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Grazing management and impact in the Canary islands: Rethinking sustainable use

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On an oceanic island, the positive relationship between livestock management and biodiversity conservation is not as clear as on the mainland. In the sensitive island’s ecosystems, introduced herbivores have been considered to cause devastating effects on vegetation, and be responsible for overgrazing, ecosystem degradation, and biodiversity loss. Eradication of introduced herbivores has been proposed as a conservation tool in some islands. However, this proposal needs to be carefully considered, since there are complex and established ecological interactions between native and introduced species. The goal of this chapter is to discuss the livestock management for biodiversity conservation, with special attention on the Canary Islands (Spain) as an example. We present a review of the research done on this topic in the Canaries, looking for general conclusions and explanations of the conflicting results. Much of the research is restricted in area, however, consistent works are presented that can help us to understand the answer of the environment to grazing impact on these islands. Although some negative impacts of grazing were revealed, in general they have been restricted to some specific areas or species. In those cases where goat grazing is threatening endemic and endangered populations, control of goat densities, grazing restrictions and use of fences should be encourage, however drastic measures as eradication of goats are not ecologically or socially feasible. On the other hand, grazing of small goat herds on traditionally managed ecosystems seems to be a sustainable activity, which removal have been related with a reduction in the number of species, changes in species composition and also an increase in exotic species.
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In: Grazing Ecology: Vegetation and Soil Impact ISBN 978-1-62100-436-3
Editor: José Ramón Arévalo, pp. © 2011 Nova Science Publishers, Inc.
Chapter 4
G
RAZING
M
ANAGEMENT AND
I
MPACT IN THE
C
ANARY
I
SLANDS
:
R
ETHINKING
S
USTAINABLE
U
SE
José Ramón Arévalo
1
, Silvia Fernández-Lugo
1
,
Lea de Nascimento
1
, Luis Alberto Bermejo
2
and Agustín Naranjo
3
1
Department of Ecology, Faculty of Biology, University of La Laguna. Avda.
Astrofísico Francisco Sánchez, s/n, 38206 La Laguna (Tenerife), Spain
2
Department of Agricultural Engineering, Production and Economy,
Technical School of Agricultural Engineering, University of La Laguna.
Ctra. de Geneto, nº 2, 38201 La Laguna (Tenerife), Spain
3
Department of Geography, Faculty of Geography and History,
University of Las Palmas de Gran Canaria. 35003
Las Palmas de Gran Canaria (Gran Canaria), Spain
A
BSTRACT
On an oceanic island, the positive relationship between livestock management and
biodiversity conservation is not as clear as on the mainland. In the sensitive island’s
ecosystems, introduced herbivores have been considered to cause devastating effects on
vegetation, and be responsible for overgrazing, ecosystem degradation, and biodiversity
loss. Eradication of introduced herbivores has been proposed as a conservation tool in
some islands. However, this proposal needs to be carefully considered, since there are
complex and established ecological interactions between native and introduced species.
The goal of this chapter is to discuss the livestock management for biodiversity
conservation, with special attention on the Canary Islands (Spain) as an example. We
present a review of the research done on this topic in the Canaries, looking for general
conclusions and explanations of the conflicting results. Much of the research is restricted
in area, however, consistent works are presented that can help us to understand the
answer of the environment to grazing impact on these islands.
Although some negative impacts of grazing were revealed, in general they have been
restricted to some specific areas or species. In those cases where goat grazing is
threatening endemic and endangered populations, control of goat densities, grazing
Author for correspondence (Email: jarevalo@ull.es)
José Ramón Arévalo, Silvia Fernández-Lugo, Lea de Nascimento et al. 2
restrictions and use of fences should be encourage, however drastic measures as
eradication of goats are not ecologically or socially feasible. On the other hand, grazing
of small goat herds on traditionally managed ecosystems seems to be a sustainable
activity, which removal have been related with a reduction in the number of species,
changes in species composition and also an increase in exotic species.
Keywords: Canary Islands, conservation, eradication, grazing management, goats.
I
NTRODUCTION
Grazing is one of the most important management activities worldwide. This has allowed
for the development of an extensive bibliography on the responses of plant communities to
grazing. However, we are still far away from a consensus regarding the effects of grazer
animals on ecosystems. Grazing effects on species richness and composition are contradictory
in many studies (Olff and Ritchie, 1998). Researchers have documented that herbivores can
enhance, have a negative impact, or have weak or even no effects on species diversity and
plant community composition (e.g. Olff and Ritchie, 1998; Stohlgren et al., 1999; Osem et
al., 2002; Casado et al., 2004; de Bello et al., 2007), as well as, a variety of effects on soil
nutrients (McIntosh et al., 1997; Bakker et al., 2004; Peco et al., 2006; Fernández-Lugo et al.,
2009a). The lack of consistent responses of vegetation to grazing, confirmed in a range of
research studies, has been attributed to evolutionary history of grazing, productivity gradients
and grazing intensity (Milchunas and Lauenroth, 1993). Herbivore type and size has also been
proven to differently shape plant community responses to grazing (Olff and Ritchie, 1998).
Other causes related to these contradictory results are the differences in the amount of plant
and animal species biodiversity (Sanderson et al., 2004; Clergue et al., 2005).
A comprehensive analysis of all the factors described above is necessary to understand
the impact of grazing, and its positive or negative effects on ecological processes such as
regeneration, diversity, biomass production, etc. The effects of different environmental
gradients or human activity (i.e. altitude, precipitation, temperature, management regime,
etc.), should also be taken into account in order to isolate the impact of grazing on plant
communities. These environmental variables are in many studies more important than grazing
to explain species diversity and composition, e.g. altitude (Brinkmann et al., 2009; Zhang and
Dong, 2009), precipitation (Milchunas et al., 1988), productivity (Osem et al., 2004), specific
plant community (Briske and Noy-Meir, 1989) or soil nutrient content (Fernández-Lugo et
al., 2009a). Consequently, grazing impact on plant communities cannot be evaluated on its
own. Although it is an important element in shaping plant communities, there are a multitude
of factors (as above mentioned) that interact with grazing, leading to a variety of effects on
ecosystems. In addition, other factors related to methodology can also affect the result of a
research. For instance, the scale of sampling appears to play a significant role in conditioning
the response of plant communities to grazing (Olff and Ritchie, 1998; Fuhlendorf and Smeins,
1999).
Numerous scenarios can be found in managed ecosystems, as a result of the interaction of
the different factors previously mentioned. It is common to find discordant discourse about
the compatibility between livestock grazing and diversity conservation. There are those in the
Grazing Management and Impact in the Canary Islands 3
scientific community who defend the removal of grazing as a way to ensure conservation of
ecosystems (e.g. Hill et al., 1998; Fraser and Chisholm, 2000), as well as defenders of the
maintenance of this activity as the only way to conserve agroecosystem diversity (e.g.
Perevolotsky and Seligman, 1998; Peco et al., 2006), and the cultural, social, and economic
values that these traditional activities support. Awareness of biodiversity conservation has
burgeoned in the past two decades (Wilcove, 1993; Baydack and Campa, 1999; Millennium
Ecosystem Assessment, 2005). While the initial, and almost exclusive, focus of conservation
was on preserves, hot spots and natural ecosystems (Eken et al., 2004), over the past several
years, interest has expanded to include areas managed for agricultural production (Krebs et
al., 1999; Benton et al., 2003). This has resulted in a noticeable increase of the literature on
farmland biodiversity (e.g. Aviron et al., 2009; Swagemakers et al., 2009). The inclusion of
lands grazed by domestic herbivores in the analysis of biodiversity conservation has lead to
an interesting paradigm shift in managing ecosystems. In the last century common and
habitual management practices led to the homogenization of the farmland landscapes
worldwide (Jongman, 2002), and recent works suggest that homogeneous land management is
one of the main reasons for biodiversity loss (Benton et al., 2003), something that appears to
be proven in the case of grasslands birds (Fuhlendorf et al., 2006; Derner et al., 2009). As a
result, these works suggest that livestock should be used as ecosystems engineering, applying
different intensities (even high grazing pressure) and combining it with other tools like fire, to
maintain heterogeneous landscapes that can sustain high levels of biodiversity.
