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sustainability
Article
Rangeland Land-Sharing, Livestock Grazing’s Role in the
Conservation of Imperiled Species
Sheila Barry 1, 2, * and Lynn Huntsinger 2,*
Citation: Barry, S.; Huntsinger, L.
Rangeland Land-Sharing, Livestock
Grazing’s Role in the Conservation of
Imperiled Species. Sustainability 2021,
13, 4466. https://doi.org/10.3390/
su13084466
Academic Editors: Iain J. Gordon,
Pablo Gregorini and Fred Provenza
Received: 31 March 2021
Accepted: 13 April 2021
Published: 16 April 2021
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1University of California Agriculture and Natural Resources, San Jose, CA 95112, USA
2
Environmental Science, Policy and Management, University of California Berkeley, Berkeley, CA 94720, USA
*Correspondence: sbarry@ucanr.edu (S.B.); huntsinger@berkeley.edu (L.H.); Tel.: +1-408-282-3106 (S.B.)
Abstract:
Land sharing, conserving biodiversity on productive lands, is globally promoted. Much of
the land highest in California’s biodiversity is used for livestock production, providing an opportunity
to understand land sharing and species conservation. A review of United States Fish and Wildlife
Service listing documents for 282 threatened and endangered species in California reveals a complex
and varied relationship between grazing and conservation. According to these documents, 51%
or 143 of the federally listed animal and plant species are found in habitats with grazing. While
livestock grazing is a stated threat to 73% (104) of the species sharing habitat with livestock, 59%
(85) of the species are said to be positively influenced, with considerable overlap between species
both threatened and benefitting from grazing. Grazing is credited with benefiting flowering plants,
mammals, insects, reptiles, amphibians, fish, crustaceans, and bird species by managing the state’s
novel vegetation and providing and maintaining habitat structure and ecosystem functions. Benefits
are noted for species across all of California’s terrestrial habitats, except alpine, and for some
aquatic habitats, including riparian, wetlands, and temporary pools. Managed grazing can combat
anthropomorphic threats, such as invasive species and nitrogen deposition, supporting conservation-
reliant species as part of land sharing.
Keywords:
livestock grazing; species conservation; land-sharing; invasive species; nitrogen deposi-
tion; conservation-reliant species
1. Introduction
Livestock grazing is the widespread agricultural use of natural and seminatural
landscapes throughout the world. Although estimates vary, as much as 50 percent of
the world’s land area is grazed by domestic livestock [
1
]. People have relied on grazing
livestock as a source of high-quality protein for thousands of years, especially in ecosystems
not usable for cultivation due to a lack of water, poor soils, harsh climate, rough topography,
or high elevation. Throughout their history, grazing domestic livestock have generally
shared grasslands with wild grazers and a host of other wild animals. Traditionally taking
place on lands that are not arable, livestock producers are adapted to rearing animals on
lands in a seminatural condition, sometimes with natural or anthropogenic fire, and other
land management practices to keep woody vegetation in check and improve the forage for
both wild and domestic grazers.
Despite technological and production shifts initiated in the twentieth century, the life
cycle of commercial beef cattle in the United States still most often includes a significant pe-
riod on grazing lands [
2
,
3
]. Such lands have been promoted for conservation through land
sharing under the rubric of “working landscapes” [
4
,
5
]. Land sharing, which encompasses
wildlife-friendly farming practices, integrates biodiversity conservation with agricultural
production on the same land [
6
,
7
]. To better understand the relationship between livestock
grazing and species conservation from land sharing, this study assesses the current impacts
of livestock grazing, detrimental and beneficial, on the conservation of federally listed plant
Sustainability 2021,13, 4466. https://doi.org/10.3390/su13084466 https://www.mdpi.com/journal/sustainability
Sustainability 2021,13, 4466 2 of 20
and animal species in California as stated in listing documents published in the United
States Federal Register.
Listing documents used to implement the US Endangered Species Act of 1973 (ESA)
identify plants and animals vulnerable to extinction, designate their critical habitat, and
inform their recovery, including recognizing threats to the species and their habitats.
The United States Fish and Wildlife Service (USFWS) administers and enforces the ESA
for terrestrial species. The USFWS is required to use scientifically valid information
to describe reasons for a species’ demise and recommend actions for its recovery. The
descriptions as outlined in Section 4(a) (1) of the ESA consider five factors: (A) habitat loss,
(B) overutilization, (C) disease or predation, (D) inadequate regulatory mechanisms, and (E)
other natural or human-made factors affecting a species’ survival. The impact of livestock
grazing on a listed species and its associated habitat is included in the USFWS’s analysis of
the five factors when livestock grazing occurs with the species or within its habitat. The
information provided is the current state of knowledge and continually changing; when
new information is learned about a species’ needs and survival, the five-factor information
is updated through 5-year reviews and recovery plans.
A previous highly cited study, Wilcove et al. [
8
], used ESA listing information pub-
lished in the US Federal Register to quantify threats to listed species. They found 22% of
all US-listed endangered, threatened, or candidate species (n = 1207) were impacted by
habitat degradation or destruction resulting from livestock grazing. This finding is similar
to Czech et al. [
9
], which compared Federal Register documents and World Wildlife Fund
compendium data for causes of the endangerment of 877 species. They found 16.0% were
threatened by livestock grazing and 20.8% of the species by ranching, respective of the
data source.
Both Wilcove et al. and Czech et al. provided little explanation of livestock grazing’s
role in species decline. Wilcove et al. [
8
] categorized grazing as an extractive land use
along with logging and mining. Czech et al. [
9
] found a strong relationship between
grazing threats and non-native species, which they noted was at least, in part, explained
by grazing’s modification of plant and animal community composition. However, there
is a growing body of research from grazed lands worldwide that recognize the potential
of domestic animal grazing to modify or maintain habitat in ways that benefit certain
species [
10
–
16
]. In recent reviews, for example, positive impacts from livestock grazing
maintaining open habitats were found for amphibian [
10
] and small mammal [
11
] species.
Livestock grazing affects biota and their ecological systems in varied and complex
ways. Through consumption, physical impact, and nutrient redistribution, grazing live-
stock can change vegetation, soils, and habitats [
17
]. Although these effects of grazing
are well-known, whether they have negative or positive impacts in a particular ecosys-
tem and on a specific plant or animals species depends on the species, the ecosystem,
the current environmental conditions, as well as the management of the livestock and
their grazing [
18
–
20
]. In terms of livestock’s influences on ecosystems and threatened and
endangered species, herbivory should not be treated as a “black box”.
Despite the varied and contrasting impacts of grazing, to date, there is no assessment
of threats to imperiled species that considers livestock grazing’s varied impacts on spe-
cific species and their habitats, positive as well as detrimental. If nothing else, Wilcove’s
concerns with the importance of conservation on private lands and the need for active man-
agement [
21
] calls for such an assessment since so much land in a natural and seminatural
state is owned by ranchers, who rely on grazing for income and use it as a tool of active
habitat management.
California is well suited for such an assessment. First, with a varied climate and
topography and a growing population, the California Floristic Province, which includes
most of the state and small parts of adjacent areas in Oregon, Nevada, and Baja California,
Mexico, is one of the world’s most biologically rich and endangered ecoregions; it is a
globally recognized biodiversity hotspot [
22
]. Six thousand one hundred forty-three plant
species are native to the province; 42% of these species are endemic [
23
]. California has
Sustainability 2021,13, 4466 3 of 20
more federally listed species (282 in 2017) than any other state in the continental United
States. With so much biodiversity at risk, threats to species and recovery activities have
been identified for a large number of plants and animals across many species groups.
