Tree Invasion

by Randy Rodgers wildlife biologist, Hays photos by Mike Blair

It’s time to change the way we look at trees on the prairies. While trees provide habitat for some wildlife, they pose a serious threat to grassland-dependent species.

Randy Rodgers photo

think that I shall never were Daniel Boone and Davy As early as 1873, Nebraska see, anything so lovely Crockett, woodsmen of the Senator Phineas Hitchcock “Ias a tree.” At least, highest caliber, at least on TV. introduced the Timber Culture that’s the version of the first Now, I better understand the Act. As federal law, this legisla- two lines of Joyce Kilmer’s values of trees for shade, for tion offered 160 acres of prairie poem, “Trees,” that I had in my respite from the wind, and as land to anyone who would head for years. I recently habitat for many species. plant 40 of those acres to trees. learned that the poem actually Perhaps those of us who live Years later, University of begins “I think that I shall never in prairie states value trees Nebraska botany professor see/A poem lovely as a tree.” more than those who live in Charles Bessey advanced the Either way, these words reflect more timbered regions. Those idea that the vast grasslands of deeply-held values for genera- roots go way back. Who hasn’t the Nebraska Sandhills should tions of Americans. heard accounts of European set- rightfully be pine forest. The No doubt, I stand among the tlers cursing the incessant wind, level of enthusiasm with which countless people who place the blazing summer sun, and his idea was embraced then, great value on trees. As a boy, I sheer exposure of the Great and even now, is evidenced by climbed them, drew them, and Plains? It’s not hard to under- the Bessey Ranger District of the explored kid-sized wilderness stand why they and their Nebraska National Forest near wherever I could roam through descendants were determined Halsey. There, about 30 square even an acre of them. My heroes to change this land. miles of man-planted forest, in

1 the middle of one of North America’s greatest remaining grasslands, attest to our love for trees — and perhaps to our underdeveloped appreciation of grassland. The weather of the can be harsh and the beauty of our grasslands subtle. But I can’t help but believe that Kilmer would also have waxed poetic had he seen a bluestem prairie’s rosy glow in the refracted light of an October sunset. Unfortunately, too few of us appreciate the beauty or Randy Rodgers photos comprehend the true value of Eastern redcedars pose a serious threat to this midgrass prairie in Russell County. our Great Plains grasslands. Trees can be controlled with fire, cutting, or spraying — sooner better than later. This poor understanding of grasslands, coupled with our bring the more moderate condi- immune. Eastern redcedar, culture’s love of trees, has laid tions and the wildlife of the east hedge (Osage orange), and the foundation for a change that out onto the plains, at least on blackjack oak have invaded sub- threatens our signature land- small scales. Alone, these tree stantial parts of our largest and scape — the prairies — like plantings have altered, but per- best known prairie region, the nothing since John Deere’s haps not seriously threatened, . Russian olive, cedar, invention of the moldboard our remaining prairie ecosys- black locust, and honeylocust plow. tems. But our collective failure have rapidly spread across our For more than a century, we to understand the needs of our central sand prairies. have planted and nurtured trees prairies has often resulted in Redcedar is devouring the across the Great Plains. The ben- grassland management or, more prairies of the Red Hills. In the efits were clear: windbreaks for correctly, lack of management , cedar and hedge farmsteads, crop fields, live- that has permitted some species are the main culprits. Even in stock, and wildlife allowed us to of trees to escape their original western Kansas, where dry con- planting sites. Fire, ditions might seemingly prevent the prairie’s natural tree invasion, a hodgepodge of ally, was often sup- trees are making inroads into pressed and midgrass and shortgrass grazing was some- prairies, as well as many times misapplied, Conservation Reserve grass- leading to a weak- lands. ened prairie com- So, what’s so bad about a mix munity vulnerable of grassland and trees? After all, to what has become there are many natural savannas an onslaught of where trees and grasslands com- invasive trees. Such bine to make diverse and beau- species are now tiful landscapes. It’s not so swallowing our much that there’s anything Osage orange, commonly called hedge, can’t be killed grasslands at an intrinsically wrong with this with fire. Reclaiming this pasture will require cutting and alarming rate. combination. But it’s the immediate treatment of the stumps with a herbicide. It seems no prairies, places that Kansans Kansas prairie is often take for granted, that actu-

