&ER&
United States
Environmental Protection
Agency
Office of
Federal Activities
(2252)
EPA 300-B-94-004
February 1994
Background for NEPA
Reviewers
Grazing On Federal Lands
-------
BACKGROUND FOR NEPA REVIEWERS:
GRAZING ON FEDERAL LANDS
February 1994
U.S. Environmental Protection Agency
Office of Federal Activities
401 M Street SW
Washington, DC 20460
EPA Headquarters Library
-------
Background for NEPA Reviewers - Grazing
DISCLAIMER AND ACKNOWLEDGEMENTS
The mention of company or product names is not to be considered an
endorsement by the U.S. Government or by the U.S. Environmental
Protection Agency (EPA). This document was prepared by Science
Applications International Corporation (SAIC) in partial fulfillment of
EPA Contract 68-C8-0066, Work Assignment C-4-71.
February 1994
-------
Background for NEPA Reviewers Grazing
TABLE OF CONTENTS
INTRODUCTION 1
Overview of Grazing Practices and Associated Impacts 1
TECHNICAL DESCRIPTION OF GRAZING ON FEDERAL LANDS 4
National and Regional Perspectives 4
Grazing Fundamentals 6
Rangeland Management 10
POTENTIAL SIGNIFICANT ENVIRONMENTAL IMPACTS 11
Direct Impacts 12
Indirect Physical Impacts 17
Indirect Impacts on Terrestrial Ecosystems 25
Indirect Impacts on Aquatic Ecosystems 26
POSSIBLE PREVENTION/MITIGATION MEASURES 30
SUMMARY OF INFORMATION THAT SHOULD BE ADDRESSED IN NEPA
DOCUMENTATION 32
STATUTORY AND REGULATORY FRAMEWORK 33
REFERENCES 36
February 1994
-------
Background for NEPA Reviewers - Grazing
LIST OF FIGURES
Figure 1. Federal and Non-Federal grazing land in the United States,
by Farm Production Regions 5
Figure 2. The Interrelationship of Grazing Impacts 13
Figure 3. Sediment production as a function of vegetation cover 15
Figure 4. Mean infiltration rates of the midgrass community for various grazing practices
at the Texas Experimental Ranch 18
Figure 5. Stream Channel Morphology 21
Figure 6. CZARA Grazing Management Measures 35
LIST OF TABLES
Table 1. Summary of studies of the influence of livestock grazing on infiltration
on the Northern Great Plains 16
Table 2. Watershed parameter means for the midgrass interspace areas
in each grazing treatment at the Texas Experimental Ranch 19
Table 3. Mean Values of Stream Habitat Variables Measured in Heavily and Lightly Grazed
Reaches of Pete Creek in 1984 23
iii February 1994
-------
Background for NEPA Reviewers - Gradng
BACKGROUND FOR NEPA REVIEWERS - GRAZING ON FEDERAL LANDS
INTRODUCTION
The primary purpose of the Guidance for NEPA Reviewers - Grazing On Federal Lands is to assist
U.S. Environmental Protection Agency (EPA) staff in providing scoping comments and comments on
National Environmental Policy Act (NEPA) documents associated with grazing on Federal lands, such
as grazing Environmental Impact Statements (EISs) and Resource Management Plans. Pursuant to
NEPA and Section 309 of the Clean Air Act (CAA), EPA reviews and comments on proposed major
Federal agency actions significantly affecting the quality of the human environment. This document
has been developed to assist the EPA reviewer in considering issues related to grazing in the
development of NEPA/Section 309 comments.
This guidance is not intended to be all inclusive; rather, the document focuses on EPA's major
concerns with surface and ground water, soils, and ecosystems as related to livestock overgrazing and
provides technical background material explaining these issues. It does not restate traditional NEPA
concerns about impacts on archaeological resources, economics, and so on, but rather addresses the
technical environmental concerns related to overgrazing.
EPA realizes that rangeland management is often complex, and recognizes that each livestock grazing
operation and each EIS is unique. Thus, reviewers will have to conduct additional analyses to fully
understand projected impacts. The reviewer should not rely solely on this document as a definitive
list of potential impacts or areas that should be covered by NEPA documentation. This document is
more of a guide or introduction to issues associated with livestock overgrazing on Federal lands and
does not replace early involvement in the NEPA process, defining objectives, developing alternatives,
and determining effects based on knowledge of the issues and characteristics of specific areas.
Overview of Grazing Practices and Associated Impacts
Grazing on the open ranges of the Great Basin began in the mid 1800's and became a major industry
in the western U.S. as early as the 1870's, with peak numbers of cattle and sheep being grazed by
1890. By 1900, many unrestricted lands were overstocked and significantly, sometimes even
permanently, impacted. Impacts included trampled and compacted soils, lowered water tables in
some areas, and replacement of quality vegetation with less desirable, more shallow-rooted species.
As early as 1889, writers acknowledged that destructive grazing appeared responsible for denuding
slopes of vegetation, increased runoff, erosion, and severe flooding in some western States (Gifford,
NRC 1984).
In 1934, the system of free access to Federal lands ended with the passage of the Taylor Grazing Act
and the establishment of the Division of Grazing, later to become the Bureau of Land Management,
within the Department of the Interior. Although the Act was intended to rehabilitate rangelands,
livestock numbers were not controlled and little rehabilitation occurred. This act was the first of
many statutes directing the use of public lands for grazing. These statutes include the Multiple Use -
Sustained Yield Act of 1960, the Forest and Rangelands Renewable Resources Planning Act of 1974,
the National Forest Management Act of 1976, the Federal Land Policy and Management Act of 1976,
and the Public Rangelands Improvement Act of 1978. National grasslands were bought under Forest
Service management through the Bankhead-Jones Farm Tenant Act. The Fish and Wildlife Service
oversees grazing on National Wildlife Refuges and in National Parks.
February 1994
-------
Background for NEPA Reviewers Grating
Both the Bureau of Land Management (BLM) and the Forest Service, acting as caretakers for lands
under their jurisdiction, use an allotment system to control livestock grazing on Federal lands. Ten
year renewable permits are issued for each allotment with the total fee based on the number of
livestock and length of stay, calculated in terms of Head Months (HMs), or Animal Unit Months
(AUMs). The Forest Service defines a Head Month as one month's use and occupancy of the range
by one animal (one weaned or adult cow with or without calf, bull steer, heifer, horse, burro, mule
or 5 sheep or goats). An AUM is defined as the amount of forage needed to support a 1000 pound
cow and calf or 5 sheep for one month and consists of between 800 to 1000 pounds of forage.
Currently, Federal grazing allotments cover approximately 30 percent of the total 853 million acres
grazed nationwide, with most grazing on Federal Lands occurring in the western U.S.
Both the Forest Service and the BLM have separate requirements that apply to grazing. As part of
their management responsibilities, both the Bureau of Land Management and the Forest Service
develop area-specific management plans called Resource Management Plans or Forest Plans. These
plans provide a comprehensive framework for managing and allocating uses of public lands and
resources, such as fluid and locatable minerals, riparian resources, wildlife and fish habitat, and
livestock grazing. Based on the management plans, the Bureau of Land Management and the Forest
Service develop allotment management plans and issue grazing permits for those allotments, which
present decisions on grazing at a more detailed level. More detail on these activities is provided in
Forest Service and BLM Handbooks.
Each of these activities or decisions, ranging from developing a plan to issuing a lease or taking a
specific range management action, may be subject to NEPA review. Typically the Bureau of Land
Management or the Forest Service prepares an EIS for each Resource Management Plan or Forest
Plan. For more detailed or allotment-specific activities, additional NEPA documentation is usually
tiered (based on the existing Resource Management or Forest Plan EISs). Activities that are not
addressed in existing NEPA documentation may require additional NEPA review, such as an
Environmental Assessment (EA) and/or an EIS, if the proposed action "significantly affects the
quality of the human environment." Under the CAA Section 309, EPA has the authority to review
and comment on each EIS.
Despite attempts to control environmental impacts caused by overgrazing and recent improvement in
rangelands according to some sources (Platts, 1990), many problems still exist in both upland and
riparian areas. Issues characterizing upland areas, especially in arid environments, include the
sensitivity of desert ecosystems and the extreme difficulty in reclaiming upland areas after impacts
have occurred. Riparian areas are often of more concern to the public and Federal land managers for
several reasons. Cattle tend to congregate in riparian areas, using them for shade and drinking water
and spending a disproportionate amount of time foraging and trampling these areas rather than upland
areas, posing a potentially higher level of damage. Also, riparian areas support a higher diversity of
terrestrial and aquatic organisms than upland areas and provide critical habitat for both terrestrial and
aquatic organisms. Erosion caused by overgrazing can reduce a streambank's water retention
capabilities, lowering the surrounding water table and often changing the character of the stream from
perennial to intermittent (GAO, June 1988a). Livestock and wildlife overgrazing can cause direct
impacts on upland and riparian areas, such as loss of vegetation and soil compaction that lead to
indirect impacts on the hydrology of an area and the ecosystems, both terrestrial and aquatic, that rely
on it.
The remainder of this document describes important issues associated with the grazing of livestock on
Federal Lands. Specifically, the document is arranged in the following sections:
February 1994
-------
Background for NEPA Reviewers - Grazing
technical description of grazing;
potential environmental impacts, both direct and indirect, associated with grazing;
possible prevention/mitigation measures;
types of questions that can be posed as part of the Agency's response to review of NEPA
documentation; and
explanation of the statutory and regulatory framework under which grazing on Federal lands
occurs.
As discussed above, this document does not substitute for indepth knowledge of rangeland
management concepts and site-specific issues.
February 1994
-------
Background for NEPA Reviewers - Grazing
TECHNICAL DESCRIPTION OF GRAZING ON FEDERAL LANDS
National and Regional Perspectives
Over 95 percent of livestock grazing on Federal lands occurs in the western U.S. The BLM and the
Forest Service manage a total of 461 million acres of public land. Of this, approximately 367 million
acres are in the western U.S.1 with grazing allotments covering about 70 percent of this area.
Specifically, the BLM has approximately 165 million acres with approximately 22,000 separate
grazing allotments (BLM, 1990). Of the Forest Service's 191 million acres, 104 million acres are
allotted to grazing (95 percent of these allotments are located in the west) with approximately 50
million acres classified as suitable for grazing (e.g., slopes are not too steep) (GAO, May 1991).
This compares with private grazing lands of approximately 603 million acres nationwide with 372
million acres of private grazing acreage in the western states1. Figure 1 shows both Federal and non-
Federal grazing lands in the U.S. Texas has the most non-federal grazing lands with approximately
115 million acres; however, there are no BLM or Forest Service lands in Texas (Department of
Agriculture, 1982).
BLM and the Forest Service manage public lands through allotments that typically have ten year
permits and sometimes yearly or seasonal licenses (which are more specific than 10 year permits).
Permits specify the number and type of livestock, an authorized season of use, and the AUMs (a
measure of the amount of grazing available). The acreage required to provide one AUM varies from
region to region, ranging from a low of 6.1 acres in Montana to a high of 21.8 acres in Nevada. The
overall average AUM is 13.7 acres. The average grazing allotment is approximately 8,500 acres (13
square miles) with allotments as small as 40 acres and as great as 1 million acres (GAO, June 1988b).
In many cases, allotments are interspersed with private lands, creating the checkerboard pattern seen
on most Federal lands maps. This checkerboard pattern hampers effective control by Federal land
managers, and requires constant cooperation between land mangers and ranchers.
According to 1990 statistics, BLM had about 165 million acres of grazing allotments, with almost
20,000 operators and 4 million head of livestock using 13.5 million AUMs (BLM, 1990). In 1986,
the Forest Service had about 102 million acres in grazing allotments (in 36 states) with 13,805
permits using a total of 8.6 million AUMs. GAO estimates that 25 to 30 percent of the Forest
Service allotments are in a declining condition and/or are overstocked.
