Straight from the horse’s mouth

Institutionen för naturgeografi

Examensarbete grundnivå

Biogeovetenskap, 15 hp

Straight from the horse’s mouth

How horse grazing affects the diversity in

semi-natural grasslands

Lotta Wallander

Förord

Denna uppsats utgör Lotta Wallanders examensarbete i Biogeovetenskap på grundnivå vid

Institutionen för naturgeografi, Stockholms universitet. Examensarbetet omfattar 15

högskolepoäng (ca 10 veckors heltidsstudier).

Handledare har varit Emelie Waldén, Institutionen för naturgeografi, Stockholms universitet.

Examinator för examensarbetet har varit Regina Lindborg, Institutionen för naturgeografi,

Stockholms universitet.

Författaren är ensam ansvarig för uppsatsens innehåll.

Stockholm, den 27 juni 2017

Abstract

Biodiversity is a prerequisite for stable ecosystems and in northern latitudes it is closely connected to semi-natural grasslands used for haymaking and grazing. Increasing demands for profitability in agriculture and decreasing numbers of cattle has led to overgrowth of these grasslands and a

deficiency in grazers. Meanwhile, the number of horses increase and they could potentially fill the gap left by cattle. Combining a literature review with a spatial analysis, I examine effects on biodiversity from grazing by cattle and horses to determine whether horses can be utilized to conserve and/or restore semi-natural grasslands. Horse grazing seems to promote diversity and are well suited for clearing grasses and maintaining woody pastures. Cattle seem better suited for clearing shrubs, and combined grazing has positive effects on biodiversity. The location of the semi-natural grasslands in Sweden is ideal for utilizing horses, making them a potential replacement for the diminishing number of cattle.

Sammanfattning

Table of contents

1. Introduction ... 3

1. 1. Background

1. 2 Aim of study and research question

2. Materials and methods ... 4

2.1. Review

2. 1. 1. Search terms

2. 1. 2. Search engines

2. 2. Spatial analyses

2. 2. 1. ArcMap source data

2. 3. Statistical analyses

3. Results ... 5

3. 1. Effects on biodiversity

3. 2. People, horses and semi-natural grasslands

4. Discussion ... 8

4. 1. Effects on biodiversity

4. 2. People, horses and semi-natural grasslands

5. Conclusions ... 12

6. Acknowledgements ... 12

3

1. Introduction

1. 1. Background

Biodiversity is the foundation of our natural environment and a prerequisite for ensuring the survival of the ecosystems ant their ability to adapt to new circumstances (Darwin 1859; Holling 1973; Peterson et

al. 1998). Today, global warming changes the conditions for all living things (Marcott et al. 2013),

emphasizing the need to conserve diversity to ensure resilient ecosystems. In northern latitudes, one of the most species-rich habitats is semi-natural grasslands connected to the agricultural landscape (e. g. Svensson 1988; Bakker 1989; Luoto et al. 2003). These grasslands have a relatively low productivity (Bakker 1989; Luoto et al. 2003; Emanuelsson 2009) and intensification of agriculture with increasing demands for productivity and profitability has led to a decrease in semi-natural grasslands along with increased fragmentation (e. g. Hansson & Fogelfors 2000; Luoto et al. 2003; Jordbruksverket 2005a). Habitat destruction and deterioration along with fragmentation are some of the major causes of loss of biodiversity (e. g. Soulé 1987; Tilman et al. 1994; Luoto et al. 2003) and thus it is important to conserve the remainder of semi-natural grasslands.

Historically, semi-natural grasslands were used for haymaking and grazing and today most of it is maintained by grazing (e. g. Bakker 1989; Pykälä 2000; Eriksson et al. 2002). By consuming highly competitive plats such as grasses, herbivores help upholding species diversity by benefitting a wider range of less competitive plants (e. g. Belsky 1992; Olff & Ritchie 1998; Marion et al. 2010). Thus, to maintain species diversity in this type of landscape, intermediate disturbance in the form of for example grazing is a necessity (e. g. Connell 1978; Hobbs & Huenneke 1992; Luoto et al. 2003). Without it the diversity of disturbance dependent herbs will be replaced by a less diverse plant community of efficient competitors and eventually overgrow as a result of succession (e. g. Connel & Slatyer 1977; Bakker 1989; Ihse 1995), leading to loss of biodiversity.

Traditionally a lot of the semi-natural grasslands in Sweden have been grazed by cattle (Ihse 1995; Emanuelsson 2009). In modern agriculture, with increasing specialization and demands for productivity, the cattle often graze on cultivated pastures with higher productivity than the semi-natural grasslands (Ihse 1995; Luoto et al. 2003). Combined with a decreasing number of cattle, with 1 935 022 cattle in 1980 (Statistics Sweden 1982) compared to 1 436 000 in 2016 (Jordbruksverket 2017a), this leads to a deficiency in the number of animals that can help uphold biodiversity in this type of landscape. Additionally, interviews with farmers reveal that they themselves perceive it as unrealistic to maintain semi-natural grasslands using only their own animals for grazing (Kumm 2003).

