Henning Steinfeld’s research while affiliated with Food and Agriculture Organization of the United Nations and other places

Soils contribute to the achievement of the UN Sustainable Development Goals through carbon sequestration. By enhancing soil health and fertility, soils can play a crucial role in climate action, land degradation neutrality, and alleviating hunger. The present study provides a spatially explicit report on the state of grassland soils and can be used as a baseline for future work to explore the impacts of livestock management on soil carbon at regional, country and farm levels. Assessing the current state of grassland systems and their potential to sequester carbon in the soil is of key importance to understand the trade-offs between grassland services on food security, biodiversity conservation and climate mitigation.

Global livestock supply chains have significantly altered nitrogen (N) flows over past years, thereby threatening environmental and human health. Here, we provide a disaggregated assessment of the livestock sector’s impacts on global N flows and emissions, including international trade. The results show that the sector currently emits 65 Tg N yr−1 , equivalent to one-third of current human-induced N emissions and sufficient to meet the planetary boundary for N. Of that amount, 66% is allocated to Asia and 68% is associated with feed production. Most emissions originate from locally produced animal-sourced food, although N emissions embedded in international trade are significant for some importing countries. Given the magnitude of its impacts and its central role in both domestic and international N challenges, the livestock sector urgently requires a global initiative to tackle N pollution while supporting food security.

The global pork sector contributes to food security and supports livelihoods for millions of households but also causes nitrogen (N) pollution. Here we assess N flows, losses, and N use indicators for global pork supply chains, from “cradle-to-primary-processing-gate” and for three production systems: the backyard, intermediate and industrial systems. Subsequently, we evaluate the effects of feeding swill to industrial pigs on N flows and land use. To produce 3.5 Tg N of pork globally, 14.7 Tg N are lost into the environment, of which 68% is lost to watercourses in the form of nitrates and organic N and the reminder emitted to the atmosphere as N-gas (e.g., NH3, NOx and N2O). We found that the efficiency of N use, hotspot and magnitude of N losses per unit of area depend chiefly on the region (agro-ecological and economic context), origin of feed, and manure management systems. Swill feeding increases N use efficiency and reduces N losses at the feed production stage. It achieves a saving of 31 Mt of soybeans and 20 Mt of grains on dry matter basis, equivalent to 16 M ha of land used. Its adoption would require innovative policies to preserve food safety and public health. Future research may explore the feasibility and requirements to adopt swill feeding at a country level and may investigate potential impacts on other sustainability objectives.

This paper draws on a recent multi-donor study on livestock and the environment and highlights how its findings might impact on research agendas worldwide. The soaring demand for meat and milk puts great pressure on the global natural resource base. About one-quarter of the world's total land area is used for grazing livestock. In addition, about one-fifth of the world's arable land is used for growing cereals for livestock food. Livestock production is the world's largest land user and may soon he its most important agricultural activity in terms of economic output. Livestock produce 13 billion tons of waste each year. A large part of this is recycled but, where animal concentrations are high, waste poses an environmental hazard. Water, already scarce in many parts of the world, is required not only for animals' drinking but also to grow food crops and for waste disposal. Pollution of land and water is another concern as is the impact by livestock, directly or indirectly, on biodiversity. Greenhouse gases from livestock and livestock waste contribute to global warming. The paper provides an overview of critical livestock environment interactions, so-called hotspots, notably the overgrazing/degradation issue, deforestation, the ‘involution’ of mixed farming systems and the waste problem in areas of high animal concentrations. Measures that tackle only the superficial effects of environmental damage will never be as effective as a policy which attacks the underlying causes. Those causes are often deeply entrenched in what has become an almost universal fact: those who gain benefits from over-exploitation and degradation of the environment have not paid the full cost. Incorporating the environmental cost into the price of livestock products is critical to achieving sustainable development. The technological opportunities, and, therefore, the scope, for increasing livestock production, while simultaneously reducing the use of natural resources per unit of product, are enormous. Research needs to be channelled to reflect real scarcities of natural resources while respecting the need to maintain and improve livelihoods.