As described above, Federal livestock grazing allotments cover about 30 percent of the total area
grazed in the U.S. (not including Alaska); however, Federal lands produced 13 percent of the total
AUMs nationally. According to 1988 estimates, less than 5 percent of the nations beef cattle and 30
percent of the sheep graze on Federal lands. In western states, one third of the beef cattle is grazed
at least part of the year on Federal Lands. About 2.2 million cattle and 2.1 million sheep graze on
BLM allotments each year. In many cases, large (greater than 500 head of cattle) livestock operators
use the public rangelands (15 percent of the operators use 58 percent of the allotments) (GAO, June
1988a and b).
1 Includes the states of Arizona, California, Colorado, Idaho, Kansas, Nebraska, Nevada, New
Mexico, North Dakota, South Dakota, Oklahoma, Utah, Washington and Wyoming.
February 1994
-------
Pacific
50.8 Million
Acres NR
Lake States
12.1 Million
Acres NF
Northern
Plains
83.4 Million
Acres NF;
Mountain i
211.3 Million
'jAcres NF;
f Corn Belt
30.7 Million
Acres NF
Appalachian
23 Million
Acres NF
26.8 Million
Acres NF
Delta
States
19.5 Million
Acres NF
Southern
Plains
Federal
Grazing
Lands
(BLM&FS)
Southeast
21 Million
Acres NF
Non-Federal
Grazing
Lands
115.3 Million
Acres NF
"142.2"!
Million
NF - Non-Federal lands, acreage based on 1982 figures.
Figure 1. Federal and Non-Federal grazing land in the United States, by Farm Production Regions.
Source: U.S. Grazing Lands: 1950-1982, Department of Agriculture.
-------
Background for NEPA Reviewers - Grazing
Grazing Fundamentals
Livestock grazing on Federal lands usually involves either cattle or sheep operations. Typically,
cattle are grazed in one of two types of operations, "cow/calf or "steer." In cow/calf operations,
cows and their calves are grazed until the calves are weaned to produce a calf crop. Each year, the
calf crop is sold between the ages of 6 and 12 months, to feed lot operations or to other ranchers as
breeding stock. A limited number of calves may be retained by the rancher to become breeding
stock. Unlike cow/calf operations, steer operations are seasonal and use forage for 3 to 9 months to
fatten cattle that are then sold to feedlots. Unlike cow/calf and steer operations, sheep are typically
herded through allotments and graze on a seasonal basis to take advantage of more succulent and
palatable forage. As the prune forage is consumed, the sheep are moved to new areas. Different
species of livestock graze in different ways. Herded sheep usually use slopes and upland areas, while
unherded cattle prefer lesser slopes or bottom lands. Of the forage consumed by livestock, cattle
consume the most, estimated by the Bureau of Land Management and Forest Service as 87 to 89
percent of allotted Federal land forage (GAO, June 1988b). Wildlife grazing, in addition to livestock
grazing, will also impact forage allotments.
When and where to graze livestock in order to optimize profits and provide ecologically-desirable
results depends on many factors. Availability of forage such as grasses, forbs, or even brush is one
of the prime considerations, as is easy access to water. Grazing animals prefer leaf tissue over stem
tissue, and green plant material over dry material (Wallace, 1984). As would be suggested by these
general rules, in some areas, streamside grazing by cattle often is more than twice the overall pasture
use, with reports of riparian areas comprising less than 2 percent of the total allotments providing
over 80 percent of the forage (Platts, 1986). Allotment management plans, however, can moderate
this phenomenon.
Although prediction of forage growth and proper grazing may be scientifically modelled,
sustainability of forage production from one year to the next depends on how heavily the area is
grazed, as well as other site specific factors and variables such as annual precipitation. Most plants
can withstand some loss of foliage and maintain their competitive position in the ecosystem and, in
some instances, moderate grazing may increase the production of plant material. However, the
approach to estimating the proper grazing intensity is complex, weighing site specific factors such as
plant physiology, soils, micrometeorology, plant demography, and competitive ecology.
In monitoring grazing areas, plant vigor and species composition and diversity are major elements in
determining if the area is too heavily grazed. Plant vigor reflects the capacity to rapidly produce both
vegetative and reproductive shoots, the storage of nutrient reserves and effective root system volume,
especially depth, when soil moisture and temperature are conducive to growth. Specific measures of
vigor include numbers of tillers produced following defoliation, total plant height, leaf length, seed
production, soluble carbohydrate concentrations, and root growth (CaJdwell, 1984). In some cases,
empirical measures are used to evaluate plant vigor. These include the ability to overwinter, to
endure subsequent drought following defoliation, or to produce seed in a year following defoliation.
However, less than positive results of empirical evaluations may not be known until the impact has
occurred.
In general, livestock grazing can be characterized in terms of intensity, duration and timing. In a
simplistic manner, grazing intensity is indicative of the amount of forage in a pasture that is grazed.
Grazing intensity is measured by number of animals per unit month and ranges from light to heavy;
light grazing is considered as use of 20 to 40 percent of the available forage, and moderate grazing is
February 1994
-------
Background for NEPA Reviewers - Grazing
estimated as use of between 40 and 60 percent of available forage. The term moderate grazing also
indicates that stocking rates are between those in a lightly grazed pasture and those in a heavily
grazed pasture. Heavy grazing, 60 to 80 percent of available forage, is still practiced, and is
considered a likely cause of poor conditions of riparian and other areas. Heavy grazing may also be
defined as the amount of forage consumed in a pasture in excess of its sustainable capability. In
assessing the impacts, however, much more is required than just the level of forage use. No grazing
strategy is implemented the same on every allotment. Rangeland management requires the integration
of complex site-specific factors, only a few of which are described here.
The timing for a first release of livestock into an area is an important factor in grazing management,
sustaining plant growth from season to season, and in trapping of sediment to rebuild riparian areas.
Early grazing begins when the cool season plant growth has peaked and warm season plants are
beginning their growth. Early grazing ends with the flowering of key species. Late grazing is
conducted only after seed ripe time when the period of maximum warm season plant growth is over
and seeds have been produced; the seeds then may be trampled into the ground by livestock. Some
growth of cool season plants may occur if moisture and soil temperatures allow. In order to maintain
seasonal grazing, livestock are often rotated from pasture to pasture, utilizing different pastures at
different stages of the growing season. Though rotation of livestock has typically been associated
with heavy stocking for short durations, it has also been used for short or long periods and with light
stocking.
Using these concepts, grazing systems have been developed to manage livestock. Grazing systems are
plans that differ with respect to periods of grazing, intensity of grazing, season, and stage of growth
of vegetation. Grazing systems are useful in that they may increase productivity of the land and,
ultimately, of livestock, by controlling grazing by both wildlife and livestock. Certain specific
systems have proven to be especially effective in riparian areas that are more susceptible to
degradation from overgrazing. Examples of various grazing systems are provided below for
descriptive purposes. Actual design and implementation of a grazing system requires the collection of
site-specific data and the analysis and integration of complex site-specific variables by personnel
trained in the field.
In addition, no grazing system is implemented the same on every allotment. Allotments are unique,
and management can only be designed through a comprehensive, integrated approach. Management
strategies are only as good as the permittee responsible for implementing the system. The best
possible system will fail without the commitment from the permittee to make it work. It should not
be assumed that a system will work in every situation. For example, while rotational grazing using
sheep is generally a good system for riparian protection, the system may not work if the herder
concentrates the sheep in streamside areas. Examples of grazing strategies are described below
(Platts, 1986, 1990, and 1991).
Continuous Season-Long. Under this grazing scenario, livestock have unrestricted access to a
specified range area for an entire vegetation growing season. Advantages are that season-long
continuous grazing permits maximum forage selectivity, while minimizing disturbances to livestock by
gathering, moving, and change in quality of vegetation (Platts, 1990). Drawbacks may be that
livestock overgraze certain vegetation or areas before others. In addition, livestock will generally
obtain much of their diet along riparian areas, typically minor portions of grazing allotments (Platts,
1986).
February 1994
-------
Background for NEPA Reviewers - Grazing
A 1977 study by Marcuson found that average channel width in a riparian area to be much wider after
season long grazing at 0.11 ha/AUM than in a comparable ungrazed area. This study also found that
heavy grazing and trampling by cattle left only 224 meters of undercut bank per kilometer in the
grazed area versus 686 meters of undercut bank per kilometer in the ungrazed area. As a result of
these erosional impacts to riparian areas under this grazing scenario, Platts does not consider this
strategy to be useful in those areas, as fishery productivity would be seriously impacted.
Short Duration - High Intensity. Short duration, high intensity grazing generally describes high
stocking, high intensity use in a designated area, over a short period of time. Livestock are placed in
an area for a period of one day to several weeks before being moved to the next area. This type of
strategy requires numerous pastures in order to ensure that a grazed section is unused for a significant
amount of time to permit regrowth. The layout of pastures is sometimes subdivided to resemble a
"wagon-wheel." This method requires almost daily checks on vegetative conditions to prevent
overuse. In general, this method is out-dated and is infrequently used.
Three Herd - Four Pasture. Also referred to as the Merrill Pasture System, this strategy allows each
pasture a period of nonuse within one four year cycle. Useful in upland areas, the Merrill Pasture
System requires less animal movement than other heavy use strategies, and has succeeded in
generating higher plant productivity in conditions with sufficient precipitation. However, one four-
month period of nonuse over a four year period is not sufficient to rehabilitate a heavily impacted
riparian area.
Seasonal Suitability. This strategy requires substantial fencing and frequent movement of animals
from pasture to pasture, providing heavily used areas with periods of nonuse for regeneration, during
selected periods of the grazing season. Depending on the extent of use prior to periods of nonuse,
riparian areas may not be able to regenerate sufficiently before livestock are re-introduced to the area.
In addition, there is seasonal variation in streambank stability, with greater potential for erosion
during the dryer hot season.
Holistic Method. This grazing strategy may be less straight-forward than others, requiring training
and management skills to enable heavy stocking and frequent movement dependant upon the growth
cycle of plants and other environmental factors. This method also utilizes livestock as a soil churning
mechanism to break up the soils, and increase soil porosity (its effectiveness is under debate). While
upland areas may benefit from this type of management, this grazing method may erode streambanks
in riparian areas, impacting streamside vegetation and overall riparian habitats.
Deferred. Deferred grazing strategy defers grazing in one or more pastures to permit desired growth
or regrowth or to produce ripe seeds prior to being grazed. The period of deferment may continue
for several years to allow vegetation to reestablish itself. This grazing strategy requires a substantial
amount of fencing and cattle movement, though the periods of rest offer opportunity for regrowth of
preferred grazing vegetation. Deferred rotation in a riparian area may be a useful grazing strategy in
a riparian area if overstocking is prevented in order to avoid streambank shear and erosion.
Deferred Rotation. The deferred rotation strategy delays grazing of key species until seeds have
matured by systematically rotating livestock among a number of pastures. If one pasture is grazed
early one year, pasture use sequence would change the following year so that a different pasture was
grazed early. This method requires a fair amount of fencing, however, vegetation is able to store
carbohydrates and set seed every other year. The period of nonuse will vary throughout the each
year, allowing areas of nonuse during critical periods to allow plant cover to increase.
February 1994
-------
Background for NEPA Reviewers - Grazing
Stuttered Deferred Rotation. Similar to the deferred rotation strategy, one pasture is deferred for part
of the plant growth period. The deferment is passed on to a different pasture but in the stuttered
method grazing use occurs on one pasture early for the first two years and another late the following
two years, whereas deferred rotation changes every year. A great deal of fencing, and movement of
livestock is required under this grazing scenario. However, as with the use of Deferred Rotation,
brushy species are given an opportunity for regrowth.