Thus, additional grazers are needed and while the number of cattle is decreasing, horses have increased by over 70 000 in the last 12 years, from 283 100 in 2004 to 355 500 in 2016 (Jordbruksverket 2017b). Only 34% of these horses are registered to riding schools or agricultural companies (Jordbruksverket 2017b), indicating that a large proportion of horses in Sweden are simply used for recreation and thus are not connected to demands for productivity or profitability. This excludes the need for grazing on highly productive cultivated lands to ensure sufficient growth to produce, for example, meat, thus meaning that horses could be a resource for preserving and restoring semi-natural grasslands. However, horses and cattle are anatomically different and therefore graze in different ways (Janis 1976; Bakker 1989; Menard et al. 2002). It has even been suggested that cattle and horses are so different from each other that they occupy different niches in natural ecosystems (Janis 1976), although this is debated.

4

potential of horses as a resource for maintaining- and/or restoring this type of landscape, and as cattle have been used for grazing large parts of semi-natural grasslands historically (Ihse 1995; Emanuelsson 2009), cattle grazing will be used as comparison to horse grazing.

1. 2 Aim of study and research question

This study aims to determine whether the growing number of horses in Sweden can be used as a resource in managing semi-natural grasslands of importance for conserving biodiversity by answering the following questions:

How does horse grazing affect plant species diversity? Can horses be utilized a resource in preserving and/or restoring semi-natural grasslands in Sweden and if so, how?

2. Materials and methods

2.1. Review

To compile- and compare existing data on the effects of grazing by cattle and/or horses, a review

of literature was performed. The large part of this study consists of data from that review.

2. 1. 1. Search terms

The search terms used to find relevant literature for the review are based on the subject and outcome of the question, in line with the systematic review methodology suggested by Pullin & Stewart (2006). Cattle were used as comparison to determine the potential changes in flora as a response to changes in herbivore species and will therefore be included in the search terms. The following terms were used: forag* AND horse* AND cattle OR livestock

graz* AND diversity AND horse* AND cattle OR livestock semi-natural grass* AND horse*

Capital letters denote Boolean operators and * denote wildcards.

2. 1. 2. Search engines

Searches were executed in Google Scholar and Web of Science. The first 100 results, sorted for relevance, were examined. Additionally, citations in articles viewed in full text were also examined. Articles comparing grazing by cattle and horses, or only examining grazing patterns and behaviors of one of the species were considered and no limitations based on geographical location was utilized.

2. 2. Spatial analyses

By combining data on locations of urban areas with data on locations of semi-natural grasslands and restorable semi-natural grasslands in Sweden using the operator “near” in ESRI ArcMap 10.5, information on the location of desirable land areas in relation to urban areas was extracted. Using Microsoft Office Excel 2016, this data was then compiled and presented in a diagram.

5

grasslands and restorable semi-natural grasslands, excluding grasslands deemed as not applicable (“ej aktuell”), was created with “select by attributes” and total area of semi-natural grasslands per county was summarized. This layer was then joined to the county polygon layer usin the operator “spatial join”. From that, thematic maps showing surface area of- and percentage of coverage by semi-natural grasslands per Swedish county were created.

2. 2. 1. ArcMap source data

Data from TUVA (Ängs- och betesmarksinventeringen vektor, © Jordbruksverket) was used in

the spatial analyses and all land classified as grazed, meadow or restorable was included in the

analysis. Information on the locations of urban areas was retrieved from Statistics Sweden

(Tätorter vektor, © Statistics Sweden). Further, country- and county borders were retrieved

from Lantmäteriet (GSD-Sverigekartan 1:5 miljoner vektor,

Lantmäteriet).

2. 3. Statistical analyses

A Pearson Correlation test with data on number of horses- (Jordbruksverket 2017c) and human population (Statistics Sweden 2017) per county was performed using IBM SPSS Statistics 24.

3. Results

3. 1. Effects on biodiversity

The human mediated semi-natural grasslands are seen by some as a substitute for the large natural grasslands that is thought to have been maintained by the megafauna before their extinction in Pleistocene (Andersson & Appelqvist 1990; Pykälä 2000). It is argued that the keystone species for maintaining these natural grasslands were aurochs and tarpan, whose domesticated counterparts are cattle and horses (van Wieren 1995; Olff et al. 1999; Pykälä 2000).

Cattle and horses are anatomically different and therefore graze in different ways (Bakker 1989; Hongo & Akimoto 2003). Cattle feed on forbs and shrubs to a larger extent than horses do, whereas horses spend more time feeding on grass (e. g. Fleurance et al. 2001; Menard et al. 2002; Lamoot et al. 2005). However, the large part of their respective diets seem to overlap and both species spend most of their foraging time feeding on grasses (e. g. Krysl et al. 1984; Cymbaluk 1990; Menard et al. 2002). This dietary overlap has been shown to lead to both additive and compensatory effects (Loucougaray et

al. 2004).

In comparison to cattle, horses consume a larger amount of plant matter in relation to their body weight (Duncan et al. 1990; Fleurance et al. 2001; Menard et al. 2002). They prefer short grasses to tall-, promoting structural diversity in the grassland (e. g. Fleurance et al. 2001; Menard et al. 2002; Lamoot

et al. 2005). Due to this, combined with the cattle’s preference for shrubs, Loucougaray et al. (2004)

argue that if combining grazing by cattle and horses, the proportion of cattle should be kept low to maintain structural diversity.

6

kg of dry weight of bark per individual (Kinnaird et al. 1979; Mitchell & Kirby 1990). When there is a lack of grass, horses exhibit the same behavior, consuming bark to some extent (Duncan 2012; Ferreira

et al. 2013). Even in winter however, both cattle and horses will choose grasses and herbs if given the

opportunity (Krysl et al. 1984; Menard et al. 2002; Duncan 2012).

