Introduction
The United Nations1 expects the world's human population to rise to 9 billion by 2050—and each of these people needs to eat. Currently, agricultural use comprises up to 50% of the world's land and more will surely become subject to conversionReference Scherr and McNeely2. Habitat fragmentation is a primary cause of biodiversity loss at the landscape level, often occurring in conjunction with agricultural useReference Primack3. With more pressure on land resources due to increasing agricultural demand, it is likely that the planet's biodiversity will continue to suffer. Regions where population growth is expected to make the sharpest increases lie in designated biodiversity hotspots, or areas with large concentrations of ecologically threatened speciesReference Meyers, Mittermeier, Mittermeier, da Fonseca and Kent4, Reference Wrage, Strodthoff, Cuchillo, Isselstein and Kayser5. This presents a concern for the preservation of nature and biodiversity in these regions. Without an agricultural system that maximizes productivity while supporting habitat for diverse wildlife, the biodiversity of the planet will continue to decline at an alarming rateReference Aguiar, Reynolds and Frame6. Essentially, the planet is running out of land for food production and humans will be faced with the choice of preserving either food systems or wildlife biodiversity—unless we can choose both.
Farms, often comprised of acres of open fields, have the potential to play a key role in the preservation of grassland ecosystems. Grassland communities, spread across the globe, are increasingly threatened by human development, urban sprawl and even natural succession when farmland is abandonedReference Watkinson and Ormerod7. Although some environmentalists may consider the semi-natural grassland found on farmland in conflict with native grassland species, preservation of agricultural land is crucial because the current state of biodiversity in these areas has evolved along with the human development of farmlandReference Wrage, Strodthoff, Cuchillo, Isselstein and Kayser5, Reference Kumm8. Therefore, proper management of semi-natural pastures on working farms can play an active role in providing habitat to threatened grassland speciesReference Watkinson and Ormerod7, Reference Nilsson9.
Despite encompassing such a large portion of inhabitable land, farms (and the farmers who operate them) have been largely absent from the conversation regarding wildlife biodiversity conservationReference Scherr and McNeely2, Reference Berry10. Yet, farmers and ranchers have the opportunity to affect biodiversity preservation, soil conservation and climate change more than any other groupReference Sherr11. As global demand for agricultural products increases, farmers and environmentalists must collaborate for the benefit of the ecosystems upon which so many organisms rely. Farmers can contribute to the planet's biodiversity by adopting practices designed to preserve the species richness conserved within and surrounding their farmlandReference Jackson, Pascual and Hodgkin12, Reference Smeding and Joenje13.
This commentary explores the basis for portable electric-net fencing as a tool for the implementation of rotational grazing (RG) and multi-species pastures (MSPs) as wildlife-friendly pasture management systems. Utilizing systems like these on semi-natural grassland pastures can promote biodiversity conservation and ecosystem services while maintaining high levels of animal productivity. Despite literature on the topic as early as the mid-20th centuryReference Voisin14, the adoption of RG and MSP are far from widespread. The hypothesis is that portable electric plastic net fencing for RG and MSP systems can allow modern pastoralists to assist in the protection of Earth's biodiversity resources.
Dynamics of Grassland Ecosystems within Agricultural Landscapes
Natural grassland ecosystems occur throughout the world and are home to many speciesReference Primack3, Reference Watkinson and Ormerod7, Reference Nilsson9. In the wild, native grasses provide forage for herds of herbivores that move in dense groups across a large area, following desirable plant species throughout each plant's life cycle. This natural movement prevents overgrazing and allows grazed plant species to recover in the absence of their predators. Tall grasses provide shelter for ground-nesting birds that prefer habitats far from trees and buildings; it is also ideal habitat for arthropods and other invertebrates upon which these birds feast. There are instances, as with the cattle egret and domesticated cows, in which natural symbiotic relationships have developed among groups of domesticated herbivores and other grassland species. In general, pastureland research indicates that grazed pastures outperform non-grazed sites in overall species richnessReference Sollenberger, Agouridis, Vanzant, Franzluebbers and Owens15. Fertile soil characterizes many grassland environments, and holds rich microorganism biodiversity. Soil microorganisms provide numerous benefits to grassland ecosystems, such as transforming nutrients, breaking down organic matter, pest destruction and building soil aggregation. Agricultural practices, such as tilling, overgrazing and pesticide application have each contributed to the decline of soil microorganisms in agricultural areasReference Scherr and McNeely16. Grassland plants and soil also provide carbon sequestration as well as water and nutrient cycling. Across every region of the world, the biodiversity and ecosystem services provided by grasslands benefit farmers and ranchers as well as the general health of the planet.
Naturally occurring temperate grassland habitat has declined sharply at the hands of agriculture because the characteristics that grasslands possess make them desirable for the cultivation of food products by humansReference Primack3, Reference Watkinson and Ormerod7, Reference White, Murray and Rohweder17. Most significant to the decline of wildlife biodiversity is the alteration of species composition and changes to natural patterns of disturbance. Often in cropland systems, wild species are removed and replaced with a single domestic species, sometimes referred to as monoculture. This change in habitat, along with changes to disturbance patterns, can result in local extinction and emigration of native fauna. Developments in nitrogen-based fertilizers led the way for increases in plant productivity, but often at the cost of overall plant-species biodiversityReference Aguiar, Reynolds and Frame6, Reference Hopkins and Wilkins18. The introduction (both unintentional and intentional through cultivation) of non-native species has, in many cases, resulted in biodiversity losses. Unnatural grazing patterns facilitated by high livestock stocking rates has changed the species composition of grassland plants, necessitating supplemental sowing by ranchers of less diverse or non-native forages. Biodiversity is often used as a barometer for the overall health of an ecosystem, and so this decline would indicate a decrease in grassland health.