Rest-Rotation. This grazing strategy involves rotating livestock from one range area to another in
order to prevent overgrazing. Though this method may be costly since it may require fencing to
carve out range areas within an allotment, it allows grazed rangeland to rehabilitate while cattle are
occupying another portion of an allotment. This strategy has shown measurable success in some
habitats.
The rest rotation strategy is a multi-pasture design strategy that provides at least one year of rest for a
grazed pasture. This strategy is frequently combined with deferred, early, and late grazing techniques
so that pastures are rested until seed ripe time, and rested for seedling establishment. Depending
upon vegetation types and soil moisture content and temperature, three or more pastures are needed
for rest rotation to be successful.
Double Rest-Rotation. Under this strategy, an area or pasture with the highest riparian and stream
values would receive twice the amount of rest compared to the amount of rest allocated under the
normal rest-rotation grazing cycle. In a three pasture system, the most valuable riparian-stream area
would receive 2 years rest. A Forest Service study of a double-rest-rotation system, graze early
then rest 2 years, then graze late and rest 2 years, snowed no adverse riparian-stream impacts.
Rest-Rotation with Seasonal Preference. This strategy is most often applied to sheep since this
method requires frequent movement of the livestock in response to signs of range, riverine or riparian
habitat deterioration. The strategy encourages use of areas during periods of least impact to
vegetation, allowing plants to be grazed at particular times to allow rest to recover from past grazing
use.
Riparian Pasture. This grazing strategy places the riverine-riparian system within a controlled unit, to
permit grazing only in those areas of the stream that can provide vegetation without being negatively
impacted. Additional fencing is required under this scenario to prepare riparian pastures that
encourage utilization of both riparian and upland areas. Overuse of upland areas of the pastures is
also a concern in the event of increased sediment, or overland flows impacting the stream. The
advantage of individual pastures is the ability to encourage distribution evenly within each pasture.
Seasonal Riparian Preference. As with the Riparian pasture method, use of this strategy encourages
grazing of plants and streambanks during periods when the vegetation is less vulnerable to sustaining
damaging impacts. Fencing and frequent animal movement are also necessary in order for this
strategy to be successful, and grazing within each pasture must happen over a narrow period of time.
Winter. A form of seasonal grazing, winter grazing takes place when range vegetation is dormant
and streambanks frozen. Impacts to riparian areas may diminish under these conditions, since
streambanks tend to be more capable of withstanding the impacts of hooves while frozen. In riparian
areas, winter grazing in areas of low temperatures but little snow can be beneficial to the extent that
streambanks are sturdier, and vegetation dormant.
February 1994
-------
Background for NEPA Reviewers - Grazing
Holding. The holding strategy is a short to long term method of containing livestock in a specific
area of land prior to moving diem. This strategy permits animals freedom to move within a
designated area. These holding areas are useful not only to allow other pastures to be prepared for
grazing, but can also be used as disease treatment facilities, and for breeding purposes. Pros and
cons associated with this grazing strategy are similar to those under the season long continuous
strategy, such as preferred plants and riparian areas receiving excessive use (Platts, 1990).
Corridor fencing. Stream corridor fencing in riparian areas prevents overuse of streamside
vegetation, and assists in the rehabilitation of denuded portions of a riparian zone. This strategy
usually requires extensive fencing and involves high maintenance costs.
Rest. Certain areas may be rested until vegetation and/or riparian habitats are permitted to re-
establish themselves and regrow.
Rangeland Management
Modifications to rangelands can be used to mitigate impacts of livestock and wildlife grazing and are
discussed in a later section on mitigation. While modifications to rangeland can enhance grazing
opportunities, modifications may also result in adverse effects on water quality, as well as aquatic and
terrestrial ecosystems, if not properly planned and managed. Platts (1991) alluded to the variety of
activities that could occur as part of rangeland management, including the fertilization of lands;
irrigation and drainage of wetlands; brush, forb, and pest control; debris disposal; mechanical
treatment of the soil; seeding, prescribed burning; water supply development; fencing; and timber
thinning. Depending on the frequency, extent and appropriate implementation of these range
improvement practices, both positive and negative effects can occur. Potential negative impacts
include erosion and sedimentation, hydrologic modification, chemical contamination (pesticide and
fertilizer), and unfavorable ecosystem alteration. However, if rangeland improvements are tied to the
attainment of specific resource objectives, then such improvements may reduce the severity of grazing
impacts, thus the implementation of sound grazing practices.
10 February 1994
-------
Background for NEPA Reviewers - Grazing
POTENTIAL SIGNIFICANT ENVIRONMENTAL IMPACTS
Both livestock and wildlife overgrazing may cause direct impacts resulting in physical changes to the
rangeland, such as the removal of protective plant cover and damage from hoof action and trampling
to ground surfaces. These direct impacts may contribute to a host of indirect impacts such as erosion
and stream channel modification. Both direct and indirect physical impacts often result in changes to
terrestrial and aquatic ecosystems. These changes to the rangeland from overgrazing occur in both
upland and riparian areas. Impacts in both environs can affect stream water quality, although
activities in the riparian zone often cause more immediate and severe impacts. While it is difficult to
make generalizations concerning the effects that livestock and wildlife grazing practices have on
rangeland due to the geographic variability of vegetation, soils, climate, and topography, the majority
of the research reviewed for this document points out some common trends. To fully assess the
applicability of these trends, a knowledge of the site-specific conditions is important. Even the
grazing species is important; cattle and sheep have different impacts on streambanks. The stream and
its watershed function as a unit and therefore, management is most effective on a basin-wide approach
(Platts, 1986). Because much Federal land is intermingled with private land in a checkerboard
pattern, it is important to plan for the total ecosystem, considering grazing activities on adjacent and
nearby private land, as well as the activities on Federal land. For example, overgrazing on private
land upstream of public land may cause impacts to the public land. Although the land manager's
administrative responsibility does not apply on private land, recognizing impacts on a watershed basis
and integrating these into grazing management strategies is important.
One of the more significant hydrologic and water quality effects associated with overgrazing results
from impacts on soil from livestock hoof action and trampling. For example, hoof action and
trampling can disrupt natural soil conditions (e.g., soil structure, bulk density, and permeability) and
cause soil compaction, which leads to increased runoff and associated soil erosion and loss. The
removal of plant cover by the grazing animals exacerbates these problems by leaving even more soil
bared to disruption and compaction. Also, the removal of plant cover by grazing animals frequently
changes the overall density and composition of the native vegetation. As grazing-related activities
create conditions that increase runoff and soil erosion from the rangeland, stream water quality is
primarily affected by the increased amount of sedimentation. Also, hydrologic changes to the stream
channel due to increased water velocity and flow can occur. The reduction in plant cover can
indirectly affect water temperatures, especially expanding the range of temperatures experienced in the
stream and increasing maximum temperatures. Compaction can also affect the ability of vegetation
to establish, thus exacerbating erosion.
The effects caused by overgrazing result from a variety of interrelated factors such as climate,
vegetation, topography, soil characteristics, and the intensity, type and duration of livestock and
wildlife grazing. Therefore, the nature and extent of impacts from overgrazing will vary from
location to location due to the normal variability of ecosystem specific factors. Despite these
variabilities, the mechanisms causing the impacts (e.g., soil compaction and increased runoff) are
similar. Impacts can also vary significantly between grazing strategies. Because activities throughout
a stream's watershed (i.e., upland and riparian areas) can affect stream water quality, grazing
strategies should address both areas.
Livestock and wildlife grazing activities are associated with other causes of surface water degradation
such as bacterial/fecal contamination of water bodies, stream bank erosion and modification associated
with hoof or head (scratching, butting or digging) action, withdrawal of water for irrigation of
grazing areas, and drainage of wet meadows.
11 February 1994
-------
Background for NEPA Reviewers - Grazing
Figure 2 illustrates some of the interrelated impacts that stem from livestock and wildlife foraging and
trampling, such as changes in vegetative cover (density and type), affecting physical soil condition or
surface water hydrology. In general, the adverse effects associated with grazing increase as the
intensity of grazing increases.
This chapter is divided into two major sections: Direct Impacts and Indirect Impacts. Indirect
Impacts are further divided into physical impacts and ecosystem impacts. The major direct effects
includes a description of the effects of overgrazing and livestock trampling on vegetation and ground
surface conditions and the ensuing changes to physical characteristics of the rangeland, and changes to
infiltration rates. The discussion of the indirect impacts addresses erosion and sedimentation, channel
modification, water table changes, bacterial contamination, and temperature changes. While not all
grazing results in adverse impacts, and there may be some favorable impacts that are the result of
grazing, this section focuses on the potential adverse impacts of grazing activities.
Direct Impacts
Overgrazing of livestock and wildlife can affect rangeland in two major ways: (1) by reducing the
density (i.e., percent-cover) and quality of vegetation, and (2) by disrupting soil conditions and
causing soil compaction by hoof action and trampling. Each of these effects creates conditions which
lead to increased surface water runoff, sedimentation, and erosion. Livestock foraging reduces the
amount of cover provided by vegetation (including plant litter), which in turn creates a situation
where soil compaction, reduced rainfall infiltration, increased runoff, and soil erosion can occur. The
trampling by livestock further compacts soil, reducing infiltration and increasing surface runoff and
resulting soil erosion. (Blackburn, 1984 and Kauffman and Krueger, 1984)
Vegetation. Livestock overgrazing can reduce the health and vitality of rangeland vegetation,
therefore, reducing the amount of ground cover provided by the vegetation. Vegetation is specifically
affected by livestock in the following ways:
trampling causes soil compaction, thus decreasing water infiltration, causing increased runoff, and
decreased water availability to plants;
herbage is removed, which allows soil temperatures to rise and increases evaporation to the soil
surface;
physical damage to the vegetation occurs by rubbing, trampling, and browsing (Kauffman and
Krueger, 1984).
An additional factor is that as foliage is removed, plants put a greater portion of energy into regrowth
of leaves and less toward root growth which has the effect of reducing root biomass which in turn
reduces soil stability and leads to increased erosion. Altering vegetation patterns can result in greater
susceptibility to draught, fire, insects, and exotic plant competition.
As vegetation is harvested, total plant density and cover may decline, and a compositional change
may occur (e.g., decrease of grasses and forbs and increase of sagebrush). In some cases, less
desirable species may result. By altering the amount of vegetative cover and composition,
overgrazing ultimately increases the amount of bare soil on the rangeland that is subject to runoff and
erosion. It also creates conditions that can modify stream temperatures, thus causing a host of
ecological changes. Also, changes to vegetation from overgrazing can often result in an overall
decrease in the grazing capacity of the rangeland.
12 February 1994
-------
Background for NEPA Reviewers - Grazing
LIVESTOCK GRAZING
CAUSES
Reduction in amount of cover provided
by vegetation (including plant litter)
Disruption to ground surfaces and soil from
hoof action and trampling
WHICH LEADS TO:
Soil compaction
Decreased Rainfall infiltration
Decreased soil moisture
Increased runoff
Change in soil properties (e.g., Increased bulk density,
decreased permeability)
Increased soil erosion
Change in timing and magnitude of stream
flow events
RESULTING IN:
i
HYDROGEOLOGIC AND WATER QUALITY IMPACTS
Increased soil sedimentation in streams
Change in stream channel morphology
Change in temperature regime (expanded daily range,
increased temperature maximums)
Streambank erosion
Bacterial/fecal contamination of water bodies
Figure 2. The Interrelationship of Grazing Impacts.
