Effects of livestock grazing and trampling on aquatic and riparian habitats in the western United States

Influence On Response Causes Impacts References
Water quality
Nutrient concentrations Increase Runoff from disturbed stream banks; livestock urine and manure deposited into stream; nutrients concentrated in reduced quantity of water Possible water salinization and eutrification of isolated pools and downstream lakes; alteration of instream species composition Schepers et al. 1982, Taylor et al. 1989
Bacteria/protozoa Increase Direct fecal deposition into water; fecal material in runoff; sediments containing buried microorganisms churned up by hoof action Higher human and wildlife disease-producing potential from pathogens; human health endangered by swimming and other contact Johnson et al. 1978, Stephenson and Street 1978, Stephenson and Rychert 1982, Tiedemann and Higgins 1989, Tiedemann et al. 1987
Sediment load and turbidity Increase Instream trampling; disturbance and erosion from denuded banks; reduced sediment trapping by streambank and instream vegetation Sediments blanket spawning gravel, entombing or suffocating fish embryos and juveniles; reduced dissolved oxygen levels; reduced foraging success by aquatic organisms; disruption of fish migration and respiratory systems of invertebrates; reservoir storage capacity diminishes more rapidly than projected; increased costs for filtration of domestic water supplies Winegar 1977, Johnson et al. 1978, Stevens et al. 1992
Water temperature Increases Increased solar exposure due to reduced shade from streamside vegetation and to loss of undercut streambanks; widened stream channel, exposing more water surface to solar radiation; lower summer flow Increased evaporation and salinity; reduced pool volume; poor to lethal environment for salmonids and other temperature-sensitive species; reduces fish growth due to increased metabolic rate; shift from salmonids to non-game fish; changes in growth rate and population size of cyanobacteria, algae and other aquatic organisms; increased incidence of lethal water-borne diseases; higher decomposition rates Duff 1977, Tiedemann and Higgens 1989, Platts 1991
Dissolved oxygen levels Decline Higher water temperatures Insufficient oxygen in spawning gravels; reduced food consumption, growth and survival of salmonids and other aquatic species, especially at their early life stages; reduced prey items for fish; reduced decomposition rates; increased toxicity of toxicants  
Influence On Response Causes Impacts References
Stream channel morphology
Channel depth Increases Downcutting from higher flood energy Lowered groundwater table; narrowing of riparian zone; high flows contained within channel, thus precluding build-up of flood plain Winegar 1977
Channel width Increases Breakdown of streambanks by trampling; increased erosion from greater flood velocity; erosion of stream banks due to loss of vegetation to cattle Further loss of riparian vegetation; higher water temperatures; decreased water depth Duff 1977, Marcuson 1977, Platts 1981a, Kauffman et al. 1983b, Hubert et al. 1985, Stuber 1985
Channel stability Decreases Bare streambanks and channel bed easily eroded. Wider stream bed Widening of channel; loss of pools and meanders. Higher water temperatures; reduced habitat for aquatic organisms Marcuson 1977m Dudley et al. (in prep), Platts 1981a, Hubert et al. 1985, Stuber 1985
Channel bed—Gravel Lost Increased flood velocity and energy; reduction in large woody debris Reduced spawning habitat and habitat for benthic organisms Duff 1977
Channel bed—Sediments Increase Increased streambank erosion Suffocation of fish eggs and fry due to low intragravel oxygen levels; degraded stream habitat for benthic organisms; filling in of pools Duff 1977, Hubert et al. 1985, Owens et al. 1996, Myers and Swanson 1996a,b
Streambanks Destabilized Loss of vegetation; trampling by livestock Increased streambank sloughing; increased erosion and water turbidity; increased channel width Duff 1977, Gunderson 1968, Marcuson 1977, Platts 1981a, Kauffman et al. 1983b, Rinne 1985, Stuber 1985, Myers and Swanson 1991 & 1992, 1996a, Kleinfelder et al. 1993
Streambank angle Laid back Streambank sloughing; livestock trampling Increased channel width; decreased water depth Platts 1981a, Myers and Swanson 1995
Streambank undercuts Reduction in quality and quantity Streambank breakdown by livestock and loss of stabilizing vegetation Fewer hiding spaces and pools for fish Platts 1981a, Kauffman et al. 1983b, Hubert et al. 1985