Despite all of this, it is worth noting that throughout human history, grassland habitats evolved with varying degrees of human use and often supported a wide range of species uniquely adapted to the semi-natural or agricultural grassland ecosystemReference Wrage, Strodthoff, Cuchillo, Isselstein and Kayser5. Organisms such as ground-nesting birds, pollinating arthropods, rodents and raptors continue to thrive in grassland environments under agricultural cultivation. Research on farmland in Europe and North America demonstrates a degree of biodiversity increase that has followed the development and maintenance of pasturelandReference Kumm8, Reference Budd and Thorpe19, Reference Tryjanowski, Hartel, Baldi, Szymanski, Tobolka, Herzon, Golawski, Konvicka, Hromada, Jerzak, Kujawa, Lenda, Orlowski, Panek, Skorka, Sparks, Tworek, Wuczynski and Zmihorski20. Although this land has been altered from its natural state, semi-natural grasslands continue to support a wide variety of wildlife and provide essential ecosystem services. In addition to the threat to natural grasslands, increasing human development also threatens semi-natural grasslands and cultivated pastures, thus applying further stresses on grassland species. Additional baseline studies quantifying wildlife biodiversity on agricultural landscapes could benefit future scientific studies of these habitats.
Negative effects of industrial agriculture on grassland ecosystems
Farmers value the health of the land as a matter of their livelihood. However, farmers also value productivity as a result of their efforts. The use of agricultural technologies such as nitrogen-based fertilizers, mechanized implements suited for large fields of single crops and advanced pesticides and herbicides have meant that production per unit of land has increased dramatically in the last century. This has allowed farmers and ranchers to condense livestock into smaller parcels of land and rely on supplements of grain grown from massive single-crop fields to raise meat animals. Unfortunately, these developments toward agricultural simplification have not been beneficial to the surrounding ecosystemReference Lemaire, Franzluebbers, de Faccio Carvalho and Dedieu21.
The application of chemical fertilizer changes the soil composition; runoff into local waterways creates a nutrient imbalance that can lead to eutrophication of waterways, which results in the overgrowth of plant-like organisms and oxygen depletion, creating ‘dead zones‘Reference White, Murray and Rohweder17, Reference Kremen, Iles and Bacon22. Additionally, converting natural grassland into cropland drastically and suddenly changes its characteristics as native vegetation is removed and soil is left vulnerable to erosionReference Aguiar, Reynolds and Frame6, Reference White, Murray and Rohweder17. As a result, cropland is often rendered unfavorable to native fauna that either perish or migrate to a more favorable habitat, thus decreasing local biodiversity. Additionally, high livestock density with uncontrolled, continuous grazing causes the disturbance of plant life without adequate recovery time and produces an overabundance of animal wasteReference White, Murray and Rohweder17. All of these approaches have negatively affected grassland ecosystems and the effects could be alleviated with conversion to biodiversity-friendly pasture systems.
Poorly managed grazing patterns of domesticated ruminants in the late 19th, and much of the 20th centuries resulted in damage to grassland environments. Overgrazing put stress on native grass populations and allowed for the spread of invasive species, either through supplemental sowing by humans or natural means. Bare patches in grasslands due to overgrazing and trampling causes enhanced nutrient runoff, release of greenhouse gasses and unacceptable rates of soil erosionReference Wrage, Strodthoff, Cuchillo, Isselstein and Kayser5. A reduction in forage height may leave a lack of desirable habitat for ground-nesting bird species and make them susceptible to increased predation. Low forage height can also make it more difficult for grassland plant species to recover, in contrast with forage that is allowed to recover over a period of timeReference Voisin14. A high stocking rate on managed grassland can result in excessive trampling of nest sites for ground-nesting birdsReference Undersander, Temple, Bartlet, Sampel and Paine23. Although a variety of grazing techniques have allowed some degree of rebound for these ecosystems, an increase in demand for meat may result in the need for more intensively managed pasture and is sure to further stress these ecosystems to a point that is even more ecologically damaging. Further study of the effects of specific agricultural practices on local biodiversity would provide data to better inform interested farmers and conservationists.
Benefits of established pastures on grassland ecosystems
Despite some negative effects to biodiversity with the loss of native grassland, there is evidence that using semi-natural permanent pasture for livestock grazing can positively affect biodiversity. Grazing can have a positive effect on grassland preservation and overall biodiversity within the landscape by allowing field plants to flower and go to seedReference Wrage, Strodthoff, Cuchillo, Isselstein and Kayser5, Reference Nilsson9, Reference Ignatiuk and Duncan24, Reference O'Connor, Kuyler, Kirkman and Corcoran25. This supports biodiversity of native, self-seeding plants and reduces the need for artificial sowing, helping to preserve the most natural state of grassland possible. Permanent pasture preserves species richness to a higher degree than intensively managed livestock operations or monoculture crop fields cultivated to supplement the diet of livestock raised off-pasture, particularly in regard to arthropod species (grasshoppers, butterflies and Heteroptera) studied on active pasturesReference Watkinson and Ormerod7, Reference Wallis De Vries, Parkinson, Dulphy, Sayer and Diana26, Reference Di Giulio, Holderegger and Tobias27. A study completed in the plains of central Canada determined that pastures grazed throughout the grazing season may enhance biodiversity over pastures left ungrazed because the grazing behavior of animals creates microhabitats within the pastureland that would not otherwise existReference Ranellucci, Koper and Henderson28. Herbaceous vegetation in the grassland ecosystem contributes to carbon sequestration, primarily below ground, as grassland plants store a significant amount of carbon in extensive root systems and are not negatively affected by most grazing systemsReference Sherr11, Reference White, Murray and Rohweder17. Permanent pasture systems allow the recovery of vegetation, stabilize the soil and do not disrupt the carbon stores in a significant way.
