Adjusting agricultural emissions for trade matters for climate change mitigation

Water-land-energy efficiency and nexus within global agricultural trade during 1995-2019

Agricultural product demand driven by population and economic growth poses challenges to water, land, and energy utilization, and this increasing local demand is largely met through trade. However, the efficiency and nexus pattern of the water, land, and energy embodied in agricultural trade are not well understood. This study uses the multi-regional input-output framework to analyze agricultural water, land, and energy utilization efficiency of resource footprints per unit economic output as well as their transfer and nexus pattern in global agricultural trade for 1995-2019. The results show that many international agricultural trade paths are inefficient in the water, land, and energy resource use because the agricultural products in these paths are exported from relatively low- to high-efficiency economies/regions. However, these inefficient transfer paths show an increasing trend over the study period. Regarding the water-land-energy nexus, conflicts are prevalent in land-energy and water-energy couplings. Most trade paths are conducted to alleviate the pressure on a specific resource, inadvertently increasing the pressure on other resources. Although agricultural trade is important for meeting global food demands, it is not consistently beneficial to the local environment when considering agricultural resources use efficiency. This study is expected to improve our understanding of agricultural trade impacts to the agricultural resources and support the sustainable development of global agriculture.

Global production patterns: Understanding the relationship between greenhouse gas emissions, agriculture greening and climate variability

Climate change due to increased greenhouse gas emissions (GHG) in the atmosphere has been consistently observed since the mid-20th century. The profound influence of global climate change on greenhouse gas (GHG) emissions, encompassing carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), has established a vital feedback loop that contributes to further climate change. This intricate relationship necessitates a comprehensive understanding of the underlying feedback mechanisms. By examining the interactions between global climate change, soil, and GHG emissions, we can elucidate the complexities of CO2, CH4, and N2O dynamics and their implications. In this study, we evaluate the global climate change relationship with GHG globally in 246 countries. We find a robust positive association between climate and GHG emissions. By 2100, GHG emissions will increase in all G7 countries and China while decreasing in the United Kingdom based on current economic growth policies, resulting in a net global increase, suggesting that climate-driven increase in GHG and climate variations impact crop production loss due to soil impacts and not provide climate adaptation. The study highlights the diverse strategies employed by G7 countries in reducing GHG emissions, with France leveraging nuclear power, Germany focusing on renewables, and Italy targeting its industrial and transportation sectors. The UK and Japan are making significant progress in emission reduction through renewable energy, while the US and Canada face challenges due to their industrial activities and reliance on fossil fuels.

The spatial and source heterogeneity of agricultural emissions highlight necessity of tailored regional mitigation strategies

Agriculture contributes considerable greenhouse gas emissions while feed the constantly expanding world population. The challenge of balancing food security with emissions reduction to create a mutually beneficial situation is paramount. However, assessing targeted mitigation potential for agricultural emissions remains challenging, lacking comprehensive sub-national evaluations. Here, we have meticulously compiled the agricultural greenhouse gas emission inventories of China spanning the years 2000 to 2019, employing spatial analysis techniques to identify regional characteristics. We find that the peak of China's agricultural production emissions occurred in 2015 (1.03 × 109 tCO2 equivalent), followed by a valley in 2019 (0.94 tCO2 equivalent), largely attributed to shifts in livestock-related activities. Notably, methane emissions were the most dominant greenhouse gas, the Hunan province emerged as a prominent contributor, livestock raising stood out as a major activity, and enteric fermentation ranked as the primary emission source. There were substantial differences in the emission structure and sources among the provinces. Further spatial analysis showed geographical disparities in both total emissions and per capita emissions. The west-east blocked spatial characteristics of per capita emissions at the Hu Line sides emerged. We advocate that tailored mitigation strategy focusing on specific emission sources and regions can achieve substantial progress with minimal effort.