Regardless of season, too intense grazing by either species seems to have negative effects on plant diversity (e. g. Olff et al. 1999; Beever & Brussard 2000; Stewart & Pullin 2008). Beever & Brussard (2000) examined the effect of feral horse grazing near springs using exclosures that had been present for either four or eight years in areas that had been grazed by horses for 15-20 years prior to that. They found a rise in vegetation cover, plant species richness and plant height in the exclosures compared to the areas still accessible to the horses. As water sources can be expected to be visited by all members of the heard daily (Ganskopp & Vavra 1986; Beever & Brussard 2000; Prishutova 2010) and thus be trampled and perhaps even grazed more than other areas, their results are heavily related to the subject of grazing intensity. Prishutova (2010) found similar effects when studying feral horses in Russia, with degraded plants damaged from heavy grazing and trampling near water sources.

In studies using similar methods as Beever & Brussard (2000) and Prishutova (2010), but on areas farther from water sources, Loydi et al. (2012) and Catling et al. (2015) found and increase in plant species diversity in the grazed- compared to the ungrazed areas. Furthermore, at optimal stocking rates horse grazing promotes a higher plant species diversity than cattle grazing (e. g. Yunusbaev et al 2003; Loucougaray et al. 2004; Catling et al. 2015) and too few animals render no effect at all, leaving the pastures to overgrow (Sýkora et al. 2009).

7

3. 2. People, horses and semi-natural grasslands

In Sweden, 76% of horses are located in urban areas and the counties with the largest human population also sustain the largest number of horses (Jordbruksverket 2017c). The number of horses per county correlates with the size of the population (Pearson Correlation, n= 21, r=0,769**, r2_{=0,591; Fig. 1).}

Additionally, the large part of semi-natural grasslands that are used for grazing are categorized as restorable are located less than one kilometer from the nearest urban area (Fig. 2).

With regards to the total area of grasslands, most of the desirable land is located in the south of Sweden (Fig. 3. a.). The percentage of land covered by semi-natural grasslands is also larger in the south (Fig. 3. b.), especially near the coast. The largest cohesive patch of semi-natural grassland found in the database TUVA (Jordbruksverket 2017d) is a little over 11 km2 _{(1100 ha) in size, but most of the}

patches in the inventory are well under 1 km2_{. How much land is needed to support}

horses is likely to vary depending on, for example, plant species composition, soil properties and the horses’ nutritional needs, but in USA it is recommended that horses are stocked at 0,6-0,8 hectares per animal (Hall 1992). However, additional management and/or differences in time spent in the pasture is not considered, leading Singer et al. (2001) to conclude that further research is needed to determine optimal stocking rates.

< 1 km

1 km - 5 km

5 km - 10 km

> 10 km

8

4. Discussion

4. 1. Effects on biodiversity

The semi-natural grasslands connected to agriculture seem to be a refuge for plant species originating from prehistoric natural grasslands mediated by large grazers that have become extinct (Andersson & Appelqvist 1990; Pykälä 2000), perhaps as a result of human intervention. Aurochs and tarpan, the wild ancestral relatives of cattle and horses, have been identified as keystone species for that type of landscape (van Wieren 1995; Olff et al. 1999; Pykälä 2000), meaning the plant species composition of this landscape is likely adapted to the type of disturbance created by these herbivores.

If this is the case, the importance of considering the species of the herbivores to maintain plant species diversity in this type of landscape also becomes apparent. The diets of cattle and horses, perhaps best suited for maintaining the diversity created by their relatives, are not completely consistent but to a relatively large extent overlapping. Both species prefer grasses (e. g. Krysl et al. 1984; Cymbaluk 1990; Menard et al. 2002) but cattle feed on shrubs to a larger extent than horses do whereas horses prefer short grasses (e. g. Fleurance et al. 2001; Menard et al. 2002; Lamoot et al. 2005). Combined grazing by the two species can therefore have both additive- and compensatory effects (Pykälä 2000; Loucougaray et al. 2004), meaning it is important to take into consideration what effects and efforts are needed in a particular location before determining when and how to mix or not mix these species.

9

In cases where the main object is to clear rapidly growing grasses from overgrown semi-natural grasslands, horses are well suited as they consume a larger amount of plant biomass in relation to body weight than cattle do (Fleurance et al. 2001; Menard et al. 2002). Thus, they are more effective than cattle in clearing grasses, whereas cattle seem to be more efficient in clearing invading shrubs (e. g. Fleurance et al. 2001; Menard et al. 2002; Lamoot et al. 2005). Cosyns et al. (2001) found that horses do not graze enough on shrubs to aid in clearing overgrown grasslands from that type of plants, indicating the need for cattle when restoring pastures that have reached a later successional stage. Thus, depending on what type of land you want to restore and/or maintain, one or the other, or a combination of both species, should be preferred.

Still, with regards to the conservation of structural diversity, which has a strong correlation with species diversity (Olff & Ritchie 1998; Marion et al. 2010), perhaps horses are best suited. By preferring short grasses and consequently leaving areas with taller grass, horse grazing alone promotes structural diversity in grasslands (e. g. Fleurance et al. 2001; Menard et al. 2002; Lamoot et al. 2005). This renders many potential micro habitats of importance to, for example, invertebrates (Ausden et al. 2005) as well as protective vegetation for trees and shrubs to establish in. Tall grass in horse pastures is often found in latrine areas, and it is suggested that the horses avoid grazing them to avoid endoparasites (Taylor 1954; Hart 1992). However, the avoidance of tall grass could also be due to, for example, differences in nutritional content (Fleurance et al. 2001; Fleurance et al. 2005). Putman et al. (1991) found differences in species composition between the latrine areas and the grazed areas, perhaps indicating that species composition is in fact the reason for the horses’ preference for shorter grass. If that is the case, it might be important to examine horses’ preferences for specific plant species to determine, for example, whether they are likely to consume plants that are particularly important to preserve.

