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Anthropogenic disturbance has generated a significant loss of biodiversity worldwide and grazing by domestic herbivores is a contributing disturbance. Although the effects of grazing on plants are commonly explored, here we address the potential multi‐trophic effects on animal biodiversity (e.g. herbivores, pollinators and predators). We conducted a meta‐analysis on 109 independent studies that tested the response of animals or plants to livestock grazing relative to livestock excluded. Across all animals, livestock exclusion increased abundance and diversity, but these effects were greatest for trophic levels directly dependent on plants, such as herbivores and pollinators. Detritivores were the only trophic level whose abundance decreased with livestock exclusion. We also found that the number of years since livestock was excluded influenced the community and that the effects of grazer exclusion on animal diversity were strongest in temperate climates. These findings synthesise the effects of livestock grazing beyond plants and demonstrate the indirect impacts of livestock grazing on multiple trophic levels in the animal community. We identified the potentially long‐term impacts that livestock grazing can have on lower trophic levels and consequences for biological conservation. We also highlight the potentially inevitable cost to global biodiversity from livestock grazing that must be balanced against socio‐economic benefits. Livestock grazing reduces the abundance and diversity of animals, but the effects are dependent on trophic level of responding species. Herbivores and pollinators are most impacted, while detritivores increase with livestock present. There is also an effect of livestock exclusion over time on the animal community.
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SYNTHESES The effects of livestock grazing on biodiversity are multi-
trophic: a meta-analysis
Alessandro Filazzola,
Charlotte Brown,
Margarete A. Dettlaff,
Amgaa Batbaatar,
Jessica Grenke, Tan Bao,
Isaac Peetoom Heida and
James F. Cahill Jr
Department of Biological Sciences,
University of Alberta, Edmonton,
AB T6G 2E9,Canada
*Correspondence: E-mail: filaz-
The peer review history for this arti-
cle is available at https://publons.-
Anthropogenic disturbance has generated a significant loss of biodiversity worldwide and grazing
by domestic herbivores is a contributing disturbance. Although the effects of grazing on plants
are commonly explored, here we address the potential multi-trophic effects on animal biodiversity
(e.g. herbivores, pollinators and predators). We conducted a meta-analysis on 109 independent
studies that tested the response of animals or plants to livestock grazing relative to livestock
excluded. Across all animals, livestock exclusion increased abundance and diversity, but these
effects were greatest for trophic levels directly dependent on plants, such as herbivores and polli-
nators. Detritivores were the only trophic level whose abundance decreased with livestock exclu-
sion. We also found that the number of years since livestock was excluded influenced the
community and that the effects of grazer exclusion on animal diversity were strongest in temper-
ate climates. These findings synthesise the effects of livestock grazing beyond plants and demon-
strate the indirect impacts of livestock grazing on multiple trophic levels in the animal
community. We identified the potentially long-term impacts that livestock grazing can have on
lower trophic levels and consequences for biological conservation. We also highlight the poten-
tially inevitable cost to global biodiversity from livestock grazing that must be balanced against
socio-economic benefits.
Conservation, disturbance, exclosure, domestic grazers, global, graze, herbivory, trophic cascade.
Ecology Letters (2020)
Global change from human disturbance has created unprece-
dented loss of biodiversity and degradation of natural habitats
worldwide (Wake & Vredenburg 2008; Barnosky et al. 2012).
Food production can be especially impactful to biodiversity
through native land conversion into croplands or rangelands
(Barnes et al. 2009; Machovina et al. 2015). Strategies of land
sharing have been proposed to reconcile food production with
goals of conservation (Phalan et al. 2011; Tscharntke et al.
2012), but the effects of grazing by domestic herbivores on
biodiversity remain contentious (Yuan et al. 2016). Empirical
evidence has identified livestock grazing to have complex
effects on communities such as promoting invasive species
(Kimball & Schiffman 2003), controlling non-native domi-
nance (Stahlheber & D’Antonio 2013), maintaining plant
diversity via the intermediate disturbance hypothesis (Yuan
et al. 2016), and replacing the functional role of an extirpated
native grazer (Milchunas et al. 1998; Bengtsson et al. 2000;
Kohl et al. 2013). As grazing by domestic livestock currently
occupies 26% of our terrestrial land cover (UN Food & Agri-
culture Organization 2017) much of which is either protected
land or remnant natural habitat (e.g. grazing on public lands
or crown lands), there is a need to better understand the over-
all effects of livestock grazing on ecosystems in relation to
biodiversity to appropriately meet future goals of food secu-
rity and conservation.
The effects of livestock grazers have on plant communities
(Olff & Ritchie 1998; Jones 2000; Stahlheber & D’Antonio
2013; Koerner et al. 2014; T
alle et al. 2016) and soil-biota
(Bardgett & Wardle 2003; Andriuzzi & Wall 2017; Zhou et al.
2017) are well documented, but the effects on other animal
trophic levels, especially vertebrates, has not been quantita-
tively synthesised (but see van Klink et al. 2015; Graham
et al. 2019). There have been repeated and recent calls in ecol-
ogy to include multi-trophic approaches in community analy-
ses (Fraser et al. 2015; Soliveres et al. 2016; Seibold et al.
2018). Understanding multi-trophic interactions are important
for the management of biodiversity because different organ-
isms are expected to respond differently to the same distur-
bance events (Fraser et al. 2015; Gossner et al. 2016).
Additionally, factors that alter the composition of one trophic
group can have indirect impacts on other trophic levels, e.g.
bottom-up or top-down effects (Borer et al. 2006; Beschta &
Ripple 2009; Lefcheck et al. 2015). For instance, livestock
have been identified to have multi-trophic effects on below-
ground biota through consumptions of plant biomass and
non-trophic effects, such as modifying soil characteristics and
dung deposition (Bardgett & Wardle 2003; Andriuzzi & Wall
2017). However, there are likely differences in the response of
aboveground and belowground trophic levels to disturbance
(Gossner et al. 2016). Aboveground animals can directly com-
pete with livestock grazers for similar resources, such as native
grazing ungulates (Voeten & Prins 1999; Mishra et al. 2004)
©2020 John Wiley & Sons Ltd/CNRS
Ecology Letters, (2020) doi: 10.1111/ele.13527
or herbivorous insects (Branson & Vermeire 2016; Pryke et al.
2016), that can extend to higher trophic levels through bot-
tom-up regulation. If the abundance of certain trophic levels
is reduced, there can be loss of consumer species reliant on
these specific prey items. For instance, a reduction of herbivo-
rous insects can negatively impact bird diversity or abundance
(Wilson et al. 1999) or removal of specific plant flowers can
extirpate an obligate pollinator. Grazers can also have non-
consumptive effects such as increasing plant turnover or dung
deposition that favours detritivores (Petersen et al. 2004;
Schon et al. 2011). Not all trophic levels or ecosystems are
expected to respond equally to the presence of domestic graz-
ers in an ecosystem. As such, to make proper and targeted
decisions within the realms of biological conservation and
rangeland management, there is a need to better understand
and include multi-trophic interactions when determining graz-
ing effects on ecosystems.
The effect of grazing on biodiversity patterns can depend
on climate. In areas sensitive to disturbance, even minimal
grazing can significantly alter the abundance or diversity of
taxa within the community. For instance, ecosystems that
have high abiotic stress with extremes in precipitation or tem-
perature (e.g. the alpine or deserts) can be particularly
impacted by grazing which damages soil characteristics (e.g.
increase erosion, decrease water infiltration), reduces already
limited plant biomass, and decreases animal diversity (Jones
2000; Sankaran & Augustine 2004; Evju et al. 2006). How-
ever, in ecosystems with low stress, grazing can stimulate
plant growth via a compensatory response (McNaughton
et al. 1989; Ramula et al. 2019), resulting in a lower impact
from livestock on the plant community. Previous meta-analy-
ses have identified precipitation as mediating the effects of
livestock grazing on plants (Herrero-Jauregui & Oesterheld
2018) and nutrient cycling (Zhou et al. 2017), that are likely
to extend to animals in those communities. The effects of live-
stock grazing on community composition are dependent on
temperature or precipitation and thus will vary along environ-
mental gradients.
There are many areas globally that were previously grazed
by livestock and can display biological effects of that legacy
(Valone et al. 2002). Livestock grazing can induce changes in
species composition, such as the introduction of exotics (Sink-
ins & Otfinowski 2012) or extirpation of species sensitive to
disturbance (Andresen et al. 1990), and these effects can per-
sist years after livestock exclusion. When grazing is frequent,
exclusion may not elicit any significant change in composition
because the community is now adapted to grazing (Augustine
et al. 1998; Sasaki et al. 2008; Davies et al. 2016). Therefore,
with the exclusion of domestic grazers the community may
not respond linearly over time, but instead may have thresh-
olds for changes to occur in community composition (Sasaki
et al. 2008). The inclusion of climate and records of previous
grazing are required to effectively quantify the effects of graz-
ing on the trophic structure of an ecosystem.