Crop byproducts supplemented in livestock feeds reduced greenhouse gas emissions

Crop byproducts can be supplemented in livestock feeds to improve the utilization of resources and reduce greenhouse gas (GHG) emissions. We explored the mitigation potential of GHG emissions by supplementing crop byproducts in feeds based on a typical intensive dairy farm in China. Results showed that GHG emissions associated with production of forage were significantly decreased by 25.60 % when no GHG emissions were allocated to crop byproducts, and enteric methane emission was significantly decreased by 13.46 % on the basis of CO2 eq, g/kg fat and protein corrected milk. The supplementation did not affect lactation performance, rumen microbiota and microbial enzymes at the gene level. Metabolomics analysis revealed changes in amino acid catabolism of rumen fluid, which were probably responsible for more propionate production. In conclusion, supplementing crop byproducts in feeds can be a potential strategy to reduce GHG emissions of livestock.

Construction of a methodology framework to characterize dynamic full-sector land-use carbon emissions embodied in trade

The globally massive land-use changes associated with unprecedented urbanization rate are leading to prodigious quantities of carbon emissions. Nonetheless, the dynamics of land-use carbon emissions, particularly driven by supply-chain activities across all relevant industrial sectors, remain largely unexplored, especially in non-agricultural sectors. Here, we constructed a novel methodological framework to quantify full-sector land-use carbon emissions in Shenzhen, China, an international megacity grappling with acute land resource scarcity. Then, we integrated this framework with multiregional input-output analysis to uncover the multi-scale embodied land-use emissions propelled by Shenzhen's supply-chain activities. Our results indicate a marked increase in Shenzhen's embodied carbon emissions, approximately two orders of magnitude greater than its physical emissions, tripling during 2005-2018. Remarkably, non-agriculture sectors contributed 81.3-90.5 % of physical and 46.6-58.4 % of embodied land-use emissions. The land-use changes occurred outside Shenzhen accounted for 6.5-13.3 % of Shenzhen's total embodied land-use emissions. The sectoral analysis revealed a transition from traditional manufacturing (e.g., metallurgy, chemical products, textiles, wood products) in 2010-2015 to high-tech sectors (e.g., electronic equipment and other manufacture) in 2015-2018. This shift was primarily attributed to concurrent industry transfer actions, leading to aggressive changes in land-use emission intensity discrepancies within and outside Shenzhen. This study provides a scientific basis for designing effective strategies to mitigate land-use carbon emissions associated with supply-chain activities.

Tracing global N2O emission mitigation strategies through trade networks

Nitrous oxide (N2O) is the third most potent greenhouse gas (GHG) and the most important ozone depleting substance. But how global N2O emissions are connected through the interwoven trade network remains unclear. This paper attempts to specifically trace anthropogenic N2O emissions via global trade networks using a multi-regional input-output model and a complex network model. Nearly one quarter of global N2O emissions can be linked to products traded internationally in 2014. The top 20 economies contribute to about 70% of the total embodied N2O emission flows. In terms of the trade embodied emissions classified by sources, cropland-, livestock-, chemistry-, and other industries-related embodied N2O emissions account for 41.9%, 31.2%, 19.9%, and 7.0%, respectively. Clustering structure of the global N2O flow network is revealed by the regional integration of 5 trading communities. Hub economies such as mainland China and the USA are collectors and distributors, and some emerging countries, such as Mexico, Brazil, India, and Russia, also exhibit dominance in different kinds of networks. This study selects the cattle sector to further verify that low production-side emission intensities and trade cooperation can lead to N2O emission reduction. In view of the impact of trade networks on global N2O emissions, achieving N2O emission reduction calls for vigorous international cooperation.

Structural chokepoints determine the resilience of agri-food supply chains in the United States

The agricultural and food systems of the United States are critical for ensuring the stability of both domestic and global food systems. Thus, it is essential to understand the structural resilience of the country's agri-food supply chains to a suite of threats. Here we employ complex network statistics to identify the spatially resolved structural chokepoints in the agri-food supply chains of the United States. We identify seven chokepoints at county scale: Riverside CA, San Bernardino CA, Los Angeles CA, Shelby TN, Maricopa AZ, San Diego CA and Cook IL; as well as seven chokepoints at freight analysis framework scale: Los Angeles-Long Beach CA, Chicago-Naperville IL, New York-New Jersey NJ, New York-New Jersey NY, Remainder of Texas, Remainder of Pennsylvania, and San Jose-San Francisco-Oakland CA. These structural chokepoints are generally consistent through time (2007, 2012, 2017), particularly for processed food commodities. This study improves our understanding of agri-food supply-chain security and may aid policies aimed at enhancing its resilience.

