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Livestock grazingand the

aquatic environmentA thorough understanding of relationships between

livestock grazing and fisheries is neededto manage range adjacent to coldwater streams

WILLIAM R. MEEHAN and WILLIAM S. PLATTS

LIVESTOCK regularly uses valley bot-toms adjacent to streams in the West as

grazing and loafing areas. Until recently,the effects of this use on aquatic resourcesin coldwater streams had not been iden-tified or quantified. As a result, livestockgrazing and fisheries generally were andstill are managed without a thorough un-derstanding of their interrelationships.

The combined effects of geology,climate, geomorphology, soil, vegetation,and water runoff often result in unstablestream conditions in the natural state.When land uses place additional stress onaquatic habitats, damage usually occurs.

Extent of Range Resources

Rangeland is usually defined as land onwhich grasses, forbs, or shrubs predomi-nate as the native vegetation. Even com-mercial forest can be used for livestockgrazing. Forest range includes all naturalecosystems that either produce or are

William R. Meehan and William S. Platts areresearch fishery biologists with the Forest Ser-vice, U.S. Department of Agriculture, located atthe Pacific Northwest Forest and Range Experi-ment Station, Corvallis, Oregon 97331, and theIntermountain Forest and Range ExperimentStation, Boise, Idaho 83706, respectively.

274 JOURNAL OF SOIL AND WATER CONSERVATIONReprinted from the Journal of Soil and Water Conservation

November-December 1978, Volume 33, Number 61978 Soil Conservation Society of America

"Purchased by the Forest Service, U.S. Departmentof Agriculture, for official use."

leek- .,1140-,

capable of producing forage (16). This en-compasses 1.2 billion acres in the 48 con-terminous states, 622 million acres in the11 western states.

In 1970 livestock grazed on 834 million(70 percent) of these forest range acres.This use amounted to 213 million animalunit months (AUM).

Research Interest in Forest Range

Conservation and management of rangegenerally began and focused on the nation-al forests (59). National forests resulteddirectly from the action of leaders whorecognized the widespread exploitationand depletion of forest and watershed re-sources. A system of forest reserves estab-lished in 1891 was transferred in 1905 towhat has since become the U.S. Forest Ser-vice. The areas later were renamed na-tional forests.

Serious concern about national forestland management developed in the late1920s. The concern focused primariy ongrazing lands. Research showed that thedegree of soil erosion caused by livestockgrazing varied with slope gradient, aspect,soil condition, plant type, vegetation den-sity, and accessibility to livestock (48) butdemonstrated that soil disturbance wasgreater in areas overused by livestock (13).The susceptibility of soils to erosion in-creased as vegetation deteriorated. Live-stock trampling reduced ground cover den-sity and increased bare soil openings (39),which usually resulted in increased water-shed runoff and erosion.

Proper grazing use, however, causesminimal, if any, resource damage, and bythe mid-1960s new approaches were beingconsidered. Rest-rotation grazing, for ex-ample, was found to benefit range condi-tions (22). Livestock grazing research con-tinued to focus on impacts on forage andphysical watershed characteristics, how-ever. What these influences meant toaquatic ecosystems did not receive ade-quate attention.

This changed in the early 1970s, whenconcern began to grow about the effects oflivestock grazing on biotic resources.Severe changes were found in streamsideenvironments from livestock use that couldaffect the quality of the fishery (41).Management officials (8) concluded thatlivestock grazing severely damagedstreams in Nevada. The supporting evi-dence was subjective, however. Never-theless, researchers began to look at in-fluences on resources other than the land.

History of Range Use

Several documents trace the history oflivestock production on public and private

ranges (8, 37, 40, 59). Before white settlersmoved into the western states, wild ungu-lates grazed compatibly with the carryingcapacity of natural ecosystems. If, for somereason, the forage species on a given rangebecame scarce during a particular seasonor year, wild grazing animals eithermigrated to more favorable range or in-creased mortality brought the herds intobalance with range capacity.

The grazing potential of the vast range-lands became apparent early in the na-tion's westward expansion. As mansaturated the ranges with livestock andconfined them within manmade barriers,drastic changes in vegetation occurred.Livestock trampled and compacted thesoil. High quality, deep-rooted plantsgradually gave way to shallow-rootedspecies that were less nutritious and oftenonly of seasonal benefit.