Here we use a meta-analysis to investigate multi-trophic
impacts of domestic grazing and represent ecological commu-
nities as a food chain model. We synthesised the scientific lit-
erature on grazing to compare the effects of livestock grazing
on trophic structure. We specifically compared grazed areas to
those where grazers were excluded and categorised each of the
responding species into a trophic level (detritivores, herbi-
vores, pollinators, omnivores, predators and parasites) based
on main diet. These species were further separated into inver-
tebrates and vertebrates because there are likely different
mechanisms that each can interact with livestock. For exam-
ple, we might expect interference competition with native, ver-
tebrate herbivores and apparent competition with invertebrate
herbivores. Invertebrates also tend to have a narrower dietary
breadth relative to vertebrates. We examined a subset of the
selected studies that included measures of plants, but did not
explicitly look for studies that only tested plants. We excluded
studies that examined soil micro-organisms because there are
previous meta-analyses that explore these groups in detail
(e.g. Bardgett & Wardle 2003; Andriuzzi & Wall 2017; Zhou
et al. 2017) and our intention was to focus on mechanisms
affecting above-ground trophic levels. Using 109 published
manuscripts with relevant data, we compared the abundance
and diversity within vertebrate and invertebrate trophic levels
in grazed and grazer excluded areas. We hypothesise that live-
stock exclusion will increase the abundance and diversity of
all trophic levels because of reduced competition for plant
biomass (herbivores, pollinators anddetritivores) and an
increase in prey items (omnivores and predators). We predict
the effects of livestock exclusion on plants will parallel the
effects on animals. We also predict that the effects of livestock
exclusion on plants and animals will respond nonlinearly
overtime relative to sites that continue to be grazed (i.e. time-
since-exclusion). Finally, we predict that ecosystems with at
extremes in precipitation or temperature (e.g. desert, tundra)
will be the most sensitive to the presence of livestock grazers.
Systematic review
We conducted a literature search using Web of Science for all
peer-reviewed journal articles between 1970 and Nov 2019,
examining the effects of livestock grazers. We selected papers
based upon both response variable suitability and study
design. A study was only included if a response variable was
included that measured some aspect of animal diversity or
abundance. We excluded if a study only included data on
plants, fungi or soil biota. When available, we also extracted
plant response data from included papers, though that was
possible in only 46% of cases.
We used the following search terms in two searches to cap-
ture all studies that compared areas exposed to livestock graz-
ers to areas that were ungrazed: Search 1) graz* OR livestock
AND exclosure* OR exclusion OR exclude* OR ungrazed
OR retire* OR fallow* OR fence* OR paddock*; Search 2)
grazing intensity OR grazing gradient OR stocking rate OR
rotation* grazing. The search included all studies globally on
Web of Science. We did not include any studies that tested
marine grazing, such as molluscs; nor did we include the
effects of livestock grazing on aquatic systems. Using these
search terms and criteria we identified 3489 published manu-
scripts. These manuscripts were individually screened for rele-
vancy using three criteria 1) a test of livestock grazing relative
©2020 John Wiley & Sons Ltd/CNRS
2A. F. Filazzola et al. Review and Syntheses
to a livestock excluded area, 2) a measured response species
being an animal and 3) there was empirical data that could be
extracted or obtained from the author. We removed dupli-
cates and any study that did not fit these criteria, such as
reviews, policy documents, and manuscripts on grazer health
(e.g. cattle antibiotics, sheep shearing methods). We removed
studies that provided indirect estimates of grazers being
absent, such as biomass of plants, evidence of defoliation or
distance to water source. We were able to identify 109 studies
that matched these requirements. An individual not involved
with the initial screening validated a small subset of studies to
ensure that our criteria for inclusion and exclusion were effec-
tive (Cote et al. 2013).
Data compilation
The 109 selected studies were reviewed to determine the
reported species or functional groups, the response variable
measured (e.g. abundance or diversity) and species of the live-
stock grazer. We obtained details about the experimental
design from each study including the GPS coordinates, the
time-since-exclosures were established and the number of sites
used. There were few studies that tested domestic grazers
other than sheep or cattle in isolation. Therefore, we refined
the studies to include livestock grazing by cattle and sheep
either in isolation, together, or in the presence of other
domesticated species (e.g. horses, goats and donkeys). Each
responding species or functional group was categorised using
available literature into its respective vertebrate class and
trophic level. We separated by vertebrate class because there
may be significant differences in the mechanisms that grazing
affects species within each of these groups. In instances where
the description of the examined taxa was too coarse to deter-
mine trophic level (e.g. coleoptera, birds), we excluded these
comparisons from further analysis. A list of the most common
taxa found in each trophic level can be found in Table 1. The
response variables of each study were summarised into abun-
dance or diversity. To prevent pseudo-replication, where
authors reported multiple responses that included the same
sampled individuals, we selected the coarsest taxonomical
response estimate that retained information about trophic
position. For example, if a study included abundance of all
butterflies, abundance of polyphagous butterflies and abun-
dance of specialist butterflies, we only included abundance of
all butterflies. A full list of the original reported response vari-
ables and our categorisation of the response variables can be
found in Appendix A. We were able to identify 109 published
manuscripts that included 205 independent pair-wise compar-
isons of livestock grazed and livestock excluded areas. A com-
parison was treated as independent if it was from a unique
study, tested a specific trophic level, and measured either
abundance or diversity. These comparisons were categorised
into tests of plant abundance (n=40), plant diversity
(n=14), animal abundance (n=122) and animal diversity
(n=29). A workflow and rationale for manuscripts that were
excluded can be found in Appendix B. For each of the 205
comparisons, we extracted the means, standard deviations and
number of replicates. In studies where the raw data were pro-
vided, these statistics were calculated.
We conducted a meta-analysis to compare the effects of graz-
ing on different trophic levels using data that were extracted
from relevant studies. We followed the methodology described
by Koricheva et al. (2013) that provides a clear workflow
including data aggregation, calculating effect sizes, and con-
ducting statistical models. Each of the 205 comparisons was
categorised based on vertebrate class, trophic level and
response variable (i.e. abundance or diversity). To contrast
livestock grazing and livestock excluded areas, we calculated
the log-transformed ratio of means using eqn 1 (Lajeunesse
2011) as an effect size for each unique comparison (function
escalc, package metafor) (Viechtbauer 2010). We used this log-
transformed response ratio because the value is symmetrical
around zero (Viechtbauer 2010) and is commonly used in
ecology (Lajeunesse 2011).
Positive values of LRR indicate livestock exclusion increases
biodiversity relative to grazed areas. Negative values of LRR
indicate livestock grazing increases biodiversity relative to an
area where livestock grazers were excluded. We recognise an
alternative interpretation exists, such that positive values of
LRR would indicate grazing increases biodiversity and nega-
tive values indicate grazer exclusion increases biodiversity.
The only difference between these is whether an individual
view grazing or its exclusion as the active treatment. Most of
our studies (>90%) previously had livestock grazers that were
excluded rather than sites where grazing never occurred.
Therefore, we chose to frame the control as grazing and the
treatment as grazers excluded.
LRR ¼ln Xlivestock excluded
Xlivestock grazing
 ð1Þ
To compare the effects of livestock exclusion on different
trophic levels, we fit meta-analytic random and mixed models
with the effect sizes determined from each study. To separate
the direct effects of grazing on plants from the indirect effects
on the animal community, we ran separate models for plants
and animals. We identified 54 unique effect sizes that compared
plant abundance or diversity in livestock grazed and livestock
excluded areas. We used random-effects models with the effect
sizes as the response variable and corresponding sampling
Table 1 Dominant taxa observed in each of the trophic levels separated
by vertebrate class
Trophic level Common taxa
Detritivores Collembola, Coleoptera, Diptera, Formicidae, Isoptera,
Herbivores Coleoptera, Hemiptera, Gastropoda
Omnivores Coleoptera
Parasitic Acari, Culicadae, Nematoda, Thysanoptera
Pollinator Coleoptera, Diptera, Hymenoptera, Lepidoptera
Predator Araneae, Coleoptera
Herbivores Aves, Lagomorpha, Macropodidae, Rodenta, Equidae,
Bovidae, Giraffidae
Omnivores Aves, Squamata, Testudines
Predator Amphibians, Aves, Dasyuromorphia, Carnivora
©2020 John Wiley & Sons Ltd/CNRS
Review and Syntheses Livestock can reduce animal biodiversity 3
variances as the error term that includes inverse-variance
weights. We ran separate random-effects models for plant
abundance (40 effect sizes) and diversity (14 effect sizes). Ran-
dom-effects models were used because they account for differ-
ences in study methodologies and assumes the selected
comparisons are a random subset of a large population of stud-
ies conducting similar comparisons (Viechtbauer 2010). To
compare the effects of grazing on animal trophic level, we ran
random-effect models for animal abundance (122 effect sizes)
and diversity (29 effect sizes). To determine if the response to
grazing varied by trophic level, we also ran mixed-effects mod-
els with trophic level and vertebrate class of the species exam-
ined treated as a fixed effect. We tested the effects of grazing
across trophic levels by comparing the effects of livestock exclu-
sion on plants and animals. We fit mixed-effects models with
animal abundance and diversity as the response variables and
plant abundance or diversity as the predictor variables. To
ensure there were no differences in the effects of grazing among
grazer composition (e.g. cattle, sheep, both), we also conducted
a mixed-effects model with the response ratio as the response
variable and grazer as the moderator.