Tools for Pasture Management
Portable electric fences
Electrically charged fences have existed for more than 100 years in one form or another. Mentions of the technology occur in literature as early as 1870 and the first US patent was issued in 1886. Useful practical applications came during World War I and in the 1930s for agricultural uses. Electric fences have come a long way since then. Typical electric fences utilize permanent wood or metal posts with conducting wire wrapped around a plastic or ceramic insulator. Often, permanent electric fences are connected to a power source that ties into the electrical power grid. These fences are beneficial because they are less expensive and can be built to withstand less pressure than non-electric fencing.
A technology for temporary electric fencing developed in the 1990s consists of stainless steel wire woven into a plastic mesh grid that attaches to plastic step-in posts. These fences can be installed, taken down and moved within a matter of minutes. To preserve their portable nature, small solar or battery powered charging units were developed alongside the technology. These units are weatherproof and about the size of a briefcase. This technology is relatively inexpensive (<US$200 for 165′ of fence), and because of its portability, is well suited to rotational pasture systems.
RG and MSPs are among the most popular pasture management systems for the use of portable electric fences. Many farmers choose permanent fence for their property line and use portable electric fence to divide a large pasture into a small paddock as needed. Others, especially those just beginning to raise livestock, are able to rotate stock around a large sward without committing to the expense of permanently fencing an entire pasture. Additionally, subsistence farmers in rural areas or the developing world may take advantage of the solar nature of this fencing system when reliable electric power is not available.
Rotational grazing
RG is one strategy that helps to preserve the health and biodiversity of the grassland ecosystem. In RG, the pasture is separated into at least two, and sometimes up to 100, paddocks and livestock are systematically moved from one paddock to another, allowing the grazed paddock to rest for a sufficient period before being grazed again. Paddock division using permanent fences is often cost prohibitive for small and beginning farmers. Division into temporary paddocks can be accomplished using portable electric fencing with less resource input. Therefore, RG provides benefits to both the ecosystem and the farmer.
RG, when practiced responsibly, can serve as an avenue toward increasing the species richness and ecological health of a managed grassland. This stocking method can result in a 30% advantage in forage production, which could allow for greater carrying capacity of the pasture or greater animal performanceReference Voisin14, Reference Sollenberger, Agouridis, Vanzant, Franzluebbers and Owens15. Portable electric fencing allows paddocks to be configured in the most flexible manner possible with the least time commitment to the farmer, thus incorporating both efficiency and ease of use.
Species composition
Qualities of RG systems have been shown to positively contribute to increased species richness on the landscapes they occupy. Biodiversity increased when Mediterranean pastures contained grazing-excluded plots, a quality inherent in RG systemsReference Bugalho, Lecomte, Goncalves, Caldiera and Branco29. This was true of various species, including density and species richness of bumblebees and butterflies found on sheep pastures in Central FranceReference Scohier, Ouin, Farruggia and Dumont30. Two species of ground-nesting birds in Vermont experienced greater reproductive success within RG systems when rest time between grazing periods was extendedReference Perlut and Strong31. When pastures were planted with a greater number of native species at an agricultural research facility in the loess hills region of Iowa, the USA, animal production, plant production, biodiversity and value from ecosystem services were increasedReference Isbell and Wilsey32. These specific cases suggest that RG systems may benefit biodiversity on a larger scale and further study is warranted.
Wildlife habitat
Wildlife habitat improves when rotational stocking is practiced. Greater connectivity among microhabitats was observed due to seed dispersal by ruminants on RG systems in BavariaReference Rico, Boehmer and Wagner33. RG results in decreased soil erosion and less pasture runoff than other forms of high- and medium-density stocking, the results of which contribute to an increase in the health of both the pasture and the surrounding ecosystemReference Undersander, Temple, Bartlet, Sampel and Paine23. In riparian ecosystems in the USA, RG systems have been shown to positively affect aquatic habitats, resulting in larger substrate size and increased stability of stream banks, all of which have the potential to facilitate greater macro-invertebrate diversityReference Raymond and Vondracek34. RG systems have even been suggested to moderately reduce greenhouse gas emissions and increase carbon sequestrationReference Bosch, Stephenson, Groover and Hutchins35, Reference Manning36.