As soil compaction increased, infiltra-tion of water into deep soils decreased andsurface runoff increased (20, 30, 46, 54,56). This accelerated erosion (5, 31) hadtwo major effects on terrestrial and aquaticproductivity. The erosive action of windand water began to strip the naturalecosystems of their rich top soils, and waterquality began to decline (15, 37) as the soilwas dumped into streams and rivers. Finesediment smothered spawning beds andaltered the habitat of invertebrate and fishpopulations.

As the livestock industry grew during the1800s and into the mid-1930s, livestocknumbers increased far beyond the carryingcapacity of the available range. Manyranges deteriorated badly. In response tothe situation, Congress in 1934 passed theTaylor Grazing Act to stop the damage tothe remaining public domain, to providefor its orderly use and improvement, andto attempt to stabilize the livestock in-dustry using these lands. While the intentof the act was good, the objectives werenot achieved. Grazing privileges were allo-cated largely on the basis of use prior to theact. Little attempt was made to regulategrazing according to the carrying capacityof rangelands. Also, there was little publicinterest in rangeland conditions during thisperiod.

By the mid-1960s management by allot-ment had become an accepted practice.The situation remains essentially the sametoday. Public awareness of environmentalquality, including the condition and use ofrangelands, has brought the original goalsof the Taylor Act more clearly into focus.

A number of recent publications sum-marize the literature on various aspects ofgrazing resources. One lists availablematerial on grazing in the Pacific North-

west (3). Another summarizes many of theeffects of grazing management and re-search in Europe and Asia as well as somework in the United States (1). Still anotherlists numerous documents pertaining to theeffects of livestock grazing on water quali-ty and associated factors (37). In addition,the Environmental Protection Agency pre-pared an annotated bibliography con-cerned with animal wastes (44, 45).

Effects on Water Quantity

Early livestock growers generally wereunaware of the grazing limits of vegetationand soil (11). Only recently have theseresources been given full credit for theirabilities to control water on the land (14).Range practices significantly affect wateryield, peak stream discharge, stormflowrunoff, and associated water quantity fac-tors. Water management and managementof rangelands are closely interrelated.

Many studies show that as grazing inten-sity increases water runoff increases (2, 21,27, 28, 30, 31, 39, 46, 51, 54, 56). Theprimary causes are soil compaction and re-sulting reduction in infiltration rate, aswell as cover depletion.

Other studies specifically demonstratedthat infiltration rates decrease as grazingintensities increase (7, 12, 23, 35, 47, 49,58). In one study (49), for example, in-filtration rates obtained with a sprinklinginfiltrometer over a 2-hour period werefive times greater on an ungrazed controlarea than on a heavily grazed area (12acres per animal unit), three times greaterthan on a moderately grazed area (17 acresper animal unit), and two-and-one-halftimes greater than on a lightly grazed area(22 acres per animal unit).

Effects on Water Quality

Range management practices can alterwater quality. Although a half century ofresearch has been devoted to this problem,the true effects on living systems remainunknown. Most studies to date have cen-tered on sediment accrual and increasedbacterial concentratons through the addi-tion of animal wastes to streams.

SedimentLarge quantities of fine sediment change

the structure of aquatic communities, di-minish productivity, and reduce the waterpermeability of channel materials used byfish for spawning (9, 34). In one case in-creases in fine sediment reduced the bioticproductivity of an aquatic environment by37 percent (52). In another case the reduc-tion was 59 percent (10).

Stream channel sedimentation caused bysoil erosion on rangelands was recognized

NOVEMBER-DECEMBER 1978 275

long ago as a major problem (37). Thegeneral impacts of sediment from range-lands on water quality have been docu-mented (11, 15, 18). The effects on fish ofsediment directly attributable to bad rangemanagement practices are not well docu-mented, however.

While several studies demonstrate thatrangeland abuses result in adverse hydro-logic consequences, including acceleratedsediment transfer from the land to streams(5, 6, 17), evaluations of the effects of graz-ing systems, such as rest-rotation and de-ferred-rotation, on instream sediment ac-crual are lacking. In a study of the grazingeffects on watershed hydrology in westernColorado, ungrazed watersheds producedonly 71 to 76 percent as much sediment asgrazed watersheds (30). Soils in this areaare poorly developed and generally consistof a shallow, weathered mantle overlyingthe widely distributed Mancos Shale.Sediments came from both gullies andhillsides, with site-derived sediments morepredominant on steeper slopes.