Second, despite California’s rich biodiversity, non-native annual grasses and forbs
or broad-leaved plants are widely established and dominant across most of California’s
rangelands. These annuals are part of a novel ecosystem with large numbers of species from
Mediterranean environments worldwide, many originating in the “Fertile Crescent”, a
domestication hearth [
24
–
26
]. Biological introductions, both intentional and unintentional,
are pervasive, impacting native species and ecosystems in California and throughout the
world [27].
Third, like much of the western United States, livestock grazing across the state is
extensively managed, with about 40% grazed by livestock to some extent [
28
]. While Cali-
fornia’s Mediterranean climatic zone, which includes grasslands, hardwood woodlands,
and chaparral, provides most of the forage consumed by livestock, two other zones also
support extensive livestock production. The cold desert steppe, which is characterized by
sagebrush grassland and pinyon-juniper woodlands, and the warm desert, which includes
barren lands and, at higher elevations, montane meadows and conifer forest, provide
seasonal grazing, primarily for cattle [29].
Another reason that California is well suited for an assessment of grazing impacts
on listed species and associated habitats is that it is a natural laboratory to study land
sharing. Although livestock grazing in the western United States has a relatively short
history (<300 years) compared to Europe and Asia, native species found on California’s
rangelands evolved with herbivory by now-extinct megafauna, including medium to
large herbivores, such as ground sloth, bison, camel, horse, mammoth, mastodon, and
ox [
30
]. Like in other parts of the world, conservation efforts in California increasingly
consider livestock grazing a way to maintain extensive natural landscapes and their native
diversity [
31
], expanding available habitat well beyond the possibility for nature reserves.
Land sharing provides an income to landowners through livestock production and reduces
the risk of development or land-use conversion [
28
,
32
]. While land sparing strategies
emphasize separating nature conservation and agriculture, relying on intensification of
agriculture on smaller areas to “spare” conservation areas, land sharing strategies seek to
accomplish both biodiversity conservation and agriculture within the same landscape [
33
].
This strategy is often presented as requiring trade-offs, where either agricultural yields
or species conserved are reduced [
34
]. For instance, Butsic and Kuemmerle [
35
] have
suggested considering land-sharing and land-sparing across a spectrum where agricultural
yields and species conservation are optimized depending on the ecosystems and species.
Given the limited feasibility of intensifying agricultural production on many grazing
lands [
36
], including California’s rangelands, livestock grazing may provide a decisive land-
sharing opportunity where conservation is not compromised for agricultural production
and species conservation and recovery for some species is enhanced.
A quantitative assessment from USFWS listing documents for multiple species across
a wide variety of habitats grazed by domestic livestock allows detection of patterns that
may explain the varied and sometimes contradictory responses from livestock grazing
observed and often reported in the literature. This assessment of all federally listed species
in California addresses the following questions (i) What is the role of grazing in the
conservation of federally listed species? (ii) Does grazing’s role in species conservation
differ by taxonomic groups and across different ecosystems? Moreover, (iii) What are the
specific reasons that plants or animals are threatened by or benefit from grazing? These
three questions allow us to understand better land sharing’s potential for conservation on
livestock grazing lands in California. It is important to keep in mind that “grazing” occurs
on all rangelands, by everything from caterpillars to elephants depending on location.
However, in this paper, the term grazing refers to the agricultural pursuit of managed
livestock grazing unless otherwise stated.
Sustainability 2021,13, 4466 4 of 20
2. Materials and Methods
Federal Register documents published by the USFWS for all federally listed threatened
or endangered species (182 plants and 100 animals) in California as of 1 December 2017,
were reviewed. A searchable database of ESA documents developed by the Center for
Conservation Innovation of the Defenders of Wildlife [
37
] was initially used to identify
species associated with grazing. ESA listing documents search through the database
included the final rule for listing, 5-year reviews, and recovery plans.
Federally listed species were determined to be associated with grazing if “graz*”,
“overgraz*”, or “trampl*” appeared in the text of at least one of the listing documents
associated with an imperiled species in California (Table 1). Mentions of “grazing” and
“trampling” were verified as being related to domestic livestock versus wild or feral
animals. The term “livestock” was searched, but it did not yield additional species affected
by grazing livestock or ranching. Other terms for herbivory, “browsing” and “foraging”,
were also searched but were not found to be used in the USFWS documents reviewed to
describe interactions with livestock.
From the search results, an Excel database was developed with the document’s title,
type, date, web URL, and the associated listed species, as well as statements from the text
regarding grazing (Data S1). The data were sorted by species and date, and the newest
listing document associated with each species with a grazing interaction identified. The
complete listing documents were accessed from the Environmental Conservation Online
System (ECOS), managed by the USFWS [
38
]. The most recent listing document was
typically a 5-year review, but a recovery plan or the final rule was the latest in some cases.
From listing documents, species type (plant or animal), animal species group, plant guild,
and date of the latest listing document were recorded for each species. Information on the
species’ terrestrial and aquatic habitat was obtained from NatureServe Explorer Species
reports under ecological and life history [
39
]. NatureServe Explorer Species reports, a
product of NatureServe in collaboration with the Natural Heritage Network, are referenced
on the USFWS ECOS website as an authoritative source of additional species information.
NatureServe reports terrestrial habitat for species based on US National Vegetation Classifi-
cations at the formation level [
40
]. Some species are found in multiple terrestrial or aquatic
habitats, and all habitats were recorded for each species. From the NatureServe listing, the
primary terrestrial and aquatic habitats, if applicable, were recorded for each listed species
and included in the Excel database (Data S1).
The USFWS uses various statements to describe the effects of livestock grazing on
listed species and their habitats (Table 1). Statements on grazing were coded and catego-
rized. A category for a grazing benefit and a grazing threat was independently assigned
for each listed plant and animal species. Stated threats from “grazing”, “overgrazing”, or
“trampling” were categorized as grazing threats. The threat of “loss or cessation of grazing”
was considered to indicate a benefit from grazing. In USFWS documents, this threat results
from lack of grazing leading to habitat degradation because grazing is acting to maintain
habitat structure or function. “Inappropriate grazing” was typically categorized as both
an indication of potential threat and benefit from grazing. The USFWS generally uses
inappropriate grazing to mean that grazing at the wrong time or intensity is detrimental to
the species or its habitat, while grazing at the right time and intensity may be beneficial.
The benefit of appropriate grazing is indicated by statements like, “too little grazing is
detrimental to the species or its habitat”.
For species with mentions of grazing in initial listing documents but no statement
on grazing’s threat or benefit in the newest listing document, the categories, “no grazing
threat” and “no grazing benefit” were used. The category “no grazing threat” also includes
species where the USFWS states that “grazing is not a threat”. The statement “grazing is a
not threat” typically reflects a change in the USFWS’s understanding of grazing’s effect on
a listed species, where previous listing documents had mentioned grazing as a threat to
the imperiled species or its habitat.
Sustainability 2021,13, 4466 5 of 20
Table 1.