2 ally are among Earth’s most threatened landscapes. Even where mechanical removal of trees has While there may be rela- occurred (note piles), tively fewer species present failure to follow up with in any one place, the controlled burning has per- prairie’s unique assemblage mitted small cedars to of wildlife is a rare treasure rapidly reinvade this pas- on the global scale. Many of ture. Piling cut trees is not a good idea as this removes us who live on the prairie grassland from production suffer from the illusion that for many years and creates meadowlarks are somehow habitat for mammalian ordinary, when nothing predators. could be further from the truth. Taken as a group, Randy Rodgers photos populations of grassland birds wise suitable prairie habitat in next. While other factors like have shown sharper and more many parts of our state. Greater prairie conversion and fragmen- widespread declines over recent prairie chickens have rapidly tation may be involved, it’s a decades than any other ecolog- lost ground in southeastern good bet that tree invasion has ical or behavioral guild of birds Kansas, as shown by long-term played a significant role in the in North America. surveys. The last time prairie greater prairie chicken’s demise. Grassland birds are probably chickens were observed on the Despite the fact that grasslands the best indicator of the decline 20-square -mile survey area in of adequate size are still present, of our prairies because many of Montgomery County was in lesser prairie chickens no longer these species are sensitive to 1987. They disappeared from occupy significant portions of change. Foremost among them the Wilson County area by 2000, their former range in Barber, are our two species of prairie the Elk County area by 2002, Harper, Kingman, Pratt, Reno, chickens. These birds are crea- and are all but gone on the Rice and Stafford counties. The tures of open spaces with clear Chautauqua County area. most evident explanation is tree horizons, but invasive trees Survey areas in Woodson, Allen, invasion. And trees now threaten have forced them from other- and Anderson counties may be occupied prairie chicken range farther west and north. It may be confusing to hear that prairie chickens in the Flint Hills are disappearing in some areas because of too little fire. More attention has gone to the opposite situation; annual spring burning of vast sections of the central Flint Hills and the associated early-intensive grazing system have left greater prairie chickens and other ground dwelling birds with little or no residual nesting cover. Neither of these fire extremes are what’s needed. Most prairie wildlife are adapted to a shifting mosaic of The manager of one Barber County pasture (left of fence) has done a good job of con- burned and unburned areas like trolling cedar invasion, but his neighbor has not. This creates a situation of continuous reinvasion of the well managed pasture with seed from the neighbor’s trees. that provided in the “patch burning – patch grazing”

3 system that mimics the dynamic is not an issue just for prairie landscape once created by fire chickens. Accumulating scien- and bison. That innovative tific evidence suggests that rela- system, developed at Oklahoma tively few trees can have major State University, is worthy of its negative impacts on those own story. Suffice it to say that species of birds that are highly burning once every three years dependent on open prairie — or even three years out of five the so-called grassland obligate would go far to improve the species. A recent study in future of greater prairie Arizona indicated that commu- chickens in the Flint Hills by nities of grassland songbirds maintaining prairie health, begin to decline in habitats with leaving nesting cover, and sup- as few as four junipers per acre. pressing tree invasion. Research in Oklahoma and Recent research has begun to other states have shown that offer an explanation of prairie grassland birds directly decline As trees encroach, the variety and chickens’ intolerance of number of predators increases. as trees encroach. Part of this invading trees. By radio decline may be tied to behav- marking lesser prairie chickens, ioral avoidance of vertical struc- students of Kansas State chickens than we might have ture, as has been seen with University professor Robert originally believed. This behav- prairie chickens. Research in Robel have revealed some ioral avoidance means it won’t southwestern Missouri found important clues. While tree take a sweeping front of wood- that even diminutive Henslow’s invasion was not an issue on the land but only widely-scattered sparrows avoided woody cover, sandsage prairie study area, trees to eliminate prairie albeit to a lesser degree. But lesser prairie chickens showed a chickens from what would oth- decreases in ground-nesting strong avoidance of man-made erwise be suitable habitat. This birds as trees encroach are not structures. These birds were vir- may be doubly true if trees just a consequence of some tually never located within a establish on the higher ground behavioral quirk. As trees quarter-mile of power lines preferred by prairie chickens. increase in prairie habitats, so despite quality habitat near Unfortunately, tree invasion does the variety and numbers of these structures. We can predators, both feath- only guess why prairie ered and furred. chickens avoid vertical Before I go further, structures. A reasonable understand this: Pred- explanation is that eons ators are important and of predation have beautiful, and we must favored survival of indi- not make them scape- viduals that perceived goats. Direct predator vertical structures, trees control aimed at bene- included, as hunting fiting grassland birds is perches for hawks and neither desirable nor owls and, consequently, practical. If the decline dangerous places for in grassland birds is to plump, meal-sized birds. be halted, it must If that’s the case, then happen through grass- the prospect of even land reclamation (tree minor tree invasion of removal) and better open prairie is more Tree encroachment in many Kansas counties is partly responsible grassland management threatening to prairie for the disappearance of prairie chickens. systems that favor