We examined the potential for bottom-up effects in which
the effects of livestock exclusion on plants had indirect effects
on animal abundance or diversity. We ran mixed-effect mod-
els with the effect size of plants as the fixed effect and the
effect size of animals as the response variable. Four models
were run to compare plant abundance or diversity with ani-
mal abundance or diversity, orthogonally crossed. In these
models, a linear increase would suggest effects of livestock
exclusion on plants are paralleled in animals, no effect would
suggest effects on animals are independent of effects on
plants, and a linear decrease would suggest animals respond
inversely to changes in plants from livestock grazing.
We tested whether the effects of livestock exclusion on
plants and animals increased over time by comparing the
effect size against years since grazers were excluded. We ran
mixed-effects models with time-since-exclusion as the fixed
effect and the effect sizes of livestock exclusion on plant abun-
dance (n=34), plant diversity (n=13), animal abundance
(n=107) and animal diversity (n=26) as the responses.
We tested whether the effects of livestock exclusion on the
community was mediated by climate by comparing the effect
sizes to temperature and precipitation. We used the GPS coor-
dinates associated with each study to extract the mean annual
temperature and precipitation during the duration of the
experiment from the Climatic Research Unit (CRU) (http:// We selected mean annual tempera-
ture and precipitation because these variables are frequently
used for predicting ecosystem productivity (e.g. Del Grosso
et al. 2008) and the effects on grazing (e.g. Herrero-Jauregui
& Oesterheld 2018). These variables were downloaded to the
30-arc second (c. 1 km) spatial resolution. We fit mixed-effect
models for the effects of grazing on plant abundance, plant
diversity, animal abundance and animal diversity with mean
annual precipitation and mean annual temperature as the
fixed effects. We expected the effects of livestock exclusion to
decrease linearly with increasing temperature and precipitation
as abiotic stress is reduced. However, we included polynomials
because some previous research has suggested the effects of
grazing to be nonlinear with changes in climate (Herrero-Jau-
regui & Oesterheld 2018). We used a second-order polynomial
fit for the analyses with time-since-exclusion and climate when
it explained greater variation (R
value increase of 0.10 or
more) and had a lower AICc than a linear model.
The above models were calculated using restricted maxi-
mum-likelihood estimations (REML) because they are unbi-
ased to estimations of population heterogeneity relative to
other methods such as maximum likelihood (Viechtbauer
2005). Confidence intervals for models were calculated using
Wald-type intervals. The amount of residual heterogeneity
generated from these models was obtained iteratively through
the Q-statistics method (Hartung & Knapp 2001). To deter-
mine if there were publication biases towards certain results
and absence of heterogeneity (Egger et al. 1997), we generated
funnel plots for all the mixed-effect models. We did not find
publication biases within our tests because our funnel plots
were observed to be symmetrical that was confirmed using a
regression test recommended by Egger et al. (1997). Tests of
publication bias within models can be seen in Appendix C.
All analyses and data aggregation were conducted in R Ver-
sion 3.4.3 (R Core Team 2019) and an open workflow can be
found online at (
Trends in grazing literature
Experiments of grazing exclusion on animals were conducted
globally in 20 countries and on every continent except Antarc-
tica (Appendix E). However, there were biases in the global
distribution of studies with most experiments conducted in
Europe, North America and Australia (72%). Using the Kop-
pen-Geiger climate classification, we identified that studies
were distributed in a large range of climates (i.e. from deserts
to tundra), but most were conducted in Cfb temperate
humid warm (24%), BSk arid summer dry cold (20%) and
Dfb/Dfc warm summer (20%). In studies that tested live-
stock grazing with non-domestic grazers co-occurring in the
same ecosystem, the response of the native grazer was infre-
quently measured (8%). Most studies focused on examining
the effects of arthropods (69%) or small mammal composition
(47%). Other commonly examined taxa included reptiles
(13%) and birds (20%). Of the studies that measured animals,
46% of the studies had also measured plants.
Grazing effects on multiple trophic levels
Across all studies, the exclusion of livestock increased plant
abundance (mean effect SE =0.43 0.09; t
P<0.001; I
=96.1%) but had no effect on plant diversity
(mean effect SE =0.11 0.06; t
=1.78, P=0.075;
=67.1%). We found no relevant heterogeneity between
studies in both the meta-analysis on plant abundance and
plant diversity (Appendix E).
Across all animals, livestock exclusion increased abundance
(mean effect SE =0.21 0.07; t
=3.02, P=0.002;
=92.8) and diversity (mean effect SE =0.18 0.05;
=3.59, p<0.001; I
=72.4). The inclusion of trophic level
(e.g. invertebrate herbivore, invertebrate pollinator) explained a
©2020 John Wiley & Sons Ltd/CNRS
4A. F. Filazzola et al. Review and Syntheses
considerable amount of variability for mixed effects models of
abundance (I
=89.9, Q
=3.0; P=0.003) and diversity
=56.5; Q
=3.63; P<0.008). Livestock exclusion signifi-
cantly increased the abundance of vertebrate herbivores and
vertebrate predators (Fig. 1). Livestock exclusion also signifi-
cantly increased the diversity of invertebrate pollinators and
invertebrate herbivores (Fig. 1). The abundance of invertebrate
detritivores was the only animal group that significantly
declined with grazer exclusion (Fig. 1). The diversity of omni-
vore and predator trophic levels were not impacted by grazing
for either vertebrate class (Fig. 1). We found no relevant
heterogeneity between studies in both the meta-analysis on ani-
mal abundance and animal diversity (Appendix E). The differ-
ent types of grazer assemblages (e.g. cattle, sheep, cattle and
sheep) caused no significant difference in the effects of grazing
on plant abundance (Q
=3.99, P=0.41), plant diversity
=2.93, P=0.57), animal abundance (Q
P=0.42) or animal diversity (Q
=0.37, P=0.55).
We found evidence of potential bottom-up effects of grazing
as livestock exclusion effects on plant diversity were correlated
with exclusion effects on animal abundance (t
P=0.003; Fig. 2). This suggests livestock caused decreases or
increases in plant diversity result in the same response for
animal abundance (Fig. 2). We did not observe a pattern
when comparing plant abundance animal abundance
=1.39, P=0.17), plant abundance animal diversity
=0.02, P=0.98), or plant diversity animal diversity
=0.08, P=0.94). However, comparisons with animal
diversity had relatively small sample sizes (n=8;
Appendix F).
Effect of time-since-exclusion
The effects of grazing on animal metrics persisted for years
after exclusion of grazers from control sites (Fig. 3). However,
time-since-exclusion had no effect on plant abundance
=0.60, P=0.44) or plant diversity (t
=0.35, P=0.73;
Fig. 3). With longer time-since-exclusion, animal abundance
increased when compared to a site that was grazed (mean
effect SE =1.81 0.68; t
=2.66, P=0.008; Fig. 3). The
effect of increasing time-since-exclusion on animal diversity
was nonlinear with significantly greater diversity relative to
grazed sites at intermediate timeframes (between 5 and
30 years), but not significantly different at shorter or longer
timeframes (t
=2.00, P=0.057; Fig. 3).
Figure 1 Effect sizes (LRR) of livestock exclusion on different trophic levels separated by vertebrate class for abundance (left) and diversity (right) of
respective taxa. Mean effect sizes that are significantly different from zero are denote by asterisk (*** <0.001, ** <0.01, * <0.05). The number of
comparisons per trophic level (i.e. sample size) is in parentheses beneath the effect size. Positive values indicate grazing sites have higher measured values
and negative values indicate grazing sites have lower measured values. Confidence intervals, test statistics and p-values can be found in Appendix F.