13
February 1994
-------
Background for NEPA Reviewers - Grating
Impacts to the rangeland (and ensuing water quality impacts) are intensified as the amount of
vegetative cover decreases. Blackburn (1984) summarized two studies which attempted to define a
cover threshold (i.e., percentage cover by vegetation) below which serious impacts to soil infiltration
and associated increased runoff (and soil erosion) occurred.
For example, Figure 3 shows that sediment production increases exponentially as plant cover
decreased. These findings represent one study area, and the percent cover that serves as the threshold
point varies with location according to a variety of site specific conditions. Generally the cover
thresholds range from SO percent cover (Dadkhah and Gifford, 1980) to 70 percent cover (Packer,
1953). However, the threshold point can vary depending on the initial amount of vegetation at the
site and the intensity of use at the site.
Grazing intensity (as measured by the percentage of ground trampled) is one of the major factors that
affects the maintenance of the cover threshold. As common sense dictates, the impacts of grazing on
vegetation increase with increased grazing intensity; high intensity grazing (i.e., high density) causes
serious impacts, while there may be little difference between light, moderate, and ungrazed areas.
The impacts of overgrazing on vegetation result in surface water quality problems and hydrologic
modification largely due to the amount of soil that is exposed from the reduction in vegetative cover.
This can increase the impact of raindrops on soil, possibly causing a decrease in infiltration rates,
increase in surface runoff, and/or an increase in soil erosion. In a similar manner, livestock hoof
action and trampling can also affect soil properties and ground surface conditions which can cause a
range of subsequent impacts to water quality. Each of these impacts (infiltration rates, sedimentation)
are described below.
Infiltration Rates. Not only does livestock grazing affect the rangeland through foraging, but the hoof
action and trampling causes soil compaction which leads to decreased infiltration rates, and increased
runoff, and/or soil erosion. Innumerable studies have shown that infiltration rates decrease as a result
of trampling. These impacts increase as the intensity of grazing increases (Warren et al., 1986;
Wood and Wood, 1988; Wood and Blackburn, 1981; Weltz and Wood, 1986). The most important
factors affecting infiltration rates are: soil aggregate stability, bulk density, organic matter content,
and initial soil moisture content; and extent of mulch, standing crop, ground cover, perennial grass
cover, and total grass cover (Wood and Blackburn, 1981).
Dadkhah and Gifford (1980) conducted research on the effects of different grazing intensities on
infiltration rates. Infiltration rates decreased significantly with increased trampling percentages up to
40 percent trampling. In this study, 40 percent trampling served as the threshold for infiltration
reductions; at trampling rates 40 percent or higher, the researchers found no significant differences in
infiltration rates regardless of the extent of vegetative cover. Blackburn (1984) also summarized a
number of infiltration studies conducted on the Northern Great Plains that compared infiltration rates
to grazing intensity (Table 1).
14 February 1994
-------
Background for NEPA Reviewers - Grazing
5000 r
§ 1000
IOO
VEGETATIVE COVER (ptrcint)
Figure 3. Sediment production as a function of vegetation cover*.
Source: Dadkhah and Gifford, 1980.
* will vary widely depending on geography, soils, climate
15
February 1994
-------
Background for NEPA Reviewers Grazing
Table 1. Summary of studies of the influence of livestock grazing
on infiltration on the Northern Great Plains.
Study Sit*
and Reference
Infiltration Capacity (cra/h)
by Grazing Intensity
Equipment
Ungrazed Light Moderate Heavy
Remarks
Fort Peck, Montana
Nuttail saltbush
and crested wheat-
grass (Branson et
al., 1962)
Southwest Alberta
Fescue grassland
(Johnson, 1962)
USGS tube- type 0.65
sprinkling 3.02
infiltrometer
Mobile
infiltrometer
0.45
2.29
5.69
0.92
1.10
4.06 4.14
3.53
Un fur rowed
Furrowed ,
seeded averaged
over soil type
and years
Very heavy
grazing
Hays, Kansas
Blue grama and
Buffalograss
(Knoll and
Hopkins, 1959)
Mandan, North Dakota
Mixed Prairie
(Rauzi, 1963)
Cottonwood, South
Dakota
Mixed Prairie
(Rauzi and
Hanson, 1966)
Nunn, Colorado
Blue grama and
Buffalograss
(Rauzi and
Smith, 1973)
Miles City, Montana
Mixed Prairie
(Reed and
Peterson, 1961)
Western North
Dakota
Mixed Prairie
(Whitman ee al.,
1964)
Single-ring
infiltrometer
Mobile
infiltrometer
Mobile
infiltrometer
Mobil*
infiltrometer
Single-ring
infiltrometer
6.55
10.84
18.58
Single-ring
infiltrometer
15.24
7.49
1.40
4.32
5.00
11.04
12.29
17.12
5.28
6.10
4.24
1.14
5.33
5.13
10.96
4.01
3.76
2.76
1.27
2.03
2.03
7.19
5.69
6.74
7.87
Exclosure had not
been grazed for
13 years
Exclosure had r.ot
been grazed for
21 years
Shingle sandy
loam
Nunn loam
Ascalon sandy
loam
Blue grama
upland
Western wheat-
grass bench
Western wheat-
grass bench
16
February 1994
-------
Background for NEPA Reviewers - Grazing
While there was some variability among the results due to site-specific conditions and variations in
study methodology, the following general trends were noted for all of the research evaluated:
Differences between light and moderate grazing were usually very small.
Heavy grazing almost always caused a reduction in infiltration rate.
Soil bulk densities appeared to increase with grazing intensity and were higher on grazed pastures
than on ungrazed pastures.
Some researchers have attempted to examine infiltration rates in the context of different grazing
strategies. In general, these findings supported the above assertions that as stocking intensity and
density increase, infiltration rates tend to decrease. Wood and Blackburn (1981) noted that
infiltration rates in deferred-rotation treatments approached the near-optimum infiltration rates
demonstrated in the grazing exclosures and exceeded those in the heavily stocked, continuously grazed
treatment. Infiltration rates in a high intensity, low frequency (HILF) treatment were similar to those
of the heavily stocked, continuously grazed treatment (Figure 4). Research by McGinty, et al. (1978)
also found that infiltration rates for a pasture subject to a 4-pasture deferred-rotation grazing system
were similar to those of a 27-year exclosure, while infiltration rates were significantly lower for a
heavily, continuously grazed pasture.
Indirect Physical Impacts
The previous section described how poor management of livestock grazing may create conditions that
can decrease infiltration, increase runoff, and increase sedimentation and erosion from rangelands.
These direct impacts can affect the hydrologic regime and water quality of receiving streams, ranging
from channel modification to problems associated with sedimentation. The following section
describes some of these indirect impacts, including sedimentation, channel modification, changes in
the water table, bacterial contamination, and changes to a stream's temperature regime.
Erosion and Sedimentation. The decrease in infiltration normally associated with increased grazing
intensities results in an increase in overland flow. This increase in runoff (especially volume and
velocity) often results in increased erosion and sediment production. Also, the loss of vegetation
resulting from livestock grazing leaves more ground bare further exacerbating the sedimentation
problems associated with grazing. As mentioned earlier, Dadkhah and Gifford (1980) found that
sediment yield increased exponentially as the amount of plant cover decreased.
Lusby (1979) conducted extensive research on the effects of overgrazing on the hydrology of salt-
desert shrub rangeland in west central Colorado. Runoff and sediment were measured in reservoirs at
the lower end of grazed and ungrazed reservoirs and watersheds. Runoff from grazed watersheds
averaged from 131 to 140 percent of that from ungrazed watersheds from 1954 through 1966.
Sediment yields during the same time period ranged from 134 to 196 percent of that from ungrazed
watersheds.
Studies examining sediment production as function of grazing intensity generally echoed the results of
the studies examining infiltration rates, finding that sedimentation increases as grazing intensity
increases. Wood and Blackburn (1981 a,b) conducted research examining the effects of various
grazing strategies on sediment production, as well as a number of other physical parameters at the
Texas Experimental Ranch. Table 2 summarizes these results. Wood and Blackburn (1981a) found
that sedimentation rates from the heavily stocked, continuously-grazed pastures and the HILF pasture
exceeded those of the deferred-rotation pastures and exclosures at the site in Texas.
17 February 1994
-------
Background for NEPA Reviewers - Grazing
18
10
0
HMVIIV SIOCKM. Continuously Grutd
Uodwattiv StockM. Continuously Grutd
a«tM 0
-------
Background for NEPA Reviewers - Grazing
Grazing
Treatment
Heavy continuous
Moderate continuous
Grass
Standing
Crop
(kg/ha)
1508 d -
3333 abc
Mulch
(ton/ ha)
1.2 d
4.S be
Bare
Ground
25
6
a
b
Bulk
Density
(g/cc)
1.8 a
Organic
Hatter
2.6 c
Aggregate'
Stability
CO.
35 d
48 be
Infiltration
rate after 30
in (cM/h)
8
11
.1 c
.4 be
Sediaent
Product ion
(kg/ ha)
115 a
28 abc
Rested deferred-
rotat ion
Grazed deferred-
3865 ab
S.I be 1 b 1.6 b 5.5 a
57 ab
13.1 ab
10 c
rotation
Rested IIILF
Grazed IIILF
bxclosure 1
bxclosure 2
All treatments
2894 c
2437 c
2414 c
4569 a
4243 a
2988
6.1 b
3.2 cd
4.5 be
12.2 a
11.5 a
6.1
5 b
17 b
17 a
1 b
4 b
9
1.8 a
1.9 a
1.9 a
1.3 c
1.8 a
1.7
4.1 b
4.3 b
3.5 b
4.3 b
2.3 c
3.8
56
60
45
62
39
SO
ab
a
c
a
cd
13.9
9.6
8.2
16.5
13.9
11.6
ab
be
c
a
ab
14
28
39
4
17
32
be
abc
ab
c
be
_ M* n a C**. 1 1 IM i* il WL* IbA m 1 A* * A« u > Ik K &*» «»« 1 »^^ A & «& 1 AK fl^A^*lk« j^i ££^»^^+ A* »|*A flC
level of probability.
Table 2. Watershed parameter means for the midgrass interspace areas
in each grazing treatment at the Texas Experimental Ranch.
Source : Wood and Blackburn, 1981a, 1981b.
19
February 1994
-------
Background for NEPA Reviewers Grating
Weltz and Wood (1986) also conducted research supporting the above assertions. At a study site in
central New Mexico, they asserted that total sediment production was greater on all grazed treatments
than on the exclosure. Doubling the stocking rate and applying a short-duration system resulted in
significantly greater sediment concentrations and total sediment production. The researchers
attributed these findings to the changes in vegetation to a less desirable weedy condition, a decrease in
the amount of litter load, and an increase in bare ground resulting from overgrazing. Overall, the
researchers concluded that after rangelands were grazed in a short-duration paddock the soil surface
was susceptible to accelerated erosion, whereas scattering the cattle over a larger area created
problems with distribution and herd control, but seemed to have lower risks of environmental damage
as expressed by soil erosion, at least in the short-term.
One of the primary impacts of livestock overgrazing to surface water bodies is the increase in
sedimentation associated with grazing activities (e.g., vegetation removal, trampling). The increase in
runoff and sedimentation from rangelands can significantly increase sediment loads in water bodies.
This can result in many serious water quality impacts, particularly those relating to the health of the
aquatic ecosystem. The water quality impacts associated with sedimentation are discussed in more
detail in a later section of this document on aquatic ecosystems.
Channel Modification. As described in the previous section, the impacts of livestock overgrazing
associated with vegetative removal and trampling can create conditions (i.e., bared and compacted
soil) which may result in increased volume and velocity of runoff and increased peak flow discharges.
