Agricultural and forestry trade drives large share of tropical deforestation emissions

Deforestation, the second largest source of anthropogenic greenhouse gas emissions, is largely driven by expanding forestry and agriculture. However, despite agricultural expansion being increasingly driven by foreign demand, the links between deforestation and foreign demand for agricultural commodities have only been partially mapped. Here we present a pan-tropical quantification of carbon emissions from deforestation associated with the expansion of agriculture and forest plantations, and trace embodied emissions through global supply chains to consumers. We find that in the period 2010–2014, expansion of agriculture and tree plantations into forests across the tropics was associated with net emissions of approximately 2.6 gigatonnes carbon dioxide per year. Cattle and oilseed products account for over half of these emissions. Europe and China are major importers, and for many developed countries, deforestation emissions embodied in imports rival or exceed emissions from domestic agriculture. Depending on the trade model used, 29–39% of deforestation-related emissions were driven by international trade. This is substantially higher than the share of fossil carbon emissions embodied in trade, indicating that efforts to reduce greenhouse gas emissions from land-use change need to consider the role of international demand in driving deforestation. Additionally, we find that deforestation emissions are similar to, or larger than, other emissions in the carbon footprint of key forest-risk commodities. Similarly, deforestation emissions constitute a substantial share (˜15%) of the total carbon footprint of food consumption in EU countries. This highlights the need for consumption-based accounts to include emissions from deforestation, and for the implementation of policy measures that cross these international supply-chains if deforestation emissions are to be effectively reduced.     

Greenhouse gas emissions from Mediterranean agriculture: Evidence of unbalanced research efforts and knowledge gaps

Designing effective mitigation policies for greenhouse gas (GHG) emissions from agriculture requires understanding the mechanisms by which management practices affect emissions in different agroclimatic conditions. Agricultural GHG emissions and carbon sequestration potentials have been extensively studied in the Mediterranean biome, which is a biodiversity hot spot that is highly vulnerable to environmental changes. However, the absolute magnitude of GHG emissions and the extent to which research efforts match these emissions in each production system, are unknown. Here, we estimated GHG emissions and potential carbon sinks associated with crop and livestock production systems in the Mediterranean biome, covering 31 countries and assessing approximately 10,000 emission items. The results were then combined with a bibliometric assessment of 797 research publications to compare emissions estimates obtained with research efforts for each of the studied items. Although the magnitude of GHG emissions from crop production and the associated carbon sequestration potential (261 Tg CO₂eq yr⁻¹) were nearly half of those from livestock production (367 Tg CO₂eq yr⁻¹), mitigation research efforts were largely focused on the former. As a result, the relative research intensity, which relates the number of publications to the magnitude of emissions, is nearly one order of magnitude higher for crop production than for livestock production (2.6 and 0.4 papers Tg CO₂eq⁻¹, respectively). Moreover, this mismatch is even higher when crop and livestock types are studied separately, which indicates major research gaps associated with grassland and many strategic crop types, such as fruit tree orchards, fiber crops, roots and tubers. Most life cycle assessment studies do not consider carbon sequestration, although this single process has the highest magnitude in terms of annual CO₂eq. In addition, these studies employ Tier 1 IPCC factors, which are not suited for use in Mediterranean environments. Our analytical results show that a strategic plan is required to extend on-site field GHG measurements to the Mediterranean biome. Such a plan needs to be cocreated among stakeholders and should be based on refocusing research efforts to GHG balance components that have been afforded less attention. In addition, the outcomes of Mediterranean field studies should be integrated into life cycle assessment-based carbon footprint analyses in order to avoid misleading conclusions.     

Brazil beyond 2020: from deforestation to the energy challenge

The main assumptions and findings are presented on a comparative analysis of three GHG long-term emissions scenarios for Brazil. Since 1990, land-use change has been the most important source of GHG emissions in the country. The voluntary goals to limit Brazilian GHG emissions pledged a reduction in between 36.1% and 38.9% of GHG emissions projected to 2020, to be 6–10% lower than in 2005. Brazil is in a good position to meet the voluntary mitigation goals pledged to the United Nations Framework Convention on Climate Change (UNFCCC) up to 2020: recent efforts to reduce deforestation have been successful and avoided deforestation will form the bulk of the emissions reduction commitment. In 2020, if governmental mitigation goals are met, then GHG emissions from the energy system would become the largest in the country. After 2020, if no additional mitigation actions are implemented, GHG emissions will increase again in the period 2020–2030, due to population and economic growth driving energy demand, supply and GHG emissions. However, Brazil is in a strong position to take a lead in low-carbon economic and social development due to its huge endowment of renewable energy resources allowing for additional mitigation actions to be adopted after 2020.