©2020 John Wiley & Sons Ltd/CNRS
Review and Syntheses Livestock can reduce animal biodiversity 5
Figure 3 Effect over time of excluding livestock grazers relative to a grazed site on plant/animal abundance and diversity. Each point represents mean effect
size calculated from a study using the log-response ratio. Solid line represents mean model fit for meta-regression of time since grazed on the effect of
grazing for animal diversity and shaded areas are 95% confidence intervals. Values above the dashed line represent livestock excluded sites have higher
animal abundance or diversity relative to sites that were continuously grazed. The taxa surveyed within each study are represented by circles for
invertebrates and triangles for vertebrate.
–0.4 –0.2 0.0 0.2
Effect of livestock exclusion on plant diversity (LRR)
Effect of livestock exclusion on animal abundance (LRR)
Figure 2 Effect of livestock exclusion on plant diversity was found to increase linearly with the effects on animal abundance (t
=3.63, P=0.003). The
taxa surveyed within each study are represented by circles for invertebrates and triangles for vertebrate. Models that compared the other combinations of
animal abundance, animal diversity, plant abundance and plant diversity were not significant and are presented in Appendix G.
©2020 John Wiley & Sons Ltd/CNRS
6A. F. Filazzola et al. Review and Syntheses
Local climate effects on grazing
The effect of livestock exclusion on plant abundance was
independent of mean annual temperature (t
P=0.32), total annual precipitation (t
=1.14, P=0.25) and
their interaction (t
=0.72, P=0.47). The effect of livestock
exclusion on plant diversity also did not change with tempera-
ture (z
=0.23, P=0.81), precipitation (z
P=0.13) or their interaction (z
=0.35, P=0.73).
Livestock exclusion increased animal abundance more in
warmer climates (mean effect SE =1.50 0.76;
=1.97, P=0.051), but had no effect with precipitation
=1.60, P=0.11) or any interaction (t
P=0.15). The effect of livestock exclusion on animal diversity
had a unimodal relationship with mean annual temperature
=2.41, P=0.025; Fig. 4), where exclusion increased ani-
mal diversity the most at average annual temperatures
between 5 and 15 °C. Precipitation did not mediate the effect
of livestock grazing on animal diversity (t
=0.95, P=0.34)
and there was no interaction with temperature (t
Livestock grazing can be a significant driver of global biodi-
versity patterns by affecting multiple trophic levels (Fig. 1).
Across all animals, we found excluding livestock increased
animal abundance and diversity that was likely driven by
strong effects on trophic levels directly dependent on plants
(i.e. herbivores and pollinators; Fig. 2). Detritivores were the
only trophic level that decreased in abundance with livestock
exclusion. We found evidence that the number of years since
livestock were excluded affected the animal community
(Fig. 3), indicating that our study sites were able to recover
from livestock grazing over time. We also observed the effects
of livestock exclusion to be most pronounced in relatively
mild climates, with decreasing effects at temperature extremes
(Fig. 4). Our results suggest that domestic grazers can influ-
ence the trophic structure of ecological communities, and
these effects can persist after their removal.
Grazing effects on trophic levels
We found evidence that livestock exclusion increased the
abundance of plants and over time, plant diversity. Livestock
grazers were expected to decrease the abundance of the plant
community because indigenous grazers are rarely present at
the same density as livestock domestic grazers (Steuter &
Hidinger 1999; du Toit et al. 2017). However, the relationship
between plant diversity and grazing remains more mixed. For
instance, stocking rate has been identified to decrease the
number of plant species in a community, but this relationship
dissolves when using more complex measures of diversity,
such as those that include relative plant abundances (Herrero-
Jauregui & Oesterheld 2018). The effects of herbivores on
plant diversity are also largely dependent on the impact for
the dominant plant species, which if palatable tend to increase
biodiversity or if herbivore resistant decrease biodiversity
(Koerner et al. 2018). Other meta-analyses have supported the
idea that the effect of grazing on the plant community is
highly species specific, benefiting certain native species and
grasses, but negatively affecting exotics and flowering forbs
(Stahlheber & D’Antonio 2013; T
alle et al. 2016). Although
not tested here, there are likely significant changes in the com-
position of plants occurring with increases in plant diversity
worthy of further investigation.
0 5 10 15 20
Mean annual temperature (°C)
Effect of livestock exclusion (LRR)
50 100 150
Mean annual precipitation (mm)
Figure 4 Relative difference between the diversity of animals on livestock grazed and livestock excluded sites was related to mean annual temperature, but
not mean annual precipitation. Each point represents mean effect size calculated from a study using the log-response ratio. Solid line represents mean
model fit for meta-regression of temperature on the effect of grazing for animal diversity and shaded areas are 95% confidence intervals. Values below the
dashed line represent livestock excluded sites have higher animal diversity relative to grazed sites. The taxa surveyed within each study are represented by
circles for invertebrates and triangles for vertebrate.
©2020 John Wiley & Sons Ltd/CNRS
Review and Syntheses Livestock can reduce animal biodiversity 7
As we predicted, domestic grazers impacted the trophic
levels directly reliant on the plant community (Fig. 1). We
observed a decline in vertebrate herbivore abundance and
invertebrate herbivore diversity when livestock grazers were
present, likely because of competition for food resources. The
vertebrate herbivores that were most commonly tested (89%)
for effects of grazing exclusion were rodents and lagomorphs
(e.g. rabbits, hares and pikas). Small mammals are particu-
larly affected by livestock grazing because trampling can dam-
age burrows (Schmidt et al. 2005; Horncastle et al. 2019) or
reduce vegetation cover that results in increased predation risk
from raptors (Torre et al. 2007) or other visual predators.
Grazing impacts on small mammals can have effects that
extend beyond a decline in their population. For instance,
exclusion of cattle can increase small mammal populations
(Sullivan & Sullivan 2014), which can improve nitrogen min-
eralisation (van Wijnen et al. 1999) and maintain grassland
diversity by limiting shrub encroachment (Ceballos et al.
2004). However, reduced small mammal densities may not be
viewed as negative in all human contexts, and rodent control
by livestock could be a positive ecosystem service.
The abundance of detritivores was significantly higher at
grazed sites, which appears contradictory to a lower availabil-
ity of plant biomass (Fig. 1). Although grazing can reduce
biomass, the quality of remaining plant tissue may increase
(e.g. higher nitrogen to fibre content), which can promote
arthropod abundance (Moran 2014; Coq et al. 2018). Grazers
may also be facilitating detritivores species through non-con-
sumptive effects, such as dung deposition by livestock or
greater soil turn over (Floate 2011). Additionally, detritivores
may not be impacted by some negative effects that vertebrate
herbivores experience, such as trampling, and could take
advantage of reduced competition for plant material (Heske &
Campbell 1991).
Grazing had little effect on the higher trophic levels but did
reduce the abundance of vertebrate predators (Fig. 1). Verte-
brate predators could be lower in abundance because of fewer
prey items (i.e. vertebrate herbivores) and thus livestock could
have bottom-up effects on animal abundance. Management
practices can also negatively affect vertebrate predators, such
as fences or deterrent strategies (e.g. guard dogs, trapping),
that limit predation of livestock (e.g. van Bommel & Johnson
2012). The diversity of omnivores and predators were not
affected by livestock grazing potentially because there were
enough prey items in grazed areas to support some predators
or that these animals forage over an area larger than the cat-
tle enclosure. Omnivore abundance was also not affected,
potentially because of the larger dietary breadth relative to
predators. Secondary consumers are less affected by livestock
grazing relative to herbivores or pollinators, but further work
is necessary to determine the difference in response.
An increase in invertebrate herbivore and pollinator diver-
sity with livestock exclusion was also detected (Fig. 1).
Replacement of certain plant species, such as grazing promot-
ing grasses over forbs (Stahlheber & D’Antonio 2013; T
et al. 2016), can affect herbivores or pollinators that are obli-
gates to specific species. Pollinators can be particularly
affected by livestock grazing because even though plant diver-
sity remains the same, removal of flowers still reduces pollen
and nectar resource abundance (Hatfield & LeBuhn 2007). For
instance, livestock grazing has been identified to alter plant-pol-
linator visitation networks (Vanbergen et al. 2014). Grazing has
been previously demonstrated in another meta-analysis to
reduce arthropod diversity more than plant diversity because of
homogenisation of the landscape (van Klink et al. 2015). We
also found evidence that changes to plant diversity because of
livestock grazing reflected in the abundance of animals (Fig. 2).
Shifts in the composition of plants and a lack of landscape
heterogeneity due to grazing could be driving the observed dif-
ferences in animal diversity from grazing.