Rangelands account for an estimated 28percent of the annual sediment productionwithin Region 10 (excluding Alaska) of theEnvironmental Protection Agency and aresecond only to croplands in total sedimentproduction (37). Depleted plant cover andtrampled soils are the factors contributingmost to erosion on grazed, particularlyoverstocked, lands.

Animal Wastes

Considerable research has been done onthe effects of livestock wastes from feed-lots, pasture, and wildlands on waterquality (32, 36, 43, 55). Bacterial con-tamination has been the primary consider-ation in these studies.

In one of many specific studies on streampollution from animal wastes, dissolvedoxygen stress and high ammonia concen-trations killed essentially all the gamefish—largemouth bass, white crappie, andchannel catfish—in a 45-acre; flood con-trol reservoir (53). Inadequately treatedfeedlot runoff was pumped into the reser-voir. At the time of the fish kills, bio-chemical oxygen demand (BOD) concen-tration was 86.5 milligrams per liter. Thiscompared with 5 milligrams per liter in acontrol reservoir. Ammonium nitrogenconcentrations were 6 milligrams per literin the affected reservoir and 0.85 mil-ligrams per liter in the control reservoir.

While land spreading of animal wastes isan effective means of minimizing waterpollution because of the soil's natural wastetreatment capabilities, direct dumping offresh animal wastes into streams causes ex-cessive pollution (50). Concentrations of

animals, as in feedlots or heavily stockedareas, should be located away fromstreams and other drainageways.

Maintenance of water quality also re-quires care in the use of cattle manure slur-ries for irrigation (4). Lagoons or collectionpools for irrigation runoff must be isolatedfrom natural drainages or flood-proneareas so the wastes do not contaminaterunoff or groundwater.

Three groups of bacteria are indicatorsof pollution by livestock and wild ungu-lates: the coliform group, fecal coliformbacteria, and the fecal streptococci. In aColorado study (26), concentrations for allthree groups in a small, high-elevationstream were highest in the evening andlowest in the afternoon. This cycle ap-parently related to rising stream levels inearly evening that flushed streambanks.Highest concentrations of the coliformgroups in cattle-contaminated sites oc-curred during peak runoff periods in thespring. Fecal streptococci concentrationswere highest during mid-summer lowflows. Summer storm flows increased theconcentrations of all three bacterialgroups.

An earlier study involving several Colo-rado watersheds produced similar results(25). Still another study (38) identifiedoverland flow from summer rainstorms asthe single, most important factor regulat-ing bacterial counts.

While bacterial concentrations do notrelate directly to the suitability of fishhabitat, they are important to water quali-ty and, therefore, relate indirectly to fishhabitat.

Grazing Effects on Fish Habitat

There is a lack of quantitative data inthe literature pertaining directly to inter-relations between livestock grazing andcoldwater fish habitat. Some informationhas been gathered but remains unpub-lished (personal communication with ErrolClaire, Oregon Department of Fish andWildlife).

The most detailed, published researchwas conducted on Rock Creek in south-central Montana (19). The quantity ofbro • n trout in pounds per acre was 32.5percent greater in the stream sections adja-cent to an ungrazed area than in the sec-tion adjacent to a grazed area. Streamsidecover, such as overhanging banks, brush,and debris, was 76.4 percent greater in theungrazed area than in the grazed area.Other stream parameters in the RockCreek study were average eroded channelwidth and average water width (consider-ably greater in the grazed area than in theungrazed), percent of total stream as riffles

(greater in grazed areas), and percent oftotal stream as pools and runs (greater inungrazed area).

In a follow-up study to the initial workon Rock Creek, the pounds per acre ofbrown trout were 42.3 percent greater inthe stream along an ungrazed section thanalong a grazed section (33).

The density of brown trout in centralOregon's Little Deschutes River appearedin a recent study (29) to be determinedprimarily by the physical environment,particularly cover. While the researcherlacked quantitative data relating cover tolivestock grazing along the stream, thistreatment was an implied source of stream-side cover reduction.

