 years ago, leaving prairie remnants to the destruction caused by the “inexorable” extension of woody plants into them, in Illinois at least, wouldn’t have made sense, because we needed every remnant to build local seed banks, in order to plant larger areas and expand “restorations” into adjacent farmlands to link other remnants.
These days, though, I can see the logic of focusing on extending these larger areas, because remnants won’t make the survival and renewal of the tall-grass prairie ecosystem, east of the Mississippi at least, a reality- but supporting the expansion of the Nachusas of the country into formerly farmed lands will. That doesn’t mean that people shouldn’t support maintaining and improving remnants- they’re often the only options available locally for experiencing what the prairies once were. And it certainly doesn’t mean that hundreds of thousands of Chicagoans, say, planting prairie plants in their yards, should stop.
On the contrary. The mix of prairie plant backyards, healthy remnants, and expanding large reserves are all essential to the long-term viability of prairie plants and animals. But you can definitely make an argument for the “big environmental money” going to the big projects.
While focusing attention on larger areas that have less woody encroachment has merit, we cannot overlook the importance of establishing corridors to connect them. Such corridors, even if degraded and narrow, provide food and refuge for residents and migrants, helping to retain biodiversity. Landscape-level connectivity is especially important to enable adaptation and migration in response to a changing climate.
Corridors have become a paradox. As you say, corridors of intact habitat are vital. Unfortunately, many corridors aren’t corridors anymore. In many areas, especially in the East, existing corridors of open, “natural” space have been co-opted by invaders, which cause them to become impenetrable to much of our native flora and fauna, and these invaders tend to have traits that allow them to exploit and move along corridors better.
Great post Chris, here in NZ we have a huge problem with Douglas Fir spreading through our sub-alpine and alpine zones, and yet government and councils refuse to ban it as it’s used so much in forestry – go figure.
Our landscapes draw people here and tourism earnings ate NZ$16B , while douglas fir earnings are $400M. If you want to plant Douglas fir here you have to get an industry-friendly ecologist to state that you can control seed spread! Douglas fir will establish itself in deep native forest and grow on our tallest mountains.
Anyway huge problem, I think a Douglas-specif Dothistroma may do the trick but controversial here. High-country farmers can solve it with sheep and fire but increasing non-farm ownership of high country, along with utopian views from government sector is making this un-viable.
That’s really fascinating. I hadn’t heard that Doug Fir was an issue there. Good luck!!
I live on a quarter section of pasture in eastern Nebraska and will be fighting the cedars until the day I die. None of the neighbors surrounding me do anything to their trees so there is an abundance of seed for the birds to spread. They all ask me how I keep the trees at bay but then do nothing to them and their pastures look horrible.
I graze cattle June through mid-October so there is never enough grass to burn. I have found that the best method to control the cedars in the pasture is by mowing. As soon as the cows are off, I mow about a third of the quarter. I do a third every year and it looks good when the trees are gone. By the time the next third needs mowing, there are small cedars popping up all over. The fence lines are another story. I have to manually cut them from under the fence.
I empathize with your situation. Just curious – are your neighbors also grazing their pastures, or are they recreational for them? When I bought my place it was overrun with cedars – grazed heavily but eventually cedars overtook it, leaving it with too little grass to make it worth grazing. Restoration has been slow, but as the prairie has rejuvenated without grazing pressure, the cedars have had a harder time re-establishing.
Yes, they rent their pasture out to graze. Their grass isn’t as good as mine since the cedars take a lot of the water the grass needs and also shades the grass. I could see where the grass would probably take over the cedars if it was not grazed for a long time. Nature is amazing.
Imagine prairies and oak openings in Wisconsin, considering the surrounding landscape their. Indeed, the only way shrub and tree encroachment is kept at bay effectively is with an initial triage of shrub herbicide treatment followed by a fire return interval of two or less, which is employed in a few places with spectacular results, but more often the response is an intermittent hodge-podge of wasted effort. One exception is the rare island in the middle of a lake or large wetland complex that never saw high stocking rates early in the last century (or ever). In some of those places open oak savanna and woodland understories remain, even some prairies, without any management to this day (usually with herbaceous communities packed with the various critical partially parasitic plants like bastard toadflax, puccoons, and wood betony), but these are generally vanishingly small–just enough to tease us.