Categorization of grazing impacts on species conservation stated in the most recent United States Fish and Wildlife
Service (USFWS) listing documents (5-year reviews or recovery plans) from 2000 to 2016 for each listed species in California
where grazing is mentioned.
Categories for
Grazing’s Mention Impact Statements or Category Descriptions
Livestock grazing current •Livestock grazing has a current relationship with listed species
No longer a factor
•“Grazing is no longer a threat” because livestock is not present, or the habitat has been
protected, and livestock has been excluded.
No current threat
•Grazing was listed as present or threatening in previous listing documents, but there is no
current mention of grazing.
Other grazing threatens
•“Wild or feral animals, including burros, deer, gophers or rabbits, are a threat”. This category
was used only when grazing threats were limited to feral or wild animals.
Island species
•
Species and their habitat on the Channel Islands have been impacted by uncontrolled grazing of
non-native feral and wild species, including cattle, sheep, goats, deer, elk, bison, and pigs. Most
of these animals have been removed, but historical impacts persist.
Categories of grazing’s current threats
Grazing or overgrazing
threatens
•“Grazing or trampling by livestock is a threat”.
•
“Overgrazing, severe, heavy, intensive, improper, inappropriate, poor or unmanaged grazing or
trampling is a threat”.
•“Goat grazing for fuels breaks is a threat”.
Unknown grazing threat •The impact of grazing on the species is unknown.
No grazing threat
•“Grazing is not a threat”.
•No grazing threat is stated.
Categories of grazing’s current benefit
Grazing benefits
•“Appropriate, managed, controlled, optimal, moderate or light grazing benefits, enhances,
restores or maintains”.
•“Loss of grazing or cessation of grazing is detrimental or a threat”.
•“Inappropriate grazing (which includes too little grazing) is a threat”.
Unknown grazing benefit •“Grazing’s benefit is unknown”.
No grazing benefit •No benefit is stated.
“No longer a factor”, “other grazing threat”, “no current grazing threat”, and “island
species” are additional categories used in this study that describe the stated relationship
between grazing and a listed species in listing documents (Table 1). The USFWS states that
grazing is no longer a threat when grazing no longer occurs within the species’ habitat,
often due to protections that restrict grazing, e.g., reserve status. “Other grazing threatens”
was used when listed plants or animals are not known to be impacted by domestic livestock,
but the stated threat is from wild or feral herbivores, horses, or burros. “No current grazing
threat” was assigned to species where the presence of livestock grazing was noted as a
threat in early listing documents, e.g., USFWS final listing rule, but in the most recent
documents, e.g., five-year reviews, livestock grazing was not mentioned.
Sustainability 2021,13, 4466 6 of 20
Both “no longer a factor” and “other grazing threat” describe the threat of grazing
to listed species endemic to the Channel Islands off the coast of California, but because of
the unique grazing history of these islands, the 21 plants and three animals found only
on the islands are categorized as “island species”. Grazing threats were primarily from
uncontrolled grazing by feral sheep and goats, deer, bison and elk. These animals were
introduced to the islands and were generally not managed; they have now been nearly
entirely removed.
Although initial results identified 209 species or 74 percent of the listed species in
California where grazing is mentioned, the review of most recent documents found a
current livestock grazing relationship with 143 species or 51 percent of the listed species
(Table 2). Further analysis of grazing threats and benefits for this assessment was only
considered for species with a current livestock grazing relationship.
Table 2.
Number of listed animal and plant species in California with grazing mentioned in USFWS listing documents,
oldest and current.
Livestock Grazing Mentions # of Animal
Species
% of Listed
Species
# of Plant
Species
% of Listed
Species Total % of Listed
Species
Other grazers (feral, wild) 1 7 8 3%
Island species (historic, feral) 3 21 24 9%
No Longer (historic) 2 17 13 5%
No Current 6 9 14 5%
Livestock grazing current 56 56% 87 48% 143 51%
Total grazing mentions 68 68% 141 78% 209 74%
Total listed species 100 182 282
The association between grazing’s role on listed species and species attributes, in-
cluding type, i.e., animal versus plant, animal species groups, plant guilds, and habitat
types within terrestrial and aquatic systems, was determined using Pearson’s chi-squared
tests. Calculating the chi-squared statistic and comparing it against the chi-squared distri-
bution indicates whether the observed pattern of responses is significantly different from
expected if the variables were truly independent of each other [
41
]. In this case, Pearson’s
chi-squared allows us to determine if grazing’s role as a threat or benefit is independent of
species’ type, animal group, plant guild and habitat type.
To illuminate the specific assertions about the nature of grazing impacts beyond the
broad categories of threats and benefit, reasons for grazing’s stated role in the newest
listing documents were coded and categorized and included in the database (Data S1).
Multiple reasons for grazing’s benefit or threat are recorded for some species. Direct threats
to an individual animal or plant or its natal site were differentiated from indirect impacts
to habitat or ecological processes, e.g., plant succession, impacts to soil and water quality.
All benefits were identified as indirect impacts.
3. Results
Grazing was considered an impact in listing documents for most of California’s feder-
ally listed species (74%, 209 species). However, based on the most recent listing documents,
the impact of livestock grazing on federally listed species is currently considered for
143 species or 51% of federally listed species in California (Table 2). The United States
Fish and Wildlife Service (USFWS) updated listing documents based on the review of
new information, including research findings, expert opinion and reports, and in some
cases, the presence or absence of grazing animals. Among federally listed species with a
current grazing relationship, the USFWS states threats from livestock grazing for 73% (104)
species but recognizes benefits from grazing for 59% (85) of the listed species occurring
in the state (Table 3). Since a grazing benefit and threat were independently assigned
for each species, there is considerable overlap. Both negative and positive impacts from
grazing are reported for 65 species with a current grazing mention (Figure 1). Threats
Sustainability 2021,13, 4466 7 of 20
and benefits to federally listed species from livestock grazing in California are primarily
attributed to cattle, although the USFWS notes impacts from sheep and goat grazing for
some species’ populations.
Table 3.
Number of listed animal and plant species in California (2017) with current grazing mention, percent of species
threatened and benefiting.
Livestock Grazing Current
(Threats and Benefits)
# of Animal
Species
n = 56
% of
Current
Animals
# of Plant Species
n = 87
% of Current
Plants Total % of Listed
Species
Grazing threat 47 84% 57 66% 104 37%
Unknown grazing threat 2 4% 5 6% 7 2%
No grazing threat 7 13% 25 29% 32 11%
Grazing benefit 36 64% 49 56% 85 30%
Unknown grazing benefit 0 4 5% 4 1%
No grazing benefit 20 36% 34 39% 54 19%
Both grazing threat and benefit
30 53% 35 40% 65 23%
Sustainability 2021, 13, x FOR PEER REVIEW 7 of 21
cattle, although the USFWS notes impacts from sheep and goat grazing for some species’
populations.
Table 3. Number of listed animal and plant species in California (2017) with current grazing mention, percent of species
threatened and benefiting.