Channel form Fewer meanders in unvegetated gravel bars Increased water velocity; removal of stabilizing vegetation; erosion of streambank Increased erosion; fewer pools for fish; decreased streambank roughness Marcuson 1977
Pools Decrease in number and quality Loss of large woody debris; increased sedimentation Loss of fish habitat Duff 1977, Marcuson 1977, Hubert et al. 1985, Myers and Swanson 1991 & 1994 &1996a
Influence On Response Causes Impacts References
Hydrology (stream flow patterns)
Overland flow (runoff) Increases Reduced water infiltration into soils due to compaction and loss of streamside vegetation Increase in sheet and rill erosion; increased flooding; reduced groundwater recharge; lowered water table Orr 1975, Meehan and Platts 1978, Stevens et al. 1992
Peak flow Increases Larger volume of runoff flowing directly into channel Increased stream energy for channel erosion, downcutting of channel bed and gully formation  
Flood water velocity Increases Reduced resistance from streambank and instream vegetation; increased flood water volume Increased erosive energy and downcutting; removal of submerged vegetation and woody debris for pool formation; reduced habitat diversity Platts 1981a
Summer and late-season flows Decrease Less water stored in soil; lowered water table Aquatic organisms stressed by degraded water quality; less aquatic habitat; livestock impacts magnified Kovalchik and Elmore 1992
Water table Lowered Reduced water infiltration and increased runoff; incised stream channel Loss of aquatic and riparian species; perennial streams become ephemeral; loss of ephemeral streams Kovalchik and Elmore 1992
Influence On Response Causes Impacts References
Riparian zone soils
Bare ground Increases Vegetation consumed and trampled by livestock Drier soil surfaces; higher erosion potential Marcuson 1977, Hubert et al. 1985, Schultz and Leininger 1990, Clary and Medin 1990, Stevens et al. 1992, Popolizia et al. 1994
Water, ice, wind erosion Increases Streambanks exposed due to vegetation loss and livestock disturbance Higher sediment load to receiving stream; loss of fertile topsoil; suffocation of fish eggs; reduction of reservoir capacity Bohn and Buckhouse 1985a, Kauffman et al. 1983b
Litter layer Decreases Removal of aboveground plant biomass by livestock Lower infiltration rates; greater runoff and erosion; reduced soil organic matter; warmer, drier soils Marcuson 1977, Kauffman et al. 1983a, Shultz and Leininger 1990, Popolizia et al. 1994, Green and Kauffman 1995
Compaction Increases Trampling by livestock on wet, heavy soils; reduced litter and soil organic matter Decreased infiltration rates and more runoff; reduced plant productivity and vegetative cover Orr 1975, Clary and Medin 1990m Clary 1995
Infiltration Decreases Increased soil compaction from hoof action; reduced plant cover, litter, and organic matter Increased overland flow and erosion; reduced soil water content and plant growth; lowered water table Orr 1975, Bohn and Buckhouse 1985a
Fertility Declines Less soil organic matter; loss of top soil; loss of soil structure due to trampling Fewer soil organisms; reduced plant growth Marcuson 1977
Influence On Response Causes Impacts References
Instream vegetation
Algae Increase (bloom) More sunlight; higher temperatures; higher concentrations of dissolved nutrients Low night-time levels of dissolved oxygen US-EPA 1995
Higher plants (submerged and emergent) Decrease Trampled; buried in eroded sediments Reduced trapping of sediments; less food for aquatic organisms; higher water velocity and erosive force  
Influence On Response Causes Impacts References
Streambank vegetation
Herbaceous cover, biomass, productivity, and diversity Decline Grazing and trampling by livestock; selective grazing on palatable species; loss of vulnerable species; lowered water table; drier, warmer, more exposed environment Less detritus (food inputs) for stream and aquatic organisms; higher water temperatures in summer and cooler temperatures in winter; degraded habitat for fish and wildlife; reduced biodiversity; loss of moisture-and shade-loving species; replacement of riparian specialists with weedy generalists; loss of ecosystem resiliency; higher water velocities during floods; reduced sediment trapping Duff 1977, Marcuson 1977, Winegar 1977, Kauffman, et al. 1983a, Elmore and Beschta 1987, Medin and Clary 1989, Schultz and Leininger 1990, Clary and Medin 1990, Stevens, et al. 1992, Dudley et al. (prep), Popolizia et al. 1994, Clary 1995, Green and Kauffman 1995