Multi-species pasture
As an add-on to the RG philosophy, an MSP system combines the movement of an RG system with multiple domestic species. Designed as a way to mimic symbiotic patterns in natural grasslands, animals are rotationally pastured so that one species is introduced to a paddock after another has been removed. This kind of stacked pasture, specifically when poultry follow ruminants, provides for numerous ecosystem and livestock benefitsReference Baumann37. First, ruminants decrease forage height as they graze, allowing for ease of movement and foraging by the birds. Secondly, the dung left behind by grazing ruminants attracts insects and consequently their offspring in the form of grubs. Finally, in the process of foraging, the birds scratch through the dung, distributing it over the pasture for optimal absorption of nutrients into the soil and a decrease in the presence of parasitesReference Thomas38. This method effectively ‘cleans’ the pasture following a grazing episode, increases the production value for a given sward and enhances, rather than harms, the ecological performance of the pasture. Additionally, different species may choose to graze on the specific plants, resulting in greater efficiency for a given pasture space if forages are selected specific to the species present. Diversity in pasture management systems provides benefits in both farm production quantities as well as off-farm factors that positively affect the sustainability of the surrounding ecologyReference Vandermeer, van Noordwijk, Anderson, Ong and Perfecto39. Portable electric fencing can make this type of management system easier on the farmer because the flexibility of a temporary paddock can allow the farmer to make decisions based on changing ecological conditions.
Criticism of RG Systems
The most controversial aspect of this system is a body of evidence that demonstrates little difference between animal performance and plant production in rotational and continuous grazing systemsReference Ranellucci, Koper and Henderson28, Reference Bailey and Brown40–Reference Dorrough, McIntyre, Brown, Stol, Barrett and Brown42. All but one of these studies, though, focuses on livestock productivity and/or productivity and biodiversity of forage grass, but not the complete species biodiversity of the pasture and surrounding area, including wildlife. A study in Manitoba, Canada investigated the richness and abundance of songbird species on rangeland and found no difference between the treatments of rotational and continuous grazingReference Ranellucci, Koper and Henderson28.
Many of the studies referenced in this paper conclude a need for additional study on the effect of pasture management systems on wildlife biodiversity. Some criticize highly controlled experiments as poor reflections on the complex nature of ecosystems found on active farmlandReference Scherr and McNeely2, Reference Wrage, Strodthoff, Cuchillo, Isselstein and Kayser5, Reference Budd and Thorpe19, Reference Ranellucci, Koper and Henderson28, Reference Briske, Sayre, Huntsinger, Fernandez-Giminez, Budd and Derner43, Reference Teague, Dowhower, Baker, Ansley, Kreuter, Conover and Waggoner44. Additionally, many of these studies were conducted on arid ecosystems and expansive rangesReference O'Connor, Kuyler, Kirkman and Corcoran25, Reference Briske, Derner, Brown, Fuhlendorf, Teague, Havstad, Gillen, Ash and Willms41, Reference Dorrough, McIntyre, Brown, Stol, Barrett and Brown42. Considering the vast diversity in grassland climates and the fact that many extension offices are located in more humid temperate climatesReference Undersander, Temple, Bartlet, Sampel and Paine23, Reference Russell and Dunn45–48 and organizations advocating sustainable agricultureReference Vandermeer, van Noordwijk, Anderson, Ong and Perfecto39, Reference Russell and Dunn47, 48 continue to recommend RG and MSP systems, these methods are worth continuing to study as a means to foster biodiversity on active pastures.
Conclusion
Portable electric fencing provides an easy, cost-effective way for farmers to graze single- or multi-species livestock rotationally on permanent pasture. Unfortunately, livestock grazers have not universally adopted this potentially effective system. This could be due to the significant commitment of time and money required for permanent fencing systems, or to contradicting scientific findings regarding the benefits of RG systems on animal productivity. Advances in portable electric fencing have the ability to make adopting RG and MSP systems more attractive to farmers with limited acreage and those entering the livestock business. A growing body of research has suggested RG systems as a way to promote pasture healthReference Wrage, Strodthoff, Cuchillo, Isselstein and Kayser5, Reference Undersander, Temple, Bartlet, Sampel and Paine23, Reference Baumann37, Reference Thomas38, Reference Teague, Dowhower, Baker, Ansley, Kreuter, Conover and Waggoner44, increase species richness within the pasture and throughout the surrounding ecosystemReference Wrage, Strodthoff, Cuchillo, Isselstein and Kayser5, Reference Bugalho, Lecomte, Goncalves, Caldiera and Branco29–Reference Isbell and Wilsey32, Reference Cerezo, Conde and Poggio49, and provide numerous ecosystem services to benefit humans and wildlifeReference Wrage, Strodthoff, Cuchillo, Isselstein and Kayser5, Reference Isbell and Wilsey32–Reference Manning36. Additional study of active farmland in a variety of climates is necessary if there is to be increased adoption of RG and MSP systems worldwide, and portable electric fencing is one tool to aid in such research.
Though farmland has not historically been considered a landscape to be preserved for ecological conservation, farmers and conservationists are going to have to find common ground as the amount of land available for each purpose continues to decline. Increasing world populations, and consequently increasing demands on food systems, will require farmers to consider their ecological impact if global biodiversity loss is to be slowed. Popular or not, farmland will become a valuable commodity for conservation; technologies like portable electric fencing will make it easier for more farmers to adopt biodiversity-friendly practices.
Most significant throughout the course of this topical review was the lack of peer-reviewed study directly related to the ecological benefits of RG and MSP conducted in an active and dynamic agricultural setting. If conservationists and agriculturalists alike are to take biodiversity preservation on farmland seriously and invest time and resources into practices that can promote species richness, dedicated and further study of the complex nature of this topic is necessary. The introduction of flexible technologies such as portable electric fencing is likely to make both the practice and research of RG and MSP systems more feasible.