Changes in global food consumption increase GHG emissions despite efficiency gains along global supply chains

Greenhouse gas (GHG) emissions related to food consumption complement production-based or territorial accounts by capturing carbon leaked through trade. Here we evaluate global consumption-based food emissions between 2000 and 2019 and underlying drivers using a physical trade flow approach and structural decomposition analysis. In 2019, emissions throughout global food supply chains reached 30 ±9% of anthropogenic GHG emissions, largely triggered by beef and dairy consumption in rapidly developing countries-while per capita emissions in developed countries with a high percentage of animal-based food declined. Emissions outsourced through international food trade dominated by beef and oil crops increased by ~1 Gt CO₂ equivalent, mainly driven by increased imports by developing countries. Population growth and per capita demand increase were key drivers to the global emissions increase (+30% and +19%, respectively) while decreasing emissions intensity from land-use activities was the major factor to offset emissions growth (-39%). Climate change mitigation may depend on incentivizing consumer and producer choices to reduce emissions-intensive food products.

Harnessing the connectivity of climate change, food systems and diets: Taking action to improve human and planetary health☆

With climate change, the COVID-19 pandemic, and ongoing conflicts, food systems and the diets they produce are facing increasing fragility. In a turbulent, hot world, threatened resiliency and sustainability of food systems could make it all the more complicated to nourish a population of 9.7 billion by 2050. Climate change is having adverse impacts across food systems with more frequent and intense extreme events that will challenge food production, storage, and transport, potentially imperiling the global population’s ability to access and afford healthy diets. Inadequate diets will contribute further to detrimental human and planetary health impacts. At the same time, the way food is grown, processed, packaged, and transported is having adverse impacts on the environment and finite natural resources further accelerating climate change, tropical deforestation, and biodiversity loss. This state-of-the-science iterative review covers three areas. The paper's first section presents how climate change is connected to food systems and how dietary trends and foods consumed worldwide impact human health, climate change, and environmental degradation. The second area articulates how food systems affect global dietary trends and the macro forces shaping food systems and diets. The last section highlights how specific food policies and actions related to dietary transitions can contribute to climate adaptation and mitigation responses and, at the same time, improve human and planetary health. While there is significant urgency in acting, it is also critical to move beyond the political inertia and bridge the separatism of food systems and climate change agendas that currently exists among governments and private sector actors. The window is closing and closing fast.

Cradle-to-grave emissions from food loss and waste represent half of total greenhouse gas emissions from food systems

Global greenhouse gas (GHG) emissions from food loss and waste (FLW) are not well characterized from cradle to grave. Here GHG emissions due to FLW in supply chain and waste management systems are quantified, followed by an assessment of the GHG emission reductions that could be achieved by policy and technological interventions. Global FLW emitted 9.3 Gt of CO₂ equivalent from the supply chain and waste management systems in 2017, which accounted for about half of the global annual GHG emissions from the whole food system. The sources of FLW emissions are widely distributed across nine post-farming stages and vary according to country, region and food category. Income level, technology availability and prevailing dietary pattern also affect the country and regional FLW emissions. Halving FLW generation, halving meat consumption and enhancing FLW management technologies are the strategies we assess for FLW emission reductions. The region-specific and food-category-specific outcomes and the trade-off in emission reductions between supply chain and waste management are elucidated. These insights may help decision makers localize and optimize intervention strategies for sustainable FLW management.

