Year: 2019
Type: article
Abstract: Sustainable livestock systems contribute to food security, economic and environmental stewardship, and sociocultural needs and are vital for achieving most of the United Nation’s Sustainable Development Goals. Livestock production contributes to sustainability through use of uncultivable land for food production, conversion of energy and protein sources that cannot be used by humans into highly nutritious animal-sourced food and reduction of environmental pollution with agroindustrial by-products, while generating income and supporting livelihoods of millions of people all over the world. Some livestock systems are particularly effective at carbon sequestration and hence reducing greenhouse gas emissions that contribute to global warming. Livestock production offers the greatest potential to reduce greenhouse gas emissions from agriculture and animal scientists have devised several effective strategies that can reduce such emissions from livestock systems by up to 30%. Most of the current discourse on sustainability focuses on one albeit important factor—the environment. Equally important factors are the need to ensure food and nutritional security for the growing global population in a culturally acceptable manner that ensures its accessibility, affordability, and safety. While livestock systems generally contribute to sustainability, poorly managed livestock systems may have adverse effects on the environment and human and animal health and welfare. The most common words associated with sustainability are “environment,” “social,” and “economic.” Thus, sustainability is a holistic concept that jointly considers ecological, social, and economic dimensions of a system or intervention for long-lasting prosperity. Experience shows that economic development at the cost of ecology does not last; therefore, it is critical to harmonize ecology with development. This also applies to livestock systems, which should be economically viable for farmers, environmentally friendly or at least neutral, and socially acceptable in order to be considered sustainable. There are different types of livestock production systems, depending on availability of resources, environmental conditions, and social and economic contexts, and they vary considerably in sustainability. These livestock systems include the grassland-based extensive systems, intensive landless systems, and mixed farming systems among others. These systems contribute significantly to human nutrition and livelihoods and provide important ecosystem services. However, if not properly managed, they can also cause nutrient and environmental pollution and land degradation. With increasing global awareness about climate change and studies indicating that livestock is one of the contributors to greenhouse gases, environmental degradation, and loss of biodiversity, various concerted efforts have been aimed at developing and or ensuring the sustainability of livestock systems that deliver economic and ecosystems services without compromising the future integrity, health, and welfare of the environment, humans, and animals. Increasing competition for the requisite resources for feed and food production, especially under more intensive livestock production systems, has raised concerns about the economic and environmental sustainability of some livestock production systems. Feed production and processing, and enteric fermentation of feed contribute to 45% and 39%, respectively, of the total emissions from agriculture (Steinfeld et al., 2006). About 90% of livestock emissions are produced by ruminants through enteric fermentation (188 million tons) and the remaining 10% from manure (Swamy and Bhattacharya, 2006). In addition, inadequately managed livestock production systems may cause negative environmental consequences such as eutrophication in intensive high input systems, overgrazing, and soil and rangeland degradation in extensive systems and negative human health outcomes. Even though inadequately managed livestock systems may have adverse effects on the environment, widely quoted statistics about their contribution are misleading. Most do not reflect the diversity of livestock production systems nor differences between production systems dominant in various countries even for a given species. For instance, an often-cited statistic is that livestock contribute 18% of greenhouse gases globally (Steinfeld et al., 2006), more than that for the transportation industry, but that analysis is incorrect and has been corrected by the authors (Mottet and Steinfeld, 2018). Moreover, interventions can help reduce the carbon footprint of livestock production, while improving productivity. For example, with improved management and feeding strategies, the carbon footprint per billion kilograms of beef produced in 2007 was reduced by 16.3% compared with equivalent beef production in 1977 (Capper, 2011). When comparing greenhouse gas emissions of various livestock production systems, it is critical to take the need for environmental stewardship as well as food security into account to ensure the sustainability of the system. An index which takes both into account is the emissions intensity measure, which relates greenhouse gas emissions to food produced by the system. This important index shows that methane production per unit of food produced in several low- and middle-income countries is much greater than in some developed countries (Figure 1). This does not imply that the production systems in the developed countries should be copied entirely by low- and middle-income countries; rather, each country should evaluate and implement the aspects of developed country production systems that will sustainably intensify their production systems and thereby increase food production while reducing greenhouse gas emissions. Regional variation in greenhouse gas emission intensities. Reprinted with permission from “Tackling