Policy relevance

The period beyond 2020 is now relevant in climate policy due to the Durban Platform agreeing a ‘protocol, legal instrument or agreed outcome with legal force’ that will have effect from 2020. After 2020, Brazil will be in a situation more similar to other industrialized countries, faced with a new challenge of economic development with low GHG energy-related emissions, requiring the adoption of mitigation policies and measures targeted at the energy system. Unlike the mitigation actions in the land-use change sector, where most of the funding will come from the national budgets due to sovereignty concerns, the huge financial resources needed to develop low-carbon transport and energy infrastructure could benefit from soft loans channelled to the country through nationally appropriate mitigation actions (NAMAs).     

Country-specific dietary shifts to mitigate climate and water crises

Undernutrition, obesity, climate change, and freshwater depletion share food and agricultural systems as an underlying driver. Efforts to more closely align dietary patterns with sustainability and health goals could be better informed with data covering the spectrum of countries characterized by over- and undernutrition. Here, we model the greenhouse gas (GHG) and water footprints of nine increasingly plant-forward diets, aligned with criteria for a healthy diet, specific to 140 countries. Results varied widely by country due to differences in: nutritional adjustments, baseline consumption patterns from which modeled diets were derived, import patterns, and the GHG- and water-intensities of foods by country of origin. Relative to exclusively plant-based (vegan) diets, diets comprised of plant foods with modest amounts of low-food chain animals (i.e., forage fish, bivalve mollusks, insects) had comparably small GHG and water footprints. In 95 percent of countries, diets that only included animal products for one meal per day were less GHG-intensive than lacto-ovo vegetarian diets (in which terrestrial and aquatic meats were eliminated entirely) in part due to the GHG-intensity of dairy foods. The relatively optimal choices among modeled diets otherwise varied across countries, in part due to contributions from deforestation (e.g., for feed production and grazing lands) and highly freshwater-intensive forms of aquaculture. Globally, modest plant-forward shifts (e.g., to low red meat diets) were offset by modeled increases in protein and caloric intake among undernourished populations, resulting in net increases in GHG and water footprints. These and other findings highlight the importance of trade, culture, and nutrition in diet footprint analyses. The country-specific results presented here could provide nutritionally-viable pathways for high-meat consuming countries as well as transitioning countries that might otherwise adopt the Western dietary pattern.     

Globalized supply chains: Emergent telecouplings in Mexico’s beef economy and environmental leakages

This article analyzes how trade liberalization in Mexico, particularly following the North American Free Trade Agreement (NAFTA), has transformed that nation’s cattle economy into a feedlot system manifesting multiple telecouplings and based on the transnational provision of inputs. A conceptual model is presented that suggests how environmental effects involving land use and GHG emissions emerge from changes in the beef supply chain. The article then presents an empirical analysis establishing that the production of corn and beef has intensified in the wake of NAFTA, and that deforestation rates have declined over the same period. Evidence is also presented showing that this has not precipitated a land sparing effect, given the leakage of deforestation into Central America, which supplies Mexican feedlots with 36 % of their source materials. The article calculates associated GHG emissions and establishes that enteric fermentation dominates deforestation as a source, and that ∼14% of GHGs produced by the post-NAFTA Mexican supply chain are emitted in Central America. This raises accounting questions for signatories to the Paris Climate Treaty, given commitments are nation-based.     

Biofuels and carbon management

Public policy supports biofuels for their benefits to agricultural economies, energy security and the environment. The environmental rationale is premised on greenhouse gas (GHG, “carbon”) emissions reduction, which is a matter of contention. This issue is challenging to resolve because of critical but difficult-to-verify assumptions in lifecycle analysis (LCA), limits of available data and disputes about system boundaries. Although LCA has been the presumptive basis of climate policy for fuels, careful consideration indicates that it is inappropriate for defining regulations. This paper proposes a method using annual basis carbon (ABC) accounting to track the stocks and flows of carbon and other relevant GHGs throughout fuel supply chains. Such an approach makes fuel and feedstock production facilities the focus of accounting while treating the CO₂ emissions from fuel end-use at face value regardless of the origin of the fuel carbon (bio- or fossil). Integrated into cap-and-trade policy and including provisions for mitigating indirect land-use change impacts, also evaluated on an annual basis, an ABC approach would provide a sound carbon management framework for the transportation fuels sector.     