Consequences of excluding grazers overtime
The effects of livestock grazing on the biodiversity of plants
and animals can persist after herds are removed from an
ecosystem (Fig. 3). We found evidence that time since grazer
exclusion increased animal abundance and had a unimodal
relationship with diversity. The intensity of livestock grazing
is expected to mediate the effect of grazing on plants, and
consequently, animal diversity (e.g. Milchunas et al. 1998;
Boerschig et al. 2013). Unfortunately, inconsistent estimates
of livestock densities (e.g. AUM, livestock/ hectare, number
of days grazed) across studies prevented us from including
such a comparison within our meta-analysis and encourage
standardisation of livestock quantities in the future. Instead,
we observed a pattern of recovery in the relatively short-term
absence of grazers (i.e. 1020 years). Beyond that time, the
livestock exclusion did not have an effect on animal diversity
relative to sites that were grazed. A frequently recommended
approach in rangeland recovery is passive restoration where
domestic grazers are removed without other interventions (e.g.
Beschta et al. 2013), but this might not be effective if animal
diversity benefits from some frequency of grazing. For
instance, the absence of grazers can promote the dominance
of grasses (Stahlheber & D’Antonio 2013; Koerner et al.
2018) that do not support specialist herbivores or pollinators.
Restoring the diversity of a previously grazed ecosystem can
require complementary management practices, such as
increasing the number of flowering plants over grasses to sup-
port invertebrates (Vaudo et al. 2015). Grazer exclusion can
also affect the physical characteristics of the landscape includ-
ing soil nitrogen (van Wijnen et al. 1999; Knops et al. 2000),
soil compaction (Halde et al. 2011), and fire frequencies
(Davies et al. 2009). Evaluating the effects of grazing requires
long-term experimentation, since the effects can change in sign
and magnitude over decadal time scales.
The continued effects of grazing on ecosystems after removal
are also complicated by previous strategies for managing live-
stock. For example, legacy effects persist today from high inten-
sity grazing that occurred a century ago in the United States
with cattle (Svejcar et al. 2014) and in Sweden with reindeer
(Egelkraut et al. 2018). Exclusion of livestock might not return
the ecosystem to its original composition, but rather a different
composition with higher animal abundance or diversity. In
some environments, continued grazing is a required manage-
ment technique to support native biodiversity (Diamond et al.
2012; Germano et al. 2012; Moranz et al. 2012). However, if
managed poorly, overgrazing could also cause the reverse,
©2020 John Wiley & Sons Ltd/CNRS
8A. F. Filazzola et al. Review and Syntheses
facilitating invasive species and encouraging shrub encroach-
ment (Roques et al. 2001; D’Odorico et al. 2012). Future
research should explore the frequency of disturbance that is
occurring with the livestock grazers and the impacts it has on
species provenance (i.e. native vs. non-native).
Interactions of grazing and climate
The effects of livestock exclusion on biodiversity were depen-
dent on temperature, but not precipitation (Fig. 4). Previous
ecological models have described co-occurring gradients of
herbivore pressure and environmental stress as driving shifts
in the sign of interactions among species in the stress gradient
hypothesis (Bertness & Callaway 1994; Smit et al. 2009; Dan-
gles et al. 2013) or changing the complexity of trophic struc-
ture in the exploitation hypothesis (Oksanen et al. 1981;
Oksanen & Oksanen 2000). Each of these models proposed
that in high-stress environments, the effects of natural her-
bivory are intense compared to other ecosystems because
plant species in these systems have traits that are targeted at
tolerance of abiotic stress instead of disturbance (sensu Grime
1977) and natural predators are mostly absent to regulate her-
bivory (Oksanen et al. 1981). However, we found evidence
that contradicts these models, as the effects of livestock graz-
ing appeared to be neutral in high-stress environments with
cold annual temperatures. These cold ecosystems may have
less diversity relative to temperate ecosystems (Gaston 2000),
and thus livestock grazers have a larger potential to reduce
species richness in mild climates where diversity is higher. Spe-
cies at climate extremes could also be more tolerant to distur-
bance and have greater capacity to recover following grazing.
For instance, in cold ecosystems adaptations to abiotic stress
could overlap with traits that inhibit herbivory (D
ıaz et al.
2007; Fensham et al. 2011, 2014) and in relatively ‘hot’
ecosystems, animal abundances might be less affected because
of high plant productivity. This pattern is supported by the
neutral relationship that we observed between climate and
grazing effects on plant diversity. Although not tested here,
variation in soil texture or resources from grazing can also
have significant effects on plant composition (Schrama et al.
2013) and thus animal diversity. Inclusion of soil variables
and soil biota that have been identified to vary with livestock
(Bardgett & Wardle 2003; Andriuzzi & Wall 2017; Zhou et al.
2017) could further disentangle the indirect effects of grazing
on above-ground trophic levels.
Implications for conservation
Livestock exclusion can benefit the abundance and diversity of
multiple trophic levels. However, abandoning grazing in certain
environments may not result in an increase to biodiversity and
in some instances can cause further loss. For instance, we
observed grazing having a positive effect on plant diversity and
four studies within our meta-analysis where animal diversity
increased with livestock grazing, contradicting the general trend
(Ranellucci et al. 2012; Schmidt et al. 2012; Verga et al. 2012;
Tabeni et al. 2013). In all four studies, livestock grazing main-
tained grassland structure by suppressing woody encroachment,
which supports specific animal species. Although the conversion
of grasslands to shrublands has been attributed to overgrazing
(Archer et al. 1995; Van Auken 2009), continued grazing in
these systems might be required to minimise shrub cover. In
other ecosystems, such as forests, livestock production is some-
times described as causing habitat loss because the generated
rangelands do not provide the same ecosystem services or func-
tions as the previous native habitat (Machovina et al. 2015). If
there are persistent effects of grazing, restoration to previous
conditions can be impractical and instead these rangelands rep-
resent novel ecosystems with a different set of species composi-
tion and functions (Cingolani et al. 2005; Hobbs et al. 2009).
Our analysis used coarse estimates of community composition,
such as abundance and diversity that neglect species-level
changes in composition. When examined at the species-level the
effects of grazing can be significantly magnified relative to com-
munity measures (Supp & Ernest 2014). For instance, at-risk
species may be especially sensitive to livestock relative to other
species if grazing reduces the abundance of plant species that
they are dependent (Ausden et al. 2005; Schtickzelle et al. 2007).
The impacts of livestock grazing on conservation are thus
dependent on target organism (plants, primary consumers,
predators) and goals set by land managers (improving diversity
or productivity).
The production of livestock has increased significantly in
spatial extent since the 1960s and is projected to continue to
expand in developing countries (Thornton 2010), potentially
threatening indigenous animal diversity on a global scale.
Future increases in climate variability is also expected to
threaten food security and increase conversion of land into
rangelands (Sloat et al. 2018). To meet this demand, livestock
grazers will continue to be placed on land shared by indige-
nous animal species, thereby potentially threatening the global
biodiversity of herbivores and pollinators. These impacts are
expected to be most pronounced in mild climates, such as
temperate ecosystems, and are likely to persist after grazers
are removed. Identifying the aspects of grazing that most
impact animal biodiversity could be used to further develop
more effective management practices. For example, some
forms of rotational grazing are effective in environments with
low abiotic stress and when precipitation less variable (Haw-
kins 2017). Techniques for mitigation will not erase all the
effects of livestock grazing and these negative cascading
effects may be an inevitable consequence that society will need
to balance with the socio-economic benefits.
The authors thank Dr. Jens Roland for comments on an ear-
lier draft. The authors also thank three anonymous reviewers,
Dr. Eric Seabloom, and Dr. Jonathan Chase for their com-
ments that significantly improved the quality of the manu-
script. This research was funded by a Killam Post-Doctoral
Fellowships, a NSERC Post-Doctoral Fellowship awarded to
A.F, and an NSERC Discovery Grant awarded to JFC.
All authors contributed to developing the purpose of the
manuscript and participated in the data extraction from
©2020 John Wiley & Sons Ltd/CNRS
Review and Syntheses Livestock can reduce animal biodiversity 9
published articles. AF analysed the data and wrote the manu-
script. AB, CB, JG, JC and MD provided comments on the
Raw data and extracted manuscript data are available at
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Additional supporting information may be found online in
the Supporting Information section at the end of the article.
Editor, Eric Seabloom
Manuscript received 22 August 2019
First decision made 8 February 2020
Second decision made 26 March 2020
Third decision made 1 April 2020
Manuscript accepted 3 April 2020
©2020 John Wiley & Sons Ltd/CNRS
12 A. F. Filazzola et al. Review and Syntheses
... During the last 30 years, livestock grazing has progressed along two opposing trajectories: intensification in productive areas (increased livestock densities) and abandonment in marginal and less productive ones (Winkler et al., 2021). High livestock densities reduce plant height and biomass, consequently diminishing the abundance of invertebrates and small vertebrates, and ultimately impacting large ones, including predators (Dennis et al., 2008;Evans et al., 2015;Filazzola et al., 2020;Weiss et al., 2013). Overgrazing is one of the most important non-climatic factors behind the degradation of semi-natural ecosystems (IUCN, 2019), because it alters edaphic properties and promotes soil loss by erosion (Podwojewski et al., 2006;Liu et al., 2013;Cai et al., 2020). ...
