CHAPTER 13
Indeed, it is the interaction of ungulate grazing activities and fire, operating in a shifting mosaic across the landscape, that is the key to conserving and restoring the biotic integrity of the remaining tracts of tallgrass prairie.—Knapp et al. 1999
The heterogeneity-based approach to rangeland management that we propose is an attempt to mimic historical grazing-fire interactions on mesic North American prairies, which have a long evolutionary history of ungulate grazing.—Fuhlendorf and Engle 2001
Fire-grazing interaction may provide a management alternative that enables sustainable livestock production, through increased carrying capacity in focally disturbed patches, concomitant with biological diversity in tallgrass prairie.—R. H. Anderson et al. 2006
The shifting mosaic created by the Patch Burn treatment provides habitat that meets requirements for a broad range of invertebrate species.—Engle et al. 2008
So, in contrast to rotational grazing, patch-burn grazing subjects a prairie to extended periods of intensive grazing followed by multiyear rest periods, creating a very heterogeneous array of vegetation structure across the pasture.—Helzer 2010
Management strategies such as patch-burn grazing offer opportunities to restore landscape heterogeneity to benefit bird communities while maintaining livestock production goals.—Davis et al. 2016
IN 1832, GEORGE CATLIN painted Prairie Bluffs Burning. In this painting fire moves across a hilly, grass-covered landscape. There are two deer in the foreground. One is at rest before the flames. The other is jumping over the flames into the black, not fleeing in front of the flames. Catlin knew that wildlife were attracted to recent burns almost two centuries ago, as Native Americans knew before that. We’ve finally been able to put some science and numbers behind those historic observations over the last two decades.
Earlier chapters made the argument that prairie is largely defined by fire, grazing, and climate. Fire and grazing are the two factors managers have control over. Fire and grazing also strongly interact at landscape scales. Bison and other grazers are strongly attracted to the flush of succulent new growth after a fire.
These results indicate that grazing distribution can be controlled with some precision using prescribed fire. (Vermeire et al. 2004)
Fire can control where bison graze. At the same time, grazing removes biomass, fuel for fires. Grazing can control where fires go. Fire can attract grazers, but grazing can prevent fire.
Areas that are heavily grazed won’t have enough fuel to carry a fire. In other cases, where the grazing is patchy and heterogeneous, the resulting fire will also be patchy and heterogeneous. The fire will burn the ungrazed patches and be stopped at the grazed patches. In this way, a fire can percolate across an area. Instead of ten- or twenty-foot tall flames racing through an area leaving solid black in its path, the fire may creep slowly through a grazed area with flames only inches high and leave a complex mosaic of ungrazed and burned, grazed and unburned, and ungrazed areas surrounded by grazed areas that serve as a firebreak. This mosaic leaves refugia for insects and other wildlife.
Traditionally, the goal of livestock operators is to graze an entire pasture or set of pastures as evenly as possible. Ranchers rotate cattle from paddock to paddock, put up fencing and cross-fencing, and space water and mineral blocks across the pasture to evenly distribute grazing pressure by the livestock. The more homogeneous the pasture looks at the end of the growing season the better (reviewed in Fuhlendorf and Engle 2001). From a wildlife perspective, this means that there’s only one habitat structure across all that grass.
Almost by definition, a fence is designed to keep an animal within an area or out of an area. A fence is designed to block movement, to keep animals from going where they want to be or keep them in an area where they don’t want to be. This works against the natural behaviors of the livestock, trying to get them to go where we want them instead of where they want to be. This of course creates a lot of work for the people managing the livestock.
Native Americans frequently burned the prairie to attract wildlife. Today, we are able to apply science to those historic anecdotal observations and explain those patterns. At the same time, we can use natural grassland processes and the behaviors of livestock to our benefit. We can get the livestock to work with us instead of against us, creating less work for people, presumably happier and healthier livestock, and better habitat for wildlife. And we can do all that at the same time. Just as important for this book, the process called patch-burn grazing shows how multiple aspects of prairie ecology interact.