Introduction
The United Nations1 expects the world's human population to rise to 9 billion by 2050—and each of these people needs to eat. Currently, agricultural use comprises up to 50% of the world's land and more will surely become subject to conversionReference Scherr and McNeely2. Habitat fragmentation is a primary cause of biodiversity loss at the landscape level, often occurring in conjunction with agricultural useReference Primack3. With more pressure on land resources due to increasing agricultural demand, it is likely that the planet's biodiversity will continue to suffer. Regions where population growth is expected to make the sharpest increases lie in designated biodiversity hotspots, or areas with large concentrations of ecologically threatened speciesReference Meyers, Mittermeier, Mittermeier, da Fonseca and Kent4, Reference Wrage, Strodthoff, Cuchillo, Isselstein and Kayser5. This presents a concern for the preservation of nature and biodiversity in these regions. Without an agricultural system that maximizes productivity while supporting habitat for diverse wildlife, the biodiversity of the planet will continue to decline at an alarming rateReference Aguiar, Reynolds and Frame6. Essentially, the planet is running out of land for food production and humans will be faced with the choice of preserving either food systems or wildlife biodiversity—unless we can choose both.
Farms, often comprised of acres of open fields, have the potential to play a key role in the preservation of grassland ecosystems. Grassland communities, spread across the globe, are increasingly threatened by human development, urban sprawl and even natural succession when farmland is abandonedReference Watkinson and Ormerod7. Although some environmentalists may consider the semi-natural grassland found on farmland in conflict with native grassland species, preservation of agricultural land is crucial because the current state of biodiversity in these areas has evolved along with the human development of farmlandReference Wrage, Strodthoff, Cuchillo, Isselstein and Kayser5, Reference Kumm8. Therefore, proper management of semi-natural pastures on working farms can play an active role in providing habitat to threatened grassland speciesReference Watkinson and Ormerod7, Reference Nilsson9.
Despite encompassing such a large portion of inhabitable land, farms (and the farmers who operate them) have been largely absent from the conversation regarding wildlife biodiversity conservationReference Scherr and McNeely2, Reference Berry10. Yet, farmers and ranchers have the opportunity to affect biodiversity preservation, soil conservation and climate change more than any other groupReference Sherr11. As global demand for agricultural products increases, farmers and environmentalists must collaborate for the benefit of the ecosystems upon which so many organisms rely. Farmers can contribute to the planet's biodiversity by adopting practices designed to preserve the species richness conserved within and surrounding their farmlandReference Jackson, Pascual and Hodgkin12, Reference Smeding and Joenje13.
This commentary explores the basis for portable electric-net fencing as a tool for the implementation of rotational grazing (RG) and multi-species pastures (MSPs) as wildlife-friendly pasture management systems. Utilizing systems like these on semi-natural grassland pastures can promote biodiversity conservation and ecosystem services while maintaining high levels of animal productivity. Despite literature on the topic as early as the mid-20th centuryReference Voisin14, the adoption of RG and MSP are far from widespread. The hypothesis is that portable electric plastic net fencing for RG and MSP systems can allow modern pastoralists to assist in the protection of Earth's biodiversity resources.
Dynamics of Grassland Ecosystems within Agricultural Landscapes
Natural grassland ecosystems occur throughout the world and are home to many speciesReference Primack3, Reference Watkinson and Ormerod7, Reference Nilsson9. In the wild, native grasses provide forage for herds of herbivores that move in dense groups across a large area, following desirable plant species throughout each plant's life cycle. This natural movement prevents overgrazing and allows grazed plant species to recover in the absence of their predators. Tall grasses provide shelter for ground-nesting birds that prefer habitats far from trees and buildings; it is also ideal habitat for arthropods and other invertebrates upon which these birds feast. There are instances, as with the cattle egret and domesticated cows, in which natural symbiotic relationships have developed among groups of domesticated herbivores and other grassland species. In general, pastureland research indicates that grazed pastures outperform non-grazed sites in overall species richnessReference Sollenberger, Agouridis, Vanzant, Franzluebbers and Owens15. Fertile soil characterizes many grassland environments, and holds rich microorganism biodiversity. Soil microorganisms provide numerous benefits to grassland ecosystems, such as transforming nutrients, breaking down organic matter, pest destruction and building soil aggregation. Agricultural practices, such as tilling, overgrazing and pesticide application have each contributed to the decline of soil microorganisms in agricultural areasReference Scherr and McNeely16. Grassland plants and soil also provide carbon sequestration as well as water and nutrient cycling. Across every region of the world, the biodiversity and ecosystem services provided by grasslands benefit farmers and ranchers as well as the general health of the planet.
Naturally occurring temperate grassland habitat has declined sharply at the hands of agriculture because the characteristics that grasslands possess make them desirable for the cultivation of food products by humansReference Primack3, Reference Watkinson and Ormerod7, Reference White, Murray and Rohweder17. Most significant to the decline of wildlife biodiversity is the alteration of species composition and changes to natural patterns of disturbance. Often in cropland systems, wild species are removed and replaced with a single domestic species, sometimes referred to as monoculture. This change in habitat, along with changes to disturbance patterns, can result in local extinction and emigration of native fauna. Developments in nitrogen-based fertilizers led the way for increases in plant productivity, but often at the cost of overall plant-species biodiversityReference Aguiar, Reynolds and Frame6, Reference Hopkins and Wilkins18. The introduction (both unintentional and intentional through cultivation) of non-native species has, in many cases, resulted in biodiversity losses. Unnatural grazing patterns facilitated by high livestock stocking rates has changed the species composition of grassland plants, necessitating supplemental sowing by ranchers of less diverse or non-native forages. Biodiversity is often used as a barometer for the overall health of an ecosystem, and so this decline would indicate a decrease in grassland health.