Overhanging vegetation Declines Grazing and browsing by livestock Less shade; higher water temperatures; less detritus to stream organisms Marcuson 1977
Tree and shrub biomass and cover Decline Browsing by livestock on shrubs and tree saplings when they are most vulnerable Decline in streambank stability; increased erosion; reduced stream shade and higher water temperatures; reduction in detritus and essential nutrients; loss of complex vegetation structure for wildlife Marcuson 1977, Kauffman et al. 1983a, Taylor 1986, Schulz and Leininger 1990, Sedgwick and Knopf 1991, Boggs and Weaver 1992, Kovalchik and Elmore 1992, Green and Kauffman 1995
Species composition Altered Lowered water table; warmer, drier environment; livestock selection of palatable species; compacted and disturbed soils Replacement of riparian species by upland species and exotic weeds; reduction in riparian area Kauffman et al. 1983a, Clary and Medin 1990, Schulz and Leininger 1990, Green and Kauffman 1995
Structure (vertical and horizontal) Simplified Loss of trees and large shrubs; reduced plant establishment in drier soils Loss of sensitive bird species; reduction in wildlife habitat Taylor 1986, Knopf et al. 1988, Medin and Clary 1989
Plant age-structure Becomes even-aged Reduced plant establishment and survival due to browsing and grazing Reduced wildlife habitat Kauffman et al. 1983a
Plant phenology Altered Less shade and soil litter create warmer, drier environments Increased frost damage plants in fall Kauffman et al. 1983a
Plant succession Impeded Late-successional species grazed and browsed Retrogression Kauffman et al. 1983a, Green and Kauffman 1995
Influence On Response Causes Impacts References
Aquatic and riparian wildlife
Fish—Species diversity, abundance, and productivity Decrease Higher temperatures increase fish mortality by breaking down physiological regulation of vital processes such as respiration and circulation, and negatively affects fish spawning, rearing, and passage; greater water turbidity, increased siltation and bacterial counts, lower summer flows, and low dissolved oxygen levels reduce fish survival; damage to spawning beds; less protective plant cover; fewer insects and other food items; streambank damage; decreased hiding cover; reduced resistance to water-borne diseases Loss of salmonids and other sensitive species; loss of avian and mammalian predators; replacement of cold-water, riparian species with warm-water species Duff 1977, Marcuson 1977, Stuber 1985, Dudley and Embury 1995
Macroinvertebrates (mayflies, stoneflies, caddisflies, etc.)—Diversity, abundance, and species composition Altered Higher water temperatures from loss of shade; lower dissolved oxygen levels, increased sedimentation; reduced plant detritus for food Loss of species that require cleaner waters; less food for higher trophic levels; reduced litter breakdown Rinne 1988
Amphibians and reptiles—Diversity, abundance, and species composition Decline Decline in structural richness of vegetative community; loss of prey base; increased aridity; loss of thermal cover and protection from predators; water temperatures lethal to tadpoles Loss of biodiversity and prey for higher trophic levels Jones 1981, Szaro et al. 1985, Dudley and Embury 1995
Birds—Diversity, abundance and species composition Altered Reduction in food, water quality and water quantity; loss of perches, nesting sites, and protective plant cover; loss of complex vegetational structure Reduction in biodiversity; replacement of riparian specialists by upland species and generalists; loss of some neotropical migrants Taylor 1986, Sedgwick and Knopf 1987, Knopf et al. 1988, Schulz and Leininger 1991, Clary and Medin 1992, Stacey 1995
Mammals (large and small)—Diversity, abundance, and species composition Altered Loss of riparian habitat and food sources; warmer, drier, more exposed environment; behavioral characteristics such as avoidance of livestock Habitat shifts by wildlife; suboptimal nutrition for females and offspring; changes in predator-prey relations; altered herbivory and other ecosystem processes; lower beaver activity with their creation of wetlands; riparian species replaced by upland species and generalists Winegar 1977, Loft et al. 1991, Medin and Clary 1989, Schulz and Leininger 1991, Clary and Medin 1992
Threatened and endangered species Abundance Reduced Loss of habitat; disturbance; livestock herbivory; competition with livestock; habitat fragmentation Possible extinction Dudley and Embury 1995, USDI 1994a