An important factor related with the homogenization of agroecosystems is the
abandonment of extensive livestock management (Jongman, 2002). In many parts of the
planet, especially in developed or developing countries, there is continuous depopulation of
rural areas, reducing the amount of people dedicated to agriculture or farming. This is
obviously reflected in the landscape, and can have noticeable negative effects in species
composition or ecosystem sustainability (Torrano and Valderrábano, 2004; Altesor et al.,
2005; Mayer et al., 2009; Farris et al., 2010). Another problem in the field of biodiversity
conservation, is that worldwide, grasslands are being converted to either croplands or
desertified scrublands after overgrazing by livestock (Peters et al., 2006).
On an oceanic island, the positive relationship between livestock management and
biodiversity conservation, described by authors like Fuhlendorf et al. (2006), or Perevolotsky
and Seligman, (1998), is not as clear as on the mainland. In the sensitive island’s ecosystems,
introduced herbivores have been considered to cause devastating effects on vegetation, and be
responsible for overgrazing, ecosystem degradation, and biodiversity loss (Coblentz, 1978;
Donlan et al., 2002; Campbell and Donlan, 2005). Eradication of introduced herbivores has
been proposed as a conservation tool in some islands. However, this proposal needs to be
carefully considered, since there are complex and established ecological interactions between
native and introduced species. The disappearance of these introduced species could increase
damage to the ecosystems (Courchamp et al., 2003). In addition, introduced herbivorous have
evolved over centuries into rare native breeds, and the conservation of the valuable genetic
resources of these breed varieties, at risk nowadays, has become a goal in conservation
biology (Bratton, 1988; Hall and Ruane, 2003; Alderson, 2009). Moreover, we cannot negate
the social, environmental and biological benefits of sustainable exploitation (Perevolotsky
and Seligman, 1998), even on island environments.
The goal of this chapter is to continue the discussion of livestock management for
biodiversity conservation, with special attention on the Canary Islands (Spain) as an example.
José Ramón Arévalo, Silvia Fernández-Lugo, Lea de Nascimento et al. 4
We present a review of the research done on this topic in the Canaries, looking for general
conclusions and explanations of the conflicting results. Much of the research is restricted in
area, however, consistent works are presented that can help us to understand the answer of the
environment to grazing impact on these islands. The results of this review can provide useful
information that will help managers continue with this activity, which is of high cultural value
at present.
G
RAZING
S
ITUATION IN THE
C
ANARY
I
SLANDS
In this archipelago, the debate about the compatibility of grazing management and
biodiversity conservation becomes especially relevant. Traditional goat grazing has to cope
with the environmental protection of more than the 40 % of the territory, and with more
sensitive endemic species, which represent 26% of the flora (Báez et al., 2001). In addition,
traditional management has important socioeconomic, cultural and landscape values,
recognized, for instance, by the Canarian Law of Natural Protected Spaces (Gobierno de
Canarias, 1994) by means of the Rural Park figure of protection, which has the objective to
conserve and promote the traditional activities (e.g. extensive grazing and agriculture), as
well as the landscapes that have evolved from them (Gobierno de Canarias, 1994). Even
though, it is necessary to combine both, biodiversity and traditional grazing conservation,
there are few studies concerning goat management effects on the ecosystems of the Canary
Islands. Furthermore, as in many other geographical areas, these studies have shown
contradictory results, especially regarding the effects of grazing on species diversity and plant
community composition.
Management history of the islands started with the arrival of the first inhabitants,
approximately in 600 B.C. (Cabrera, 2001) and dramatically intensified after the Spanish
conquest in the 15
th
century. In the past, land use was characterized by a transhumant grazing
system, but due to the increase of tourism activity, the new protected areas created in the last
decade and changes in the farming industry in the last half of the twentieth century, have led
to these extensive livestock systems either being intensified or abandoned, and continuous or
rotational grazing management are dominant at the present (Bermejo, 2003). Extensive
grazing is carried out mainly with Canary goat breeds, evolved from the prehispanic goats
into at least three genetically different native breeds (Martínez et al., 2006). Traditional
grazing is being subsidized by the European Common Agricultural Policy (CAP), which aims
to maintain and promote traditional activities, promote a sustainable development of the
outermost region, and conserve ecosystems, biodiversity and native breeds. The tendency
towards the abandonment of the extensive grazing systems has not been reverted by public
funding, and abandonment becomes more evident every day endangering the future of this
traditional practice. At present times, majority of the herds’ owners are of advanced age, and,
due to the hardness of the work and the attractiveness of service sectors, this activity is not
appealing to younger generations (Bermejo, 2003). Additionally, the limited seasonal pasture
resources result in feeding supplementation with forages, corn, grain and fodder, implying a
great dependence on foreign market products (Bermejo et al., 2000). Furthermore, restrictions
to open new grazing areas, due to environmental protection, make it more difficult to attract
people to this activity.
Grazing Management and Impact in the Canary Islands 5
G
RAZING
I
MPACT ON
V
EGETATION
This has been one of the first aspects of grazing impact that have been studied in the
Canary Islands. Although the published results have been only minor, a discordant discourse
about the compatibility between livestock grazing and ecosystem conservation arises from
them. We can classify the research done in two groups: the experimental studies, those which
have been specifically designed to analyze the impact of grazing on managed ecosystems; and
the observational studies, where the impact on vegetation is described, but do not contain an
experimental design.
Nogales et al. (1992) studied the impact of feral goats in the native vegetation of the
protected pine forest of Pajonales, Ojeada e Inagua, in the island of Gran Canaria (Figure 1).
By means of direct observation of the goats and herbivore damage in the plants, they
determined which plant species were consumed by goat grazing. Researchers found that a
total of 24 species of phanerogams were affected by goats, 14 of these species were endemic
of Gran Canaria, 4 to the Canary Island archipelago, 2 endemic to Macaronesia region and
only 3 had a wider distribution. Based on these results and having taken into account that
some of these species are endangered, the authors concluded that total eradication of feral
goats is necessary in these protected areas. They proposed controlling goat farms around these
natural spaces, setting up physical controls to avoid the entrance of animals, and the
establishment of a program of genetic rescue for the endangered species.
Figure 1. Canary Islands archipelago. Main areas used for grazing study are indicated.
Another observational study was carried out by Rodríguez-Piñero and Rodríguez Luengo
(1993). These authors studied the impact of introduced herbivores through stomach content
analyses of Corsican mouflons (Ovis ammon musimon) and Barbary sheep (Ammotragus
lervia), two species introduced in the Canary Islands (in the mountain shrublands of Tenerife
and the pine forest of La Palma, respectively) in the seventies for hunting aims. Nowadays,
the populations of these two introduced species are mostly restricted to the Teide National
Park and the surrounding Natural Park (in the case of the mouflon) in Tenerife, and in the
José Ramón Arévalo, Silvia Fernández-Lugo, Lea de Nascimento et al. 6
Caldera de Taburiente National Park in La Palma (in the case of the Barbary sheep). In
addition, this study provides observational results of goats and rabbits grazing. The results of
this work showed an important consumption of protected and native species by the mouflons,
Barbary sheep, as well as by goats and rabbits. In spite of the few observations of the study
the results were very consistent, and authors concluded that herbivores appear to be one of the
primary factors negatively affecting the Canarian flora. The difficulty to control the mouflons
and Barbary sheep, and their location in the National Parks, becomes a significant concern for
the authors of the study. Eradication and control of these two big vertebrates is suggested in
this study. In the case of these two recent introductions, eradication seems to be a reasonable
conservation measure, but appears to be complicated due to the pressure of an important
social sector, the hunters.