Despite all of this, it is worth noting that throughout human history, grassland habitats evolved with varying degrees of human use and often supported a wide range of species uniquely adapted to the semi-natural or agricultural grassland ecosystemReference Wrage, Strodthoff, Cuchillo, Isselstein and Kayser5. Organisms such as ground-nesting birds, pollinating arthropods, rodents and raptors continue to thrive in grassland environments under agricultural cultivation. Research on farmland in Europe and North America demonstrates a degree of biodiversity increase that has followed the development and maintenance of pasturelandReference Kumm8, Reference Budd and Thorpe19, Reference Tryjanowski, Hartel, Baldi, Szymanski, Tobolka, Herzon, Golawski, Konvicka, Hromada, Jerzak, Kujawa, Lenda, Orlowski, Panek, Skorka, Sparks, Tworek, Wuczynski and Zmihorski20. Although this land has been altered from its natural state, semi-natural grasslands continue to support a wide variety of wildlife and provide essential ecosystem services. In addition to the threat to natural grasslands, increasing human development also threatens semi-natural grasslands and cultivated pastures, thus applying further stresses on grassland species. Additional baseline studies quantifying wildlife biodiversity on agricultural landscapes could benefit future scientific studies of these habitats.
Negative effects of industrial agriculture on grassland ecosystems
Farmers value the health of the land as a matter of their livelihood. However, farmers also value productivity as a result of their efforts. The use of agricultural technologies such as nitrogen-based fertilizers, mechanized implements suited for large fields of single crops and advanced pesticides and herbicides have meant that production per unit of land has increased dramatically in the last century. This has allowed farmers and ranchers to condense livestock into smaller parcels of land and rely on supplements of grain grown from massive single-crop fields to raise meat animals. Unfortunately, these developments toward agricultural simplification have not been beneficial to the surrounding ecosystemReference Lemaire, Franzluebbers, de Faccio Carvalho and Dedieu21.
The application of chemical fertilizer changes the soil composition; runoff into local waterways creates a nutrient imbalance that can lead to eutrophication of waterways, which results in the overgrowth of plant-like organisms and oxygen depletion, creating ‘dead zones‘Reference White, Murray and Rohweder17, Reference Kremen, Iles and Bacon22. Additionally, converting natural grassland into cropland drastically and suddenly changes its characteristics as native vegetation is removed and soil is left vulnerable to erosionReference Aguiar, Reynolds and Frame6, Reference White, Murray and Rohweder17. As a result, cropland is often rendered unfavorable to native fauna that either perish or migrate to a more favorable habitat, thus decreasing local biodiversity. Additionally, high livestock density with uncontrolled, continuous grazing causes the disturbance of plant life without adequate recovery time and produces an overabundance of animal wasteReference White, Murray and Rohweder17. All of these approaches have negatively affected grassland ecosystems and the effects could be alleviated with conversion to biodiversity-friendly pasture systems.
Poorly managed grazing patterns of domesticated ruminants in the late 19th, and much of the 20th centuries resulted in damage to grassland environments. Overgrazing put stress on native grass populations and allowed for the spread of invasive species, either through supplemental sowing by humans or natural means. Bare patches in grasslands due to overgrazing and trampling causes enhanced nutrient runoff, release of greenhouse gasses and unacceptable rates of soil erosionReference Wrage, Strodthoff, Cuchillo, Isselstein and Kayser5. A reduction in forage height may leave a lack of desirable habitat for ground-nesting bird species and make them susceptible to increased predation. Low forage height can also make it more difficult for grassland plant species to recover, in contrast with forage that is allowed to recover over a period of timeReference Voisin14. A high stocking rate on managed grassland can result in excessive trampling of nest sites for ground-nesting birdsReference Undersander, Temple, Bartlet, Sampel and Paine23. Although a variety of grazing techniques have allowed some degree of rebound for these ecosystems, an increase in demand for meat may result in the need for more intensively managed pasture and is sure to further stress these ecosystems to a point that is even more ecologically damaging. Further study of the effects of specific agricultural practices on local biodiversity would provide data to better inform interested farmers and conservationists.
Benefits of established pastures on grassland ecosystems
Despite some negative effects to biodiversity with the loss of native grassland, there is evidence that using semi-natural permanent pasture for livestock grazing can positively affect biodiversity. Grazing can have a positive effect on grassland preservation and overall biodiversity within the landscape by allowing field plants to flower and go to seedReference Wrage, Strodthoff, Cuchillo, Isselstein and Kayser5, Reference Nilsson9, Reference Ignatiuk and Duncan24, Reference O'Connor, Kuyler, Kirkman and Corcoran25. This supports biodiversity of native, self-seeding plants and reduces the need for artificial sowing, helping to preserve the most natural state of grassland possible. Permanent pasture preserves species richness to a higher degree than intensively managed livestock operations or monoculture crop fields cultivated to supplement the diet of livestock raised off-pasture, particularly in regard to arthropod species (grasshoppers, butterflies and Heteroptera) studied on active pasturesReference Watkinson and Ormerod7, Reference Wallis De Vries, Parkinson, Dulphy, Sayer and Diana26, Reference Di Giulio, Holderegger and Tobias27. A study completed in the plains of central Canada determined that pastures grazed throughout the grazing season may enhance biodiversity over pastures left ungrazed because the grazing behavior of animals creates microhabitats within the pastureland that would not otherwise existReference Ranellucci, Koper and Henderson28. Herbaceous vegetation in the grassland ecosystem contributes to carbon sequestration, primarily below ground, as grassland plants store a significant amount of carbon in extensive root systems and are not negatively affected by most grazing systemsReference Sherr11, Reference White, Murray and Rohweder17. Permanent pasture systems allow the recovery of vegetation, stabilize the soil and do not disrupt the carbon stores in a significant way.