Oil palm expansion in Cameroon: Insights into sustainability opportunities and challenges in Africa

Oil palm production expanded 1.2 million hectares in sub-Saharan Africa since 1990, with expansion accelerating in several heavily forested countries since 2000. Despite a narrative of expansion driven by multinational corporations, we provide evidence of a dynamic non-industrial oil palm production sector linked to a burgeoning informal milling enterprise. Surveys were conducted with oil palm farmers in Cameroon (n = 546), the third largest palm oil producer on the continent with the greatest amount of deforestation due to recent expansion, to determine who is expanding into forest. Seventy-three percent of survey respondents reported clearing forest, the magnitude of which was explained by differences in milling strategies and supply chain integration. Large-scale, non-industrial producers played a disproportionate role in deforestation, many of which were engaged in informal supply chains through the use of non-industrial mills. Farms associated with more clearing tended to use high-yielding seedlings. Even the highest yielding farms, however, averaged only 7.7 tons fresh fruit bunches (FFBs) ha⁻¹ yr⁻¹, well below the potential 20 tons FFBs ha⁻¹ yr⁻¹ yield for Cameroon. We also found a strong relationship between deforestation and land claims. Most farms claimed ownership of their land, although only 5% had official land titles. Conservation challenges in the region arise from land tenure laws that incentivize forest clearing. This study sheds light on the role of informal supply chains in deforestation and highlights the need for strict implementation and enforcement of land use zoning policies.     

Supply of carbon sequestration and biodiversity services from Australia's agricultural land under global change

Global agroecosystems can contribute to both climate change mitigation and biodiversity conservation, and market mechanisms provide a highly prospective means of achieving these outcomes. However, the ability of markets to motivate the supply of carbon sequestration and biodiversity services from agricultural land is uncertain, especially given the future changes in environmental, economic, and social drivers. We quantified the potential supply of these services from the intensive agricultural land of Australia from 2013 to 2050 under four global outlooks in response to a carbon price and biodiversity payment scheme. Each global outlook specified emissions pathways, climate, food demand, energy price, and carbon price modeled using the Global Integrated Assessment Model (GIAM). Using a simplified version of the Land Use Trade-Offs (LUTO) model, economic returns to agriculture, carbon plantings, and environmental plantings were calculated each year. The supply of carbon sequestration and biodiversity services was then quantified given potential land use change under each global outlook, and the sensitivity of the results to key parameters was assessed. We found that carbon supply curves were similar across global outlooks. Sharp increases in carbon sequestration supply occurred at carbon prices exceeding 50 $ tCO₂⁻¹ in 2015 and exceeding 65 $ tCO₂⁻¹ in 2050. Based on GIAM-modeled carbon prices, little carbon sequestration was expected at 2015 under any global outlook. However, at 2050 expected carbon supply under each outlook differed markedly, ranging from 0 to 189 MtCO₂ yr⁻¹. Biodiversity services of 3.32% of the maximum may be achieved in 2050 for a 1 $B investment under median scenario settings. We conclude that a carbon market can motivate supply of substantial carbon sequestration but only modest amounts of biodiversity services from agricultural land. A complementary biodiversity payment can synergistically increase the supply of biodiversity services but will not provide much additional carbon sequestration. The results were sensitive to global drivers, especially the carbon price, and the domestic drivers of adoption hurdle rate and agricultural productivity. The results can inform the design of an effective national policy and institutional portfolio addressing the dual objectives of climate change and biodiversity conservation that is robust to future uncertainty in both national and global drivers.     

Explaining the stickiness of supply chain relations in the Brazilian soybean trade

The global trade of agricultural commodities has profound social-ecological impacts, from potentially increasing food availability and agricultural efficiency, to displacing local communities, and to incentivizing environmental destruction. Supply chain stickiness, understood as the stability in trading relationships between supply chain actors, moderates the impacts of agricultural commodity production and the possibilities for supply-chain interventions. However, what factors determine stickiness, that is, how and why farmers, traders, food processors, and consumer countries, develop and maintain trading relationships with specific producing regions, remains unclear. Here, we use data on the Brazilian soy supply chain, a mixed methods approach based on extensive actor-based fieldwork, and an explanatory regression model, to identify and explore the factors that influence stickiness between places of production and supply chain actors. We find four groups of factors to be important: economic incentives, institutional enablers and constraints, social and power dimensions, and biophysical and technological conditions. Among the factors we explore, surplus capacity in soy processing infrastructure, (i.e., crushing and storage facilities) is important in increasing stickiness, as is export-oriented production. Conversely, volatility in market demand expressed by farm-gate soy prices and lower land-tenure security are key factors reducing stickiness. Importantly, we uncover heterogeneity and context-specificity in the factors determining stickiness, suggesting tailored supply-chain interventions are beneficial. Understanding supply chain stickiness does not, in itself, provide silver-bullet solutions to stopping deforestation, but it is a crucial prerequisite to understanding the relationships between supply chain actors and producing regions, identifying entry points for supply chain sustainability interventions, assessing the effectiveness of such interventions, forecasting the restructuring of trade flows, and considering sourcing patterns of supply chain actors in territorial planning.     

