Food and feed trade has greatly impacted global land and nitrogen use efficiencies over 1961-2017

Decline in carbon emission intensity of global agriculture has stagnated recently

Using global data for around 180 countries and territories and 170 food/feed types primarily derived from FAOSTAT, we have systematically analyzed the changes in greenhouse gas (GHG) emission intensity (GHGi) (kg CO2eq per kg protein production) over the past six decades. We found that, with large spatial heterogeneity, emission intensity decreased by nearly two-thirds from 1961 to 2019, predominantly in the earlier years due to agronomic improvement in productivity. However, in the most recent decade, emission intensity has become stagnant, and in a few countries even showed an increase, due to the rapid increase in livestock production and land use changes. The trade of final produced protein between countries has potentially reduced the global GHGi, especially for countries that are net importers with high GHGi, such as many in Africa and South Asia. Overall, a continuous decline of emission intensity in the future relies on countries with higher emission intensity to increase agricultural productivity and minimize land use changes. Countries with lower emission intensity should reduce livestock production and increase the free trade of agricultural products and improve the trade optimality.

Did the International Trade in Crops Lead to Global Cropland Saving or Wasting in the Period 2000-2022?

The international food trade is beneficial for enhancing global food security but also raises issues such as global cropland redistribution, land use efficiency, and environmental problems. While current studies have examined the impacts of the international food trade on these issues, its long-term effects on global cropland use efficiency remain unclear, especially when considering different crops and countries. Utilizing the international trade theory and the principle of virtual cropland, this study explores the relationship between international food trade and global cropland use efficiency from 2000 to 2022. The results illustrate that the global crop trade surged by 142%, outpacing the 102% increase in virtual cropland trade, which was attributed to crop yield enhancements. By 2022, the global virtual cropland trade encompassed 10.7% of the total croplands, with China emerging as the foremost importer, particularly due to soybean imports. Notably, the global crop trade led to substantial cropland savings and higher cropland use efficiency, totaling 1244.9 million hectares (Mha) between 2000 and 2020. These gains were largely attributed to the superior yields of major crop-exporting countries. Despite these gains, socio-economically vulnerable countries face significant challenges, potentially compromising their food security amidst the complexities of the global trade dynamics.

Uneven agricultural contraction within fast-urbanizing urban agglomeration decreases the nitrogen use efficiency of crop production

Diverse development paths among cities within an urban agglomeration can lead to uneven changes in their agricultural production scale, which reshape the inter-city food supply patterns and the spatiotemporal characteristics of nitrogen (N) pollution from the food system. Here, using Guangdong-Hong Kong-Macao Greater Bay Area of China as a case, we found a substantial decrease in N use efficiency of crop production from 45.2% to 29.3% during 1989-2007, along with a growing level of concentration of food N production in less-urbanized cities. From 1989 to 2018, 12.3% to 42.2% of total N pollution in food production became embedded in inter-city trade, leading to aggregation of N pollution in peripheral cities with relatively low levels of economic development. We suggest that protection and intensification of cropland from urban encroachment, as well as enhancing the economic and technical synergies among cities, can serve the sustainable transition of the food system with coordinated N pollution mitigation.

Redistribution of nitrogen to feed the people on a safer planet

Lack of nitrogen limits food production in poor countries while excessive nitrogen use in industrial countries has led to transgression of the planetary boundary. However, the potential of spatial redistribution of nitrogen input for food security when returning to the safe boundary has not been quantified in a robust manner. Using an emulator of a global gridded crop model ensemble, we found that redistribution of current nitrogen input to major cereals among countries can double production in the most food-insecure countries, while increasing global production of these crops by 12% with no notable regional loss or reducing the nitrogen input to the current production by one-third. Redistribution of the input within the boundary increased production by 6-8% compared to the current relative distribution, increasing production in the food-insecure countries by two-thirds. Our findings provide georeferenced guidelines for redistributing nitrogen use to enhance food security while safeguarding the planet.

Current investigations on global N2O emissions and reductions: Prospect and outlook

Global nitrous oxide (N2O) emissions merit scrutiny, because N2O is the third most important greenhouse gas for global warming and the predominant ozone-depleting substance in this century. Here we recapitulate global natural and anthropogenic N2O sources, comprehensively depict global sectoral human-induced N2O emissions by country, thoroughly survey all existing approaches for mitigating human-induced N2O emissions, preview the economic costs and social benefits from abating N2O emissions, and summarize roadblocks for achieving its emission reductions. From 1970 to 2018, the annual global anthropogenic N2O emissions increased by 64%-about 3.6 teragrams (Tg); agricultural sources primarily accounted for 78% of this increment. We find the social benefits from reducing N2O emissions override the economic costs for abatements, only except precision farming for agricultural sources and replacement by Xe for anesthetic, thus justifying the motivation for crafting policies to limit its emissions. Net zero N2O emissions cannot be achieved via applying current technologies and breeding N2O-reducing microbes is a potential method to accrue N2O sinks.