However, there is no way of distinguishing cause and effect in this case, as the exclusion of feces in itself could be a reason for the horses to graze the area and there is no indication as to where the horses’ latrine areas are located. Perhaps they are situated in areas with unpalatable plants, or perhaps the addition of nutrients from the feces causes changes in the flora. Edouard et al. (2009) found that when species composition is the same in the tall- and short grass and no feces are present, i.e. the only difference is plant height, horses choose the taller grass, in line with foraging theory stating that animals should maximize energy intake in relation to energy output (Stephens & Krebs 1986). This indicated that the height of the plants is not the most important factor making horses discard taller plants, although it could still play a role. Regardless of the reason for it, the latrine areas as well as other patches of taller plants seem to be left untouched by horses, promoting structural diversity in grasslands not only with regards to presence of shrubs and trees.

Areas with shrubs and trees are, however, also of importance to conserve. In addition to contributing to both structural- and species diversity by themselves, these areas can act as protection for saplings of palatable woody species such as deciduous trees (Olff et al. 1999; Kuiters & Slim 2003) and thus are important for managing- and restoring woody pastures. Compared to cattle, who spend more time grazing on shrubs (e.g. Fleurance et al. 2001; Menard et al. 2002; Lamoot et al. 2005), horses might be more suitable for maintaining this type of landscape. However, when there is a lack of grasses and herbs, horses tend to consume larger amounts of shrubs and can even start gnawing the bark of the trees (Duncan 2012; Ferreira et al. 2013). Therefore, it is important to ensure sufficient access to grass in order to prevent horses from feeding on trees, possibly indicating a need for examining the optimal relation of forest/woody pasture to open meadows in semi-natural grasslands to be grazed by horses.

Like horses, cattle have been found to strip the bark off deciduous trees in winter (Kinnaird et al. 1979; Mitchell & Kirby 1990), i. e. when deprived of their preferred forage. Therefore, perhaps both species could theoretically be utilized to clear shrubs and trees from overgrowing pastures if deprived of access to their preferred food sources. However, to ensure their nutritional needs are met in that case, they would have to be given supplemental feed, leading to an inflow of nutrients to the semi-natural grassland and to potential deterioration of biodiversity.

10

Marrs 1993; Pykälä 2000). This leads to a potential transport of nutrients from the fields to the grasslands. In addition to this, supplemental feed leads to further inflow of nutrients, changing the premises for the flora and possibly leading to deterioration of the grasslands. Therefore, to maintain the semi-natural grasslands’ nutritional status and protect trees, it is important to move the animals off the pasture when the growing season is over and the animals require additional nutrients.

It is sometimes argued that horses need supplemental feed to ensure good performance in, for example, competitions (Williamson et al. 2007; Jansson & Lindberg 2012), which is possibly one of the reasons as to why horses are not already grazing the semi-natural grasslands. However, during the growing season most horses should do well on forage only, even though the nutritional demands of the horses as well as the nutritional contents of the plants vary. Muhonen et al. (2008) and Jansson & Lindberg (2012) showed that standardbred horses active in competition can perform at equal- or higher levels on a forage only diet compared to the traditional diet with starch- and energy rich supplemental feed (Williamson et al. 2007; Jansson & Lindberg 2012). In these experiments the nutritional values of the forage were analyzed and adapted to ensure performance and if this type of energy demanding horse is to be maintained on semi-natural grasslands, similar analyses of the feed available there needs to be executed. However, as horses are mainly used for pleasure there are plenty of horses with significantly less demanding tasks to preform than the standardbreds in those experiments, suggesting many horses have a significantly lesser demand for, for example, energy. In addition, many breeds, such as for example ponies and draught horses, are adapted to a less energy rich diet and have a slower metabolism (Pehrson 2001; Duncan 2012). While horses seem well suited to maintain biodiversity in semi-natural grasslands, the importance of assigning the right type of horse to the right type of land becomes evident to ensure the wellbeing of the animals. The importance of allocating the right animal to the right pasture is likely to apply to cattle as well as, like in horses, different breeds and different developmental stages have different nutritional needs (Ferrell & Jenkins 1985; Nuernberg et al. 2005).

Animal welfare is also related to the stocking rates of the pastures as the number of endoparasites increases with stocking densities (Ciordia et al. 1971; Waller 2006). Too many animals per surface area promotes negative effects on diversity (e. g. Olff et al. 1999; Beever & Brussard 2000; Stewart & Pullin 2008). Beever & Brussard (2000) and Prishutova (2010) found a significant decrease in diversity as a result of grazing near water sources, an area that can be expected to be exposed to excessive trampling (Ganskopp & Vavra 1986; Beever & Brussard 2000; Prishutova 2010). These studies used feral horses but of course, such areas are likely to be present in semi-natural pastures with domestic animals as well. Increased load on grounds near water sources should be expected and if water is supplied, troughs should be placed on grounds that can withstand increased wear and perhaps are not essential for survival of rare plant species. In any case, too intense grazing always leads to negative effects for the flora (e. g. Olff et

al. 1999; Beever & Brussard 2000; Stewart & Pullin 2008) Grazing intensity is thus a very important

factor to consider, perhaps even more so than herbivore species, emphasizing the need for large enough enclosures to avoid both too heavy grazing and trampling.