climate change through livestock—A global assessment of emissions and mitigation opportunities” (Gerber et al., 2013). Often ignored is the fact that livestock systems contribute to global sustainability by providing various ecosystem services. For instance, a recent meta-analysis of 86 studies that examined various agroforestry systems revealed that net accumulation of soil carbon or sink of greenhouse gases was greatest when grassland was converted to silvo-pastures combining trees, forage, and livestock (Feliciano et al., 2018). Land maintained for livestock grazing has lower greenhouse gas emission than the same land converted for crop production. Rates of soil loss in U.S. croplands are more than four times that of grazing lands. Grazing lands sequester more carbon per unit area compared with cultivated croplands (Diaz et al., 2012). Furthermore, globally more than half (57%) of the 2.5 billion hectares of land used for producing forage is unsuitable for food production (Mottet et al., 2017). Thus, forage crops make productive use of noncultivable land. In addition, since only 14% of the feed consumed by livestock is edible by humans, the remaining 86%, including by-products, crop residues, and grasses or fodder, is converted into human food contributing to incomes and avoiding environmental pollution from burning or dumping the residues and by-products (Mottet et al., 2017). Even when livestock consume human-edible proteins, their net protein contribution is positive. For example, in U.S. beef production systems, the ratio of human-edible protein in animal-source foods to that in animal feed is always greater than one (Baber et al., 2018). Thus, livestock are net contributors to human protein requirements (Baber et al., 2018) and in fact livestock contribute to 13% and 28% of the global protein and energy, respectively (FAO, 2009). Animal scientists have developed nutritional, genetic, health, and management strategies to reduce greenhouse gas emission intensities by as much as 30% (Gerber et al., 2013). Indeed, the concept of sustainable diets that are profitable, ethically and socio-culturally acceptable, and environmentally benign is emerging as one of the key solutions to ensuring the sustainability of livestock production systems. Considering the competition between feed and food systems, the concept of sustainable diets stipulates that future feed systems should focus on increased efficiency of conversion of fibrous feeds such as crop residues with high content of poorly digestible structural carbohydrates (lignin and cellulose) into human-consumable animal products. Sustainable diets and feed systems, therefore, have a potential for maintaining profitability of feed systems while reducing their negative environmental and social impacts (Bocquier and González-García, 2010). The adoption of such sustainable animal diets will require multidisciplinary input into the development of objective indicators. Future research into sustainable livestock diets should target both animal physiology and farmers’ practices to develop an integral, dynamic, and flexible conceptual perspective (Bocquier and González-García, 2010). Assessment of sustainability of livestock food systems usually focuses on GHG emissions from the foods produced. However, this approach does not account for the nutritional, health, and other benefits livestock provide in various production systems. These benefits offset the greenhouse gas they produce, which are declining because of the introduction of improved livestock management systems (Capper, 2011). The larger carbon footprint generated by livestock compared with other food sources are necessary trade-offs because livestock systems provide nutrient-rich products that are vital for health and wellbeing (White and Hall, 2018). The nutrient requirements of human beings include macronutrients (carbohydrates, protein, and fat) and micronutrients (vitamins and minerals). Malnutrition is defined as a deficiency, excess, or imbalance in nutrient intake versus nutrient requirements. Both undernutrition and overnutrition may have serious consequences. Undernutrition during infancy and childhood is widespread in low- and middle-income countries and is most commonly classified as stunting (low height-for-age) or wasting (low weight-for-height). Stunting usually reflects chronic malnutrition and frequent infections while wasting indicates acute significant food shortages and/or diseased status, and is a strong predictor of mortality. About 1 in 5 or 151 million children in the world are stunted, and more than 50 million are wasted (UNICEF, 2018). Stunting rates are highest in several sub-Saharan Africa and south Asian countries, where the prevalence often exceeds 30%. In young children, stunting is associated with reduced physical and cognitive development, increased risk of infection, lower school achievement, and greater behavioral problems. Adults who were malnourished in childhood have less economic productivity, poorer maternal reproductive outcomes, and increased incidence of hypertension and glucose intolerance (UNICEF, 2018). Indeed, World Bank researchers reported that childhood stunting reduces the gross domestic product of affected countries by about 7% on average and by 10% for African and Asian countries, with the reduction being as high as 16% for certain countries (Galasso et al., 2016). Stunting abounds among the poor in low-income settings where diets are cereal-based and lack diversity. The limited gastric capacity of infants, particularly infants, makes it difficult for them to ingest adequate nutrients needed to support rapid growth. Stunting is often associated with micronutrient deficiencies. 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Source: Animal Frontiers
DOI: 10.1093/af/vfz041
Language: English
Subfield: Ecology
Field: Environmental Science
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,500
OpenAlex ID: W2975981183