The livestock sector is one of the fastest growing subsectors of the agricultural economy and, while it makes a major contribution to global food supply and economic development, it also consumes significant amounts of natural resources and alters the environment. In order to improve our understanding of the global environmental impact of livestock supply chains, the Food and Agriculture Organization of the United Nations has developed the Global Livestock Environmental Assessment Model (GLEAM). The purpose of this paper is to provide a review of GLEAM. Specifically, it explains the model architecture, methods and functionality, that is the types of analysis that the model can perform. The model focuses primarily on the quantification of greenhouse gases emissions arising from the production of the 11 main livestock commodities. The model inputs and outputs are managed and produced as raster data sets, with spatial resolution of 0.05 decimal degrees. The Global Livestock Environmental Assessment Model v1.0 consists of five distinct modules: (a) the Herd Module; (b) the Manure Module; (c) the Feed Module; (d) the System Module; (e) the Allocation Module. In terms of the modelling approach, GLEAM has several advantages. For example spatial information on livestock distributions and crops yields enables rations to be derived that reflect the local availability of feed resources in developing countries. The Global Livestock Environmental Assessment Model also contains a herd model that enables livestock statistics to be disaggregated and variation in livestock performance and management to be captured. Priorities for future development of GLEAM include: improving data quality and the methods used to perform emissions calculations; extending the scope of the model to include selected additional environmental impacts and to enable predictive modelling; and improving the utility of GLEAM output.

Gaseous emissions from animal manure are considerable contributor to global ammonia (NH3) and agriculture greenhouse gas (GHG) emissions. Given the demand to promote mitigation of GHGs while fostering sustainable development of the Paris Agreement, an improvement of management systems is urgently needed to help mitigate climate change and to improve atmospheric air quality. This study presents a meta-analysis and an integrated assessment of gaseous emissions and mitigation potentials for NH3, methane (CH4) and nitrous oxide (N2O) (direct and indirect) losses from four typical swine manure management systems (MMSs). The resultant emission factors and mitigation efficiencies allow GHG and NH3 emissions to be estimated, as well as mitigation potentials for different stages of swine operation. In particular, changing swine manure management from liquid systems to solid-liquid separation systems, coupled with mitigation measures, could simultaneously reduce GHG emissions by 65% and NH3 emissions by 78%. The resultant potential reduction in GHG emissions from China’s pig production alone is greater than the entire GHG emissions from agricultural sector of France, Australia, or Germany, while the reduction in NH3 emissions is equivalent to 40% of the total NH3 emissions from the European Union. Thus, improved swine manure management could have a significant impact on global environment issues.

The Paris Agreement, adopted in December 2015, represents a new beginning in the global effort to stabilize the climate before it is too late. It recognizes the importance of food security in the international response to climate change, as reflected by many countries focusing prominently on the agriculture sector in their planned contributions to adaptation and mitigation. To help put those plans into action, this report identifies strategies, financing opportunities, and data and information needs. It also describes transformative policies and institutions that can overcome barriers to implementation.

Livestock [inclusive of ruminant species, namely cattle (Bos Taurus and Bos indicus), sheep (Ovis aries), goats (Capra hircus), and buffaloes (Bubalus bubalis), and non-ruminant species, namely pigs (Sus scrofa domesticus) and chickens (Gallus domesticus)] are both affected by climate change and contribute as much as 14.5 % of global anthropogenic greenhouse gas (GHG) emissions, most of which is from ruminant animals (Gerber et al. 2013). This study aims to estimate the marginal costs of reducing GHG emissions for a selection of practices in the ruminant livestock sector (inclusive of the major ruminant species—cattle, sheep, and goats) globally. It advances on previous assessments by calculating marginal costs rather than commonly reported average costs of abatement and can thus provide insights about abatement responses at different carbon prices. We selected the most promising abatement options based on their effectiveness and feasibility. Improved grazing management and legume sowing are the main practices assessed in grazing systems. The urea (CO(NH2)2) treatment of crop straws is the main practice applied in mixed crop–livestock systems, while the feeding of dietary lipids and nitrates are confined to more intensive production systems. These practices were estimated to reduce emissions by up to 379 metric megatons of carbon dioxide (CO2) equivalent emissions per year (MtCO2-eq yr−1). Two thirds of this reduction was estimated to be possible at a carbon price of 20 US dollars per metric ton of CO2 equivalent emissions ($20 tCO2-eq−1). This study also provides strategic guidance as to where abatement efforts could be most cost effectively targeted. For example, improved grazing management was particularly cost effective in Latin America and Sub-Saharan Africa, while legume sowing appeared to work best in Western Europe and Latin America.

![Figure][1] A woman tends to her chickens in Uganda. PHOTO: ANDREW AITCHISON / ALAMY The Editorial “Zero hunger” by M. S. Swaminathan (1 August, p. [491][2]) rightfully points out the importance of family farms and the need to shift the focus of tackling global hunger from food