Too intense grazing can have a number of negative effects and in addition to those mentioned above, too many animals per surface area also leads to an increase of nutrients in the soil as the plats are unable to utilize them for growth (Shariff et al. 1994; Singer et al. 2001). It is however difficult to determine how many animals a surface can support and it is likely that individual assessments have to be made for different types of surfaces and different animals (Singer et al 2001). On the other hand, to get desirable effects from grazing it is also important not to stock them too sparsely, as that is likely to result in overgrowth (Sýkora et al. 2009). Additionally, it is important to consider how much time the animals will spend in the pasture, their nutritional needs in relations to the contents of the forage as well as the load carrying capacity of the ground to determine optimal stocking rates.

11

keywords designed to specifically find results on these species were used and therefore the results might be misleading. A review including these species might be advantageous to determine the effects of other species and if it is beneficial to combine grazing by more- or other species than cattle and horses.

Regardless of herbivore species, however, plant species richness in semi-natural grasslands is dependent on grazing. Perhaps the increase in diversity in response to grazing by cattle and/or horses in itself indicates that the plant communities are adapted to this type of disturbance, supporting the theory that the semi-natural grasslands are remnants of natural grasslands grazed by wild counterparts to horses and cattle. Some of the studies confirming increased biodiversity as a result of horse grazing have been conducted on lands with a history of grazing by horses (Shoji et al. 2011; Catling et al. 2015), meaning the plant species native to that environment have adapted to that type of grazing. Thus, the diversity is already dependent on that specific type of disturbance, meaning that if grazing by horses ceases or is replaced by grazing by, for example, cattle, the plant species diversity could be affected negatively. Subsequently, it might be important to take the historic land use of the site into consideration before determining what type of herbivore is best suited for maintaining diversity.

However, there are also studies conducted on lands with a history of mixed grazing by horses and cattle (Loucougary et al. 2004) and on lands with a history of grazing by other herbivores or no species-specific grazing (Yunusbaev et al. 2003; Köhler et al. 2016) confirming the positive effects of horse grazing. This might indicate that horse grazing is in fact beneficial for plant species diversity regardless of historical land use, but to fully determine the importance of historical land use in relation to present land use and choice of herbivore species, specific studies on that subject are needed.

4. 2. People, horses and semi-natural grasslands

Nevertheless, if horses are to be used as grazers the proximity to their owners is a factor to take into consideration for horse grazing to work in practice, as horses are mainly used for hobby. In Sweden, the number of horses in each county is correlated with the size of the population (Fig. 1), further emphasizing that horses are located where people are. This means that the location of the grasslands is potentially of importance if horses are to be used as grazers, as their owners likely want to keep them close even when the horses are aiding in maintaining diversity in semi-natural grasslands. Luckily, most semi-natural grasslands seem to be located under one kilometer from urban areas (Fig. 2), meaning distance should not be a problem.

However, the data in fig. 2 is based on Ängs- och betesmarksinventeringen (Jordbruksverket 2017d) and does not necessarily cover all of Sweden’s surface. The land areas included in this inventory are selected based on a couple of conditions, including all land currently in use for grazing or mowing and areas previously noted in Ängs- och betesmarksinventeringen (Jordbruksverket 2005b). This is a potential deficiency as it may have led to a bias towards accessible areas which are likely to be located close to urban areas. If this is the case, there could be more semi-natural grasslands further away from urban areas also in need of grazing, perhaps calling for other solutions than horse grazing. There are however young horses not yet used for riding that could be allegeable for grazing at such locations.

12

Despite the difficulties in determining optimal stocking rates and the land areas best suited for grazing, it seems like horses can indeed be used as a resource in helping maintain semi-natural grasslands, although perhaps with some restrictions as discussed above. If given a choice between abandoning the semi-natural grasslands and replacing cattle grazing with horse grazing, it is however evident that horses are a better choice than leaving the pastures ungrazed. It also seems like they can have positive effects on the biodiversity of semi-natural grasslands. Consequently, horses may assist in keeping the grasslands open, filling the gap left by the diminishing number of cattle and thus helping conserve the biodiversity in a nature type of utmost importance for ensuring resilient eco systems in light of impending climate change.

5. Conclusions

Horse grazing seems to have a positive effect on plant species diversity, promoting larger diversity than cattle, however studies on land use history in relation to present use are needed to determine whether the results are dependent on the plant community’s adaptions to species specific grazing. Horses are especially well suited for maintaining structural heterogeneity and woody pastures and can be used in restauration to clear fast growing and competitive grasses from overgrown areas, thereby promoting herb- and forb diversity. However, for clearing shrubs cattle seem to be a better choice than horses. Thus, it is important to consider what effects are desirable on a specific location when determining what herbivore species is best suited, and perhaps different species can be used at different times to promote diversity. Regardless of species, grazing intensity seems to be a very important factor, emphasizing the need for large enough areas of cohesive semi-natural grasslands to support the animals’ nutritional needs without risking damage to trees or causing an increased inflow of nutrients by fencing in cultivated land with the grassland.