This input of additional runoff water into streams can result in fairly significant channel modification
and a host of related effects (e.g., reduction in the cover and area suitable for fish habitat).
Depending on soil and subsurface conditions, these rapid adjustments may take two forms: excessive
downcutting or incision, including head-cutting (not just down cutting, but cutting back upstream as
well), or excessive lateral or sideward migration of the stream (Bureau of Land Management, 1990).
Incised channels typically occur when the stream is in early stages of development and/or is
characterized by unresistant bottom materials. For example, channels in fine, deep alluvial soils are
prone to incision. They result from either downstream base-level lowering or localized gullying
initiated by increased runoff rates and/or lowered resistance to erosion. This type of deep channel
incision can result in the following two important changes in the local stream environment,
particularly in riparian areas: (1) advancing gully systems increase peak discharge making the stream
very efficient at scouring channel beds and banks and transporting sediment, and (2) degrading
channel beds produce a drop in the local water table therefore creating a water stress on the riparian
vegetation. The subsequent loss of riparian vegetation further exacerbates hydrologic changes. For
example, it may result in an even lowered resistance to surface runoff and higher flow velocities
during flood events.
Channels will widen and become laterally unstable if stream bottoms are comprised of relatively
resistant materials. For example, coarse alluvial channels or channels with structurally controlled
beds tend to respond to increased runoff and flow by becoming wider and shallower with less steep
banks. Channels that are laterally unstable may be less capable of carrying high flows and thus can
cause serious riparian damage by bank cutting or channel realignment during times of high flow.
Increased sedimentation from upstream sources can greatly exacerbate these effects (Bureau of Land
Management, 1990). An illustration of the channel changes is shown in Figure 5.
20 February 1994
-------
Background for NEPA Reviewers Grazing
SUfe I: Unlndsed
' SUfe 2: Rapid
«downeutttaf
3 SUfe 3: OwniMl
. widenmcand
... fermlnf IMW
.'Hoodptaln
SUfe 4: Channel
widened enough to
form a new stable
channel and
Streambwiks and
channel In food
condition
Stream channel
widens and
shallows In
response to
detertoratinf
upland and/or
riparian condition*
Stream channel
very wide and
shallow: stream
moves back and
forth In channel
until stabilized by
Figure 5: Stream Channel Morphology
Source: "Livestock Grazing on Western Riparian Areas"
Northwest Resource Information Center, Inc., July 1990.
21
February 1994
-------
Background for NEPA Reviewers - Grazing
Hubert et al. (1985) examined the impact of various grazing strategies and intensities on the
hydrologic conditions of streams. The study examined selected stream parameters (e.g., width) and
noted the range of responses to light versus heavy grazing (Table 3). The data showed that, for the
most part, intensive grazing caused the widening and shallowing of streams and a subsequent
reduction in cover. These conditions lead to a reduction hi the abundance of native brook trout,
which the authors attributed to increased water temperatures associated with the changes in stream
morphology.
Overgrazing can also affect channel morphology and water quality through impacts to stream banks.
Bohn and Buckhouse (1986) compared bank stability under five different grazing options. They
found that the amount of streambank retreat differs statistically between ungrazed treatments and
grazed treatments, but does not differ significantly between the grazed treatments. The study also
suggested that bank retreat increases with animal use. Because the study was somewhat limited in
scope, the authors stated that it probably failed to simulate the full effects of large-scale cattle grazing
on stream bank morphology.
Changes in the Water Table. The water table is the naturally occurring saturated zone contained in the
pore space of soil or rock beneath the ground surface. The water table typically refers to the first
encountered or shallowest saturated water zone, although there may be isolated lenses of groundwater
above the water table. Deeper bodies of water occur as aquifers or isolated lenses of groundwater.
Lowering of the water table may have adverse impacts in that less water is available for plant root
systems, the local hydrologic conditions are disrupted, and any other use of the groundwater may be
affected such as availability for irrigation or human usage.
Precipitation is the principal source for most groundwater, although groundwater may also come from
surface water (stream or lake), agricultural activity such as irrigation, or other human activity.
Through an unconfined soil or rock layer, groundwater is recharged (replenished) by the downward
infiltration of rainwater through pore space in rock masses.
Factors influencing the location of the water table include site and regional geology, water
distribution, climate and precipitation, soil characteristics, vegetation, and land use. Aquifers are
dynamic systems with natural fluctuations occurring, usually, on a seasonal basis. The direction of
groundwater flow and the depth from the surface are constantly in flux. Human activities such as
pumping of groundwater wells or crop irrigation add to the fluctuations in the water table. A
lowering of the water table occurs when the input (recharge) is reduced or the output (discharge) is
increased. In considering the effects of overgrazing on groundwater or water table conditions, the
watershed or drainage basin and its uses, not just the specific rangeland, must be considered because
of the complex interrelationships of the hydrologic system.
Because water tables are strongly influenced by surface topography, changes in the ground surface
affect the level, quantity, volume, occurrence and flow direction of the water table. Thus, grazing
activities that affect the surface topography can adversely affect the water table.
In discussing the effects of overgrazing, there are two geographic zones to consider. First, there is
the broader regional upland area, then the more localized riparian stream bed area, which is
composed of the stream itself (water column), the stream channel, and the banks of the stream.
Beyond and above the banks is the flood plain, which forms an intermediary area between the uplands
and the stream zones.
22 February 1994
-------
Background for NEPA Reviewers - Grazing
Table 3. Mean Values of Stream Habitat Variables Measured in
Heavily and Lightly Grazed Reaches of Pete Creek in 1984.
Variable
Width (m)
Depth (m)
Width/depth ratio
Coefficient of variation in depth
% greater than 22 cm deep
% silt substrate
% gravel substrate
% rubble substrate
% bedrock-boulder substrate
SRI/CSI
% overhanging bank cover
% overhanging vegetation
% shaded area
% bare soil along banks
% litter along banks
Mean Value (n = 3)
Heavily
Grazed
2.9
0.07
43
47.3
9.0
35
35
24
1
112
2.7
0.0
0.7
19.7
7.0
Lightly
Grazed
2.2*
0.11*
21
66.6*
22.3**
52
31
14
3
110
30.0*
11.7*
18.3*
13.3
6.0
* indicates statistically significant difference at p. 0.05
** indicates difference at p. £ 0.10
23
February 1994
-------
Background for NEPA Reviewers - Grazing
In both the uplands and riparian stream zones, overgrazing can adversely impact the water table.
Direct effects of upland grazing are loss of vegetation, compaction of soil, and increased runoff (with
subsequent decrease in infiltration). Bare soil is exposed to greater evaporation of soil moisture.
Stream impacts include all of the upland impacts, plus physical degradation of the stream banks.
These effects combine to cause greater erosion of the stream channel. Increased runoff, greater
sediment load, sloughing of stream banks, loss of ground cover, and loss of root biomass all
contribute to the instability of the stream system causing increased incision (down cutting and head or
back cutting) and widening of the stream channel. Changes in the channel morphology may impact
groundwater by altering the direction and rate of ground water flow and the depth to ground water.
Downcutting lowers the streambed and the groundwater table.
Depending on site-specific conditions, groundwater may regularly or periodically flow from the
subsurface strata (water table) into stream beds, adding water to the stream flow. Such conditions
would add to the vitality of the stream life. Groundwater seeps from the stream banks or up from the
bottom into the stream. Conversely, water may discharge from a stream to the water table.
Lowering of the water table may significantly reduce or halt water flow into a stream thus
accentuating stream degradation. Physical degradation of stream banks by livestock can alter the flow
of groundwater and reduce discharge to streams by compacting the soil or otherwise altering the water
flow.
Another adverse impact of lowering the water table is the potential effects on plants. Roots obtain
their necessary moisture through capillary action that draws water (moisture) upwards through the soil
to the root zone where it is available for plant use. Excessive or improper grazing activities may
cause greater evaporation of soil moisture by denuding the ground of vegetative cover and increasing
soil temperature, thus drying out the soil and leaving insufficient moisture needed for plant life.
Bacterial Contamination. Livestock grazing can also cause increases in the level of bacterial
pollutants (i.e., fecal coliform) in water, as well as nutrient enrichment. The level of severity is
related to the intensity of grazing activities and the proximity of animals to the water. Tiedemann et
al. (1988) presented research results suggesting that increasing the intensity of cattle grazing can
increase the amount of fecal coliform (FC) in water to very high and potentially problematic levels.
In their research, Tiedemann et al. (1988) measured concentrations of fecal coliform weekly during
summer 1984 in streamwater of 13 wildland watersheds managed under four management scenarios:
(A) no grazing, (B) grazing without management, (C) grazing with management for livestock
distribution, and (D) grazing with management for livestock distribution and with cultural practices to
increase forage. Scenario D equated intensive grazing management to maximize livestock production,
including practices to attain uniform livestock distribution and improve forage production with
cultural practices such as seeding, fertilizing, and forest thinning.
The researchers found that FC levels in streams associated with scenario D were significantly higher
than those of the other streams. Most of the A and C areas had FC levels less than 100 FC/L. Only
one sample was available for scenario B and it was 150/L. FC levels for scenario D, on the other
hand, ranged from 190/L to 2,270/L. A single sample from C was almost as high, 650/L. The
higher elevations in these areas were attributed to the higher density of cattle in Strategy D areas (2.8
ha per animal unit month (AUM) compared to 8.2 and 7.7 ha/AUM for B and C. Also, vegetative
characteristics played a role in that the areas with higher FC levels also had meadows desirable for
grazing right beside the streams (Tiedemann et al, 1988).
24 February 1994
-------
Background for NEPA Reviewers - Grazing
Tiedemann et al (1988) also cited studies demonstrating that cattle noticeably increased fecal coliform
counts. Some of these studies noted fecal coliform levels having up to a 10-fold increase over
background levels (Coltharp and Darling, 1973; Doran and Linn, 1979; Gary et al., 1983; Skinner et
al, 1974). In an earlier study, Tiedemann et al. (1987) found significant increases in streamwater FC
counts with increased intensity of grazing management. The largest differences in FC concentrations
(10X) occurred between control watersheds (no grazing) and watershed managed for maximum
livestock production. Counts of FC in excess of 20000/L were observed when intensive management
was used to maximize livestock production. These levels of FC can remain a problem even after the
livestock is removed.
Stream Temperature Changes. Livestock can be extremely damaging to vegetation, as described
earlier in this section. This disruption in vegetative cover can contribute to serious water quality
degradation, especially if riparian areas are disrupted. In particular, vegetative damage (especially in
riparian areas) can result in serious damage to aquatic habitats. Therefore, most of these impacts will
be discussed in more detail in a later section of this document on aquatic ecosystems.
In terms of water quality, however, damage to vegetation can significantly alter a stream's
temperature regime, leading to changes in fisheries and other aquatic life. Streamside vegetation is
critical in terms of moderating stream temperatures. Because riparian vegetation intercepts and
reduces the intensity of incoming solar radiation and reduces back-radiation, it serves as a form of
insulator to the stream, preventing it from experiencing extreme temperatures or temperature ranges.
Its shading effects in summer help to reduce excessive heating of the water. If the vegetation cover is
decreased, summer stream temperatures can greatly increased, which contributes to a host of water
quality problems, particularly a decrease in the amount of dissolved oxygen in the water. These
changes to stream water quality may cause a shift in fish species, from salmonids to less sensitive
species in many areas. By reducing the amount of back-radiation/reflection from the stream,
vegetation also serves a moderating effect in winter. This also can enhance native fish survival,
because if winter temperatures fall low enough, anchor ice can form on the bottom of the stream
(Platts, 1991). The ability of plants to control stream temperatures depends on the size of the stream
and the plant type. As a general rule, the larger the stream, the higher the streamside vegetation must
be to effectively intercept the sun's rays over water (Platts, 1991).