Tools for Pasture Management
Portable electric fences
Electrically charged fences have existed for more than 100 years in one form or another. Mentions of the technology occur in literature as early as 1870 and the first US patent was issued in 1886. Useful practical applications came during World War I and in the 1930s for agricultural uses. Electric fences have come a long way since then. Typical electric fences utilize permanent wood or metal posts with conducting wire wrapped around a plastic or ceramic insulator. Often, permanent electric fences are connected to a power source that ties into the electrical power grid. These fences are beneficial because they are less expensive and can be built to withstand less pressure than non-electric fencing.
A technology for temporary electric fencing developed in the 1990s consists of stainless steel wire woven into a plastic mesh grid that attaches to plastic step-in posts. These fences can be installed, taken down and moved within a matter of minutes. To preserve their portable nature, small solar or battery powered charging units were developed alongside the technology. These units are weatherproof and about the size of a briefcase. This technology is relatively inexpensive (<US$200 for 165′ of fence), and because of its portability, is well suited to rotational pasture systems.
RG and MSPs are among the most popular pasture management systems for the use of portable electric fences. Many farmers choose permanent fence for their property line and use portable electric fence to divide a large pasture into a small paddock as needed. Others, especially those just beginning to raise livestock, are able to rotate stock around a large sward without committing to the expense of permanently fencing an entire pasture. Additionally, subsistence farmers in rural areas or the developing world may take advantage of the solar nature of this fencing system when reliable electric power is not available.
Rotational grazing
RG is one strategy that helps to preserve the health and biodiversity of the grassland ecosystem. In RG, the pasture is separated into at least two, and sometimes up to 100, paddocks and livestock are systematically moved from one paddock to another, allowing the grazed paddock to rest for a sufficient period before being grazed again. Paddock division using permanent fences is often cost prohibitive for small and beginning farmers. Division into temporary paddocks can be accomplished using portable electric fencing with less resource input. Therefore, RG provides benefits to both the ecosystem and the farmer.
RG, when practiced responsibly, can serve as an avenue toward increasing the species richness and ecological health of a managed grassland. This stocking method can result in a 30% advantage in forage production, which could allow for greater carrying capacity of the pasture or greater animal performanceReference Voisin14, Reference Sollenberger, Agouridis, Vanzant, Franzluebbers and Owens15. Portable electric fencing allows paddocks to be configured in the most flexible manner possible with the least time commitment to the farmer, thus incorporating both efficiency and ease of use.
Species composition
Qualities of RG systems have been shown to positively contribute to increased species richness on the landscapes they occupy. Biodiversity increased when Mediterranean pastures contained grazing-excluded plots, a quality inherent in RG systemsReference Bugalho, Lecomte, Goncalves, Caldiera and Branco29. This was true of various species, including density and species richness of bumblebees and butterflies found on sheep pastures in Central FranceReference Scohier, Ouin, Farruggia and Dumont30. Two species of ground-nesting birds in Vermont experienced greater reproductive success within RG systems when rest time between grazing periods was extendedReference Perlut and Strong31. When pastures were planted with a greater number of native species at an agricultural research facility in the loess hills region of Iowa, the USA, animal production, plant production, biodiversity and value from ecosystem services were increasedReference Isbell and Wilsey32. These specific cases suggest that RG systems may benefit biodiversity on a larger scale and further study is warranted.
Wildlife habitat
Wildlife habitat improves when rotational stocking is practiced. Greater connectivity among microhabitats was observed due to seed dispersal by ruminants on RG systems in BavariaReference Rico, Boehmer and Wagner33. RG results in decreased soil erosion and less pasture runoff than other forms of high- and medium-density stocking, the results of which contribute to an increase in the health of both the pasture and the surrounding ecosystemReference Undersander, Temple, Bartlet, Sampel and Paine23. In riparian ecosystems in the USA, RG systems have been shown to positively affect aquatic habitats, resulting in larger substrate size and increased stability of stream banks, all of which have the potential to facilitate greater macro-invertebrate diversityReference Raymond and Vondracek34. RG systems have even been suggested to moderately reduce greenhouse gas emissions and increase carbon sequestrationReference Bosch, Stephenson, Groover and Hutchins35, Reference Manning36.