... Recently, extensive grazing has been put forward as a strategy to preserve semi-natural open ecosystems (e.g., steppes, grasslands, moorlands; Boch et al., 2019) and their avian community (Leal et al., 2019;Skagen et al., 2018). Low-to-moderate grazing intensity reduces plant biomass and avoids woody encroachment (Evans et al., 2015;Filazzola et al., 2020), but it increases bare ground cover and plant species richness and diversity, as predicted by the intermediate disturbance hypothesis (Boch et al., 2019;Yuan et al., 2016). These changes produce complex responses on higher trophic levels such as arthropods, which serve as prey for open-land birds (Filazzola et al., 2020;Goosey et al., 2019). ...
... Low-to-moderate grazing intensity reduces plant biomass and avoids woody encroachment (Evans et al., 2015;Filazzola et al., 2020), but it increases bare ground cover and plant species richness and diversity, as predicted by the intermediate disturbance hypothesis (Boch et al., 2019;Yuan et al., 2016). These changes produce complex responses on higher trophic levels such as arthropods, which serve as prey for open-land birds (Filazzola et al., 2020;Goosey et al., 2019). The abundance of foliar, phytophagous arthropods decreases in moderately grazed areas compared to ungrazed ones likely because of the disruption of direct plant-insect associations (Filazzola et al., 2020). ...
... But to our knowledge, most of these studies consisted of site-specific controlled-grazing management experiments based on grazedungrazed contrasts (i.e. grazing versus enclosure, or rest grazing) [17,27], indicating that the effects of grazing regimes on plant diversity was spatial-scale dependence, which is important to understand the effect of grazing regimes on plant diversity at a larger scale (dependence) from a management strategy perspective. ...
... The mechanisms that the effect of grazing management types on plant diversity have reported various and even contradictory results [18,27,28]. Previous studies have shown that the effects of grazing regimes on species diversity depended largely on local variables (site-specific) and regional variables (vegetation types and the duration of grazing exclusion) [17,29,30]. ...
... Li et al. [37] reported that moderate grazing was the possible reason for RG as a sustainable grazing management strategy. Most of these studies were restricted to specific vegetation types, or at single scale, but very few studies attempted to derive general conclusions especially at different spatial scales from grazing management strategy perspective [27,38,39]. ...
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Grazing exclusion (GE) and rest grazing (RG) are important management to restore grassland ecosystems. In order to evaluate the effects and mechanisms of different grazing management on species diversity, vegetation community indices and soil variables were determined in the plots of Qilian Mountains in Gansu Province. The results showed that diversity effects and their regulating mechanisms had space-scale dependence under different grazing management. Species richness and species diversity indices of RG in grassland were significantly higher than that of GE at the regional scale. Additionally, three grazing management in mountain meadows had only a significant effect on species richness, but different management in mountain meadows and temperate steppes had a significantly different effect on species diversity indices. Meanwhile, soil variables only influenced species diversity at the regional scale. Most of community and soil variables at each scale had positive effects on species diversity, except that the direction of biodiversity effects was negative for species coverage, mean plant height, soil porosity (SK) and bulk density (BD) under two contrasting grazing management. In conclusion, choosing RG at the regional scale and select grazing management according to different grassland types at the local scale to restore degraded grassland vegetation.
... The intensity of grazing is not mainly practiced to meet livestock needs. Yet, the transition into the crop-land ecosystem also led to the decline of biodiversity [7,8]. Hence, it is important to explore other alternative feeds that are economic and environmentally friendly. ...
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Protein content of the substrate affects the nutritional composition of maggot ( Hermetia illucens ). This study aimed to summarize and confirm a wide range of findings about the effect of substrate protein on the nutritional composition, macrominerals, and amino acids of maggot. This meta-analysis data was acquired from papers indexed by Scopus throughout the past decade. The substrate’s protein concentration was used to define the fixed factor, whereas several studies were incorporated as the random factor. The selection and compilation of data followed the PRISMA-P. The high protein content of the substrate resulted in a significant (p<0.05) increase in dry matter and a decrease in neutral detergent fiber, but had no effect on macrominerals. The predominant of characteristics of essential and non-essential amino acids increase significantly (p<0.05) whenever protein quantities are added to the substrate. This finding implies that the protein content of the substrate had improvement on the nutrient composition (DM and NDF) and amino acid profiles (alanine, aspartic, arginine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, and valine) of the maggot.
... Large herbivores are recognized as important ecosystem engineers (sensu Jones et al. 1994), not only for their wellknown effects on biodiversity, vegetation, soil compaction or nutrient cycle (van der Waal et al. 2011, Pisanu et al. 2012, Foster et al. 2014, van Klink et al. 2015, Filazzola et al. 2020, Capó et al. 2022, Kristensen et al. 2022), but also for other less obvious effects such as wildfire prevention, or maintenance of predator populations (Dirzo et al. 2014, Ripple et al. 2015, Rouet-Leduc et al. 2021. Specifically, plant reproduction can be profoundly impacted by large herbivores in opposite ways. ...
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Interspecific ecological interactions are inherently context‐dependent. They may vary in both magnitude and sign depending on the biotic and abiotic conditions, depicting a mutualism–antagonism continuum. However, how population abundances and the activity of interacting species modulate these interactions remains underexplored. Here, we chose the interaction between the Mediterranean palm Chamaerops humilis and the feral goat Capra hircus in Mallorca (Balearic Islands, Spain). We selected three study plots with low, intermediate and high intensities of goat activity where we characterized palm distribution, seed rain, seed predation and early palm recruitment during two consecutive years. Since goats can cause both costs (e.g. florivory) and benefits (e.g. seed dispersal) to C. humilis performance, we investigated the following three questions: 1) does the spatial distribution of adult palms vary depending on the intensity of goat activity? 2) Does the intensity of goat activity influence seed rain and its potential spatial association with adult palms? 3) To what extent does the intensity of goat activity determine post‐dispersal events such as seed predation and seedling emergence? We found that adult palms showed a more clumped and complex distribution (double‐cluster process) in plots with low and intermediate goat activity compared to that with high goat activity (simple‐cluster process). In the low goat activity plot, dispersed seeds were spatially aggregated around adult palms, showing twice as much insect‐seed predation and nearly three times lower seed germination success than those in the intermediate goat activity plot. Palm seed dispersal and recruitment were almost nil in the high goat activity plot due to heavy consumption of palm inflorescences and developing fruits by goats. Our findings demonstrate how the net outcome of plant–animal interactions can change from mutualism to antagonism, from reproductive service to reproductive collapse, depending on the abundance and the activity of the interacting species.
Plant–ungulate interactions are critical in shaping the structure of Mediterranean plant communities. Nevertheless, there is a dearth of knowledge on how plant intrinsic and extrinsic factors mediate the sign and strength of plant–ungulate interactions. This is most relevant when addressing natural or assisted restoration of plant communities in human‐disturbed areas. We conducted field‐clipping experiments simulating how different intensities of ungulate herbivory may affect the natural regeneration and establishment of the Mediterranean dwarf palm ( Chamaerops humilis ), a keystone species in Mediterranean ecosystems. We quantified seedling survival and size in two human‐disturbed sites (SW Spain) where wild and domestic ungulates exert high herbivory pressure on vegetation. Severe clipping and seedling aging reduced rates of seedling survival. In contrast, moderate clipping did not affect seedling survival, suggesting a certain degree of C. humilis tolerance to herbivory. Severe clipping reduced seedling height strongly but not seedling diameter, and these effects seem to have decreased seedling survival. Nurse shrubs increased seedling size, which likely improved seedling survival. We also found seedling compensatory growth which varied between study sites. Field‐clipping experiments can help disentangle effects of plant extrinsic and intrinsic factors on the sign and strength of plant–ungulate interactions and their ecological consequences on the dynamics of human‐disturbed ecosystems. We call attention to the importance of appropriately managing scenarios of severe herbivory and summer droughts, particularly frequent in Mediterranean ecosystems, as synergic effects of such key drivers can negatively affect the structure and dynamics of plant communities and endanger their conservation.