Livestock Grazing Current (Threats and
Benefits)
# of Animal
Species
n = 56
% of Current
Animals
# of Plant
Species
n = 87
% of Current
Plants Total % of Listed
Species
Grazin
g
threat 47 84% 57 66% 104 37%
Unknown
g
razin
g
threat 2 4% 5 6% 7 2%
No
g
razin
g
threat 7 13% 25 29% 32 11%
Grazin
g
benefit 36 64% 49 56% 85 30%
Unknown
g
razin
g
benefit 0 4 5% 4 1%
No grazing benefit 20 36% 34 39% 54 19%
Both
g
razin
g
threat and benefit 30 53% 35 40% 65 23%
Figure 1. Number of federally listed species with threats or benefits from grazing in most recent
listing documents, including all federally listed species in California occurring with livestock graz-
ing or in habitats grazed by livestock (n = 143 species).
3.1. Grazing’s Impact by Species Type
Similar numbers of federally listed flowering plant and animal species in California
occur in conjunction with livestock grazing, 56% (56) of animal and 48% (87) of flowering
plant species; however, the USFWS more often states a threat to animal species from live-
stock grazing than to plant species. Grazing threatens 84% of the animal species and 66%
of the flowering plant species with a current livestock grazing mention (Figure 2, Table 4).
In contrast, there is no relationship in grazing’s stated benefits to species type, with 64%
and 56% of the animal and flowering plant species benefitting, respectively (Figure 2, Ta-
ble 4).
Figure 1.
Number of federally listed species with threats or benefits from grazing in most recent
listing documents, including all federally listed species in California occurring with livestock grazing
or in habitats grazed by livestock (n = 143 species).
3.1. Grazing’s Impact by Species Type
Similar numbers of federally listed flowering plant and animal species in California
occur in conjunction with livestock grazing, 56% (56) of animal and 48% (87) of flowering
plant species; however, the USFWS more often states a threat to animal species from
livestock grazing than to plant species. Grazing threatens 84% of the animal species and
66% of the flowering plant species with a current livestock grazing mention (Figure 2,
Table 4
). In contrast, there is no relationship in grazing’s stated benefits to species type,
with 64% and 56% of the animal and flowering plant species benefitting, respectively
(Figure 2, Table 4).
Sustainability 2021,13, 4466 8 of 20
Sustainability 2021, 13, x FOR PEER REVIEW 8 of 21
Figure 2. Livestock grazing’s impacts, threats, and benefits for federally listed species in California
by species type. The size of the circle is relative to the number of species. Pearson’s chi-squared
test level of significance represented as * p ≤ 0.05 for threats and no significance for benefits be-
tween species type p > 0.05.
Table 4. Summary of statistical analysis of differences in grazing’s role as a threat and benefit concerning listed species in
California. Level of significance represented as * p ≤ 0.05 and ** p ≤ 0.01.
Threat Benefit
Difference in Grazing’s Role for Each n Pearson’s X
2
df p-Value Pearson’s X
2
df p-Value
Animals vs. plants 143 5.931 2 0.05 * 3.04 2 0.22
Animal species group 56 10.385 12 0.58 17.07 6 0.01 **
Plant guild 87 10.001 10 0.44 17.396 10 0.07
Terrestrial habitat 105 25.835 16 0.06 29.161 16 0.02 *
Aquatic habitat 73 20.126 12 0.07 18.473 12 0.10
3.2. Grazing’s Impact by Animal Species Group and Plant Guild
All California animal and plant species groups with federally listed species have spe-
cies that may be threatened or may benefit from livestock grazing except “conifers and
cycads”. Among animal species groups, there is no association between groups and
threats from grazing (Table 4). Threats to animal species are widespread across all species
groups, with at least 75% of the species within each species group being stated as threat-
ened by grazing (Figure 3). In contrast, the potential benefit from grazing varies by animal
species group (Table 4). Amphibians, crustaceans, insects, mammals, and reptiles all have
more species that benefit from grazing than species that do not benefit. Fishes and bird
species are not likely to have a stated grazing benefit. Of listed California species, only
one bird species (California Condor, Gymnogyps californianus) and one fish species (desert
pupfish, Cyprinodon macularius) are noted to benefit from livestock grazing.
Figure 2.
Livestock grazing’s impacts, threats, and benefits for federally listed species in California
by species type. The size of the circle is relative to the number of species. Pearson’s chi-squared test
level of significance represented as * p
≤
0.05 for threats and no significance for benefits between
species type p> 0.05.
Table 4.
Summary of statistical analysis of differences in grazing’s role as a threat and benefit concerning listed species in California.
Level of significance represented as * p≤0.05 and ** p≤0.01.
Threat Benefit
Difference in Grazing’s Role for Each n Pearson’s X2df p-Value Pearson’s X2df p-Value
Animals vs. plants 143 5.931 2 0.05 * 3.04 2 0.22
Animal species group 56 10.385 12 0.58 17.07 6 0.01 **
Plant guild 87 10.001 10 0.44 17.396 10 0.07
Terrestrial habitat 105 25.835 16 0.06 29.161 16 0.02 *
Aquatic habitat 73 20.126 12 0.07 18.473 12 0.10
3.2. Grazing’s Impact by Animal Species Group and Plant Guild
All California animal and plant species groups with federally listed species have
species that may be threatened or may benefit from livestock grazing except “conifers and
cycads”. Among animal species groups, there is no association between groups and threats
from grazing (Table 4). Threats to animal species are widespread across all species groups,
with at least 75% of the species within each species group being stated as threatened by
grazing (Figure 3). In contrast, the potential benefit from grazing varies by animal species
group (Table 4). Amphibians, crustaceans, insects, mammals, and reptiles all have more
species that benefit from grazing than species that do not benefit. Fishes and bird species
are not likely to have a stated grazing benefit. Of listed California species, only one bird
species (California Condor, Gymnogyps californianus) and one fish species (desert pupfish,
Cyprinodon macularius) are noted to benefit from livestock grazing.
Plant species with federally listed species are in the “flowering plants” and “conifers
and cycads” groups. All the federally listed plant species in California impacted by livestock
grazing are in the flowering plant species group. This group includes both annual and
perennial species in the forb, grass, and grass-like plant guilds. However, most of the listed
plant species (84%) impacted by grazing are forbs or broad-leaf plants (
Figure 4
). There is
no association between plant guilds and the stated likelihood of threat or benefit (Table 4).
Sustainability 2021,13, 4466 9 of 20
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Figure 3. Livestock grazing’s impact, threat and benefit for federally listed animals in California
by species group. The size of the circle is relative to the number of species. Pearson’s chi-squared
test no significance for threats p > 0.05 and level of significance represented as ** p < 0.01 for bene-
fits.
Plant species with federally listed species are in the “flowering plants” and “conifers
and cycads” groups. All the federally listed plant species in California impacted by live-
stock grazing are in the flowering plant species group. This group includes both annual
and perennial species in the forb, grass, and grass-like plant guilds. However, most of the
listed plant species (84%) impacted by grazing are forbs or broad-leaf plants (Figure 4).
There is no association between plant guilds and the stated likelihood of threat or benefit
(Table 4).
Figure 4. Livestock grazing’s impact, threat and benefit for federally listed species in California by
plant guild. The size of the circle is relative to the number of species. No significance for Pearson’s
chi-squared test for threats or benefits by plant guild p > 0.05.
3.3. Grazing’s Impact by Ecosystem
Impacts from livestock grazing to listed species are found across a diversity of eco-
systems in California. Plant and animal species may be found in or complete their lifecycle
in multiple types of terrestrial or aquatic habitats. Of those species with a grazing rela-
tionship, 52% are found only in terrestrial habitats, 25% are found only in aquatic habitats,
Figure 3.