4 healthy prairie environments growing branches like and minimize predator oppor- eastern redcedar and tunity. Having said that, who of Russian olive can offer us has not noticed that red- pheasants winter cover. tailed hawks and great horned But as the trees grow, owls use trees and power line they become better poles as hunting perches. Crows predator habitat. and magpies, both notorious What’s more, both of nest predators, also increase in these species are highly abundance as trees encroach on invasive. In northern the prairie. The same goes for states from Montana to mammalian nest predators such Minnesota, wide plant- as skunks, raccoons, and red ings of evergreens may foxes. The increased numbers of have limited value as these predators inevitably severe winter habitat decreases the survival and for pheasants. But in Trees may allow nest parasites such as the brown- reproductive success of prairie Kansas, trees’ relatively headed cowbird to better locate grassland birds’ nests. birds. small contribution for Even popular game species winter cover does not offset the results of an excellent study in that we normally don’t associate greater risk of increasing preda- which bobwhites and raccoons with open prairie can suffer as tors. As for taller deciduous were simultaneously monitored trees improve predator habitat. trees, there’s not one lick of evi- in the same area using radio Research in northeastern dence that they significantly transmitters. Not surprisingly, Colorado showed that pheasant benefit ring-necks, either here or the very areas where quail had hens nesting within 600 meters up north. the poorest nest success were of tree plantings suffered much For bobwhites, the story is the same places where raccoons higher predation rates, mainly similar. Any quail hunter recog- spent most of their time. And by great horned owls, than hens nizes the value of woody cover. where were the raccoons that nested further away. I hate But if they’re paying attention, hanging out? They were in old to think of the number of trees they also understand that it’s fields and pastures infested that have been planted with the low-growing woody cover, as with eastern redcedar. good, if misplaced, intentions of offered by shrubs, that provides Besides increased predation, benefiting pheasants. In the the greatest benefit. I recently grassland songbirds have yet short term, trees with low- had an opportunity to hear another threat that increases with tree encroachment: nest parasitism. No, I’m not talking about lice or ticks. I am talking about cowbirds. Cowbirds don’t build their own nests but instead lay eggs in the clutches of other songbirds. The adults of the parasitized host species may not recognize the cowbird eggs as different and often raise the young cowbirds as their own. By diverting food resources, the cowbird nestlings have the effect of lowering the survival of Prairie birds, such as the grasshopper sparrow, avoid otherwise suitable grassland the host species’ own young. habitat as trees invade. Trees provide perches and nesting sites for avian predators. Several studies have docu- mented greater cowbird activity

5 with poorer grassland bird tree plantings. Because reproduction near wood- they’re vulnerable to fire, land edges. Researchers planting and maintaining suggest that elevated cedars in CRP almost perches provided by trees assures that future con- allow cowbirds to better trolled burns in these grass- locate nests of grassland lands will be more difficult. birds and to synchronize Increased difficulty often their egg laying with the translates to less frequent potential host. burns or no burns at all. Ironically, the greatest What’s more, the quality of avian threat to grassland habitat provided by these birds may be neither ungrazed grasses dimin- predator or nest parasite. ishes without fire, Among our most seriously becoming too thick and invasive tree species, matted for most wildlife to eastern redcedar is the use. Where woody plant- worst. The primary vec- ings are desired in grass- tors that spread redcedar lands, native shrubs are the are certain woodland birds best choice. They resprout Fire is an excellent tool to control trees on the prairie, but that were originally it’s far more efficient when trees are small. after fire, often producing attracted to the plains by better wildlife habitat than urban and rural tree plantings. Shrubs were a natural compo- the previous older growth, and These birds eat the cedar’s nent of many prairie systems they can even become effective berries, digest the fleshy parts, and have a legitimate, if limited, firebreaks. and expel the intact seeds while place in grasslands. Trees have Of course, conservation is an perching or in flight. The net an altogether different effect. ongoing journey with frequent effect is that redcedar has It’s critical for all of us, pro- course corrections to cope with become a metastasizing cancer fessional conservationists and ever-changing conditions. The of the prairie. laymen alike, to acknowledge first steps in making a correc- So, what can be done? For that we’ve made mistakes. tion are to recognize a problem starters, we need to get our ter- Inevitably, as our ecological and to understand its causes. A minology right. For as long as I knowledge grows, hindsight recent agreement between can remember, Kansas wildlife shows that some practices were Kansas State University’s managers, foresters, and soil not as clearly beneficial as once Kansas Forest Service and the conservationists have casually believed. Tree plantings at the Kansas Department of Wildlife referred to any woody planting hand of man, even some for per- and Parks illustrates their con- as a “tree” planting, even if all fectly legitimate purposes, were cern and has provided a good or most of what was planted the initial sources of invasive beginning. These agencies plan were shrubs. Organizations like trees in the western two-thirds to cooperate in educating their Pheasants Forever and Quail of Kansas. But far more trou- own staffs, landowners, and the Unlimited routinely have done bling is the fact that inappro- public as to where and what the same thing in counting priate tree plantings are still types of tree plantings pose a among their accomplishments common. threat to prairies and prairie some huge number of “trees” I get a knot in my stomach wildlife. At it’s heart, the agree- planted. While professional con- each time I see invasive trees ment aims to discourage tree servationists may understand planted on Conservation plantings on or near significant what this means, we’ve given Reserve grasslands. Inadequate blocks of grassland, particularly too little thought to how this management is already a if potentially invasive species “tree” vernacular may have problem for many CRP stands, are being considered. misled the general public. and this can be exacerbated by Redirecting future plantings