In Sweden, most of the semi-natural grasslands are located close to urban areas. As the horse population is connected to the human population, the location of these grasslands should be ideal for horse grazing as it allows the horse owners to keep their horses close during the growing- and grazing season. This further emphasizes the potential use of horses as a resource in maintaining and/or restoring semi-natural grasslands, promoting biodiversity and ensuring the survival of semi-natural grasslands.

6. Acknowledgements

13

7. References

Andersson, L., & Appelqvist, T. (1990). Istidens stora växtätare utformade de nemorala och boreonemorala

ekosystemen. Svensk botanisk tidskrift, 84, 335-368.

Ausden, M., Hall, M., Pearson, P., & Strudwick, T. (2005). The effects of cattle grazing on tall-herb fen

vegetation and molluscs. Biological Conservation, 122(2), 317-326.

Bakker, J. P. 1989. Nature Management by Grazing and Cutting. On the Ecological Significance of Grazing and

Cutting Regimes Applied to Restore Former Species-rich Grassland Communities in the Netherlands. Kluwer Academic Publishers. Dordrecht.

Beever, E. A., & Brussard, P. F. (2000). Examining ecological consequences of feral horse grazing using

exclosures. Western North American Naturalist, 236-254.

Belsky, A. J. (1992). Effects of grazing, competition, disturbance and fire on species composition and diversity

in grassland communities. Journal of Vegetation Science, 3(2), 187-200.

Catling, P. M., Kostiuk, B., & Thompson, D. (2015). Horse ranching increases biodiversity in a foothills

parkland prairie in northern Kananaskis Country, western Alberta. The Canadian

Field-Naturalist, 129(1), 15-23.

Ciordia, H., Baird, D., & McCampbell, H. (1971). Internal parasitism of beef cattle on winter pastures: level of

parasitism as affected by stocking rates. American journal of veterinary research, 32(9), 1353-1364.

Connell, J. H. (1978). Diversity in tropical rain forests and coral reefs. Science, 199(4335), 1302-1310. Cosyns, E., Degezelle, T., Demeulenaere, E., & Hoffmann, M. (2001). Feeding ecology of Konik horses and

donkeys in Belgian coastal dunes and its implications for nature management. In 8th Benelux congress of

zoology (Vol. 131, No. s2, pp. 111-118). Koninklijke Belgische Vereniging voor Dierkunde. Cymbaluk, N. F. (1990). Comparison of forage digestion by cattle and horses. Canadian Journal of Animal

Science, 70(2), 601-610.

Darwin, C. (1859). On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured

Races in the Struggle for Life. John Murray, London.

Duncan, P. (2012). Horses and grasses: the nutritional ecology of equids and their impact on the

Camargue (Vol. 87). Springer Science & Business Media.

Duncan, P., Foose, T. J., Gordon, I. J., Gakahu, C. G., & Lloyd, M. (1990). Comparative nutrient extraction

from forages by grazing bovids and equids: a test of the nutritional model of equid/bovid competition and coexistence. Oecologia, 84(3), 411-418.

Edouard, N., Fleurance, G., Dumont, B., Baumont, R., & Duncan, P. (2009). Does sward height affect feeding

patch choice and voluntary intake in horses?. Applied Animal Behaviour Science, 119(3), 219-228.

Emanuelsson, U. (2009). The rural landscapes of Europe - How man has shaped European nature. Stockholm, Formas.

Eriksson, O., Cousins, S. A., & Bruun, H. H. (2002). Land-use history and fragmentation of traditionally

managed grasslands in Scandinavia. Journal of vegetation science, 13(5), 743-748.

Ferreira, L. M. M., Celaya, R., Benavides, R., Jáuregui, B. M., García, U., Santos, A. S., ... & Osoro, K. (2013).

Foraging behaviour of domestic herbivore species grazing on heathlands associated with improved pasture areas. Livestock Science, 155(2), 373-383.

Ferrell, C. L., & Jenkins, T. G. (1985). Cow type and the nutritional environment: nutritional aspects. Journal of Animal Science, 61(3), 725-741.

Fleurance, G., Duncan, P., Fritz, H., Cabaret, J., & Gordon, I. J. (2005). Importance of nutritional and anti‐

parasite strategies in the foraging decisions of horses: an experimental test. Oikos, 110(3), 602-612.

Fleurance, G., Duncan, P., & Mallevaud, B. (2001). Daily intake and the selection of feeding sites by horses in

heterogeneous wet grasslands. Animal Research, 50(2), 149-156.

Ganskopp, D., & Vavra, M. (1986). Habitat use by feral horses in the northern sagebrush steppe. Journal of Range Management, 207-212.

Hall, M. H., & Comerford, P. M. (1992). Pasture and hay for horses. Penn State Coop. Ext Agronomy Facts, 32. Hansson, M., & Fogelfors, H. (2000). Management of a semi‐natural grassland; results from a 15‐year‐old

experiment in southern Sweden. Journal of vegetation science, 11(1), 31-38.

Hart, B. L. (1992). Behavioral adaptations to parasites: an ethological approach. The Journal of parasitology, 256-265.

Hobbs, R. J., & Huenneke, L. F. (1992). Disturbance, diversity, and invasion: implications for

conservation. Conservation biology, 6(3), 324-337.

Holling, C. S. (1973). Resilience and stability of ecological systems. Annual review of ecology and systematics, 4(1), 1-23.