Livestock grazing’s impact, threat and benefit for federally listed animals in California by
species group. The size of the circle is relative to the number of species. Pearson’s chi-squared test no
significance for threats p> 0.05 and level of significance represented as ** p< 0.01 for benefits.
Sustainability 2021, 13, x FOR PEER REVIEW 9 of 21
Figure 3. Livestock grazing’s impact, threat and benefit for federally listed animals in California
by species group. The size of the circle is relative to the number of species. Pearson’s chi-squared
test no significance for threats p > 0.05 and level of significance represented as ** p < 0.01 for bene-
fits.
Plant species with federally listed species are in the “flowering plants” and “conifers
and cycads” groups. All the federally listed plant species in California impacted by live-
stock grazing are in the flowering plant species group. This group includes both annual
and perennial species in the forb, grass, and grass-like plant guilds. However, most of the
listed plant species (84%) impacted by grazing are forbs or broad-leaf plants (Figure 4).
There is no association between plant guilds and the stated likelihood of threat or benefit
(Table 4).
Figure 4. Livestock grazing’s impact, threat and benefit for federally listed species in California by
plant guild. The size of the circle is relative to the number of species. No significance for Pearson’s
chi-squared test for threats or benefits by plant guild p > 0.05.
3.3. Grazing’s Impact by Ecosystem
Impacts from livestock grazing to listed species are found across a diversity of eco-
systems in California. Plant and animal species may be found in or complete their lifecycle
in multiple types of terrestrial or aquatic habitats. Of those species with a grazing rela-
tionship, 52% are found only in terrestrial habitats, 25% are found only in aquatic habitats,
Figure 4.
Livestock grazing’s impact, threat and benefit for federally listed species in California by
plant guild. The size of the circle is relative to the number of species. No significance for Pearson’s
chi-squared test for threats or benefits by plant guild p> 0.05.
3.3. Grazing’s Impact by Ecosystem
Impacts from livestock grazing to listed species are found across a diversity of ecosys-
tems in California. Plant and animal species may be found in or complete their lifecycle in
multiple types of terrestrial or aquatic habitats. Of those species with a grazing relationship,
52% are found only in terrestrial habitats, 25% are found only in aquatic habitats, and the
remainder, 23%, may use or spend different parts of their lifecycle in both terrestrial and
aquatic habitats.
Some species are threatened, and some benefit from grazing in every terrestrial habitat
type with livestock grazing in California except alpine, where Sierra Nevada bighorn
sheep may contract a disease from domestic sheep [
42
] (USFWS 2008), but no benefits from
grazing are noted. Although 60% of the species that benefit from grazing in terrestrial
habitats are found in grasslands (Figure 5), there are more species with a stated grazing
benefit than with no benefit in grasslands, barren land, and woodlands. There was no
Sustainability 2021,13, 4466 10 of 20
association between terrestrial habitat types and the number of species threatened by
grazing (Table 4).
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and the remainder, 23%, may use or spend different parts of their lifecycle in both terres-
trial and aquatic habitats.
Some species are threatened, and some benefit from grazing in every terrestrial hab-
itat type with livestock grazing in California except alpine, where Sierra Nevada bighorn
sheep may contract a disease from domestic sheep [42] (USFWS 2008), but no benefits
from grazing are noted. Although 60% of the species that benefit from grazing in terres-
trial habitats are found in grasslands (Figure 5), there are more species with a stated graz-
ing benefit than with no benefit in grasslands, barren land, and woodlands. There was no
association between terrestrial habitat types and the number of species threatened by
grazing (Table 4).
Figure 5. Livestock grazing’s impact, threat and benefit for federally listed species by terrestrial
habitat type. The size of the circle is relative to the number of species. Pearson’s chi-squared test
no significance for threats p > 0.05 and level of significance represented as * p ≤ 0.05 for benefits.
Listed species impacted by livestock grazing are also found in various aquatic habi-
tats, but most are found in temporary or vernal pools, 62% (Figure 6). On California grass-
lands, federally listed species using temporary pools for all or part of their lifecycle in-
clude 21 plant species, annuals and perennials, and 12 animal species, amphibians, crus-
taceans, fish, and insects. While grazing threats are stated for some species in every
aquatic habitat type with listed species impacted by grazing, benefits from grazing are
found for some federally listed species in temporary pools (including vernal pools), wet-
lands, riparian, and springs (Figure 6). There is no association between the likelihood of
stated grazing benefits or threats for a particular species from grazing with aquatic habitat
types.
In summary, this assessment considered the number of federally listed species in
California by species type, animal species group, plant guild, terrestrial habitat, and
aquatic habitat that is threatened by or benefit from livestock grazing. The number of spe-
cies stated as threatened by grazing in California only differs significantly by whether
they are an animal or flowering plant, not among animal species groups, plant guilds or
habitat type. In contrast, the number of species found to benefit from grazing is related to
animal species group and type of terrestrial habitat (Table 4).
Figure 5.
Livestock grazing’s impact, threat and benefit for federally listed species by terrestrial
habitat type. The size of the circle is relative to the number of species. Pearson’s chi-squared test no
significance for threats p> 0.05 and level of significance represented as * p≤0.05 for benefits.
Listed species impacted by livestock grazing are also found in various aquatic habitats,
but most are found in temporary or vernal pools, 62% (Figure 6). On California grasslands,
federally listed species using temporary pools for all or part of their lifecycle include
21 plant species, annuals and perennials, and 12 animal species, amphibians, crustaceans,
fish, and insects. While grazing threats are stated for some species in every aquatic habitat
type with listed species impacted by grazing, benefits from grazing are found for some
federally listed species in temporary pools (including vernal pools), wetlands, riparian,
and springs (Figure 6). There is no association between the likelihood of stated grazing
benefits or threats for a particular species from grazing with aquatic habitat types.
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Figure 6. Livestock grazing’s impact, threat and benefit for federally listed species by aquatic habi-
tat type. The size of the circle is relative to the number of species. No significance for Pearson’s
chi-squared test for threats or benefits by aquatic habitat type.
3.4. The Reasons Livestock Grazing Threatens Species
The primary reasons stated for grazing’s threat differ between federally listed plant
and animal species. Direct impacts, including the potential for a plant or part of a plant to
be co nsume d or trampled by l ivest ock, i s the most frequently stated threat to plant species;
58% of the listed flowering plant species occurring in grazed habitats were reported to be
threatened by direct impacts (Figure 7). Evidence of direct impact from grazing and tram-
pling is mostly anecdotal, although sometimes it is reported with observations, including
description or data.
Figure 7. Reasons for livestock grazing’s threat to federally listed plant and animal species in Cali-
fornia.
In reporting the threat from direct impact from grazing and trampling, the USFWS
recognizes that grazing threats to individuals do not necessarily result in species decline
or drive a plant species to extinction. For example, in describing grazing impacts on the
annual forb, Sidalcea keckii, the USFWS reported that cattle were observed causing dam-
age by eating the plants, but the damage was barely noticeable a week later [43]. Similarly,
the USFWS [44] reported cattle herbivory and trampling impacts to the perennial forb,
Figure 6.
Livestock grazing’s impact, threat and benefit for federally listed species by aquatic habitat
type. The size of the circle is relative to the number of species. No significance for Pearson’s
chi-squared test for threats or benefits by aquatic habitat type.