Supporting the idea of the eradication of the introduced vertebrate herbivores we would
like to highlight the experimental study done by Garzón-Machado et al. (2010). These authors
studied the effects of Barbary sheep, goats and rabbits on populations of four endemic legume
species in pine forests in Caldera de Taburiente National Park, in the island of La Palma
(Figure 1). In this research the set of endemic species was seeded along an altitudinal
gradient, in plots excluded and open to grazing, and the resulting individuals were monitored
over a period of four years. The result revealed a negative impact of introduced herbivores,
even much stronger than expected from plant populations that have evolved without herbivore
pressures, and therefore have not adaptated (Atkinson, 2001). Although this study claims the
importance of small herbivores as rabbits, other studies found limited impact of herbivory in
Pinus canariensis saplings (Arévalo et al., 2009), revealing no differences in survivorship
among individuals excluded from grazing and controls. The final conclusion of the research
of Garzón-Machado et al. (2010) is the eradication of the Barbary sheep, goats and rabbits
from the whole island, not just from the National Park. Authors state that the total eradication
is the only effective long term solution to the problem. However, these proposals need to be
assessed before being taken in consideration when long term introductions form part of the
eradication proposal. First, there is not enough knowledge with respect to the ecological
interaction established between these exotic species and native species, and the possible risk
of increased damage to the ecosystems with their removal (Courchamp et al., 2003). For
instance, rabbits are a substantial part of the diet of two native avian scavengers, the buzzard
(Buteo buteo) and the raven (Corvux corax) (Nogales and Hernández, 1994; 1997; Palacios-
Palomar, 2005). Second, social implication of this measure also needs to be considered.
Traditional grazing is an activity of tremendous socioeconomic and cultural value on the
island of La Palma. La Palma has a genetically differentiated native goat breed (Martínez et
al., 2006), and the local cheese produced on this island has been officially awarded a
Designation of Origin (Escuder et al., 2006). Consequently, restrictions affecting this sector
need to be included in the final analysis.
Gangoso et al. (2006) gather information of other observational studies in the island of
Fuerteventura (Figure 1), where the number of goats have increased to more than 100,000
heads in less than 50 years (Palacios and Tella, 2003). These authors state that goat
overgrazing is affecting no less than eleven endemic plant species, and that together with the
droughts, typical in this dry island, overgrazing is related with increased in aridity, erosion
advance and extinction of species. Nevertheless, these authors are more cautious in their
conclusions, recognizing the negative effects that grazing removal can have on avian
Grazing Management and Impact in the Canary Islands 7
scavengers, and recommending the control of grazing exploitations, and the fencing of the
most vulnerable areas.
Few studies have been developed in the islands in the last years with experimental design
orientated to reveal the impact of goats in plant community species composition and species
richness. These studies have been carried out mainly in traditionally managed ecosystems of
several islands (Tenerife, La Gomera and La Palma), and in general they reach similar results,
concluding a limited impact of traditional goat grazing in species composition as well as in
species richness.
Arévalo et al. (2011a), studied the effects of grazing abandonment (more than 10 years)
on species richness and species composition in pastures of the Rural Park of Valle Gran Rey,
La Gomera (Figure 1). The study revealed a pattern of species composition change related to
grazing, but no effects on species richness. Furthermore, there was no evidence of a
relationship between the presence of exotic species and grazing management. The detected
changes in species composition appear to be related to a higher abundance of native ruderal
species in managed pastures. However, it is worth emphasizing that some endemic species of
La Gomera (e.g. Euphorbia bertelotii), and endemic species of the archipelago (e.g.
Micromeria varia, Echium aculeatum or Kickxia scoparia) were common in the grazed areas.
Pasture origin in this area is related to the artificial removal of non-useful plants for
agriculture more than 300 years ago (González et al., 1986), and a continuous grazing
management for the last 50 years. Consequently, authors expressed their concern that grazing
abandonment could have a significant effect in the pastures’ diversity, since grazing is a
strong force in the maintenance of certain species. Due to this, they suggest promotion of this
traditional activity in order to conserve natural values as well as traditional sustainable human
activities.
A similar study was carried out by the same research group in the island of La Palma
(Figure 1). In this case, Arévalo et al. (2011b) designed an experiment to reveal the effects of
grazing on the species composition of the main vegetal communities where grazing takes
place: pastures, scrubland and pine forest. This study revealed that it is necessary to integrate
multiple control factors that act in each different plant community in order to be able to
understand the effect of grazing (Casado et al., 2004). Productivity has been considered an
important variable in explaining the herbivores effects on ecosystems (Osem et al., 2004;
Díaz et al., 2007); however the authors did not find such a relationship in these systems.
Other important variables of ecosystem functioning, such as organic matter and species
richness, were not significantly affected by grazing. In this case, distance to farms and
altitude (as an anthropogenic and an environmental variable), were the most significant
variables conditioning species composition in each different plant community, with grazing
occupying a third position in affecting the studied ecosystems. Supporting the notion that
specific plant communities can differently respond to grazing (Briske and Noy-Meir, 1989),
in this study some vegetal communities appear to be more affected by grazing than others.
Pastures showed a higher β-diversity under grazing management, this pattern, although less
evident, was also found in the pastures of La Gomera (Arévalo et al., 2011a). Ecosystems
such as the pine forest and the scrubland were most affected by grazing, this result agrees
with the common notion that scrub species become more abundant in absence of grazing
(Perevolotsky and Seligman, 1999; Carmel and Kadmon, 1999; Saïd, 2001; Castro and
Freitas, 2009). Although, this result appear to support those of Garzón-Machado et al. (2010)
and Nogales et al. (1992), some inconsistencies can be found in terms of species response to
José Ramón Arévalo, Silvia Fernández-Lugo, Lea de Nascimento et al. 8
grazing; for instance, the leguminous scrubs Chamaecytisus proliferus and Adenocarpus
foliolosus, which are negatively affected by grazing in these two studies, are more common in
grazed than in ungrazed areas in some of the plant communities studied by Arévalo et al.
(2011b). In addition, the herbaceous legume Lotus hillebrandii, endemic from La Palma and
characteristic of pine forest, is more abundant under grazing management. This is an example
of the limitations when extrapolating the results of these types of studies among different
vegetation areas (Olff and Ritchie, 1998).
In the Rural Park of Teno, in the island of Tenerife (Figure 1), different studies have been
developed to analyze the impact of traditional goat grazing in species composition and
diversity of managed pastures, including also the study of soil chemical composition (another
aspect evaluated only in a few studies in the Canary Islands). The first study was carried out
by Arévalo et al. (2007), with the main aim to determine the effects of the increase of the
number of goats, experienced in the park in the nineties decade (Barquín and Chinea, 2001),
on species composition, soil nutrient content and biomass nutrient content
.
In this study, the
long term (10 years) monitoring of grazed pastures, revealed an increase in the soil
phosphorous content, and a decrease of the species richness. Changes in biomass nutrient in
response to grazing were not detected in the study. The increase in phosphorus was attributed
to the increase in the number of goats over time. Since higher phosphorus levels have been
related to the reduction of species number in pastures (Forbes et al., 1980; Tracy and
Sanderson, 2000), these authors concluded that it was the cause of the average species
richness decrease. Due to the socioeconomic relevance of traditional grazing in the studied
region, the researchers suggest promoting this activity by restoring and opening new grazing
areas, in order to allow expansion in the number of animals with minimal effects on the
vegetation composition and soil nutrient cycles. Due to the small scale of the sampling
(species composition studied on 0.5 m x 0.5 m plots), and the fact that grazing have been
proven to differently affect soil nutrients (McIntosh et al., 1997; Bakker et al., 2004), with
other studies showing no effect or a decrease in soil phosphorus content under heavy goat
grazing (Severson and Debano, 1991), the authors recognize that more studies need to be
complete to determine the most adequate conservation measures.