Multi-species pasture
As an add-on to the RG philosophy, an MSP system combines the movement of an RG system with multiple domestic species. Designed as a way to mimic symbiotic patterns in natural grasslands, animals are rotationally pastured so that one species is introduced to a paddock after another has been removed. This kind of stacked pasture, specifically when poultry follow ruminants, provides for numerous ecosystem and livestock benefitsReference Baumann37. First, ruminants decrease forage height as they graze, allowing for ease of movement and foraging by the birds. Secondly, the dung left behind by grazing ruminants attracts insects and consequently their offspring in the form of grubs. Finally, in the process of foraging, the birds scratch through the dung, distributing it over the pasture for optimal absorption of nutrients into the soil and a decrease in the presence of parasitesReference Thomas38. This method effectively ‘cleans’ the pasture following a grazing episode, increases the production value for a given sward and enhances, rather than harms, the ecological performance of the pasture. Additionally, different species may choose to graze on the specific plants, resulting in greater efficiency for a given pasture space if forages are selected specific to the species present. Diversity in pasture management systems provides benefits in both farm production quantities as well as off-farm factors that positively affect the sustainability of the surrounding ecologyReference Vandermeer, van Noordwijk, Anderson, Ong and Perfecto39. Portable electric fencing can make this type of management system easier on the farmer because the flexibility of a temporary paddock can allow the farmer to make decisions based on changing ecological conditions.
Criticism of RG Systems
The most controversial aspect of this system is a body of evidence that demonstrates little difference between animal performance and plant production in rotational and continuous grazing systemsReference Ranellucci, Koper and Henderson28, Reference Bailey and Brown40–Reference Dorrough, McIntyre, Brown, Stol, Barrett and Brown42. All but one of these studies, though, focuses on livestock productivity and/or productivity and biodiversity of forage grass, but not the complete species biodiversity of the pasture and surrounding area, including wildlife. A study in Manitoba, Canada investigated the richness and abundance of songbird species on rangeland and found no difference between the treatments of rotational and continuous grazingReference Ranellucci, Koper and Henderson28.
Many of the studies referenced in this paper conclude a need for additional study on the effect of pasture management systems on wildlife biodiversity. Some criticize highly controlled experiments as poor reflections on the complex nature of ecosystems found on active farmlandReference Scherr and McNeely2, Reference Wrage, Strodthoff, Cuchillo, Isselstein and Kayser5, Reference Budd and Thorpe19, Reference Ranellucci, Koper and Henderson28, Reference Briske, Sayre, Huntsinger, Fernandez-Giminez, Budd and Derner43, Reference Teague, Dowhower, Baker, Ansley, Kreuter, Conover and Waggoner44. Additionally, many of these studies were conducted on arid ecosystems and expansive rangesReference O'Connor, Kuyler, Kirkman and Corcoran25, Reference Briske, Derner, Brown, Fuhlendorf, Teague, Havstad, Gillen, Ash and Willms41, Reference Dorrough, McIntyre, Brown, Stol, Barrett and Brown42. Considering the vast diversity in grassland climates and the fact that many extension offices are located in more humid temperate climatesReference Undersander, Temple, Bartlet, Sampel and Paine23, Reference Russell and Dunn45–48 and organizations advocating sustainable agricultureReference Vandermeer, van Noordwijk, Anderson, Ong and Perfecto39, Reference Russell and Dunn47, 48 continue to recommend RG and MSP systems, these methods are worth continuing to study as a means to foster biodiversity on active pastures.
Conclusion
Portable electric fencing provides an easy, cost-effective way for farmers to graze single- or multi-species livestock rotationally on permanent pasture. Unfortunately, livestock grazers have not universally adopted this potentially effective system. This could be due to the significant commitment of time and money required for permanent fencing systems, or to contradicting scientific findings regarding the benefits of RG systems on animal productivity. Advances in portable electric fencing have the ability to make adopting RG and MSP systems more attractive to farmers with limited acreage and those entering the livestock business. A growing body of research has suggested RG systems as a way to promote pasture healthReference Wrage, Strodthoff, Cuchillo, Isselstein and Kayser5, Reference Undersander, Temple, Bartlet, Sampel and Paine23, Reference Baumann37, Reference Thomas38, Reference Teague, Dowhower, Baker, Ansley, Kreuter, Conover and Waggoner44, increase species richness within the pasture and throughout the surrounding ecosystemReference Wrage, Strodthoff, Cuchillo, Isselstein and Kayser5, Reference Bugalho, Lecomte, Goncalves, Caldiera and Branco29–Reference Isbell and Wilsey32, Reference Cerezo, Conde and Poggio49, and provide numerous ecosystem services to benefit humans and wildlifeReference Wrage, Strodthoff, Cuchillo, Isselstein and Kayser5, Reference Isbell and Wilsey32–Reference Manning36. Additional study of active farmland in a variety of climates is necessary if there is to be increased adoption of RG and MSP systems worldwide, and portable electric fencing is one tool to aid in such research.
Though farmland has not historically been considered a landscape to be preserved for ecological conservation, farmers and conservationists are going to have to find common ground as the amount of land available for each purpose continues to decline. Increasing world populations, and consequently increasing demands on food systems, will require farmers to consider their ecological impact if global biodiversity loss is to be slowed. Popular or not, farmland will become a valuable commodity for conservation; technologies like portable electric fencing will make it easier for more farmers to adopt biodiversity-friendly practices.
Most significant throughout the course of this topical review was the lack of peer-reviewed study directly related to the ecological benefits of RG and MSP conducted in an active and dynamic agricultural setting. If conservationists and agriculturalists alike are to take biodiversity preservation on farmland seriously and invest time and resources into practices that can promote species richness, dedicated and further study of the complex nature of this topic is necessary. The introduction of flexible technologies such as portable electric fencing is likely to make both the practice and research of RG and MSP systems more feasible.
Acknowledgements
Miami University, Oxford, Ohio, USA and the Global Field Program, a graduate program furthering the aims of global conservation and education worldwide, supported this work. The author recognizes assistance from Miami University instructors and colleagues as well as the helpful comments from two anonymous reviewers.