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In summary, this assessment considered the number of federally listed species in
California by species type, animal species group, plant guild, terrestrial habitat, and
aquatic habitat that is threatened by or benefit from livestock grazing. The number of
species stated as threatened by grazing in California only differs significantly by whether
they are an animal or flowering plant, not among animal species groups, plant guilds or
habitat type. In contrast, the number of species found to benefit from grazing is related to
animal species group and type of terrestrial habitat (Table 4).
3.4. The Reasons Livestock Grazing Threatens Species
The primary reasons stated for grazing’s threat differ between federally listed plant
and animal species. Direct impacts, including the potential for a plant or part of a plant to
be consumed or trampled by livestock, is the most frequently stated threat to plant species;
58% of the listed flowering plant species occurring in grazed habitats were reported
to be threatened by direct impacts (Figure 7). Evidence of direct impact from grazing
and trampling is mostly anecdotal, although sometimes it is reported with observations,
including description or data.
Sustainability 2021, 13, x FOR PEER REVIEW 11 of 21
Figure 6. Livestock grazing’s impact, threat and benefit for federally listed species by aquatic habi-
tat type. The size of the circle is relative to the number of species. No significance for Pearson’s
chi-squared test for threats or benefits by aquatic habitat type.
3.4. The Reasons Livestock Grazing Threatens Species
The primary reasons stated for grazing’s threat differ between federally listed plant
and animal species. Direct impacts, including the potential for a plant or part of a plant to
be co nsume d or trampled by l ivest ock, i s the most frequently stated threat to plant species;
58% of the listed flowering plant species occurring in grazed habitats were reported to be
threatened by direct impacts (Figure 7). Evidence of direct impact from grazing and tram-
pling is mostly anecdotal, although sometimes it is reported with observations, including
description or data.
Figure 7. Reasons for livestock grazing’s threat to federally listed plant and animal species in Cali-
fornia.
In reporting the threat from direct impact from grazing and trampling, the USFWS
recognizes that grazing threats to individuals do not necessarily result in species decline
or drive a plant species to extinction. For example, in describing grazing impacts on the
annual forb, Sidalcea keckii, the USFWS reported that cattle were observed causing dam-
age by eating the plants, but the damage was barely noticeable a week later [43]. Similarly,
the USFWS [44] reported cattle herbivory and trampling impacts to the perennial forb,
Figure 7.
Reasons for livestock grazing’s threat to federally listed plant and animal species in California.
In reporting the threat from direct impact from grazing and trampling, the USFWS
recognizes that grazing threats to individuals do not necessarily result in species decline
or drive a plant species to extinction. For example, in describing grazing impacts on the
annual forb, Sidalcea keckii, the USFWS reported that cattle were observed causing damage
by eating the plants, but the damage was barely noticeable a week later [
43
]. Similarly, the
USFWS [
44
] reported cattle herbivory and trampling impacts to the perennial forb, Cirsium
fontinale var. obispoense, but cites a 1998 study where researchers determined that grazing
impacts, which were to mature plants, were offset by an increase in juvenile plants.
There are, however, a couple of examples where direct impacts of grazing were
reported to have facilitated extirpation in listing documents. A population of the shrub,
Arctostaphylos pallida, already weakened by a root fungus and shading, was considered
extirpated by goats grazing at intensities designated to reduce fuel loads [
45
]. Trampling
by cattle was reported to have extirpated a population of Cordylanthus mollis spp. mollis.
This annual forb is supported by fragile underground connections, haustoria that were
considered to have been damaged by trampling [
46
]. The USFWS in listing documents often
states that direct impacts are primarily a risk to species under situations of overgrazing
or heavy grazing, and when listed, species have small or isolated populations that are
vulnerable to stochastic expiration.
Sustainability 2021,13, 4466 12 of 20
After threats from direct impacts, “grazing”, or more often “overgrazing”, with no
specific explanation, is the most frequently stated reason livestock grazing threatens a
flowering plant species. As described in Table 1, “overgrazing” as a threat includes severe,
heavy, intensive, improper, inappropriate, poor, or unmanaged grazing or trampling.
Overall, 83% of listed flowering plant species occurring in habitats with livestock are
stated to be threatened by grazing or trampling’s direct impact on a plant, or grazing or
overgrazing (Figure 7).
On the other hand, federally listed animal species are primarily threatened by indirect
impacts from habitat loss or degradation, which is the stated reason that grazing threatens
47% of federally listed animal species (Figure 7). Impacts to habitat from livestock grazing
include introductions and increases in invasive species and loss of riparian vegetation.
Water quality degradation, which includes livestock grazing causing excess sediment and
nutrients or higher stream temperatures, is a stated impact on 26% of the federally listed
animal species found in grazed habitats in California. In addition, 26% of the animal
species are threatened by direct impacts to individuals or natal sites, e.g., burrows or nests.
Other less frequently stated threats to listed species plant and animal species from grazing
and trampling include other indirect impacts to hydrologic functions and soil condition,
e.g., erosion and compaction (Figure 7).
While threat reasons to listed species from grazing were individually identified for
analysis in this assessment, the impacts are not necessarily independent. The USFWS
describes the cascading effects of livestock’s impact on ecosystem processes leading to
habitat degradation and diminishing survival or recovery for some species. For example,
livestock impacts to water quality, stream channels, and riparian vegetation threaten
the Little Kern golden trout, Oncorhynchus mykiss whitei, and Paiute cutthroat trout
Oncorhynchus clarkii seleniris [
47
,
48
] (USFWS 2011, 2013c). As described in the listing
documents for these fish species, livestock may concentrate in riparian areas due to water
availability, green vegetation, and shade. Fish habitat is degraded by the reduction in water
holding areas, shade, and cover, resulting in increased water temperatures and decreased
water quality from excess sediment and nutrients. However, the USFWS listing also notes
that grazing has occurred in the drainage of the Little Kern golden trout for more than 100
years, and it is known that controlling the timing and intensity of grazing can minimize
impacts [
47
]. Similarly, the USFWS states that grazing threats to Paiute cutthroat trout have
been reduced because grazing has either been eliminated from their habitat or conservative
grazing management objectives have been put in place [48].
3.5. The Reasons Livestock Grazing Benefits Species
Benefits from livestock grazing to the survival or recovery of federally listed species
all result from indirect impacts. For plant and animal species in California, species benefit
from grazing that maintains or enhances habitat by controlling non-native annual plants
(biomass, cover, and height), reducing thatch (buildup of dead vegetation), maintaining
hydrologic functions (inundation period), mitigating dry atmospheric nitrogen deposition,
preventing land-use change, providing disturbance creating some bare ground, or prevent-
ing woody plant invasion from maintaining grassland (Figure 8). Controlling non-native
species, mostly non-native annual plants, is the most frequent reason stated that grazing
benefits both federally listed flowering plant and animal species in California; 89% of
species positively impacted by livestock grazing benefit from control of non-native species.
For example, in the USFWS listing documents for several insects (ten butterflies and one
moth), controlling non-native annual grasses is stated to favor native forb or broad-leaf
plant populations supporting the conservation of these species, which rely on forbs for
nectar and larvae food. Similar to grazing threats, grazing benefits were individually
recognized for this assessment, but many are related to one another.