The other two studies done in the Rural Park of Teno (Fernández-Lugo et al., 2009a;
2011), used grazing exclusion as a tool to determine the possible consequences of traditional
management abandonment on pasture ecosystems. After four years of goat grazing exclusion
Fernández-Lugo et al. (2009a) did not find changes in species richness or diversity, but a
species turnover in response to the absence of goat grazing, related to a higher soil
magnesium content in the exclusion plots. The authors hypothesize that differences in
magnesium between grazed and excluded plots can be related with a decrease of soil
magnesium content in response to grazing due to the acceleration effects of urine deposition
and soil removal on nutrient leaching. Unlike Arévalo et al. (2007) other soil nutrients, as
phosphorous, were not affected by grazing exclusion, which can be explained by the fact that
the increase in grazing pressure detected in the park has been reverted in the last decade
(personal observation). In this study, like in that of Arévalo et al. (2011b), other factors, such
as year of study and altitude, were more important in shaping plant community species
composition than grazing. An interesting aspect of this research is that more exotic species
were found in absence than in presence of grazing. However, it was only a pattern and not a
consistent result since exotic species were poorly represented in the studied pastures. After
five years of exclusion, the same authors evaluated the relationship between the effects of
Grazing Management and Impact in the Canary Islands 9
goat grazing exclusion on species richness and the scale of study (Fernández-Lugo et al.,
2011). The results revealed a higher species accumulation curves at smaller scales (0.01 to 10
m
2
) in presence of grazing, indicating a positive effect of traditional management on species
diversity. These studies concluded that a longer period of exclusion will be necessary to
detect more relevant changes in plant species composition and that additional studies are
necessary to develop a suitable pasture management strategy to maintain the stability of these
ecosystems. In addition, authors suggest the promotion of goat grazing as a way to maintain
land use, cultural values, and species richness in these pastures.
A couple of studies included the analysis of the productivity of the herbaceous species
(Fernández-Lugo et al., 2009b; de Nascimento et al., 2010). The very preliminary study of
Fernández-Lugo et al. (2009b), analyze the effects of goat grazing exclusion (only one year)
on the species composition, species richness and aboveground primary productivity of the
herbaceous species, in two Rural Parks of the islands of Tenerife and La Gomera (Figure 1).
In this study, the productivity was the only variable having a significant response to grazing
exclusion in such a short period of time, increasing after removal of goats. However, it was
only significantly affected in the most arid pasture (La Gomera), indicating that grazing
effects on productivity may depend on the precipitation range of the studied area, something
that have been generally accepted (Milchunas et al., 1988). On the other side, after three years
of monitoring in grazed and ungrazed areas of La Palma (Figure 1), de Nascimento et al.
(2010) did not find effects of traditional grazing management on net primary productivity of
the herbaceous species, and neither in the species richness. The similar values of productivity
in presence and absence of goats found in these studies can appear contradictory to the
vegetation loss produced by goat grazing detected by Carrete et al. (2009) in Fuerteventura.
Though, they can be easily explained by the most arid conditions of this eastern island, as
well as by the high gradient of grazing pressures included in this study, both main factors in
conditioning the response of plant communities to grazing (Milchunas and Lauenroth, 1993).
Moreover, in this study the heavy grazing treatment is considerably far away from the
pressure exerted by traditional extensive systems.
Although it does not focus on the impact of grazing on ecosystems, another interesting
work carried out in the Canary Islands are those of Salvà-Catarineu and Romo-Díez (2008),
and Otto et al. (2010), which found contradictory results with respect to the effects of goat
herbivory in the regeneration of the Canarian juniper (Juniperus turbinata canariensis). The
first study (Salvà-Catarineu and Romo-Díez, 2008), observed that herbivory by goats or sheep
is an important factor affecting the regeneration of this species on the island of El Hierro. On
the other hand, the second study (Otto et al., 2010), did not find effects of goat pressure on
tree regeneration. Another interesting review by Mata et al. (2010) propose different
methodologies and analytical procedures to improve the management of goat grazed areas,
recognizing that local knowledge can aid in the sustainability of goat grazing systems.
G
RAZING
I
MPACT IN
F
AUNA
This subject has not been analyzed as deeply as the impact of grazing in vegetation. The
only animal group in which grazing impact has been analyzed is the birds, and although the
José Ramón Arévalo, Silvia Fernández-Lugo, Lea de Nascimento et al. 10
bibliography is not very extensive, several studies have revealed significant impact. Gangoso
et al. (2006) did a review of the relationship between introduced herbivores and avian
scavengers, and found that goat carcasses help to maintain the population of three endangered
endemic subspecies of avian scavengers: the Egyptian vulture (Neophron percnopterus
majorensis), the Eurasian buzzard (Buteo buteo insularum) and the common raven (Corvus
corax canariensis). In the case of the Egyptian vulture their populations have experienced a
sharp decline during the last half of the twentieth century, disappearing from the westernmost
islands and surviving only on eastern islands of Fuerteventura and Lanzarote (Donázar et al.,
2002). The principal food sources of this species appear to be goat carcasses (Carrillo and
Delgado, 1991; Medina, 1999), so it is speculated that changes in the livestock practices have
had a very negative impact, being one of the reasons that have lead population of this species
almost to extinction (Donázar et al., 2002). The reduction of the extensive goat grazing
exploitations with respect to intensive exploitations is considered responsible for the decrease
of the population of this species in the islands of Lanzarote and Fuerteventura (Martín and
Lorenzo, 2001). Goat carcasses also appear to be a main food source for the buzzard
(Palacios-Palomar, 2005; Gangoso et al., 2006), species that have suffered and extinction
process parallel to the change in the farming system (Trotter, 1970). Studies on the diet of the
common raven also reflect the consumption of goat carcasses (Nogales and Hernández, 1994;
1997), and the reduction of the traditional grazing systems has been also related with the
regression of this species (Nogales, 1992).
After reviewing the situation of these three avian scavengers in Fuerteventura, Gangoso
et al. (2006) expressed their concern about the reduction, or the removal, of the introduced
herbivores as a serious threat to the raptor endemic populations of the island. The authors
argue that any conservation measure implying the eradication of goats should not be
implemented without a detailed knowledge of its ecological interaction with native fauna,
recommending a cautious study of the communities where these non-native species can play a
key role. In addition, they propose limitation of extensive grazing in areas with high number
of endemic species, to decrease the effects of grazing on vegetation, and the creation of
“vulture restaurants” for these scavenger birds, to decrease the dependence of population on
extensive farming systems.
The short-toe larck (Calandrella rufescens), is another bird species which appear to be
affected by grazing management, since overgrazing use to be pointed as one of the main
factor affecting the habitat of this species (Viada, 1998; Illera, 2001; Illera et al., 2006).
Carrete et al. (2009) evaluated direct and indirect effect of goat farming on this small steppe
passerine species. The results of this research showed an important number of interactions
between goats and this bird species. First, heavy grazing has important effects on vegetation
cover loss, determining habitat impoverishment for this species. Second, this negative impact
is, in part, compensated by the food supply that this species can find in the farms. Third,
beside of the positive effects that the availability of a constant food resource can have on the
populations, the change of the food behavior of this bird appears to be related to an increase
in the nutritious and infectious diseases. The authors concluded that urgent measures are
necessaries to guarantee the conservation of the species. They propose fencing farms to avoid
short-toe larks feeding in them, limiting goat densities to avoid overgrazing, and restore the
habitat of the species. They emphasize that these measures should be carried out together to
avoid negative effects of a decreasing food supply in the populations. Additionally, authors
Grazing Management and Impact in the Canary Islands 11
recognize that eradication of goat from this island is unfeasible due to the socioeconomic and
cultural implications.
C
ONCLUSIONS
Throughout this chapter we have demonstrated some of the conflicting results on the
impact of grazing on Canarian ecosystems. But, analyzing the presented works we can find
some explanations to these contradictions. First, the existence of two kinds of works, those
carried out in “pristine” ecosystems, and those done in traditionally managed ecosystems. The
first ones use to have high degree of endemism and population of endangered species.
Endemic species of the Canarian flora have evolved without herbivore pressures, and maybe
have not adaptations to it (Atkinson, 2001), explaining their higher sensitivity to goat grazing.
Moreover, endangered species, in general, have suffered the reduction of their populations
due to a combination of anthropogenetic factors (removal of woody species, fragmentation of
ecosystems, fire, agriculture and farming), being in a very sensitive state, in which any
damage, as herbivory, can be clearly negative. On the other hand, traditionally managed
ecosystems are dominated by native herbaceous and shrub species, mainly of a Mediterranean
origin (Santos, 2001; del Arco et al., 2010), that can be more resilient to grazing pressure
(Lavorel, 1999). Second, the broad range of climatic conditions existing on the Archipelago.