Indirect Impacts on Terrestrial Ecosystems
Terrestrial Ecosystem Impacts. Most grazing studies examine changes in vegetation composition and
the reduced range quality in terms of a loss of livestock carrying capacity. Little is known about
impacts of sustained grazing on an ecosystem-wide level, particularly, impacts on wildlife. Dwyer et
al. (1984) note that range management has focused on improvements to support increased livestock
production, with little attention to maintaining plant and wildlife diversity within an ecosystem.
Dwyer et al. (1984) cites both direct and indirect impacts on wildlife from livestock overgrazing.
Direct impacts include competition for palatable species, while stress-producing modifications to the
ecosystem induced by livestock (e.g. reduction in protective vegetation cover) are more indirect.
A consistent, direct impact of livestock overgrazing on rangeland is loss of vegetative diversity.
Selective grazing by livestock tends to reduce the presence of palatable species while allowing a few,
typically unpalatable and undesirable species to increase. The resulting change in plant composition
lowers species diversity, changes species function, and reduces both the numbers and the variety of
wildlife species the area can support (Dwyer, et al., 1984) To sustain a given wildlife population, the
pre-grazing plant composition, structure and function within an ecosystem must remain in balance,
25 February 1994
-------
Background for NEPA Reviewers - Grazing
following the introduction of livestock. Wildlife that depend on a limited number of plant species to
provide a nutritionally optimal diet may be impacted as livestock can rapidly deplete limited food
sources within a given area. The depletion of desirable vegetation species within an allotment forces
wildlife into marginal, less desirable habitat and into eating less desirable/nutritious vegetation (GAO,
1991; Dwyer, et al., 1984).
Livestock impacts on rangelands extend beyond the direct loss of vegetation to modification of native
habitat. Whole ecosystems may be impacted, and depending upon the fragility of the ecosystem, may
be permanently altered. Some ecosystems are better able to withstand livestock and wildlife use;
water sources, either in the form of precipitation or riparian zones, increase an ecosystem's ability to
recover from stress. The increase of sagebrush and other bushy species in place of grasses is an
indicator that fragile desert ecosystems have already been significantly impacted by overgrazing. The
low rainfall, high temperatures, and high evaporation rates of these areas have produced plants and
wildlife uniquely adapted to these regions. The adaptation of these ecosystems and their occupants to
inherently harsh environments reduces their capacity to recover from disturbances, such as
overgrazing (GAO, November 1991).
Over 250 native species are endangered, threatened or candidate species, in the southwestern Mojave,
Sonoran, and Chihuahuan deserts. Poor management and/or overgrazing are factors identified as
contributing to a decrease in preferred-diet plant species, destruction of habitat, and reduction of
cover needed to hide from predators. In other cases, diseases may be transmitted from domestic to
wild animals. In addition to their consumption of prime vegetation, poor management of livestock in
the Sonoran desert have forced Sonoran pronghorn antelope away from traditional birthing grounds to
less protected areas (GAO, November 1991).
Cosby (1978) noted that livestock grazing does not always impact wildlife negatively. Cosby
observed several benefits of rotation grazing systems on wildlife when he found that deferring grazing
in several units and altering the season of use actually increased vegetation diversity and cover.
Cosby found sandhill cranes utilized grazed units regularly due to an increase in insect populations in
the vicinity of "cowpattis". Similarly, native deer utilized units previously grazed to graze on new
plant regrowth. Despite these findings, Cosby explains that this same scenario may not be feasible in
a different region, and that all grazing treatments must be chosen carefully, on a site-specific basis.
Many livestock grazing researchers acknowledge the importance of avoiding grazing practices which
result in the displacement of wildlife species, and to manage rangeland to maintain a healthy
ecosystem complete with plant and wildlife diversity (Dwyer, et al., 1984; Carpenter, 1984).
However, not all changes in species distribution, should be viewed as adverse impacts. The
successional ecosystem stage (early, middle, or late) will help determine the appropriateness of
maintaining species diversity and distribution as part of an overall range management plan.
Indirect Impacts on Aquatic Ecosystems
Effects of poor livestock and wildlife grazing management on stream hydromodification and water
quality can have serious ramifications on aquatic ecosystems. Potential impacts such as bacterial
contamination, increased sedimentation, and temperature changing can reduce the quality of the
stream's ambient environment so as to affect the composition and health of aquatic organisms.
Likewise, reduction of vegetation and increased runoff and flow may damage the stream's usefulness
as aquatic habitat. Such impacts can originate from livestock and wildlife overgrazing in upland and
riparian areas, although damage to riparian areas typically cause the most serious stresses to aquatic
26 February 1994
-------
Background for NEPA Reviewers - Grazing
ecosystems. The following discussion focuses on overgrazing's adverse effects in riparian areas as
these most closely and directly effect stream ecosystems. Also, much of the discussion will center on
adverse effects on fish habitat; one important measure of the health of an aquatic ecosystem is by the
nature and type of fish species present. The ability of an aquatic system to produce and support game
fish is one way of measuring a healthy aquatic environment. For example, Van Velson (1979) found
that rough fish comprised 88 percent of a fish population before relief from grazing and only 1
percent of the population after 8 years rest from grazing. Platts (1991) also examined a number of
research studies, finding that in 20 of 21 studies, stream and riparian habitats were degraded by
livestock grazing and that those habitats improved when grazing was eliminated. The majority of the
studies also found reductions in salmonid fish populations related to the grazing-related habitat
destruction.
Earlier sections of this document described how overgrazing of livestock and wildlife can affect the
density and composition of vegetative cover. In upland areas, these impacts can lead to soil
compaction and increased runoff. The hydrologic modifications to streams associated with increased
runoff effectively destroys much of the desirable stream habitats.
As reported in Platts (1990), ideal trout spawning area is typically devoid of boulders, low in fine
sediments, and high in gravel and small rubble. It also has a number of deep pools, well-aerated
water, and ample cover and shade. Many of these necessary qualities of trout habitat can be wiped
out by excess runoff and sedimentation. For example, increased flows can wipe out cover and habitat
provided by fallen trees and brush.
Impacts of overgrazing on vegetation in riparian areas can affect aquatic ecosystems in a number of
ways. Some of the impacts are similar to those associated with upland areas, but the impacts from
damage to riparian areas are much more extensive and severe. Because of the proximity of riparian
areas to streams, they are intimately connected to the stream ecosystem. Also, they are the preferred
grazing ground of livestock and winter range for wildlife, thus concentrating much of the grazing-
related damage to those areas. Livestock prefer to graze in riparian areas because they provide easily
accessible water, favorable terrain, good cover, soft soil, a more favorable microclimate, and an
abundant supply of lush palatable forage. Even though riparian areas represent a very small
proportion of total rangeland, they provide much of the vegetation consumed by livestock because it
is such a preferred grazing area. For example, Roath and Krueger (1982) reported that although the
riparian zone constituted only 1.9 percent of the area on one allotment in Oregon's Blue Mountains, it
produced 81 percent of the vegetation removed by cattle. Some of the ways that overgrazing
(especially in riparian areas) can impact aquatic ecosystems are summarized below.
Disruption/Reduction to Ecosystem Sources. The riparian area serves as a source of energy to the
aquatic ecosystem, by providing energy to streams in the form of dissolved organic compounds and
paniculate organic detritus. Benthic detritivores, the stream bottom bacteria, fungi and invertebrates
that feed on the detritus, form the basis of the aquatic food chain. They pass on this energy when
they are consumed in turn by larger benthic fauna and eventually by fish (U.S. Department of
Agriculture, Forest Service, 1991). Riparian vegetation produces the bulk of the detritus that
provides up to 90 percent of the organic matter necessary to support the headwater stream
communities (Kauffman and Krueger, 1984). Platts (1991) stated that organic matter from riparian
vegetation comprised roughly 50 percent of the stream's nutrient energy supply for the food chain.
Disruption (i.e., change in cover density and composition) to riparian vegetation can severely reduce
the extent of organic inputs to the stream, thus alter the energy of the ecosystem. Streamside
27 February 1994
-------
Background for NEPA Reviewers - Grazing
vegetation is also important to the production of fish food. It provides habitat for terrestrial insects
which are important food for salmonids and other fish species.
Moderator of Stream Temperatures. Streamside vegetation is critical when it comes to moderating the
temperature of streams. It shades the stream and therefore influences water temperature. A loss of
vegetative cover can result in increased temperatures in summers, decreased temperatures in winter,
and a greater daily range of temperatures at all times. Kauffman and Krueger (1984) reported on
literature that showed damage to riparian areas caused increases in stream temperature (one study
showed that maximum daily temperatures outside of a grazing enclosure averaged 7 degrees
centigrade higher than those within the enclosure) and a greater range in temperature fluctuation
(average daily fluctuation was 15 C outside of the enclosure and 7 C inside the enclosure). The
increase in summer temperatures increases a trout's demand for dissolved oxygen, while at the same
time, reduces the amount of dissolved oxygen in the water. This can cause a shift in fish species,
from salmonids to nongame fish in many areas. Vegetation also serves a moderating effect in winter,
which can enhance native fish survival. If whiter temperatures fall low enough, anchor ice can form
on the bottom of the stream. Streams with little or no vegetative canopy are very susceptible to the
formation of anchor ice (Platts, 1991; U.S. Department of Agriculture, 1991).
Habitat Benefits. Riparian vegetation strongly influences the quality of habitat for anadromous and
resident coldwater fish by providing shade, ameliorating in-stream temperature fluctuations, and
providing cover (Kauffman and Krueger, 1984). Many studies have demonstrated the importance of
cover to fish by showing that declines in salmonid abundance occur as stream cover is reduced and an
increase in salmonid abundance as cover is added. The fringe of bordering riparian vegetation is
essential for building and maintaining the stream structure necessary for productive aquatic habitats.
This vegetation not only provides cover, but buffers the stream from incoming sediments and other
pollutants and the effects of excessive flow (Platts, 1991). For one, fisheries habitat in streams is
enhanced by the addition of large woody debris to the stream channel which forms pools and
important rearing areas. This debris also provides cover from predators and protection from high
flows. Large stable debris also provides the mechanism by which the detritus is held long enough to
be processed by the invertebrate community. Without debris dams, much of the organic input from
streamside vegetation would be washed downstream without contributing to the life processes of the
aquatic food chain (U.S. Department of Agriculture, Forest Service, 1991). Each type of vegetation
exerts a special function, as summarized in Platts (1991):
Trees, shrubs, and sedges provide shade and streambank stability because of their large size
and massive root systems. As trees mature and fall into or across streams, they create high
quality pools and rifles. Their large mass also helps control the slope and stability of the
channel. Input of this large organic debris is essential for maintaining stream stability. In
many aquatic habitats, if it were not for this type of input, the channel would degrade and
soon flow on bedrock, leaving insufficient spawning gravels and few high-quality rearing
pools for fish.
Brush also builds stability in stream banks through its root systems and litter fall.
Grasses form the vegetative mats and sod banks that reduce surface erosion and mass wasting
of stream banks.
Sediment Trapping. Riparian vegetation is important in slowing the overland flow of water and
trapping sediment, therefore contributing to the building of bank form (Platts, 1990). Streamside
28 February 1994
-------
Background for NEPA Reviewers - Grazing
vegetation is also important as it creates streambank stability. Vegetative mats reduce water velocity
along the stream edge, causing sediments to settle out and become part of the bank. This helps to
contribute nutrients to the bank soils and increases plant production and vigor. It also reduces the
amount of sediments input to the stream (Platts, 1991).