Sustainability 2021,13, 4466 13 of 20
Sustainability 2021, 13, x FOR PEER REVIEW 13 of 21
hydrologic functions (inundation period), mitigating dry atmospheric nitrogen deposi-
tion, preventing land-use change, providing disturbance creating some bare ground, or
preventing woody plant invasion from maintaining grassland (Figure 8). Controlling non-
native species, mostly non-native annual plants, is the most frequent reason stated that
grazing benefits both federally listed flowering plant and animal species in California;
89% of species positively impacted by livestock grazing benefit from control of non-native
species. For example, in the USFWS listing documents for several insects (ten butterflies
and one moth), controlling non-native annual grasses is stated to favor native forb or
broad-leaf plant populations supporting the conservation of these species, which rely on
forbs for nectar and larvae food. Similar to grazing threats, grazing benefits were individ-
ually recognized for this assessment, but many are related to one another.
Figure 8. Reasons for livestock grazing’s benefit to federally listed plant and animal species in
California.
In addition to controlling non-native plants to favor certain species, grazing is stated
to benefit some listed species by controlling vegetation that alters habitat, including thatch
(Figure 8). In the grasslands and shrublands of the San Joaquin Valley of California, for
example, maintaining habitat with sparse vegetation supports various listed species, in-
cluding Kern mallow (Eremalche parryi ssp. Kernesis) [49], blunt-nosed leopard lizard
(Gambelia silus) [50], giant kangaroo rat (Diposdomys ingens) [51], and San Joaquin kit
fox (Vulpes macrotis) [52]. For the small ground-dwelling native vertebrates, annual grass
Figure 8.
Reasons for livestock grazing’s benefit to federally listed plant and animal species in California.
In addition to controlling non-native plants to favor certain species, grazing is stated
to benefit some listed species by controlling vegetation that alters habitat, including thatch
(Figure 8). In the grasslands and shrublands of the San Joaquin Valley of California,
for example, maintaining habitat with sparse vegetation supports various listed species,
including Kern mallow (Eremalche parryi ssp. Kernesis) [
49
], blunt-nosed leopard lizard
(Gambelia silus) [
50
], giant kangaroo rat (Diposdomys ingens) [
51
], and San Joaquin kit
fox (Vulpes macrotis) [
52
]. For the small ground-dwelling native vertebrates, annual grass
and thatch can create an impenetrable thicket [
50
]. For the larger native vertebrate, San
Joaquin kit fox, taller, dense vegetation can obscure their visibility of predators [
52
]. Habitat
with sparse vegetation is also necessary for both listed plant and animal species in coastal
grasslands, including the Santa Cruz tarplant (Holocarpha macradenia) [
53
] and Ohlone
tiger beetle (Cicindela ohlone) [54].
Some species (five plants, annual and perennial forbs; five animals, insects and a
reptile, Figure 8) benefit from grazing that controls vegetation associated with air pollution.
The USFWS cites research that shows air pollution, specifically dry atmospheric nitrogen
deposition, creates a fertilizer load that alters plant communities and habitat, and livestock
grazing can maintain habitat by removing excess vegetation and nitrogen [
16
,
55
]. Grazing’s
control of vegetation is also associated with maintaining grasslands by preventing succes-
sion or invasion by brush to benefit some animal and plant species (Figure 8). For listed
Sustainability 2021,13, 4466 14 of 20
plants like the Western Lily, Lilium occidentale that are threatened by loss of grassland, the
USFWS [
56
] has stated that the benefits of grazing seem to outweigh the potential threat
from these plants being grazed or trampled.
Within aquatic habitats, species benefitting from grazing, which includes flowering
plants, amphibians, and invertebrates, are primarily found in temporary or vernal pools,
where livestock help maintain an adequate inundation period, for example, [
57
,
58
]. Listing
documents for species in temporary pools cite research by Marty [
59
] and Pyke and
Marty [
15
] that describe increased grass cover in and around ungrazed vernal pools leading
to increased evapotranspiration and decreased pond duration. Other benefits stated for
listed species in aquatic habitats include a couple of animal species that benefit from the
presence and maintenance of stock ponds associated with livestock grazing. Livestock
grazing is also credited with maintaining a compatible land use for six animals and four
plants (Figure 8), despite development pressure—a direct link to the land-sharing concept.
4. Discussion
Livestock grazing is a widespread land use in California and has often been considered
a threat to conservation (see [
8
,
9
]), regardless of whether or not confirming research has
been conducted [
60
,
61
]. Despite this, this assessment from the USFWS listings shows
a complex and varied response to grazing among imperiled species and their habitats.
Beginning in 1769 with the arrival of Spaniards in California, livestock grazing, among
other things, contributed to introducing and spreading non-native species [
62
,
63
], resulting
in habitat loss and a novel ecosystem. Now, as documented in this assessment, grazing is
credited with controlling non-native plants and thatch buildup and maintaining specific
habitat structures and functions for many listed plant and animal species. The fact that
USFWS identifies grazing as a threat and a benefit to many species indicates that how
grazing is done matters. Grazing management certainly affects the conservation outcome
for the listed species in California that are either negatively or positively affected by
grazing (n = 65).
4.1. Value and Limitations of Best Available Science and the USFWS Listings
In fulfilling ESA requirements to identify threats that put species at risk of extinction,
the USFWS documents indicate the relationship between livestock grazing for every threat-
ened and endangered species based on the “best scientific and commercial data available”.
In many cases, the studies needed to understand better how species and habitat respond to
grazing over time or to a particular grazing pattern have not been done. In the absence of
published research for many species, applying the best available science means that threat
information may be based on expert opinion, including observations and unpublished
data, or may be extrapolated from research findings for similar species or ecosystems [
64
].
For example, in some cases, threats to species are based on assessments of grazing’s impact
on western rangelands or aquatic habitats, including Fleischner [
60
] and Belsky et al. [
65
].
Often as not, grazing benefits are identified when grazing exclusion leads to loss of the
species targeted for protection [
16
,
66
,
67
], and these research findings may be applied to
similar species in similar habitats.
While the use of the best available science allows for thorough coverage of all listed
species potentially impacted by livestock grazing or other threats, it also means that some
statements of effects are amplified as findings are repeated. In this assessment, using
the best available science from the USFWS listings may limit our assessment of patterns
relative to grazing’s impact across species types, groups, or ecosystems. It should also
be recognized that the USFWS listing documents are not always up to date, and just
like California ecosystem conditions, things are continually changing. The full picture of
grazing impacts over time and with variation in conditions is seldom fully known [
11
,
68
].
The analysis here adds more depth and detail to the complexities of the situation in
considering the role of livestock grazing in land sharing based on the diversity of species
and their habitats that are threatened by or benefit from grazing.
Sustainability 2021,13, 4466 15 of 20
4.2. Proper Management to Minimize Threats
Terms, including severe, heavy, intense, improper, unmanaged, uncontrolled, or
overgrazing, have all been used by the USFWS to describe grazing and trampling impacts
that threaten listed species. Generally interchangeable with “overgrazing”, these terms are
not consistently defined or applied in listing documents or in the scientific literature [
69
].
Overgrazing implies that grazing is in excess of management goals [
70
] or has described
any grazing that results in negative impacts [
69
]. Whether or not a species is at risk from
“overgrazing” depends on the severity and frequency of the grazing impact, the ecosystem,
and adaptations of the plant or animal to grazing or its outcomes [11,71].