On a 40-mile segment of Bear ValleyCreek in central Idaho, fish habitat wasdamaged more along grazed sections,primarily from bank trampling, thanalong ungrazed sections (42).

Grazing Systems and Range Improvements

A grazing system designates a special-ized management strategy. Most currentsystems are based on grazing selected pas-tures, with certain types and timing ofgrazing or nongrazing recurring at yearlyintervals. The systems vary depending onthe livestock operation and the type andcondition of rangeland.

Five grazing systems are commonly usedto distribute livestock better on the rangeavailable and provide better plant growthand vigor. These systems are season-long orcontinuous grazing, rotation grazing, de-ferred grazing, deferred-rotation grazing,and rest-rotation grazing (24, 57).

Season-long grazing, one of the earliestpractices, requires the least range invest-ment. Handling and movement of live-stock are minimized. Problems with thesystem include the concentration of ani-mals at favored locations, especially inriparian habitats; inadequate use of theherbage available; and overuse of moredesirable forage plants. This system oftendisperses livestock use over more streambottomlands than some of the crowdingtechniques, such as rest-rotation.

Rest-rotation grazing has some disad-vantages because it often requires morelivestock movement. This increases thetrailing potential in riparian habitat.While trampling may help plant ripenedseeds, it also causes streambank erosionand instability. Nevertheless, the system isa popular one. Recent research indicatesthat rest-rotation grazing may have harm-ful effects on other land uses.' Its effects on

'Meiners, William R. 1974. "Rest-Rotation Grazing—A Bummer. - Paper given at the 27th Annual Meet-ing, Society for Range Management, Tucson, Arizona.

276 JOURNAL OF SOIL AND WATER CONSERVATION

f - 44,44 -1**'.A bull throwing pieces of sod into the air with his head caused this severe streambankdamage.

It•

aquatic and riparian environments havenot been thoroughly documented, how-ever.

Grazing systems are varied to meet therequirements of a livestock operation, pro-mote the growth of forage plants, andmatch soil qualities. While modern systemspromote the growth of desirable plants,research has not determined how thesesystems relate to the environment.

Many range management practices im-prove forage resources and their use bylivestock (60). Fertilization, seeding,undesirable plant and animal control,mechanical soil treatments, waterspreading and drainage, prescribed burn-ing, and timber thinning are among themethods used to improve range forageresources. Water developments, fences,trails, and similar improvements permitmore effective grazing management.Long-term closure or temporary (3- to5-year) exclusions of livestock by fencingmay be the only effective restorationmeasure in some cases.

These factors and other managementelements, such as kind of livestock, seasonsof use, and grazing intensity or stocking'rate, must be thoroughly understood be-fore resource managers can manipulategrazing systems to also protect the highquality habitats of resident as well asanadromous coldwater fishes.

Recommendations for Future Study

Further research is needed on both thephysical/chemical and biological aspects oflivestock grazing and aquatic habitat inter-relationships. The resource manager needsthis type of quantitative information tomake sound land use planning decisions.Physical and chemical considerations in-clude the effects of livestock grazing invalley bottoms on water quality, streamchannel morphology, streambed condi-tion, and the riparian zone. Biological in-formation must concern livestock impactson standing crop and species diversity offish and benthic invertebrate populations,bacteriological aspects of water quality,and recreational and esthetic values in-volved in use of the fishery and aquatic andriparian habitats.

Modern grazing systems seek to improvelivestock production while protectingrange. Resource managers need to knowhow these grazing systems influence otherresources, including anadromous and resi-dent coldwater fish populations.

Before the impacts of such land uses aslivestock grazing on fish habitats can beevaluated, researchers need to know whatthe natural or pristine conditions ofstreams are or were prior to these uses.

Pristine habitats are increasingly difficultto find. Serious consideration should begiven to locating and preserving suchstream habitats to serve as study areas andto furnish baseline data on the conditionand productivity potential of streams inthe western United States.

Once natural conditions are establishedand the effects of grazing various streamand riparian habitats are known, thenresearchers will be able to provide resourcemanagers with guidelines for predictingthe effects of alternate grazing strategies onthe condition and productivity of streamand riparian systems. This informationthen, will enable resource managers tomake decisions more effectively on the useof rangelands with maximum considera-tion of aquatic resources.

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