14

Hudson, J. M., Cohen, N. D., Gibbs, P. G., & Thompson, J. A. (2001). Feeding practices associated with colic in

horses. Journal of the American Veterinary Medical Association, 219(10), 1419-1425.

Ihse, M. (1995). Swedish agricultural landscapes—patterns and changes during the last 50 years, studied by

aerial photos. Landscape and urban planning, 31(1), 21-37.

Janis, C. (1976). The evolutionary strategy of the Equidae and the origins of rumen and cecal

digestion. Evolution, 757-774.

Jansson, A., & Lindberg, J. E. (2012). A forage-only diet alters the metabolic response of horses in

training. animal, 6(12), 1939-1946.

Jordbruksverket (2005a). Swedish Agriculture in figures 1800-2004.Statistikrapport 2005:6, Jordbruksverket. Jordbruksverket (2005b). Ängs- och betesmarksinventeringen – inventeringsmetod. Rapport 2005:2,

Jordbruksverket.

Jordbruksverket (2017a). Number of cattle in December 2016. JO 23 SM 1701, Jordbruksverket.

Jordbruksverket (2017b). Horses and horse establishments in 2016. JO 24 SM 1701, Korrigerad version 2017-02-22, Jorsbruksverket.

Jordbruksverket (2017c). Antal hästar och anläggningar med häst 2004, 2010 och 2016. Jordbruksverkets statistikdatabas. Retrieved 2017-05-31 from

http://statistik.sjv.se/PXWeb/pxweb/sv/Jordbruksverkets%20statistikdatabas/Jordbruksverkets%20statisti kdatabas__Husdjur__Hastar%20och%20anlaggningar%20med%20hastar/JO0103G8.px/?rxid=5adf4929-f548-4f27-9bc9-78e127837625

Jordbruksverket (2017d). Databasen TUVA. Jordbruksverket. Retrieved 2017-05-31 from https://etjanst.sjv.se/tuvaut/site/webapp/tuvaut.html

Kinnaird, J. W., Welch, D., & Cummins, C. (1979, November). Selective stripping of rowan (Sorbus aucuparia

L.) bark by cattle in North-East Scotland. In Transactions of the Botanical Society of Edinburgh (Vol. 43,

No. 2, pp. 115-125). Taylor & Francis Group.

Krysl, L. J., Hubbert, M. E., Sowell, B. F., Plumb, G. E., Jewett, T. K., Smith, M. A., & Waggoner, J. W. (1984).

Horses and cattle grazing in the Wyoming Red Desert, I. Food habits and dietary overlap. Journal of

Range Management, 72-76.

Kuiters, A. T., & Slim, P. A. (2003). Tree colonisation of abandoned arable land after 27 years of

horse-grazing: the role of bramble as a facilitator of oak wood regeneration. Forest Ecology and

Management, 181(1), 239-251.

Kumm, K. I. (2003). Sustainable management of Swedish seminatural pastures with high species

diversity. Journal for Nature Conservation, 11(2), 117-125.

Köhler, M., Hiller, G., & Tischew, S. (2016). Year-round horse grazing supports typical vascular plant species,

orchids and rare bird communities in a dry calcareous grassland. Agriculture, Ecosystems &

Environment, 234, 48-57.

Lamoot, I., Meert, C., & Hoffmann, M. (2005). Habitat use of ponies and cattle foraging together in a coastal

dune area. Biological Conservation, 122(4), 523-536.

Loucougaray, G., Bonis, A., & Bouzille, J. B. (2004). Effects of grazing by horses and/or cattle on the diversity

of coastal grasslands in western France. Biological Conservation, 116(1), 59-71.

Loydi, A., Zalba, S. M., & Distel, R. A. (2012). Vegetation change in response to grazing exclusion in montane

grasslands, Argentina. Plant Ecology and Evolution, 145(3), 313-322.

Luoto, M., Rekolainen, S., Aakkula, J., & Pykälä, J. (2003). Loss of plant species richness and habitat

connectivity in grasslands associated with agricultural change in Finland. AMBIO: A Journal of the

Human Environment, 32(7), 447-452.

Marcott, S. A., Shakun, J. D., Clark, P. U., & Mix, A. C., (2013). A reconstruction of regional and global

temperature for the past 11,300 years. Science, 339(6124), 1198-1201.

Marion, B., Bonis, A., & Bouzillé, J. B. (2010). How much does grazing-induced heterogeneity impact plant

diversity in wet grasslands?.

Marrs, R. H. (1993). Soil fertility and nature conservation in Europe: theoretical considerations and practical

management solutions. Advances in ecological research, 24, 241-300.

Menard, C., Duncan, P., Fleurance, G., Georges, J. Y., & Lila, M. (2002). Comparative foraging and nutrition of

horses and cattle in European wetlands. Journal of applied ecology, 39(1), 120-133.

Mitchell, F. J. G., & Kirby, K. J. (1990). The impact of large herbivores on the conservation of semi-natural

woods in the British uplands. Forestry: An International Journal of Forest Research, 63(4), 333-353.

Muhonen, S., Lindberg, J. E., Bertilsson, J., & Jansson, A. (2008). Effects on fluid balance, digestion and

exercise response in Standardbred horses fed silage, haylage and hay. Comparative Exercise

15

Nuernberg, K., Dannenberger, D., Nuernberg, G., Ender, K., Voigt, J., Scollan, N. D., ... & Richardson, R. I. (2005). Effect of a grass-based and a concentrate feeding system on meat quality characteristics and fatty

acid composition of longissimus muscle in different cattle breeds. Livestock Production Science, 94(1),

137-147.