Patch-burn grazing is simply burning part of a larger pasture each year. Livestock are attracted to the fresh green-up of grass in this area, spending more time in the recently burned grassland than unburned grassland. The next year managers burn a different area within the pasture and the livestock move to this area. In this way, managers can rotate livestock around the pasture without any cross-fencing or other infrastructure.
There are at least two explanations for livestock being attracted to recently burned areas. All the vegetation in these burned areas is lush and green. In unburned prairie, livestock have to dig through the old, brown, dead vegetation from previous years to get to the good green vegetation.
The grass isn’t just greener, it may be more nutritious. Compared to annual burned prairie, infrequently burned prairie produces more biomass of grass (J. M. Blair 1997; Knapp et al. 1998) as described in the Transient Maxima Hypothesis in Chapter 9. Another important fact from the grazing perspective, grasses in a four-year burn rotation have higher nitrogen levels than annually or biennially burned prairie (J. M. Blair 1997). Therefore, with periodic burning there is large quantity of high-quality grasses for livestock. Grazers will readily respond to these differences in forage (Raynor et al. 2015).
The reason nitrogen is so important for livestock producers, as well as wildlife, is that nitrogen is the key component of protein. Protein is one of the key components of muscle, and muscle to a livestock producer is meat. Meat is what they ultimately sell and make a living from.
With grazing, we can add another level of complexity to the nitrogen story. Grazing can increase plant nitrogen levels because the grazers urinate and defecate on the prairie. In the following days and weeks the plants are able to absorb the nitrogen from the soil and thus become more nutritious. These nutritious plants influence grazing behavior (Steinauer and Collins 1995, 2001) and can become a source of nitrogen in a grazer’s diet (Day and Detling 1990).
As livestock keep the plants grazed low, the plants are constantly regrowing and therefore remain succulent and nutritious. If fire initially attracts the animals to an area, the repeated grazing can keep them there (R. H. Anderson et al. 2006), even to the point that “bison use recent burns even after they are virtually devoid of vegetation” (Schuler et al. 2006). Grazing the same acres year after year will use up root reserves of the plant, making them slower to regrow and less nutritious. However, in the case of patch-burn grazing, this intense grazing occurs for only a summer and the plants then have three or more years to recover their root reserves.
So how can ranchers and wildlife managers use this information? Imagine a section, or square mile, of grassland, 640 acres, divided into four even-sized units of 160 acres. Traditionally, each of these areas would be fenced and cattle would be rotated from one area to another. At the end of the year the entire 640 acres will look similar and homogeneous.
With patch-burn grazing there is no cross-fencing, just one perimeter fence. In the first spring, ranchers burn the northeast quarter and livestock spend most of the summer here. The following spring, ranchers burn the northwest quarter. Now the cattle graze this area and the northeast quarter starts to recover. The southwest and southeast quarters haven’t been burned or grazed and are accumulating a fair amount of thatch. That’s a lot of structural diversity and heterogeneity across those 640 acres.
The high quantity of high-quality forage should lead to increased weight gain in cattle, and that should be more money in the rancher’s bank account. Cattle performance, weight gain, and body condition were equal to and sometimes better under patch-burn grazing compared to more traditional pasture management (Limb et al. 2011). Because cattle are grazing “new” pasture each summer, this pattern of movement could potentially help break parasite cycles in the livestock, improving health and decreasing the cost of the rancher for deworming chemicals.
This management method can maintain sustainable livestock production and biological diversity at the same time (R. H. Anderson et al. 2006; Fuhlendorf et al. 2006). Wildlife benefit primarily because there are so many different types of vegetation structure in different stages of recovery from fire and grazing (Fuhlendorf and Engle 2001). Patch-burn grazing shows that ranchers can meet production goals and conservationists can meet wildlife objectives at the same time on the same piece of land.
Conservationists can now conserve ecological patterns and evolutionary processes using patch-burn grazing (Fuhlendorf et al. 2012). This may be more important than just “preserving” the prairie as described in earlier chapters. This method of grazing management can help merge the utilitarian and preservationist schools of conservation, which date all the way back to the time of John Muir and Gifford Pinchot in the early 1900s. Most importantly, wildlife managers and ranchers can conserve land, biodiversity, patterns, processes, and local livestock economies. These ideas can also help unite the conservation and agricultural community to show how each can be mutually reinforcing and beneficial (Limb et al. 2011). What’s good for beef is good for birds, bees, and butterflies. Ranchers, bird hunters, and bird watchers have a good reason to talk together and work together.