Nitrogen is the second limited factor in arid regions. Little information is available on soil N cycling and availability under grazing in arid regions, which is required to evaluate land‐use management with respect to soil N availability and dynamics. In 2011, we established a rotational grazing field experiment in arid grassland. We conducted experiments to explore the effects of herbivores grazing on soil net N mineralization and N processes via changes in soil temperature, moisture, pH, and microbial biomass nitrogen (MBN) in 2016 and 2017. Our results showed that grazing did not alter soil N mineralization because higher soil moisture and soil MBN under grazing had positive and negative effects on soil N mineralization, thereby balancing soil N mineralization. Plant N uptake at the grazing plots was, nevertheless, 23% higher than that at the non‐grazing plots. These demonstrated that grazing potentially improved soil inorganic N availability and alleviated soil N limitation in arid regions. Soil nitrification was main pathway of N transformation in arid regions. Grazing improved soil accumulation of NO 3 ⁻ content, resulting in environmental problems (such as N 2 O emission and N leaching); however, grazing had a little effect (~15% increase) on soil N leaching and (~7% decrease) on N 2 O emission. These N processes reflect important mechanisms of resilience and ecosystem stability under grazing in an N‐limited environment. Our results provide an important perspective for grassland management, aiming to maintain soil N supplying capacity in annual pasture sustainably. Overall, our study suggests that grazing is an effective management practice for the sustainable usage of local grasslands, as it improves soil physicochemical and biological properties, which, in turn, increases N supply.
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Grazing by domestic herbivores is the most widespread land use on the planet, and also a major global change driver in grasslands. Yet, experimental evidence on the long-term impacts of livestock grazing on biodiversity and function is largely lacking. Here, we report results from a network of 10 experimental sites from paired grazed and ungrazed grasslands across an aridity gradient, including some of the largest remaining native grasslands on the planet. We show that aridity partly explains the responses of biodiversity and multifunctionality to long-term livestock grazing. Grazing greatly reduced biodiversity and multifunctionality in steppes with higher aridity, while had no effects in steppes with relatively lower aridity. Moreover, we found that long-term grazing further changed the capacity of above- and below-ground biodiversity to explain multifunctionality. Thus, while plant diversity was positively correlated with multifunctionality across grasslands with excluded livestock, soil biodiversity was positively correlated with multifunctionality across grazed grasslands. Together, our cross-site experiment reveals that the impacts of long-term grazing on biodiversity and function depend on aridity levels, with the more arid sites experiencing more negative impacts on biodiversity and ecosystem multifunctionality. We also highlight the fundamental importance of conserving soil biodiversity for protecting multifunctionality in widespread grazed grasslands.
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Large herbivores can exert pronounced top-down effects on plant communities in grassland ecosystems. Previous studies highlighted the importance of the composition and traits of living plants in regulating the impact of herbivores on plant community. However, there has been little consideration of whether and how plant litter, a ubiquitous “after-life” plant component, affects the outcome of herbivore grazing on grasslands. Here, we conducted a large-scale field experiment in temperate grasslands of northeastern China to investigate how standing plant litter influenced top-down effects of large herbivores (sheep; Ovis aries) on plant species richness, evenness, community composition, and productivity. We found that, in the presence of standing litter, sheep grazing significantly reduced living biomass of forbs by 56%, but have no effects on biomass of the dominant grass, Leymus chinensis. However, in the absence of standing litter, sheep shifted their diet preference from forbs to the grass L. chinensis, leading to a 36% decrease in the biomass of L. chinensis and a 21% decrease in total biomass. Such changes in foraging pressure on plant species led to competitive release that in turn significantly altered plant community composition and increased species evenness. Synthesis and applications. Our results demonstrate that standing litter can alter foraging behaviors of large herbivores and modifying the outcome of their top-down effects on plant community properties in grasslands. These cryptic but perhaps ubiquitous interactions between litter and herbivores may help us better understand the organization and dynamics of plant communities in the grazed grasslands, with important implications for developing effective management and conservation plans.
Large herbivores can exert pronounced top-down effects on plant communities in grassland ecosystems. Previous studies highlighted the importance of the composition and traits of living plants in regulating the impact of herbivores on plant community. However, there has been little consideration of whether and how plant litter, a ubiquitous ''after-life'' plant component, affects the outcome of herbivore grazing on grasslands. Here, we conducted a large-scale field experiment in temperate grasslands of northeastern China to investigate how standing plant litter influenced top-down effects of large herbivores (sheep; Ovis aries) on plant species richness, evenness, community composition , and productivity. We found that, in the presence of standing litter, sheep grazing significantly reduced living biomass of forbs by 56%, but have no effects on biomass of the dominant grass, Leymus chinensis. However, in the absence of standing litter, sheep shifted their diet preference from forbs to the grass L. chinensis, leading to a 36% decrease in the biomass of L. chinensis and a 21% decrease in total biomass. Such changes in foraging pressure on plant species led to competitive release that in turn significantly altered plant community composition and increased species evenness. Synthesis and applications. Our results demonstrate that standing litter can alter foraging behaviors of large herbivores and modifying the outcome of their top-down effects on plant community properties in grasslands. These cryptic but perhaps ubiquitous interactions between litter and herbivores may help us better understand the organization and dynamics of plant communities in the grazed grasslands, with important implications for developing effective management and conservation plans.
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Increasing food production while avoiding negative impacts on biodiversity constitutes one of the main challenges of our time. Traditional silvopastoral systems like Iberian oak savannas (“dehesas”) set an example, where free-range livestock has been reared for centuries while preserving a high natural value. Nevertheless, factors decreasing productivity need to be addressed, one being acorn losses provoked by pest insects. An increased and focalized grazing by livestock on infested acorns would kill the larvae inside and decrease pest numbers, but increased livestock densities could have undesired side effects on ground arthropod communities as a whole. We designed an experimental setup including areas under trees with livestock exclosures of different ages along with controls, using DNA metabarcoding (mitochondrial markers COI and 16S) to rapidly assess arthropod communities’ composition. Livestock removal quickly increased grass cover and arthropod taxonomic richness and diversity, which was already higher in short-term (1-year exclosures) than beneath the canopies of control trees. Interestingly, arthropod diversity was not highest at long-term exclosures (≥10 years), although their community composition was the most distinct. The diversity peak at short term exclosures would support the intermediate disturbance hypothesis, which relates it with the higher microhabitat heterogeneity at moderately disturbed areas. Thus, we propose a rotatory livestock management in dehesas: plots with increased grazing should co-exist with temporal short-term exclosures. Ideally, a few long-term excluded areas should be also kept for the singularity of their arthropod communities. This strategy would make possible the combination of biological pest control and arthropod conservation in Iberian dehesas.
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In order to understand how the effects of land‐use change vary among taxa and environmental contexts, we investigate how three types of land‐use change have influenced phylogenetic diversity (PD) and species composition of three functionally distinct communities: plants, small mammals, and large mammals. We found large mammal communities were by far the most heavily impacted by land‐use change, with areas of attempted large wildlife exclusion and intense livestock grazing respectively containing 164 and 165 million fewer years of evolutionary history than conserved areas (~40% declines). The effects of land‐use change on PD varied substantially across taxa, type of land‐use change, and, for most groups, also across abiotic conditions. This highlights the need for taxa‐specific or multi‐taxa evaluations, for managers interested in conserving specific groups or whole communities, respectively. It also suggests that efforts to conserve and restore PD may be most successful if they focus on areas of particular land‐use types and abiotic conditions. Importantly, we also describe the substantial species turnover and compositional changes that cannot be detected by alpha diversity metrics, emphasizing that neither PD nor other taxonomic diversity metrics are sufficient proxies for ecological integrity. Finally, our results provide further support for the emerging consensus that conserved landscapes are critical to support intact assemblages of some lineages such as large mammals, but that mosaics of disturbed land‐uses, including both agricultural and pastoral land, do provide important habitats for a diverse array of plants and small mammals. This article is protected by copyright. All rights reserved.
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Biomass removal by herbivores usually incurs a fitness cost for the attacked plants, with the total cost per unit lost tissue depending on the value of the removed tissue (i.e., how costly it is to be replaced by regrowth). Optimal defense theory, first outlined in the 1960s and 1970s, predicted that these fitness costs result in an arms race between plants and herbivores, in which selection favors resistance strategies that either repel herbivores through morphological and chemical resistance traits in order to reduce their consumption, or result in enemy escape through rapid growth or by timing the growth or flowering to the periods when herbivores are absent. Such resistance against herbivores would most likely evolve when herbivores are abundant, cause extensive damage, and consume valuable plant tissues. The purpose of this Special Feature is to celebrate the 30th anniversary of the phenomenon of overcompensation, specifically, where the finding has brought us and where it is leading us 30 yr later. We first provide a short overview of how the phenomenon of overcompensation has led to broader studies on plant tolerance to herbivory, summarize key findings, and then discuss some promising new directions in light of six featured research papers.