Olff, H., & Ritchie, M. E. (1998). Effects of herbivores on grassland plant diversity. Trends in ecology & evolution, 13(7), 261-265.

Olff, H., Vera, F. W. M., Bokdam, J., Bakker, E. S., Gleichman, J. M., Maeyer, K. D., & Smit, R. (1999).

Shifting mosaics in grazed woodlands driven by the alternation of plant facilitation and competition. Plant biology, 1(2), 127-137.

Pehrson, I. (2001). Bete och Betesdjur. Jordbruksverket, Elanders Gummessons, Falköping

Peterson, G., Allen, C. R., & Holling, C. S. 1998. Ecological resilience, biodiversity, and scale. Ecosystems, 1(1), 6-18.

Prishutova, Z. G. (2010). Feral horses (Equus caballus) as a component of protected steppe ecosystems in the

Rostovskii Nature Reserve. Russian journal of ecology, 41(1), 55-59.

Pullin, A. S., & Stewart, G. B. (2006). Guidelines for systematic review in conservation and environmental

management. Conservation biology, 20(6), 1647-1656.

Putman, R. J., Fowler, A. D., & Tout, S. (1991). Patterns of use of ancient grassland by cattle and horses and

effects on vegetational composition and structure. Biological conservation, 56(3), 329-347.

Pykälä, J. (2000). Mitigating human effects on European biodiversity through traditional animal

husbandry. Conservation Biology, 14(3), 705-712.

Shariff, A. R., Biondini, M. E., & Grygiel, C. E. (1994). Grazing intensity effects on litter decomposition and

soil nitrogen mineralization. Journal of Range Management, 444-449.

Shoji, A., Hayashi, H., Kohyama, K., & Sasaki, H. (2011). Effects of horse grazing on plant species richness and

abundance of Iris setosa in a boreal semi‐natural grassland, Japan. Grassland science, 57(1), 1-8.

Singer, J. W., Bobsin, N., Kluchinski, D., & Bamka, W. J. (2001). Equine stocking density effect on soil

chemical properties, botanical composition, and species density. Communications in soil science and

plant analysis, 32(15-16), 2549-2559.

Socher, S. A., Prati, D., Boch, S., Müller, J., Baumbach, H., Gockel, S., ... & Kalko, E. K. (2013). Interacting

effects of fertilization, mowing and grazing on plant species diversity of 1500 grasslands in Germany differ between regions. Basic and applied ecology, 14(2), 126-136.

Soulé, M. E. (1987). Viable populations for conservation. Cambridge university press.

Statistics Sweden (1982). Statistical Abstract of Sweden 1982/83. Statistics Sweden, Stockholm, Liber.

Statistics Sweden (2017). Folkmängd i riket, län och kommuner 31 december 2016 och befolkningsförändringar

1 oktober–31 december 2016. Statistics Sweden. Retrieved 2017-05-31 from

http://www.scb.se/hitta- statistik/statistik-efter-amne/befolkning/befolkningens-sammansattning/befolkningsstatistik/pong/tabell-och-diagram/kvartals--och-halvarsstatistik--kommun-lan-och-riket/kvartal-4-2016/

Stephens, D. W., & Krebs, J. R. (1986). Foraging theory. Princeton University Press.

Stewart, G. B., & Pullin, A. S. (2008). The relative importance of grazing stock type and grazing intensity for

conservation of mesotrophic ‘old meadow’pasture. Journal for Nature Conservation, 16(3), 175-185.

Svensson, R. (1988). Floravârd i jordbrukslandskapet. Svensk botanisk tidskrift.

Sýkora, K. V., Stuiver, H. J., de Ronde, I., & de Nijs, L. J. (2009). Fourteen years of restoration and extensive

year round grazing with free foraging horses and cattle and its effect particularly on dry species rich riverine levee grasslands. Phytocoenologia, 39(3), 265-286.

Taylor, E. L. (1954). Grazing behaviour and helminthic disease. The British Journal of Animal Behaviour, 2(2), 61-62.

Tilman, D., May, R. M., Lehman, C. L., & Nowak, M. A. (1994). Habitat destruction and the extinction debt. Tinker, M. K., White, N. A., Lessard, P., Thatcher, C. D., Pelzer, K. D., Davis, B., & Carmel, D. K. (1997).

Prospective study of equine colic risk factors. Equine veterinary journal, 29(6), 454-458.

Waller, P. J. (2006). Sustainable nematode parasite control strategies for ruminant livestock by grazing

management and biological control. Animal Feed Science and Technology, 126(3), 277-289.

van Wieren, S. E. (1995). The potential role of large herbivores in nature conservation and extensive land use in

Europe. Biological journal of the Linnean Society, 56(s1), 11-23.

Williamson, A., Rogers, C. W., & Firth, E. C. (2007). A survey of feeding, management and faecal pH of

Thoroughbred racehorses in the North Island of New Zealand. New Zealand veterinary journal, 55(6),

16

Willing, B., Vörös, A., Roos, S., Jones, C., Jansson, A., & Lindberg, J. E. (2009). Changes in faecal bacteria

associated with concentrate and forage‐only diets fed to horses in training. Equine veterinary

journal, 41(9), 908-914.

Yunusbaev, U. B., Musina, L. B., & Suyundukov, Y. T. (2003). Dynamics of steppe vegetation under the effect