In this assessment, the likelihood of threat to listed species from livestock grazing was
not associated with ecosystems, plant guilds, or animal species groups (Table 4). Instead,
grazing was found to threaten numerous species across all species groups and habitat
types, suggesting that some grazing level, typically unmanaged or excessive, can impact
any habitat and affect the survival of most species on grazed lands. There is evidence
in the published literature that grazing managed inappropriately can change species
composition, cause erosion and decrease productivity and fail to meet habitat conservation
goals
[65,72–74];
however, grazing can also be managed so that negative impacts are
mitigated and minimized. From a comprehensive review of literature on grazing systems
and impacts, Briske et al. [
68
] concluded that grazing intensity, a function of stocking rate
and livestock distribution is the single most important management factor influencing
conservation outcomes and livestock production in grazed systems. Controlling grazing
intensity with proper stocking rates coupled with livestock distribution practices, including
water distribution, supplement placement, herding, and fencing, have been found to reduce
impacts of livestock on rangelands, including impacts in riparian areas [68,75–79].
4.3. Grazing Supports Conservation Reliant Species
Managed grazing can reduce threats from grazing to listed species and meet livestock
production needs [
68
,
80
], but it is grazing’s benefit to species conservation that defines a
role for land-sharing and counters arguments that suggest land-sharing requires trade-offs
between species conservation and agricultural production. Ranching’s benefit in protecting
rangelands from development has been valued across the western US and throughout
much of the world where land is at risk for development [
31
,
81
]. Between 1984 and 2008,
over 195,000 hectares of California’s rangeland habitats were converted to residential
development or intensive agriculture [
82
]. In this assessment, the benefit of maintaining
ranching as compatible land use was recognized for a few listed species (seven animals,
eight plants, Figure 7), but the value of grazing as a process was recognized for many more
animals and plants.
Grazing has been described as a natural or even keystone process in ecosystems that
have evolved with grazing [
83
]. The plants and animals in these systems are considered to
have co-evolved with herbivores and exhibit adaptations that support their success while
being grazed [
19
]. In systems with ecological and evolutionary grazing histories, livestock
grazing can replace some of the functions provided by native herbivores, which may be
extirpated, or incompatible with current land uses. However, the benefits to listed species
from grazing in California are often indifferent from local evolution and grazing history
because the native flora has been largely replaced. Instead, livestock grazing is playing
a pivotal role in mitigating the environmental consequences of anthropomorphic-driven
change, including invasive and naturalized non-native species and nitrogen deposition,
and in fact, the management of a novel ecosystem comprised of plants from other places.
This value of grazing for species conservation is explained, at least in part, by the
concept of “conservation reliant” species [
84
,
85
]. Due to anthropomorphic activities’ im-
pacts on a species or its habitat, many species require ongoing conservation management
actions to recover or even persist, becoming conservation reliant. Scott et al. [
86
] examined
the management actions required by recovery plans for species listed under the ESA and
found that 84% of 1136 species are conservation reliant. The most common management
Sustainability 2021,13, 4466 16 of 20
actions reported for conservation-reliant species were control of other species, active habitat
management, and artificial recruitment.
Invasive plants are a major challenge to the conservation of native species throughout
the world and a leading driver of extinction [
87
], and several researchers have concluded
that California has some of the most heavily invaded ecosystems [
88
–
90
]. Non-native
annual grasses are naturalized across California’s grasslands, shrublands, and wood-
lands [
91
]. They have also colonized areas in California that were once sparse with vegeta-
tion like dunes [
92
] and desert [
93
] or areas once dominated by low-growing broad-leaved
plants [
94
]. They are larger statured than most native broad-leaved plants, highly resilient
to grazing and drought, and reproduce with vigor from high seed production and fertility.
The ubiquitous presence and impact of naturalized non-native grasses underlie livestock
grazing’s benefits for many species across various ecosystems. While stated benefits were
more common for listed species in grasslands than in other habitats, species benefitting
from grazing’s control of non-native species and habitat management, in general, are found
on barren lands, desert, sand, playa or salt flats, shrublands, woodlands, and conifer forest
as well as temporary pools, wetlands, and riparian zones. A decline and extirpation of
native species are evident when livestock grazing is removed from ecosystems that are
naturally open and barren but now crowded by invasive species and thatch [13,14,16].
While this study focused on grazing’s impacts on threatened and endangered species,
the effects identified are also related to species, not a risk, e.g., forage and pollinator plants
for listed insects [
16
,
55
], and may apply to other species on grazed lands. The value of
some level of grazing to support biodiversity in grasslands has been demonstrated in many
locations worldwide [
95
–
99
]. When livestock are managed to prevent over utilization
and habitat degradation, grazing can impact rangeland vegetation, increasing heterogene-
ity or patchiness and creating habitat for a greater diversity of species [
98
,
100
,
101
]. In
California, the continued and growing impact of non-native species driven by anthropo-
morphic activities, including climate change, inadvertent species introductions, and air
pollution
[16,102,103]
, extends the value of grazing to support listed species across all
terrestrial habitats and in some aquatic habitats.
Lunt et al. [
104
] proposed a framework to assess grazing’s value for achieving con-
servation objectives in different ecosystems in Australia. Like stated reasons for grazing’s
benefit to species conservation in this assessment, they found grazing to be beneficial when
it either (1) controls the biomass of potentially dominant, grazing-sensitive plants, (2) pre-
vents encroachment by undesirable, grazing-sensitive, potential dominants, (3) provides
required disturbance niches (4) maintains habitat structure or (5) enhances the diversity of
species and vegetation structures across the landscape. This framework could be used to
evaluate the role of grazing and rangeland livestock production in land sharing in many
ecosystems.
5. Conclusions
This review of the USFWS listings documents concludes that many federally listed
species in California are conservation reliant, requiring continued interventions to support
their lifecycle or maintenance of habitat and that sharing land with livestock grazing
will continue to be an important conservation strategy. Most, if not all, ecosystems on
the planet have been altered by land use and other anthropomorphic effects. Threats
to biodiversity stemming from pervasive non-native species, climate change, and the
disruption of essential ecosystem processes and disturbance regimes may not be overcome
simply by preserving land, improving regulatory protections, and removing threats [
105
].
Livestock grazing is perhaps the only ongoing land use that can be feasibly manipulated to
manage vegetation and habitats at the landscape scale.
Supplementary Materials:
The following are available online at https://www.mdpi.com/article/10
.3390/su13084466/s1, Data S1: Species Data.
Sustainability 2021,13, 4466 17 of 20
Author Contributions:
Conceptualization, S.B. and L.H.; methodology, S.B.; formal analysis, S.B.;
data curation, S.B.; writing—original draft preparation, S.B.; writing—review and editing, S.B. and
L.H. All authors have read and agreed to the published version of the manuscript.
Funding:
This research was supported by the University of California Agriculture and Natural
Resources and the University of California Berkeley, Department of Environmental Science, Policy
and Management.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Data Availability Statement: Data is in Supplementary Material Data S1: Species Data.
Acknowledgments:
The authors would like to acknowledge Elisa Mineo, Anh Thi Phuong Pham,
and Theresa Becchetti, who assisted in developing the data set, James Bartolome and Sheri Spiegal
for their review, and Chamali Dharmasiri and Lee Ann Ray for their assistance with the charts.
Conflicts of Interest: The authors declare no conflict of interest.
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