These conditions varied from arid to humid, determining the existence of different types of
vegetal communities. Both factors, specific plant community (Briske and Noy-Meir, 1989)
and environmental gradient (Milchunas et al., 1988; Osem et al., 2002), condition the
response of the vegetation to grazing. Third, the extensive grazing systems, the intensive
grazing systems, and the feral goats, (differently represented in the reviewed works), can
exert varying degrees of pressure on the territory (Bermejo, 2003). This becomes a
fundamental factor in determining grazing effects on ecosystems (Milchunas and Lauenroth,
1993). Finally, in the case of the fauna, the difference between positive and negative impact
of grazing in bird populations can be easily explained by differences in the group of birds
studied.
Although some negative impacts of grazing have been revealed, in general they have
been restricted to some specific areas or species. In those cases where goat grazing is
threatening endemic and endangered populations, control of goat densities, grazing
restrictions and use of fences should be encourage, however drastic measures as eradication
of goats are not ecologically or socially feasible. On the other hand, grazing of small goat
herds on traditionally managed ecosystems seems to be a sustainable activity, which removal
have been related with a reduction in the number of species, changes in species composition
and also an increase in exotic species.
The government of The Canary Islands considers goat grazing as both a traditional and
necessary activity as the local economy depends on it, but also the derived products such as
the goat cheese with Origin Designation, local varieties of fodder and native goat breeds are
completely related and dependent from the maintenance of this activity. For this reason, and
in order to avoid the disappearance of this activity, we suggest the promotion of goat grazing
in traditionally managed ecosystems, applying a strict control of grazing pressure and type of
management, as a way of maintaining landscape use, cultural values and biodiversity under
typical grazing pressure.
José Ramón Arévalo, Silvia Fernández-Lugo, Lea de Nascimento et al. 12
A
CKNOWLEDGMENTS
Authors thank financial and logistic support by the Cabildo de La Gomera, Cabildo de La
Palma, Cabildo de Tenerife and Cabildo de Gran Canaria. Also, the University of La Laguna
(through the ULL-Research Support Program) and the Spanish Ministry of Science and
Innovation (project CGL2006-06471 and FPU scholarship for Silvia Fernández Lugo) offered
partial financial support. We are grateful to Javier Mata, and the people who helped with our
fieldwork. We specially would like to thank goat keepers of the islands for their cooperation
with the projects of the group.
R
EFERENCES
Altesor, A., Oesterheld, M., Leoni, E., Lezama, F., and Rodríguez, C. (2005) Effect of
grazing exclosure on community structure and productivity of a Uruguayan grassland.
Plant Ecology, 179, 83-91.
Alderson, L. (2008) Breeds at risk: Definition and measurement of the factors which
determine endangerment. Livestock Science, 16,1170-1175.
Atkinson, I.A.E. (2001) Introduced mammals and modesl for restoration. Biological
Conservation, 99, 81-96.
Arévalo, J.R., Chinea, E., and Barquín, E. (2007) Pasture management under goat grazing in
Canary Islands. Agriculture, Ecosystems and Environment, 118, 291-296.
Arévalo, J.R. (2009) Treatments on the survival of Pinus canariensis Chr. Sm. Ex DC in
Buch planted seedlings in arid zones (herbivores protector-fertilizer-mulch-hydrogels).
The Open Forest Science Journal, 2, 25-30.
Arévalo, J.R., de Nascimento, L., Fernández-Lugo, S., Saro, I., Camacho, A., Mata, J., and
Bermejo, L. (2011a) Effects of abandoning long-term goat grazing on species
composition and species richness of pastures at La Gomera, Canary Islands. Spanish
Journal of Agriculture, 9, 113-123.
Arévalo, J.R., de Nascimento, L., Fernández-Lugo, S., Mata, J., and Bermejo, L.A. (2011b)
Grazing effects on species composition in different plant communities (La Palma, Canary
Islands) Acta Oecologica, 37, 230-238.
Aviron, S., Nitsch, H., Jeanneret, P., Buholzer, S., Luka, H., Pfiffner, L., Pozzi, S.,
Schupbach, B., Walter, T., and Herzog, F. (2009) Ecological cross compliance promotes
farmland biodiversity in Switzerland. Frontiers in Ecology and the Environment, 7, 247-
252.
Báez, M., Martín-Esquivel, J.L., and Oromí, P. (2001) Diversidad taxonómica terrestre. In
J.M, Fernández-Palacios, and J.L. Martín Esquivel (Eds.), Naturaleza de las Islas
Canarias, Ecología y Conservación (pp. 119-125) Santa Cruz de Tenerife, Spain:
Editorial Turquesa.
Grazing Management and Impact in the Canary Islands 13
Bakker, E.S., Olff, H., Boekhoff, M., Gleichman, J.M., and Berendse, F. (2004) Impact of
herbivores on nitrogen cycling: contrasting effects of small and large species. Oecologia,
138, 91-101.
Barquín, E., and Chinea, E. (1991) The Teno plateau, Tenerife (Canary Islands), a study of
this singular ecosystem, traditionally managed. In Proceedings of the XXXI reunión
científica de la SEEP (pp. 384-388) Murcia, Spain.
Baydack, R.K., and Campa, III H.C. (1999) Setting the context. In R.K. Baydack, III H.C.,
Campa, and J.B. Haufler (Eds.), Practical Approaches to the Conservation of Biological
Diversity (pp. 3-16). Washington, D.C.: Island Press.
Benton, T.G., Vickery, J.A., and Wilson, J.D. (2003) Farmland biodiversity: is habitat
heterogeneity the key? Trends in Ecology and Evolution, 18, 182-188.
Bermejo, L.A. (2003) Conservación de los recursos genéticos caprinos en los espacios
protegidos de Canarias: Impacto social y ambiental. (PhD thesis), Universidad de
Córdoba, Spain.
Bermejo, L.A., Mata, J., Delgado, J.V., Flores, M.P., and Camacho, A. (2000) Uso ganadero
del Parque Rural de Anaga: resultados preliminares. Archivos de Zootecnia, 49, 269-274.
Bratton, S.P. (1988) Minor Breeds and Major Genetic Losses. Conservation Biology, 2, 297-
299.
Brinkmann, K., Patzelt, A., Dickhoefer, U., Schlecht, E., and Buerkert, A. (2009) Vegetation
patterns and diversity along an altitudinal and a grazing gradient in the Jabal al Akhdar
mountain range of northern Oman. Journal of Arid Environments, 73, 1035-1045.
Briske, D.D., and Noy-Meir, I. (1998) Plant response to grazing: a comparative evaluation of
annual and perennial grasses. In V.P. Papanastasis, and D. Peter (Eds.), Ecological Basis
of Livestock Grazing in Mediterranean Ecosystems (pp. 13-26). Luxembourg: European
Commision, Science, Research and Development.
Cabrera, J.C. (2001) Poblamiento e impacto aborigen. In J.M, Fernández-Palacios, and J.L.
Martín Esquivel (Eds.), Naturaleza de las Islas Canarias, Ecología y Conservación (pp.
241-245). Santa Cruz de Tenerife, Spain: Editorial Turquesa.
Campbell, K., and Donlan, C.J. (2005) Feral goat eradications on islands. Conservation
Biology, 19, 1362-1374.
Carmel, Y., and Kadmon, R. (1999) Effects of grazing and topography on long-term
vegetation changes in a Mediterranean ecosystem in Israel. Plant Ecology, 145, 243-254.
Carrillo, J., and Delgado, G. (1991) Threats to and conservationist aspects of birds of prey in
the Canary Islands. Birds of Prey Blulletin, 4, 25-32.
Carrete, M., Serrano, D., Illera, J.C., López, G., Vögeli, M., Delgado, A., and Tella, J. (2009)
Goats, birds, and emergent diseases: apparent and hidden effects of exotic species in an
island environment. Ecological Applications, 19, 840-853.
Castro, H., and Freitas, H. (2009) Aboveground biomass and productivity in the Montado:
from herbaceous to shrub dominated communities. Journal of Arid Enviroments, 73, 506-
511.
Casado, M.A., Castro, I., Ramírez-Sanz, L., Costa-Tenorio, M., de Miguel, J.M., and Pineda,
F.D. (2004) Herbaceous plant richness and vegetation cover in Mediterranean grasslands
and shrublands. Plant Ecology, 170, 83-91.