We can return to the bird and invertebrate data to show the wildlife benefits of this system. Some species of grassland birds respond positively to grazing, “even at moderately high stocking rates” (Ahlering and Merkord 2016) or grazing so intense that the cattle create distinct grazing lawns (Hovick et al. 2012) but still leave some patches with sufficient nesting cover nearby. Grazing can be the best tool for getting the structural diversity in the prairie that the range of grassland birds require (Fuhlendorf et al. 2006) and can even work in fragmented landscapes (Pillsbury et al. 2011).
Among the invertebrates, some species are associated with taller, denser vegetation (Moranz et al. 2012), while others respond well to shorter grasses or the variability in grass height (Joern 2004). There isn’t a uniform invertebrate response to burning and grazing. Grasshoppers reached peak biomass in the second spring after the fire, twelve to twenty-four months since the fire. True bugs did well in both the fall and spring for the same period. Leafhoppers and aphids did best in unburned and in the twelve to twenty-four–month post-burn period. Spiders and ticks showed mixed results (Engle et al. 2008). Most interesting, from a bird’s perspective, is that peak invertebrate biomass was highest in the spring following the fire. Spring is when grassland birds are most in need of the high-protein diet invertebrates provide. Patch-burn grazing, “is a viable and perhaps even ideal management strategy” for regal fritillaries (McCullough et al. 2019) and presumably other prairie butterflies and insects.
We can imagine traveling back in time to what the prairies looked like from the perspective of a bird flying overhead. First, we can think of migratory sandhill and whooping cranes at high altitudes. When they looked down, they saw some areas of the prairie that hadn’t been burned or grazed in several years and had significant fuel build-up. Other areas would have recently blackened with fire. The cranes would also see heavily grazed areas that couldn’t burn.
We can imagine a similar scenario for a grassland sparrow flying from perch to perch in a lightly grazed area that a recent fire percolated through. A sparrow flying from spot to spot around a territory might have seen the same pattern of grazed areas, standing vegetation protected from fire by grazed areas around it, and recently burned areas. It would be a similar pattern as the cranes saw, but at a much smaller scale.
Last, we can imagine how spatially and temporally dynamic this was. An area that hadn’t been grazed and had heavy fuel build-up burned. The green, succulent regrowth attracted herds of bison and elk that moved into this area, thereby abandoning areas that grazed last year. The area heavily grazed this year is effectively “fire-proofed” for at least a year because the grazing removed the fuel. The area that was grazed last year now has a recovery period of one to several years before it burns again. Every year this pattern would have shifted around on the landscape and probably occurred at different scales.
The noted examples illustrate at least three principles. First, the different patterns each year are what ecologists refer to as the shifting mosaic of habitat across a landscape. Second, in many cases the patterns that occur at one scale, cranes high overhead, are very similar to the patterns at another scale, a sparrow foraging on the ground. Last, prairies can be working landscapes, on both public and private lands. Working lands both preserve and manage prairies as well as keep those acres in the local agricultural economy.
Although there are many benefits to grazing, patch-burn or otherwise, it isn’t always appropriate everywhere and it takes a lot of work. With a prescribed burn, once the fire is out and the perimeter secured, managers can essentially walk away from the site for the rest of the year. To graze “properly” to meet wildlife or habitat objectives, as well as herd health and safety, someone needs to be checking the livestock at least weekly, and probably more frequently. This can be a significant time investment for a public grassland manager with many other responsibilities. Are the livestock congregating in an area and having too much of an impact? Is it a dry summer and the cattle need to come off a little earlier than planned? Grazing is a lot of work, and unless public lands managers have the time to invest in monitoring the site, cattle can do more harm than good. Burning is a one-day commitment at most sites. Grazing is a season-long commitment at every site.