6 away from grasslands is a small to tree invasion. Many ranchers already do a step in the right direction, but Excessive grazing pressure good job of managing their pas- rescuing Kansas prairies will has left some livestock pro- tures and preventing tree inva- take much more than some ducers with few options. sion, but some land managers written agreement. More Controlled fire is the least do not. Many cases of tree inva- landowners and land managers, expensive and best means of sion are rooted in an inadver- private and public, must recog- preventing tree invasion, but it tent failure to recognize the nize the magnitude of this takes adequate fuel — residual problem. Where that’s the case, threat. It’s too easy to ignore grass — to carry a fire hot recognition of the value of our little tree seedlings scattered enough to do the job. If grazing prairies and the threat posed by around a pasture. But give them pressure has been too heavy, too tree invasion may go far toward five years, and they start lim- little fuel remains, and the pas- correcting the problem before iting livestock forage produc- ture may suffer not only from it’s too late. tion and grassland wildlife poor grazing management, but Unquestionably, ranchers are habitat. Give them another five invading trees as well. As more the most important stewards of years, and it may be too late. It’s trees invade and grow, less live- the prairies. Most recognize when they’re small that invasive stock forage is produced. If their own interest in preventing trees are easiest to control with stocking rate is kept steady, invasive trees from taking over either fire, cutting, spot grass condition further deterio- grasslands. But many will need spraying, or some combination rates, and pastures can become help from public and private of efforts. Once invasive trees trapped in a cycle of decline that sources, if prairies are to be get out of hand, costs of can be broken only by near maintained. Conservationists, removing them can become pro- heroic, expensive efforts. Some public and private, must join hibitive. The old axiom, “an of Kansas’ grasslands are with ranchers as allies in ounce of prevention is worth a already at this stage. With no turning back this invasion. It pound of cure,” may be an intervention, more are just a few will take money, time, and understatement when it comes years away. effort. The soldiers will range from ranchers to boy scouts, from government officials to private entrepreneurs. They must wield weapons like tree shears and pruning shears, chain saws and bow saws, drip torches and Tordon. In the process, they will better under-

Results of a study that monitored the activity of both bobwhites and raccoons with radio transmitters showed quail nesting success was poorest in areas where raccoons were most active. And raccoons spent much of their time in areas infested with redcedar.

7 stand the value of the prairie and the value of a helpful friend. Grassland reclamation will not be a one-pass deal. The seeds have already been sown for a second wave of trees. If reclamation isn’t done right and better grassland management doesn’t follow, the second wave will be more aggressive than the first. Cutting hedge, locusts, or Russian olives without treating the stumps with the right herbi- cides is pointless. Burning and clipping cedars without follow- up fires and better grazing man- agement could prove the same. Of paramount importance is Certain woodland birds spread redcedar by eating the berries and expelling the seeds in flight or while perched, which explains the cedars under this fence wire. the need to assure that invasive trees advance no farther. Of course, there are good of redemption for us to kill trees Complacency toward our uses and appropriate places for that invade our prairies as it is remaining uninvaded prairies trees on the plains. But we have for others to plant trees in a would prove a huge mistake. planted trees on the prairie with forest clear cut. We must realize Focusing just on the worst- a near-religious fervor only to that on the prairie, occasional invaded grasslands could leave discover that some spread like fire is an act of renewal, not our resources and resolve hell. Those of us living on the destruction. We should exhausted, only to discover new Great Plains must come to applaud, not deride, those who areas invaded. realize that it is as much an act properly and carefully apply it. It is not for us on the plains to grow second-rate versions of the great deciduous forests of the east or the conifer forests of the west. Our responsibility is to guard our precious remaining prairies for ourselves and our children, for spectacular prairie chickens and tiny grasshopper sparrows, and for the other people and creatures of the Earth. Maybe you remember the chorus of an old Joni Mitchell song. “Don’t it always seem to go that you don’t know what you’ve got ‘till it’s gone?” When it comes to our prairies, I hope Randy Rodgers photo the answer to that question is Even in far western Kansas, tree invasion is a problem. These scattered Siberian elms, “No!” with more growth, will provide perches and nest sites for avian predators and reduce the value of this Greeley County Conservation Reserve stand for grassland wildlife.

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