Recoupling livestock and feed production in the Netherlands to reduce environmental impacts

In many places on earth, livestock and feed production are decoupled, as feed is grown in one region and fed to livestock in another. This disrupts nutrient cycles by depleting resources in feed producing regions and accumulating resources in livestock areas, which leads to environmental degradation. One solution is to recouple livestock and feed production at a more local level, which enhances nutrient circularity. Recoupling livestock and feed production creates a natural ceiling for livestock numbers based on the feed producing capacity of a region. In this study we assess the consequences of recoupling livestock and feed production (i.e., by avoiding the import and export of animal feed) on ammonia and greenhouse gas (GHG) emissions, with and without feed-food competition. To this end, we used FOODSOM, an agro-ecological food system optimisation model representing the Dutch food system in this study. The Netherlands is one example of a region with high livestock densities and resource accumulation. We found that recoupling decreased livestock numbers (beef cattle: -100 %; dairy cattle: -29 %; broiler chickens: -57 %; laying hens: -67 %; pigs: -62 %; sheep -100 %) and animal-sourced food exports (-59 %) while still meeting the current human diet in the Netherlands. Consequently, ammonia emissions and GHG emissions decreased, and the nitrogen use efficiency increased from 31 % to 38 % at the food systems level. Recoupling alone was almost sufficient to meet national emission targets. Fully meeting these targets required further small changes in livestock numbers. Avoiding feed-food competition decreased livestock productivity and GHG emissions but did not improve nitrogen use efficiency. Total meat production could not meet domestic consumption levels while avoiding feed-food competition, and resulted in additional beef cattle. We show that recoupling livestock and feed production is a promising next step to enhance circularity while decreasing agricultures environmental impact.

Agricultural trade impacts global phosphorus use and partial productivity

The spatio-temporal distribution, flow and end use of phosphorus (P) embedded in traded agricultural products are poorly understood. Here we use global trade matrices to analyse the partial factor productivity of P (output per unit of P input) for crop and livestock products in 200 countries and their cumulative contributions to the export or import of agricultural products over 1961-2019. In these six decades, the trade of agricultural P products has increased global partial factor productivity for crop and livestock production and has theoretically saved 67 Tg P in fertilizers and 1.6 Tg P in feed. However, trade is now at risk of contributing to wasteful use of P resources globally due to a decline in trade optimality, as agricultural products are increasingly exported from low to high partial factor productivity countries and due to P embedded in imported agricultural products mainly lost to the environment without recycling. Integrated crop-livestock production systems and P-recycling technologies can help.

Dietary grape pomace extract supplementation improved meat quality, antioxidant capacity, and immune performance in finishing pigs

In pig production, reducing production costs and improving immunity are important. Grape pomace, a good agricultural by-product, has been thrown away as food waste for a long time. Recently, we found that it could be used as a new source of pig feed. We investigated the effect of grape pomace on inflammation, gut barrier function, meat quality, and growth performance in finishing pigs. Our results indicated that treatment samples showed a significant decrease in water loss, IL-1β, DAO, ROS, and MDA content (p < 0.05). IgA, IgG, IgM, CAT, T-AOC, SOD, and IFN-γ significantly increased compared with those in control samples (p < 0.05). Meanwhile, the relative mRNA expression of the tight junction protein occludin showed a significant difference (p < 0.05). Analysis of metagenomic sequencing indicated that grape pomace significantly decreased the relative abundance of Treponema and Streptococcus (p < 0.05). In summary, our results demonstrated that grape pomace could improve meat quality, alleviate inflammation, and decrease oxidative stress.

Climate-friendly and nutrition-sensitive interventions can close the global dietary nutrient gap while reducing GHG emissions

Sustainable food systems require malnutrition and climate change to be addressed in parallel. Here, we estimate the non-CO2 greenhouse gas emissions resulting from closing the world's dietary nutrient gap-that between country-level nutrient supply and population requirements-for energy, protein, iron, zinc, vitamin A, vitamin B12 and folate under five climate-friendly intervention scenarios in 2030. We show that improving crop and livestock productivity and halving food loss and waste can close the nutrient gap with up to 42% lower emissions (3.03 Gt CO2eq yr-1) compared with business-as-usual supply patterns with a persistent nutrient gap (5.48 Gt CO2eq yr-1). Increased production and trade of vegetables, eggs, and roots and tubers can close the nutrient gap with the lowest emissions in most countries-with ≤23% increase in total caloric production required for 2030 relative to 2015. We conclude that the world's nutrient gap could be closed without exceeding global climate targets and without drastic changes to national food baskets.

Policy-enabled stabilization of nitrous oxide emissions from livestock production in China over 1978-2017

Mitigating livestock-related nitrous oxide (N₂O) emissions is key for China to meet its 2060 carbon neutrality target. Here we present a comprehensive analysis of the magnitude, spatiotemporal variation and drivers of Chinese livestock N₂O emissions from 1978 to 2017. We developed scenarios to explore emissions mitigation potential and associated marginal abatement costs and social benefits. The average growth rate of China's livestock N₂O emissions increased by 4.6% per year through 2006, falling sharply over 2007-2015 and gradually declining in 2017 due to a slowdown in population and meat-consumption growth rates. We estimate the technical mitigation potential of livestock N₂O emissions in 2030 to be 7-21% (or 23.1-70.9 Gg N₂O), with implementation costs of US$5.5 billion to US$6.0 billion. Priority regions for intervention were identified in the North China Plain, Northeast Plain and Lianghu Plain. Among mitigation opportunities, anaerobic digestion offers the greatest social benefit, while low crude protein feed is the most cost-effective option.