Clergue, B., Amiaud, B., Pervanchon, F., Lasserre-Joulin, F., and Plantureux, S. (2005)
Biodiversity: function and assessment in agricultural areas. A review. Agronomy for
Sustainable Development, 25, 1-15.
José Ramón Arévalo, Silvia Fernández-Lugo, Lea de Nascimento et al. 14
Coblentz, B.E. (1978) The effect of feral goats (Capra hircus) on island ecosystems.
Conservation Biology, 4,261-265.
Courchamp, F., Chapuis, J.L., and Pascal, M. (2003) Mammal invaders on islands: impact,
control and control impact. Biological Reviews, 78, 347-383.
De Bello, F., Lepš, J., and Sebastià, M.T. (2007) Grazing effects on species-area relationship:
variation along a climatic gradient in NE Spain. Journal of Vegetation Science, 18, 25-34.
De Nascimento, L., Bermejo, L.A., Saro, I., Fernández-Lugo, S., and Mata J. (2010)
Relationship between herbaceous productivity and species richness in grazed areas on La
Palma (Canary Islands). In H. Schnyder, J. Isselstein, F. Taube, K. Auerswald, J.
Schellberg, M. Wachendorf, A. Herrmann, M. Gierus, N. Wrage, A. Hopkins (Eds.),
Grassland in a changing world. Vol 15: Grassland science in Europe (pp 925-927). Kiel,
Germany: European Grassland Federation.
Del Arco, M., González-González, R., Garzón-Machado, V., and Pizarro-Hernández, B.
(2010) Actual and potential natural vegetation on the Canary Islands and its conservation
status. Biodiversity and Conservation, 19, 3089-3140.
Derner, J.D., Lauenroth, W.K., Stapp, P., and Augustine, D.J. (2009) Livestock as ecosystems
engineers in semiarid rangelands: Addressing grasslands birds habitat in the Western
Great Plains of North America. Rangeland Ecology and Management, 62, 111-118.
Díaz, S., Lavorel, S., McIntyre, S., Falczuk, V., Casanoves, F., Milchunas, D. G., Skarpe,
Ch., Sternberg, G.R., Noy-Meir, I., Landsberg, J., Zhang, W., Clark, H., and Campbell,
B. (2007) Plant traits responses to grazing: a global synthesis. Global Change Biology,
13, 313-341.
Donázar, J.A., Palacios, C.J., Gangoso, L., Ceballos, O., González, M.J., and Hiraldo, F.
(2002) Conservation status and limiting factors of the endangered population of Egyptian
Vulture (Neophron percnopterus) in the Canary Islands. Biological Conservation, 107,
89-98.
Donlan, C.J., Tershy, B.R., and Croll, D.A. (2002) Islands and introduced herbivores:
conservation action as ecosystem experimentation. Journal of Applied Ecology 39, 235-
246.
Eken, G., Bennun, L., Brooks, T.M., Darwall, W., Fishpool, L.D.C., Foster, M., Knox, D.,
Langhammer, P., Matiku, P., Radford, E., Salaman, P., Sechrest, W., Smith, M.L.,
Spector, S., and Tordoff, A. (2004) Key biodiversity areas as site conservation targets.
Bioscience, 54, 1110-1118.
Escuder, A., Fernández, G., and Capote, J. (2006) Characterization of Palmera dairy goats
production systems. Options Méditerranéennes, 70, 95-100.
Farris, E., Filibeck, G., Marignani, M., and Rosati, L. (2010) The power of potential natural
vegetation (and of spatial–temporal scale): a response to Carrión and Fernández (2009)
Journal of Biogeography, 37, 2211-2213.
Fernández-Lugo, S., de Nascimento, L., Mellado, M., Bermejo, L.A, and Arévalo, J.R.
(2009a) Vegetation change and chemical soil composition after four years of goat grazing
exclusion in a Canary Islands pasture. Agriculture, Ecosystems and Environment, 132,
276-282.
Fernández-Lugo, S., de Nascimento, L., Saro, I., Bermejo, L.A., Arévalo, J.R. (2009b)
Efectos de la exclusión del pastoreo en la diversidad, riqueza, composición de especies y
productividad de dos pastizales canarios. In R. Reiné, O. Barrantes, A. Broca, and C.
Grazing Management and Impact in the Canary Islands 15
Ferrer (Eds.), La multifuncinalidad de los pastos: producción ganadera sostenible y
gestión de los ecosistemas (pp. 155-161). Huesca, Spain: S.E.E.P.
Fernández-Lugo, S., de Nascimento, L., Mellado, M., and Arévalo, J.R. (2011) Grazing
effects on species richness depends on scale: a 5 year study in Tenerife pastures (Canary
Islands). Plant Ecology, 212, 423-432.
Forbes, T.J., Dibb, C., Green, J.O., Hopkings, A., and Peel, S. (1980) Factors affecting the
productivity of permanent grassland; a national farm study. Joint permanent pasture
group, Hurley, Maidenhead, Berks.
Fraser, I., and Chisholm, T. (2000) Conservation or cultural heritage? Cattle grazing in the
Victoria Alpine National Park. Ecological Economics, 33, 63-75.
Fuhlendorf, S. D., and Smeins, F. E. (1999) Scaling effects of grazing in a semiarid grassland.
Journal of Vegetation Science, 10, 731-738.
Fuhlendorf, S.D., Harrell, W.C., Engle, D.M., Hamilton, R.G., Davis, C.A., and Leslie, D.M.
(2006) Should heterogeneity be the basis for conservation? Grassland bird response to
fire and grazing. Ecological Applications, 16, 1706-1716.
Gangoso, L., Donázar, J., Scholz, S., Palacios, C.J., and Hiraldo, F. (2006) Contradiction in
conservation of island ecosystems: Plants, introduced herbivores and avian scavengers in
the Canary Islands. Biodiversity and Conservation, 15, 2231- 2248.
Garzón-Machado, V., González-Mancebo, J.M., Palomares-Martínez, A., Acevedo-
Rodríguez, A., Fernández-Palacios, J.M., del-Arco-Aguilar, M., Pérez de Paz, P.L.
(2010) Strong negative effect of alien herbivores on endemic legumes of the Canary pine
forest. Biological Conservation, 143, 2685-2694.
Gobierno de Canarias (1994) Ley 12/1994, de 19 de diciembre, de Espacios Naturales de
Canarias. Boletín Oficial de Canarias ,24 de Diciembre de 1994, Nº157.
González, M.N., Rodrigo, J.D., and Suárez C. (1986) Flora y vegetación del archipiélago
canario. Las Palmas de Gran Canaria, Spain: Edirca S.L.
Hall, S.J.G., and Ruane, J. (1993) Livestock Breeds and Their Conservation: A Global
Overview. Conservation Biology, 7, 815-825.
Hill, J., Hostert, P., Tsiourlis, G., Kasapidis, P., and Udelhoven, Th. (1998) Monitoring 20
years of intense grazing impact on the Greek island of Crete with earth observation
satellites. Journal of Arid Environments, 39, 165-178.
Illera, J.C. (2001) Habitat selection by the Canary Islands stonechat (Saxicola dacotiae)
(Meade-Waldo, 1889) in Fuerteventura Island: a two-tier habitat approach with
implications for its conservation. Biological Conservation, 97, 339-345.
Illera, J.C., Díaz, M., and Nogales, M. (2006) Ecological traits influence the current
distribution and range of an island endemic bird. Journal of Biogeography, 33, 1192-
1201.
Jongman, R.H.G. (2002) Homogenisation and fragmentation of the European landscape:
ecological consequences and solutions. Landscape and Urban Planning, 58, 211- 221.
Krebs, J.R., Wilson, J.D., Bradbury, R.B., and Siriwardena, G.M. (1999) The second Silent
Spring? Nature, 400, 611-612.
Lavorel, S. (1999) Ecological diversity and resilience of Mediterranean vegetation to
disturbance. Diversity and Distributions, 5, 3-13.
McIntosh, P.D., Allen, R.B., and Scott, N. (1997) Effects of exclosure management on
biomass and soil nutrient pools in seasonally dry high country, New Zealand. Journal of
Environmental Management, 52, 169-186.