In sum, by affecting the health and vigor of vegetation (especially riparian areas), poor grazing
management practices can cause a number of problems that can damage aquatic ecosystems. These
are briefly reiterated in the following bullets presented in Platts (1990). Reductions/loss in vegetation
can:
Increase average stream temperatures in summer, decrease them in winter, and expand daily
temperature ranges.
Reduce stream bank strength, enabling sedimentation and erosion, and reducing bank building
through sediment deposition.
Increase the erosive energy of water.
Amplify effects of floods, ice, or debris flow, or animal trampling.
Reduce water purification benefits that vegetation provides through infiltration and sediment
removal.
Reduce the ability of riparian areas to contribute to ground water recharge.
Reduce flood control benefits.
29 February 1994
-------
Background for NEPA Reviewers - Grazing
POSSIBLE PREVENTION/MITIGATION MEASURES
This section identifies techniques that may be appropriate for mitigation of potential impacts caused
by grazing activities. Mitigation should be evaluated on a site-specific basis and the following
measures should only be used as a guide to measures that might be available should the reviewer
determine they may be appropriate.
Active management of livestock grazing allotments typically includes consideration of the
following variables in different combinations : 1. grazing frequency, includes complete rest; 2.
livestock stocking rates; 3. livestock distribution; 4. season and timing of forage use; 5. livestock
kind and class; 6. control of wildlife herd size and conflicts; 7. forage utilization; and 8.
rehabilitation. Active management using these variables may increase forage, as well as improve
habitat.
Avoid high intensity, long duration grazing. The level of utilization must allow for regrowth of
vegetation in order to maintain the productive capacity of the pasture.
Encourage a greater level of control over the numbers of livestock and wildlife and time spent on
each allotment.
Encourage a greater level of oversight on allotments: more frequent assessment of utilization
levels and quicker response to move livestock when utilization levels are attained may keep the
area from being overgrazed.
Separate riparian zone from other pastures and develop separate management plans, and if
necessary, exclude livestock from riparian (or upland) areas until the desired level of recovery is
attained.
Fence or prevent direct access to streams in riparian areas to reduce trampling, damage of
vegetation and the associated channel modification problems (may be costly to maintain,
however).
Use permanent exclosures in areas of high risk or extreme sensitivity where the likelihood of
damage is high and the potential for restoration is low.
Control livestock and wildlife grazing in areas predisposed to damage during periods of high
sensitivity (adequate management plans).
Use planned grazing systems to maintain plant vigor and desired species composition.
Intensive practices (reseeding, weed control) may be necessary for extremely degraded pastures.
Late season grazing should occur after the growth of warm season species has peaked and seeds
have been produced.
Know dynamics of plant species within an allotment and their capacity for regrowth.
Evaluate type of livestock grazed and grazing intensity based on predicted impact to wildlife.
30 February 1994
-------
Background for NEPA Reviewers - Grazing
Periodic minor ground shaping may be necessary to encourage dispersed flow and prevent
concentrated flow.
Plant compatible native trees or shrubs to reduce runoff, establish roots, and provide shade.
Monitor progress of vegetation growth, bank and channel stability, and overall vitality of
rangeland and riparian areas. Seasonal photographs may aid in this effort.
Stabilize streambanks against erosion, although natural vegetative cover is preferred, artificial
means of stabilization such as rubble, concrete or riprap may be necessary.
Consider use of "in-stream" structures such as gabions, small rock dams, debris catchers,
individual boulder placement, rock jetties, or silt log drops, to stabilize stream channels against
excessive incision and/or widening.
Plan periods of rest from grazing to stabilize streams.
Consider changes hi land use allocations, especially in or adjacent to degraded areas.
Retain flexibility in allotment permits to account for special circumstances, such as excluding
livestock during drought periods or other special circumstances, if necessary.
Monitoring of rangelands is an important activity that will provide opportunity to identify and
mitigate impacts. Conduct follow-up monitoring of range trends including conditions and
utilizations. Alter actions based on monitoring data.
31 February 1994
-------
Background for NEPA Reviewers Grazing
SUMMARY OF INFORMATION THAT SHOULD BE ADDRESSED IN NEPA
DOCUMENTATION
The following is a list of questions that may be appropriate to ask about grazing when reviewing
NEPA documentation.
What are the objectives of the management plan? Has a clear idea of the management plan
objectives been presented?
Determine what factor, such as bank instability or loss of woody plants, is of primary concern.
Is the area suitable for grazing? Has the kind and class of livestock and the duration and
intensity of livestock grazing best suited to the area been determined?
Has the document identified specific species (plant and animal) in the area, what sources were
used to determine this, how does it compare with other information on the area?
Are utilization levels related to the specific species of vegetation present?
What utilization levels are planned for this allotment? What is the planned monitoring frequency
for the allotment?
How will action be altered or modified based on monitoring information? What are the triggers
for determining alterations?
Are there any endangered or threatened species in the area?
Has sufficient forage been allocated to wild herbivores in the riparian management plan? What is
considered sufficient?
What tools (fencing, herding cattle/sheep regularly, duration) are proposed to effectively manage
the allotment?
What is the seasonal distribution of the allotment (spring, summer have higher production than
fall/spring)?
Are any special managements employed in riparian areas? How will stream areas be protected,
especially stream banks?
What is the estimated impact on local groundwater, and how will this be monitored?
Have the potential cumulative impacts been described?
What are the designated beneficial uses of water bodies potentially affected by the grazing
allotment?
Are these beneficial uses impaired due to exceedance of water quality standards? What is the
cause of the impairment?
32 February 1994
-------
Background for NEPA Reviewers - Grating
STATUTORY AND REGULATORY FRAMEWORK
In addition to the National Environmental Policy Act of 1969 (NEPA), there are specific statutes that
provide Federal land managers with authority to allow and control grazing on Federal lands under
their jurisdiction. Typically, each land managing agency has its own implementing regulations that
correlate to each statute's authorities and requirements. In addition to these statutes, there are broad-
reaching Federal statutes oriented toward environmental protection, such as the Clean Water Act, and
the Federal Insecticide, Fungicide and Rodenticide Act, mat may also apply to grazing operations on
Federal lands. Explained briefly below are the statutes most appropriately described in die context of
grazing.
Taylor Grazing Act. As discussed above, the system of free access to Federal lands ended with the
passage of the Taylor Grazing Act in 1934. This was the first official Federal effort at livestock
management and placed the administration of the public lands under the U.S. Grazing Service, later to
become the BLM.
Multiple Use Sustained Yield Act of 1960. This statute promoted multiple-use management of
national forest lands, not limiting the uses based solely on economic returns. The term "multiple-
use" denotes management of the lands and their renewable resources in a combination of ways that
would "best meet the needs of the American people."
Forest and Rangelands Renewable Resource Planning Act. Passed in 1974, four years after the
Public Land Law Review Commission completed its broad review of Federal land policies, this act
was an attempt to encourage better economic management of the national forests, as well as providing
opportunity for public participation, timber sales, and reforestation.
National Forest Management Act. This statute, passed in 1976, continued an initiative to engage in
land-use and resource planning. Like the Forest and Rangelands Renewable Resource Planning Act
of 1974, NFMA emphasizes resource inventory, cost/benefit analysis, improvement of the
environment, interdisciplinary planning, and public involvement (Clawson, 1983). Though this act
encouraged high economic standards, some sections maintain constraints on attainment of full
economic management of the federal lands and provided terms for carrying out a multiple-
use/sustained yield policy. National grasslands were bought under Forest Service management
through the Bankhead-Jones Farm Tenant Act.
Federal Land Policy and Management Act (FLPMA). Passed in 1976, this Statute serves as
comprehensive multiple-use legislation for public lands managed by the BLM and supports the notion
of public land retention to manage these lands on the basis of sustained yield. FLPMA is also a
planning act endorsing multiple-use of resources. Basic principles of the FLPMA include land use
planning with public participation, protection of the environment with the cost of damage supplied by
the user, receipt of fair market price for private use of public resources, and cooperation with state
and local officials. (Brubaker, 1984)
Public Rangelands Improvement Act. Congress passed this Act in 1978 intending to improve the
condition of the nation's public rangelands, roughly 268 million acres, and alter the grazing fee
formula on Federal lands. The Act prompted an increase in grazing fees from $1.51 per animal unit
month (AUM) to $1.89 per AUM. In 1986, Executive Order 12548 extended use of the formula
indefinitely. The Public Rangelands Improvement Act also directed the Departments of Agriculture
33 February 1994
-------
Background for NEPA Reviewers - Grazing
and Interior to maintain an on-going inventory of range conditions, authorized additional funding for
range improvement, and encouraged the development of improved allotment management plans.
Clean Water Act. Two main provisions within the Clean Water Act affect grazing activities. Both of
these provisions primarily consider grazing as an activity that contributes to nonpoint source
pollution; grazing is, therefore, addressed within the context of nonpoint source pollution programs
and regulations, specifically, the following:
Clean Water Act Section 319 - Nonpoint Source Program: This is the principal provision in the
CWA that addresses nonpoint source pollution. The program provides Federal funding to
qualifying states for the control of nonpoint sources of pollution. To be eligible for funding,
States must develop an assessment report detailing the extent of nonpoint source pollution and a
management program specifying nonpoint source programs and controls.
Clean Water Act Section 320 - National Estuary Program: This program may affect grazing
activities if such activities occur in one of the estuaries targeted for the program (e.g., Puget
Sound, Galveston Bay). This program focuses on point and nonpoint source pollution. EPA
assists state, regional, and local governments in developing comprehensive conservation and
management plans that recommend corrective actions to restore estuarine water quality.
Currently, the majority of the NEP targeted estuaries are located near fairly urbanized areas and
issues associated with grazing on Federal lands are not likely to be a high priority.
Coastal Zone Act Reauthorization Amendments (CZARA): A relatively new program, currently
being developed jointly by EPA and NOAA, CZARA has great potential for promoting broad-
based nonpoint source pollution controls (including approaches affecting grazing) in coastal areas.
Specifically, section 6217 of CZARA requires that states with an approved coastal zone
management program develop Coastal Nonpoint Pollution Control Programs to be approved by
EPA and NOAA. The major emphasis of the CZARA program is to develop and implement
"management measures" for nonpoint source control to restore and protect coastal waters.
Management measures defined as economically achievable measures (e.g. best management
practices, citing criteria, operating methods) that will control nonpoint source pollution to the
greatest degree possible, are required for many different categories of nonpoint source pollution,
including grazing.
The management measure for grazing was developed as part of the agricultural component of the
coastal nonpoint source program. The measure focuses on the protection of sensitive areas and
the implementation of conservation management systems and/or activity plans. Figure 6 defines
the grazing management measure in detail.
Each CZARA defined management measure essentially represents a specific nonpoint source
program goal. Although the States are given a great deal of flexibility in achieving the specified
management measures, EPA provided extensive technical guidance (EPA, 1993) on practices that
could be used to meet the management measure goals. In the area of grazing, EPA recommended
some of the following practices:
Grazing Management Systems (as defined by the SCS) - deferred grazing, planned grazing,
proper grazing use, proper woodland grazing, pasture and hay land management;
34 February 1994
-------
Background for NEPA Reviewers - Grazing
Alternate Water Supplies (as defined by the SCS) - pipelines, ponds, troughs or tanks, wells,
spring development;
Livestock Access Limitation (as defined by the SCS) - fencing, livestock exclusion, stabilized
stream crossings;
Vegetative Stabilization (as defined by the SCS) - pasture and hay land planting, range seeding,
critical area planting, brush and weed management, prescribed burning.
The CZARA program provides another important approach to reducing the effects of overgrazing on
the natural environment. Although CZARA currently only applies to coastal states, there is a chance
that its scope may be expanded inland as part of the overall CWA Reauthorization Amendments.