Tracing toxic chemical releases embodied in U.S. interstate trade and their unequal distribution

Toxic chemicals have severe impacts on ecosystem, climate change and human health, and the current toxic releases are inequitably distributed across regions. Investigating the toxic release embodied in final demand by states and income groups can reveal the responsibility transfer of different entities. In this paper, we extended the U.S. multi-regional input-output (MRIO) model with toxic chemical release data in 2017 to conduct the production- and consumption-based accounting of toxic release by each state, and the inter-regional transfer of embodied toxic release between states. In addition, this paper analyzed how the toxic releases and inter-state transfer of embodied toxic release have been driven by income groups across states. The results showed that the toxic release from production was highly concentrated on the central states and the Great Lakes Region, while the consumption-based accounting of toxic release was more equally distributed across regions in the US. The non-metallic and metallic products manufacturing sectors were the most important sectors for most states from both production and consumption-based perspectives and were also the most essential sectors for interregional flows of embodied toxic release from Great Lake Region to Southeast, Mid-Atlantic and Northeast. Our results also showed that the largest portion (41.88%) of embodied toxic releases were triggered by households' final demand, and that the consumption of the richest 35% of households contributed to more than 50% of the total toxic chemical releases triggered by total final demand of all households.

An Equality-Based Approach to Analysing the Global Food System's Fair Share, Overshoot, and Responsibility for Exceeding the Climate Change Planetary Boundary

The climate catastrophe is being caused by human effects on earth system processes that are surpassing several planetary boundaries. This crisis is driven significantly by the global food system. It has been increasing over recent years, yet food systems are essential in upholding food and nutrition security. This study proposed a novel method for enumerating national contributions to the cessation of the climate crisis by approximating nations’ aggregate greenhouse gas (GHG) emissions from food systems, within the equitable and sustainable planetary boundaries of climate change. This study included 221 nations, which were grouped as per their human development index (HDI) categories, income groups, and continental locations. During 1990−2018, the annual fair share, overshoot of emissions, and collective historical responsibility in the world of each country were assessed. There was a 22.52% increase in overshooting of GHG emissions from the global food system, starting in 1990. A group of 15 countries, including Brazil, China, Indonesia, and the U.S.A., were responsible for >67% of global overshoot. The primary liability is borne by countries with upper-, middle-, and high-income economies, and high to very-high HDI groups, as well as Asia and South America. Countries such as India, China, the Democratic Republic of the Congo, and others have steadily increased their share of responsibility over the last 28 years. More than 76% of countries in the world, mostly from Africa, Europe, and Asia, proved to be absolute overshooters. After contextualising the study’s findings, the global food system’s decarbonization and its limits were discussed; some recommendations for prospective research were also offered. It appears that academics, governments, and policymakers should start concentrating more on reshaping and redesigning the global food system to be climate-friendly (i.e., a carbon-neutral food system), whilst being able to fairly allocate food and nutrition security to achieve long-term Sustainable Development Goal 2 (SDG 2).

Spatiotemporal analysis of land use changes and their trade-offs on the northern slope of the Tianshan Mountains, China

The unprecedented urbanization recently has inevitably intensified the changes in land use morphology. However, current studies on land use primarily analyze a single morphology, ignoring the relationships between different land use morphologies. Taking the northern slope of the Tianshan Mountains (NSTM) as the study area, this article quantifies the spatiotemporal pattern of land use change, and estimates trade-offs and synergies between dominant (patch density, largest patch index, and landscape shape index) and recessive (land use efficiency, land use intensity, and agricultural non-point source pollution) morphologies to fully understand the dynamic characteristics of land use. Results showed bare areas and grassland were always predominant land use types, and land use change from 1990 to 2020 was characterized by the increase of impervious surfaces and the decrease of bare areas. The strongest trade-off was found between largest patch index and land use intensity, while the synergy between landscape shape index and land use intensity was strongest. There are significant disparities in terms of temporal and spatial patterns of trade-offs/synergies. The correlation coefficients in different study periods were much smaller than their estimations in the whole region, and the trade-offs/synergies in the eastern NSTM were basically identical with the whole relationships. The findings reveal the interactions among various land use characteristics, and provide significant references for coordinated land management and regional high-quality development.