José Ramón Arévalo, Silvia Fernández-Lugo, Lea de Nascimento et al. 16
Martín, A., and Lorenzo, J.A. (2001) Aves del Archipiélago Canario. San Cristobal de La
Laguna, Spain: F. Lemus Editorial.
Martínez, A., Acosta, J., Vega-Pla, J.L., and Delgado, J.V. (2006) Analysis of the genetic
structure of the Canary goat populations using microsatellites. Livestock Science, 102,
100-140.
Mata, J., Bermejo, L.A., de Nascimento, L., and Camacho, A. (2010) The problem of grazing
planning in a non-equilibrated environment, from the analytical procedure toward the
system approach. Small Ruminant Research, 89, 91-101.
Mayer, J.J., and Brisbin, Jr. I.L. (Editors) (2009) Wild pigs: Biology, damage, control
techniques and managementSRNL-RP-2009-00869. Aiken, South Carolina: Savannah
River National Laboratory.
Medina, F.M. (1999) Alimentación del alimoche, Neophron percnopterus (L.), en
Fuerteventura, Islas Canarias (Aves, Accipitridae). Vieraea, 27, 77-86.
Milchunas, D.G., Sala, O.E., and Lauenroth, W.K. (1988) A generalized model of the effects
of grazing by large herbivores on grasslands community structure. The American
Naturalist, 132. 87-106.
Milchunas, D.G., and Lauenroth, W.K. (1993) Quantitative effects of grazing on vegetation
and soil over a global range of environments. Ecological Monographs, 63, 327-366.
Millennium Ecosystem Assessment (2005) Ecosystems and Human Well-being: Biodiversity
Synthesis. Washington, DC: World Resources Institute.
Nogales, M. (1992) Problemática conservacionista del cuervo (Corvus corax) en Canarias y
estado de sus distintas poblaciones. Ecología, 6, 215-223.
Nogales, M., Marrero, M., and Hernández, E.C. (1992) Efectos de las cabras cimarronas
(Capra hircus L.) en la flora endémica de los pinares de Pajonales, Ojeda e Inagua (Gran
Canaria). Botánica Macaronésica, 19-20, 79-86.
Nogales, M., and Hernández, E. C. (1994) Interinsular variations in the spring and summer
diet of the raven Corvus corax in the Canary Islands. Ibis, 136, 441-447.
Nogales, M., and Hernández, E.C. (1997) Diet of common ravens on El Hierro, Canary
Islands. Journal of Field Ornithology, 68, 382-391.
Olff, H., and Ritchie, M.E. (1998) Effects of herbivores on grassland plant diversity. Trends
in Ecology and Evolution, 13, 261-265.
Osem, Y., Perevolotsky, A., and Kigel, J. (2002) Grazing effect on diversity of annual plant
communities in a semi-arid rangeland: interactions with small-scale spatial and temporal
variation in primary productivity. Journal of Ecology, 90, 936-946.
Osem, Y., Perevolotsky, A. and Kigel, J. (2004) Site productivity and plant size explain the
response of annual species to grazing exclusion in a Mediterranean semi-arid rangeland.
Journal of Ecology, 92, 297-309.
Otto, R., Krüsi, B., Delgado, J.D., Fernández-Palacios, J.M., Garcia-del-Rey, E., and Arevalo,
J.R. (2010) Regeneration niche of the Canarian juniper: the role of adults, shrubs and
environmental conditions. Annals of Forest Science, DOI: 10.105/forest/2010034.
Palacios, C.J., and Tella, J.L. (2003) Aves esteparias de Canarias: una comunidad en peligro.
Quercus, 209, 14-21.
Palacios-Palomar, C.J. (2005) El ratonero común (Buteo buteo insularum) en Fuerteventura,
Islas Canarias (Aves, Accipitridae). Vieraea, 33, 1-5.
Grazing Management and Impact in the Canary Islands 17
Peco, B., Sánchez, A.M., and Azcárate, F.M. (2006) Abandonment in grazing systems:
Consequences for vegetation and soil. Agriculture, Ecosystems and Environment, 113,
284-294.
Perevolotsky, A., and Seligman, N.G. (1998) Role of grazing in Mediterranean rangeland
ecosystems. Inversion of a paradigm. Bioscience, 48, 1007-1017.
Peters, D.P.C., Bestelmeyer, B.T., Herrick, J.E., Monger, H.C., Fredrickson, E., and Havstad,
K.M. (2006) Disentangling complex landscapes: new insights to forecasting arid and
semiarid system dynamics. BioScience, 56, 491-501.
Rodríguez-Piñero, J.C., and Rodríguez-Luengo, J.L. (1993) The effect of herbivores on the
endemic Canary flora. Boletin do Museo Municipal do Funchal, 2, 265-271.
Saïd, S. (2001) Floristic and life form diversity in post-pasture successions on a
Mediterranean island (Corsica). Plant Ecology, 162, 67-76.
Salvà-Catarineu, M., and Romo-Díez, A. (2008) Uso de TIG para la conservación del sabinar
de Juniperus turbinata subsp. canariensis en la isla de El Hierro. In L., Hernández, and
J.M., Parreño (Eds.), Tecnologías de la Información Geográfica para el Desarrollo
Territorial (pp. 766-776.). Las Palmas de Gran Canaria, Spain: Servicio de Publicaciones
y Difusión Científica de la ULPGC.
Santos, A. (2001) Flora vascular. In: J.M. Fernández-Palacios, and J.L. Martín (Eds.),
Naturaleza de las Islas Canarias. Ecología y Conservación (pp. 187-192). S/C de
Tenerife, Spain. Publicaciones Turquesa.
Sanderson, M.A., Skinner, R.H., Barker, D.J., Edwards, G.R., Tracy, B.F., and Wedin, D.A.
(2004) Plant species diversity and management of temperate forage and grazing land
ecosystems. Crop Science, 44, 1132-1144.
Severson, K.E., and Debano, L.F. (1991) Influence of Spanish goats on vegetation and soils
on Arizona chaparral. Journal of Range Management, 44, 111-117.
Stohlgren, T.J., Schell, L.D., and Vanden Heuvel B. (1999) How grazing and soil quality
affect native and exotic plant diversity in rocky mountain grasslands. Ecological
Applications, 9, 45-64.
Swagemakers, P., Wiskerke, H., and Van Der Ploeg, J.D. (2009) Linking birds, fields and
farmers. Journal of environmental management, 90, 185-192.
Torrano, L., and Valderrábano, J. (2004) Review. Impact of grazing on plant communities in
forestry areas. Spanish Journal of Agricultural Research, 2, 93-105.
Tracy, B.F., and Sanderson, M.A. (2000) Patterns of plant species richness in pasture lands of
the northeast United States. Plant Ecology, 149,169-180.
Trotter, W.D.C. (1970) Observations faunistiques sur lille de Lanzarote (Canaries). L’Oiseau
et le RFO, 40, 160-172.
Viada, C. (1998) Áreas Importantes para las Aves en España (2nd edition). Madrid, Spain:
SEO/ Birdlife.
Wilcove, D. (1993) Getting ahead of the extinction curve. Ecological Applications, 3, 218-
220.
Zhang, J.T., and Dong, Y. (2010) Factors affecting species diversity of plant communities and
the restoration process in the loess area of China. Ecological Engineering, 36, 345-350.
... According to Fay (1980), the spatially heterogeneous grazing pressure is the Jebel Ichkeul park's main conservation and management problem. Managed grazing would be preferential to address this issue (Arévalo et al., 2012;Lázaro et al., 2016), rather than complete eradication of livestock, which can have unintended consequences such as biological invasions or succession into less desirable plant communities (Mata et al., 2014;Arévalo et al., 2012). As such, implementing strategies to control grazing on the southern slopes of the mountain, combined with wood-cutting restrictions, could enable vegetation to re-establish on the degraded southern slopes. ...
... According to Fay (1980), the spatially heterogeneous grazing pressure is the Jebel Ichkeul park's main conservation and management problem. Managed grazing would be preferential to address this issue (Arévalo et al., 2012;Lázaro et al., 2016), rather than complete eradication of livestock, which can have unintended consequences such as biological invasions or succession into less desirable plant communities (Mata et al., 2014;Arévalo et al., 2012). As such, implementing strategies to control grazing on the southern slopes of the mountain, combined with wood-cutting restrictions, could enable vegetation to re-establish on the degraded southern slopes. ...