That said, ranchers and livestock are key to maintaining grasslands and grassland wildlife. Burning is expensive, but doesn’t have much of an economic return. There is an economic return for well-managed grazing. Government agencies and conservation organizations will never own enough acres to sustain and support the wildlife populations that the conservation community would like to see across the Midwest. The best, and in some places only way, conservationists will meet their goals is by working closely with private landowners, especially those who work the land and own cattle. Often what’s good for ranchers and livestock is also good for conservationists and wildlife. This creates a natural and mutually beneficial partnership.
By looking at the interactions of fire and grazing, instead of studying each separately (Fuhlendorf et al. 2006), scientists have been able to replicate the patterns and processes that probably occurred on the early prairie landscape, create habitat for a wide range of prairie wildlife, and do it in a way that is economically viable to the ranching community. Indeed, for many prairies, bison and other grazers play a “keystone role” in the tallgrass prairie’s ecology (Knapp et al. 1999)
Through a Lens
WHEN I WAS AN UNDERGRADUATE, many of my prairie visits were in the company of my professor, Dave. Dave introduced me not only to the prairie but also to photography. We always brought full bags of camera equipment with us. Most of my memories of those Indiana prairies are of me on my knees, getting close-ups of flowers with a macro lens.
Especially in the late summer when the bluestem and Indian grass were at their peak height, this was the only time I really felt like I was in the prairie. There were only wildflowers and grass beside me, only sky and clouds above. Even in a small remnant cemetery prairie it was easy to imagine it was just me and the prairie, and nothing else. One issue I’ve always wondered about with photography, especially close-up work, is whether I become too focused on one small area to the exclusion of the surroundings. Close-up photography is often about focusing on a single flower, or insect, to the exclusion of its landscape context.
For graduate school, I moved to the Flint Hills of Kansas. Here I could stand on a hilltop and look to the prairie horizon. I exchanged my macro lens for a wide-angle lens. The Kansas Flint Hills taught me to see the big picture. Indeed I spent most of my years there staring at satellite images of the Flint Hills studying landscape patterns at the regional scale. However, seeing the big picture makes all the details in the photo disappear.
Combined, these two experiences influenced the way I’ve learned to look at the world. Indiana’s prairies taught me to get on my knees and look down. Kansas’s prairies taught me to stand up and look out. These experiences, and all the experience since then, make me wonder about lenses in general.
The lens of history is a commonly used metaphor. How do we view the prairie, or how will we view the prairie at some future date? Asked in reverse, is there a lens of the future, and what does that tell us about the tallgrass prairie?
Is the story of the tallgrass prairie one of Native Americans having fundamental and dramatic effects on the landscape, as well as direct and indirect effects on the wildlife? What is the story of the human and nature dichotomy during those times? Is the prairie natural, and why or why not? Can natural areas and natural processes be the work of Mother Nature only, or can people play an active role in natural process, then, now, and into the future?
Is the story of the tallgrass prairie a story of technological challenge with the land being tamed and conquered? Is it about the tragedy of an earlier group of people or the triumph of a later group of people?
If nothing else, working on this book gave me an identity crisis. I like to think of myself as a prairie ecologist or prairie conservationist. But I’m not sure what the prairie is anymore. It’s very hard to define. Is a tallgrass prairie any area dominated by big bluestem or Indian grass? Is a tallgrass prairie any grassland roughly in that triangle from Indiana to Kansas to Minnesota? Or do we just default to “I can’t define a prairie, but I know it when I see it?” I’m joking of course, but defining the prairie isn’t as easy as some may think.
Then we can think about a lens into the prairie future. What if we restored grasslands on all the unproductive cropland? What if we carefully grazed and rested those acres? Would that diversify the rural economy and bring jobs back to rural areas? Would that increase ecotourism and hunting around small midwestern towns and be a welcome injection of outside dollars into local economies?
Let’s get back to that camera lens. What do we see when we look through the lens at the prairie? Is the image closely focused on a small, individual species, or is it focused on the big landscape? Is it a static image or a dynamic moving video?
What is the prairie? If there is no prairie, then what am I? Or is the prairie a metaphor for modern America? The prairie is a melting pot of plants and animals that came to the Midwest from all different directions. The United States is a melting pot of people and cultures from all different directions. That’s not a weakness, it’s a strength.