Figure 6. CZARA Grazing Management Measure (EPA, 1993)
Protect range, pasture and other grazing lands:
(1) By implementing one or more of the following to protect sensitive areas
(such as streambanks, wetlands, estuaries, ponds, lake shores, and
riparian zones):
(a) Exclude livestock,
(b) Provide stream crossings or hardened watering access for drinking,
(c) Provide alternative drinking water locations,
(d) Locate salt and additional shade, if needed, away from sensitive areas, or
(e) Use improved grazing management (e.g., herding)
to reduce the physical disturbance and reduce direct loading of animal
waste and sediment caused by livestock; and
(2) By achieving either of the following on all range, pasture, and other
grazing lands not addressed under (1):
(a) Implement the range and pasture components of a Conservation Management
System (CMS) as defined in the Field Office Technical Guide of progressive
planning approach of the USDA-Soil Conservation Service (SCS) to reduce
erosion, or
(b) Maintain range, pasture, and other grazing lands in accordance with activity
plans established by either the Bureau of Land Management of the U.S. Department
of the Interior or the Forest Service of USDA.
35 February 1994
-------
Background for NEPA Reviewers - Grazing
REFERENCES
Blackburn, Wilbert H., "Impacts of Grazing Intensity and Specialized Grazing Systems on Watershed
Characteristics and Responses," In: Developing Strategies for Rangeland Management, National
Research Council/National Academy of Sciences, Boulder, CO, Westview Press, 1984.
Bohn, C.C., and J.C. Buckhouse, "Effects of Grazing Management on Streambanks," In:
Transaction of Fifty-first North American Wildlife and Natural Resources Conference, Reno, NV,
Wildlife Management Institute, March 21-26, 1986.
Caldwell, Martyn M., "Plant Requirements for Prudent Grazing," In: Developing Strategies for
Rangeland Management, National Research Council/National Academy of Sciences, Boulder, CO,
Westview Press, 1984.
Carpenter, L.H., "Impacts of Grazing Intensity and Specialized Grazing Systems on Faunal
Composition and Productivity: A Discussant Paper," In: Developing Strategies for Rangeland
Management, National Research Council/National Academy of Sciences, Boulder, CO, Westview
Press, 1984.
Coltharp, G.B., and L.A. Darling, "Livestock Grazing - A Nonpoint Source of Water Pollution in
Rural Areas?", In: W.J. Jewell and R. Swan (ed.) Proc. Symp. Rural Environ. Engineering, Warren,
VT, Univ. Press of New England, Hanover, NH. September 1973.
Cosby, H.E., "Range Management Benefits Wildlife," Rangeman's Journal, 5: 159-161, 1984.
Dadkhah, M. and G.F. Gifford, "Influence of Vegetation, Rock Cover, and Trampling on Infiltration
Rates and Sediment Production," Water Resource Bulletin 16: 979-986, 1980.
Doran, J.W., and D.M. Linn, "Bacteriological Quality of Runoff Water from Pastureland," Appl.
Environ. Microbiol. 37:985-991, 1979.
Dwyer, D., J.C. Buckhouse, and W.S. Huey, "Impacts of Grazing Intensity and Specialized Grazing
Systems on the Use and Value of Rangeland: Summary and Recommendations," In: Developing
Strategies for Rangeland Management, National Research Council/National Academy of Sciences,
Boulder, CO, Westview Press, 1984.
Gary, H.L., S.R. Johnson, and S.L. Ponce, "Cattle Grazing Impact on Surface Water Quality in a
Colorado Front Range Stream," J. Soil Water Conserv. 38:124-128, 1983.
Gifford, Gerald F., "Vegetation Allocation for Meeting Site Requirements," In: Developing
Strategies for Rangeland Management, National Research Council/National Academy of Sciences,
Boulder, CO, Westview Press, 1984.
Gifford, Gerald F., "Watershed Response To Short Duration Grazing," in Short Duration Grazing, J.
A. Tudeman (editor), Cooperative Extension, Washington State University, pps 145 -150, 1986.
36 February 1994
-------
Background for NEPA Reviewers - Grazing
Hubert, Wayne A., R.P. Lanka, T.A. Wesche, and F. Stabler, "Grazing Management Influences on
Two Brook Trout Streams in Wyoming," In: Riparian Ecosystems and Their Management:
Reconciling Conflicting Uses, First North American Riparian Conference, USDA Forest Service
General Technical Report RM-120, 1985.
Kauffman, J. Boone, and W. C. Krueger, "Livestock Impacts on Riparian Ecosystems and Streamside
Management Implications, A Review," Journal of Range Management, Volume 37, Issue 5,
September 1984.
Lusby, G.C., "Effects of Grazing on Runoff and Sediment Yield from Desert Rangeland at Badger
Wash in Western Colorado, 1953-1973," USGS Water Supply Paper 1532-1, 1979.
Marcuson, P.E., "The Effect of Cattle Grazing on Brown Trout in Rock Creek, Montana," Fish and
Game Federal Aid Program F-20-R-2Mla, 1977.
McGinty, W.A., F.E. Smeins, and L.B. Merrill, "Influence of Soil, Vegetation, and Grazing
Management on Infiltration Rate and Sediment Production of Edwards Plateau Rangeland," Journal of
Range Management, 32:33-37, 1978.
Northwest Resource Information Center, Inc.; Livestock Grazing on Western Riparian Areas, July
1990.
Packer, P.E., "Effects of Trampling Disturbance on Watershed Condition, Runoff and Erosion,"
Journal of Forestry, 51:28-31.
Platts, William S., "Livestock Grazing," In: Influences of Forest and Rangeland Management on
Salmonid Fisheries and Their Habitats, American Fisheries Society Special Publication 19, 1991.
Platts, William S., for Nevada Department of Wildlife; Managing Fisheries and Wildlife on
Rangelands Grazed by Livestock: A Guidance and Reference Document for Biologists, December
1990.
Platts, William S. and Rodger L. Nelson, "Characteristics of Riparian Plant Communities and
Streambanks with Respect to Grazing in Northeastern Utah," 1989.
Platts, William S., "Riparian Stream Management," National Range Conference Proceedings,
Oklahoma City, OK, 1986.
Platts, William S., and Rodger Loren Nelson, "Impacts of Rest-Rotation Grazing on Stream Banks in
Forested Watersheds in Idaho," North American Journal of Fisheries Management, pps 547-555,
1985.
Roath, L.R. and W.C. Krueger, "Cattle Grazing Influence on a Mountain Riparian Zone," Journal of
Range Management, 35:100-104, 1982.
Skinner, Q.D., J.C. Adams, P.A. Rechard, and A.A. Settle, "Effect of Summer Use of a Mountain
Watershed on Bacterial Water Quality," Journal of Environmental Quality. 3:329-335, 1974.
37 February 1994
-------
Background for NEPA Reviewers - Grazing
Tiedemann, A.R., D.A. Higgins, T.M. Quigley, H.R. Sanderson, and D.B. Marx, "Responses of
Fecal Coliform in Stream Water to Four Grazing Strategies," Journal of Range Management, 40:322-
329, 1987.
Tiedemann, A.R., Higgins, D.A., Quigley, T.M., Sanderson, H.R., and Bonn, C.C, "Bacterial
Water Quality Responses to Four Grazing Strategies - Comparisons with Oregon Standards," Journal
of Environmental Quality, 17:492-498, 1988.
U.S. Department of Agriculture, Economic Research Service, Arthur B. Daugherty; U.S. Grazing
Lands: 1950 to 1982, 1982.
U.S. Department of Agriculture, Forest Service, Forest Service Handbook, Directive System User
Guide, FSH 1109.11, Amendment No. 22, July 1989.
U.S. Department of Agriculture, Forest Service; Riparian Forest Buffers: Function and Design for
Protection of Water Resources, Forest Resources Management, Radnor, PA, NA-PR-07-91.
U.S. Department of Agriculture, Forest Service Intermountain Research Station; Managing Grazing of
the Riparian Areas in the Intermountain Region, General Technical Report INT-263, Warren P.
Clary, Bert F. Webster, May 1989.
U.S. Department of Agriculture, Soil Conservation Service, National Handbook of Conservation
Practices, Washington, DC, Stock No. 001-007-0090301, 1977
U.S. Department of Interior, Bureau of Land Management; Riparian Management and Channel
Evolution, A Self Study Guide, Phoenix Training Center, Course Number SS 1737-2, 1990.
U.S. Department of Interior, Bureau of Land Management; Public Lands Statistics, Volume 175,
1990.
U.S. Environmental Protection Agency, Guidance Specifying Management Measures for Sources of
Nonpoint Pollution in Coastal Waters Washington, D.C.: U.S. EPA, Office of Water 840-B-92-002,
1993.
U.S. Government Accounting Office, Rangeland Management; BLM's Hot Desert Grazing Program
Merits Reconsideration, GAO/RCED-92-12, November 1991.
U.S. Government Accounting Office, Rangeland Management; Forest Service Not Performing Needed
Monitoring of Grazing Allotments, GAO/RCED-91-148, May 1991.
U.S. Government Accounting Office, Public Land Management; Attention to Wildlife Is Limited,
GAO/RCED-91-64, March 1991.
U.S. Government Accounting Office, Rangeland Management; BLM Efforts To Prevent Unauthorized
Livestock Grazing Need Strengthening, GAO/RECD-91-17, December 1990.
U.S. Government Accounting Office, Public Rangelands; Some Riparian Areas Restored but
Widespread Improvement Will Be Slow, GAO/RCED-88-105, June 1988. (a)
38 February 1994
-------
Background for NEPA Reviewers - Grazing
U.S. Government Accounting Office, Rangeland Management; More Emphasis Needed on Declining
and Overstocked Grazing Allotments, GAO/RCED-88-80, June 1988. (b)
Van Dyne, George M., William Burch, S.K. Fairfax, and William Huey; Forage Allocation on Arid
and Semiarid Public Grazing Lands: Summary and Recommendations.
Van Keuren, R. W., J. L. McGuinness, and F. W. Chichester, "Hydrology and Chemical Quality of
Flow from Small Pasture Watersheds: I. Hydrology," Technical Reports, Journal of Environmental
Quality, Volume 8, No. 2, 1979.
Van Nelson, R., "Effects of Livestock Grazing Upon Rainbow Trout in Otter Creek," In:
Proceedings, Forum-Grazing and Riparian/Stream Ecosystems, Trout Unlimited, Inc., 1979.
Wallace, Joe D., "Some Comments and Questions on Animal Preferences, Ecological Efficiencies and
Forage Intake," In: Developing Strategies for Rangeland Management, National Research
Council/National Academy of Sciences, Boulder, CO, Westview Press, 1984.
Warren, S.D., W.H. Blackburn, and C.A. Taylor, "Soil Hydrologic Response of Number of Pastures
and Stocking Density under Intensive Rotation Grazing," Journal of Range Management, 39:500-504,
1986.
Weltz, M., and M.K. Wood, "Short-Duration Grazing in Central New Mexico: Effects on Sediment
Production," Journal of Soil and Water Conservation, 41:262-267, 1986.
Wood, M.K., and W.H. Blackburn, "Grazing Systems: Their Influence on Infiltration Rates in the
Rolling Plains of Texas," Journal of Range Management, 34: 331-335, 1981a.
Wood, M.K. and W.H. Blackburn, "Sediment Production as Influenced by Livestock Grazing in the
Texas Rolling Plains," Journal of Range Management, 34: 228-231, 1981b.
Wood, James C. and M. Karl Wood, "Infiltration and Water Quality on Range Sites at Fort Stanton,
New Mexico," Water Resources Bulletin, Volume 24, No. 2, April 1988.
39 February 1994
------- |