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Mediterranean maquis vegetation is highly biodiverse, but widespread grazing poses a challenge for management and conservation. We sampled woody and herbaceous plants separately on a limestone mountain with strong mesic-xeric gradients in Tunisia’s Parc National de L’Ichkeul, assessed grazing pressure (on a scale of 1–3), and asked whether grazing had a significant effect on plant compositional abundance before and after controlling for environmental covariates. Sites on the more mesic lakeside face of the mountain were most compositionally unique, and forbs contributed most to the herbaceous beta-diversity on the mountain. We used variance partitioning to separate the collective and individual effects of the abiotic environment, grazing, human activity, and space on herbaceous and woody beta-diversity. However, the individual effect of grazing on overall plant community composition was confounded with space, due to the spatially autocorrelated grazing pressure on the mountain. Importantly, we found that herbaceous and woody communities responded differently to increasing levels of grazing intensity: herbaceous beta-diversity was highest between sites with no grazing pressure, while woody beta-diversity peaked under light grazing. Herbaceous community composition was sensitive to any intensity of grazing pressure, and biotic homogenization occured under moderate-to-high grazing pressure. On the other hand, woody community composition remained relatively similar under no to light grazing pressure, but differed under moderate-to-heavy grazing. Using a one-way permutational analysis of variance analysis, we showed that grazing had a significant effect when controlling for abiotic and spatial covariates. Our findings offer insight into the effects of grazing on maquis vegetation at Jebel Ichkeul, acting as a microcosm of similar conservation and management issues elsewhere in the Mediterranean. We suggest that a combination of monitoring and carefully controlled grazing may enhance plant diversity and maintain the region’s biodiverse maquis vegetation, potentially maintaining a key climate refugium for vulnerable endemic species. Importantly, our study provides a useful baseline of the plant assemblages at Jebel Ichkeul with which to compare future vegetation changes. Effets de pâturage sur la biodiversité des boisés et des herbacés sur une montagne calcaire au nord de la Tunisie. L’Abstrait : Le pâturage est une problématique de gestion et de conservation de la forte diversité des maquis méditerranéens. Nous avons échantillonné les plantes ligneuses et herbacées séparément sur une montagne calcaire avec de forts gradients mésico-xériques dans le Parc national de l’Ichkeul, en Tunisie. Nous avons testé l’effet de la pression de pâturage, évaluée sur une échelle de 1 à 3, sur l'abondance et la composition des plantes avant et après avoir contrôlé l’effet de variables environnementales. Nous avons trouvé que les sites au bord du lac sur le visage mésique de la montagne ont une composition d’espèces plus unique comparée aux autres sites, et que les phorbes ont contribué le plus fortement à la diversité bêta herbacée sur la montagne. Nous avions ensuite séparé les effets combinés et individuels de l’environnement abiotique, pâturage, l’activité humaine, et la configuration spatiale sur la diversité bêta des plantes herbacées et ligneuses, par le biais de partitionnement de variance. Cependant, l'effet individuel du pâturage sur la composition des communautés ne peut être séparée de l’effet de la configuration spatiale des sites, en raison de la distribution spatiale de régime de pâturage sur la montagne. Fait important, nous avons constaté que les communautés herbacées et ligneuses réagissaient différemment aux différentes intensités de pâturage: la diversité bêta des herbacées était plus élevée entre les sites sans pression de pâturage, tandis que la diversité bêta ligneuse a atteint son maximum lors d’un pâturage léger. La composition de la communauté herbacée était sensible à toute intensité de pression de pâturage, et une pression de pâturage modérée à élevée a entrainée l'homogénéisation biotique entre communautés. D’autre part, la composition de la communauté ligneuse est restée semblable entre les sites sous aucune ou sous une légère pression de pâturage, mais différait sous un pâturage modéré à intense. Une analyse de la variance par permutation a démontré que le pâturage avait un effet significatif sur la composition des communautés, après avoir contrôlé l’effet des variables abiotiques et spatiales. Nos résultats offrent un aperçu de l’effet du pâturage sur la végétation maquis de Jebel Ichkeul, agissant comme un microcosme de problématiques en conservation et en gestion de la biodiversité ailleurs en Méditerranée. Nous suggérons qu'une combinaison de surveillance et de pâturage contrôlée pourrait maintenir et promouvoir la diversité des plantes afin de préserver la biodiversité de la végétation maquis de la région, dans le but de potentiellement maintenir un refuge climatique vital pour les espèces endémiques vulnérables. Fait important, notre étude fournit une base de référence utile sur la communauté végétale de Jebel Ichkeul avec laquelle comparer les changements de végétation futurs.
... Therefore, assuming that higher livestock densities result in direct positive effects for endangered vulture populations can be a manifest error. An integral management strategy will be required to allow the maintenance of biodiversity in grazed areas, especially on islands sensitive to drought events and regions where the effects of environmental modifications, including climate change, are expected to be strong (Arévalo et al. 2012). ...
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Individual traits such as body mass can serve as early warning signals of changes in the fitness prospects of animal populations facing environmental impacts. Here, taking advantage of a 19‐year monitoring, we assessed how individual, population and environmental factors modulate long‐term changes in the body mass of Canarian Egyptian vultures. Individual vulture body mass increased when primary productivity was highly variable, but decreased in years with a high abundance of livestock. We hypothesized that carcasses of wild animals, a natural food resource that can be essential for avian scavengers, could be more abundant in periods of weather instability but depleted when high livestock numbers lead to over‐grazing. In addition, increasing vulture population numbers also negatively affect body mass suggesting density‐dependent competition for food. Interestingly, the relative strength of individual, population and resource availability factors on body mass changed with age and territorial status, a pattern presumably shaped by differences in competitive abilities and/or age‐dependent environmental knowledge and foraging skills. Our study supports that individual plastic traits may be extremely reliable tools to better understand the response of secondary consumers to current and future natural and human‐induced environmental changes.
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Mediterranean vegetation is characterized by high biodiversity and conservation value and grazing is controversial. We sampled woody and herbaceous plants on a limestone mountain with strong mesic-xeric gradients, ranked grazing pressure (on a scale of 1-4) and asked whether grazing had a significant effect on plant compositional abundance before and after controlling for environmental covariates. For woody species the shift in means among grazing classes was greater than for herbaceous species according to distance-based redundancy analysis (dbRDA). For herbaceous species differences in multivariate dispersion were greater among grazing classes. Both groups showed significant differences among grazing classes in multivariate location (permutational multivariate ANOVA), even after controlling for aspect. After taking into account biophysical covariates, grazing was not significant and the variation unique to grazing was small. According to best models in dbRDA, grazing was significant in two models for woody species, and all models for herbaceous species. For woody species, spatial variables were most important and confounded with grazing while for herbs, altitude, distance to road, slope, rock outcropping were important. Significant effects of grazing were found for forbs, Poaceae, and Geophytes but not woody and herbaceous legumes. We found a negative relationship between grazing intensity and beta diversity for herbs overall and especially Poaceae, but moderate grazing resulted in higher beta diversity for Geophytes and herbaceous legumes. Jebel Ichkeul provides a microcosm of similar conservation and management issues elsewhere in the Mediterranean. Carefully controlled grazing may enhance plant diversity and maintain the characteristics of maquis vegetation.
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Sobre un total de 321 cachorros nacidos de la raza Perro de Agua Español entre los años 1995 y 1998 se estudian las frecuencias de aparición de diferentes caracteres deletéreos. Los caracteres enogmatismo y monorquidia muestran unas frecuencias relativamente bajas, si bien destacamos la importancia de su control ya que su expresión afecta a la capacidad adaptativa de los animales. Asimismo, el prognatismo y la ausencia de premolares se presentan con unas frecuencias moderadamente altas que recomendamos incluir en los criterios de selección de la raza. Por otra parte, encontramos asociación significativa entre la aparición de anomalías cardíacas y niveles relativamente altos de endogamia en la población por lo que se desaconseja la endocría en las líneas raciales que presentan este defecto.
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