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Livestock grazing and fire can intensively modify montane meadows. Understanding how these factors affect habitat, species richness, and diversity of small mammals can inform management decisions. Few studies have investigated the independent and synergistic effects of grazing and wildfire on vegetation and small-mammal communities, and none have focused on montane meadows in the southwestern United States. In 2012 and 2013, we captured small mammals at 105 sites to contrast occupancy, species richness, and diversity among livestock grazing levels (present, absent), wildfire severity (unburned, low, or moderate), and meadow classifications (small or large, wet or dry) in Arizona, USA. During 13,741 trap nights, we captured 1,885 rodents of 8 species. Two species represented 88% of captures: deer mouse (Peromyscus maniculatus) and Arizona montane vole (Microtus montanus arizonensis). Deer mice, Navajo Mogollon voles (Microtus mogollonensis navaho), and thirteen-lined ground squirrels (Ictidomys tridecemlineatus monticola; a subspecies endemic to the White Mountains, AZ) had higher occupancy in large, ungrazed meadows compared to small, grazed meadows. Species richness was greater in unburned than burned sites and small meadows than large. However, higher diversity occurred in ungrazed and dry compared to grazed and wet meadows. Three species demonstrated weak relationships between wildfire and occupancy, suggesting short-term (<2 yrs) effects of low to moderate burn severity for these species or their habitat. Livestock grazing had a greater effect than wildfire on the small-mammal community by altering vegetation or other habitat elements and thus decreasing population sizes. Reducing livestock grazing would benefit small-mammal species and increase diversity and abundance of the small-mammal community in montane meadows.
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Herbivores alter plant biodiversity (species richness) in many of the world’s ecosystems, but the magnitude and the direction of herbivore effects on biodiversity vary widely within and among ecosystems. One current theory predicts that herbivores enhance plant biodiversity at high productivity but have the opposite effect at low productivity. Yet, empirical support for the importance of site productivity as a mediator of these herbivore impacts is equivocal. Here, we synthesize data from 252 large-herbivore exclusion studies, spanning a 20-fold range in site productivity, to test an alternative hypothesis—that herbivore-induced changes in the competitive environment determine the response of plant biodiversity to herbivory irrespective of productivity. Under this hypothesis, when herbivores reduce the abundance (biomass, cover) of dominant species (for example, because the dominant plant is palatable), additional resources become available to support new species, thereby increasing biodiversity. By contrast, if herbivores promote high dominance by increasing the abundance of herbivory-resistant, unpalatable species, then resource availability for other species decreases reducing biodiversity. We show that herbivore-induced change in dominance, independent of site productivity or precipitation (a proxy for productivity), is the best predictor of herbivore effects on biodiversity in grassland and savannah sites. Given that most herbaceous ecosystems are dominated by one or a few species, altering the competitive environment via herbivores or by other means may be an effective strategy for conserving biodiversity in grasslands and savannahs globally.
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Historical contingency is the impact of past events, like the timing and order of species arrival, on community assembly, and can sometimes result in alternative stable states of ecological communities. Large herbivores, wild and domestic, can cause profound changes in the structure and functioning of plant communities and therefore probably influence historical contingency; however, little empirical data on the stability of such shifts or subsequent drivers of stability are available. We studied the centennial legacy of reindeer (Rangifer tarandus) pressure on arctic tundra vegetation by considering historical milking grounds (HMGs): graminoid- and forb-dominated patches amid shrub-dominated tundra, formed by historical Sami reindeer herding practices that ended approximately 100 years ago. Our results show that the core areas of all studied HMGs remained strikingly stable, being hardly invaded by surrounding shrubs. Soil nitrogen concentrations were comparable to heavily grazed areas. However, the HMGs are slowly being reinvaded by vegetative growth of shrubs at the edges, and the rate of ingrowth increased with higher mineral N availability. Furthermore, our data indicate that several biotic feedbacks contribute to the stability of the HMGs: increased nutrient turnover supporting herbaceous vegetation, strong interspecific competition preventing invasion and herbivore damage to invading shrubs. In particular, voles and lemmings appear to be important, selectively damaging shrubs in the HMGs. We concluded that HMGs provide clear evidence for historical contingency of herbivore effects in arctic ecosystems. We showed that several biotic feedbacks can contribute to subsequent vegetation stability, but their relative importance will vary in time and space.
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Pastures and rangelands underpin global meat and milk production and are a critical resource for millions of people dependent on livestock for food security1,2. Forage growth, which is highly climate dependent3,4, is potentially vulnerable to climate change, although precisely where and to what extent remains relatively unexplored. In this study, we assess climate-based threats to global pastures, with a specific focus on changes in within- and between-year precipitation variability (precipitation concentration index (PCI) and coefficient of variation of precipitation (CVP), respectively). Relating global satellite measures of vegetation greenness (such as the Normalized Difference Vegetation Index; NDVI) to key climatic factors reveals that CVP is a significant, yet often overlooked, constraint on vegetation productivity across global pastures. Using independent stocking data, we found that areas with high CVP support lower livestock densities than less-variable regions. Globally, pastures experience about a 25% greater year-to-year precipitation variation (CVP = 0.27) than the average global land surface area (0.21). Over the past century, CVP has generally increased across pasture areas, although both positive (49% of pasture area) and negative (31% of pasture area) trends exist. We identify regions in which livestock grazing is important for local food access and economies, and discuss the potential for pasture intensification in the context of long-term regional trends in precipitation variability.
Clarifying the functional consequences of intraspecific trait variability in response to interacting trophic levels would provide a significant improvement in our understanding of above‐ground–below‐ground linkages. In particular, the effects of grazing on plant traits may translate into altered litter quality, with potentially important consequences for litter‐feeding decomposers. Plant and litter variability in response to grazing is expected to depend on soil fertility levels, with tolerance and defensive strategies more commonly expressed on fertile and poorer soils, respectively. However, how grazing and fertility interactively alter litter quality and palatability to detritivores has not been explored yet. We conducted a cafeteria experiment with three common millipede (Diplopoda) species feeding on leaf litter from two plant species, the grass Bromopsis erecta and the forb Potentilla verna. Each millipede was offered a binary choice between litter types produced by the same plant species, but sampled in plots with distinct herbivory and fertilization status: litter originating from grazed areas or from 1‐year sheep exclosures, both in native areas and in adjacent paddocks that received chemical N and P fertilization, as well as litter from a 25‐year sheep exclosures in the native area. We found that fertilization and herbivore exclusion interactively affected Bromopsis litter quality and palatability, whereas Potentilla was much less affected. Bromopsis litter palatability was not affected by grazing when litter was collected in native plots, except for the long‐term exclosure which led to low palatability. In contrast, and in line with our expectations, herbivory was associated with much higher palatability in fertilized plots. The changes in palatability were associated with important alterations of litter quality. Overall, our study demonstrates that intraspecific variation in litter can have profound consequences for soil functioning. It emphasizes the role of grazing as a key, but plant species‐specific factor controlling litter intraspecific variability, and its complex interaction with soil fertility level. Moreover, our results advocate for a better understanding of the response of the different organisms involved in the decomposition process, in particular litter‐feeding macro‐detritivores. We encourage future studies aiming at disentangling the various and complex relationships between above‐ground processes such as herbivory and soil functioning.
Trophic interactions are a fundamental part of ecosystems; yet, most ecological studies focus on single trophic levels and this hampers our ability to detect the underlying mechanisms structuring communities as well as the effects of environmental change. Here, we argue that the historical dominance of studying competition within trophic levels, and the focus on taxonomic groups without differentiating the trophic level, has led to the under-representation of multitrophic research in community ecology. There are many hurdles that challenge multitrophic approaches and we discuss solutions to overcome these. To advance our understanding of the fundamental drivers of community assembly and to provide the necessary guidance for managing and mitigating the effects of environmental change, we argue that ecologists should better align research with a trophically inclusive definition of a community.
Most of our knowledge of the effect of grazing on grassland structure is based on grazed-ungrazed contrasts. The effects of grazing in the most common scenario, where grazing intensity varies from low to high grazing intensity, are less known. The objectives of this paper were to 1) quantify the effect of stocking rates on species richness and diversity of grasslands world-wide, and 2) evaluate the response under different environmental and experimental conditions. We conducted a meta-analysis of experiments with at least two levels of controlled stocking rates and evaluated their effect on species richness and diversity. The results showed that the response of richness and diversity to either reducing or increasing stocking rate from a moderate level mostly fell within the range ± 25% or ± 5 species. Mean response of species richness and diversity to increasing stocking rate from moderate to high levels was negative. Mean response to lowering stocking rate from moderate levels was not different from zero. However, overall, species richness significantly decreased as stocking rate increased. The response of richness and diversity to stocking rate was not related to mean precipitation, productivity or aridity. However, the most negative responses of richness to stocking rate were larger in arid, low productivity systems than in subhumid and humid systems. The effects of grazing on richness and diversity found in this review were smaller than the effects on species composition shown by the literature. Thus, grazing drastically changes species composition, but the net change of species and diversity is much smaller.