Amazon forest biomass density maps: tackling the uncertainty in carbon emission estimates

As land use change (LUC), including deforestation, is a patchy process, estimating the impact of LUC on carbon emissions requires spatially accurate underlying data on biomass distribution and change. The methods currently adopted to estimate the spatial variation of above- and below-ground biomass in tropical forests, in particular the Brazilian Amazon, are usually based on remote sensing analyses coupled with field datasets, which tend to be relatively scarce and often limited in their spatial distribution. There are notable differences among the resulting biomass maps found in the literature. These differences subsequently result in relatively high uncertainties in the carbon emissions calculated from land use change, and have a larger impact when biomass maps are coded into biomass classes referring to specific ranges of biomass values. In this paper we analyze the differences among recently-published biomass maps of the Amazon region, including the official information used by the Brazilian government for its communication to the United Nation Framework on Climate Change Convention of the United Nations. The estimated average pre-deforestation biomass in the four maps, for the areas of the Amazon region that had been deforested during the 1990–2009 period, varied from 205?±?32 Mg ha^?1 during 1990–1999, to 216?±?31 Mg ha^?1 during 2000–2009. The biomass values of the deforested areas in 2011 were between 7 and 24 % higher than for the average deforested areas during 1990–1999, suggesting that although there was variation in the mean value, deforestation was tending to occur in increasingly carbon-dense areas, with consequences for carbon emissions. To summarize, our key findings were: (i) the current maps of Amazonian biomass show substantial variation in both total biomass and its spatial distribution; (ii) carbon emissions estimates from deforestation are highly dependent on the spatial distribution of biomass as determined by any single biomass map, and on the deforestation process itself; (iii) future deforestation in the Brazilian Amazon is likely to affect forests with higher biomass than those deforested in the past, resulting in smaller reductions in carbon dioxide emissions than expected purely from the recent reductions in deforestation rates; and (iv) the current official estimate of carbon emissions from Amazonian deforestation is probably overestimated, because the recent loss of higher-biomass forests has not been taken into account.     

Deforestation in the Brazilian Amazon could be halved by scaling up the implementation of zero-deforestation cattle commitments

Deforestation for agriculture is a key threat to global carbon stocks, biodiversity, and indigenous ways of life. In the absence of strong territorial governance, zero-deforestation commitments (ZDCs), corporate policies to decouple food production from deforestation, remain a central tool to combat this issue. Yet evidence on their effectiveness remains mixed and the mechanisms limiting effectiveness are poorly understood. To advance understanding of ZDCs’ potential at reducing deforestation, we developed the first spatially explicit estimates of farmers’ exposure to ZDC companies in the Brazilian Amazon cattle sector. Exposure was measured by determining the market share of ZDC firms from the first full year of ZDC adoption in 2010 until 2018. Our analysis evaluated how variation in this exposure influenced deforestation. We found the G4 Agreement, the most widespread and strongly implemented cattle ZDC, reduced cattle-driven deforestation by 7,000 ± 4,000 km² (15 ± 8%) between 2010 and 2018. Additionally, had all firms adopted and implemented an effective ZDC, cattle-driven deforestation could have dropped by 24,000 ± 13,000 km² (51 ± 28%). These results for the world’s principal deforestation hotspot suggests supply chain policies can substantially reduce deforestation. However, their effectiveness is contingent on widespread adoption and rigorous implementation, both of which are currently insufficient to prevent large scale deforestation. Increased adoption and implementation could be incentivized through greater pressure from the Brazilian government and import countries.     

The scale and drivers of carbon footprints in households,cities and regions across India

The carbon footprint (CF) has emerged as an important yardstick to understand the total contribution of countries, sectors and individuals to climate change. In contrast to conventional emissions accounting which captures only territorial or local production activities, the CF includes the emissions imposed by consumption across global supply chains for goods and services. Recent interest has grown in the application of CF assessment for municipalities owing to their large contribution to global carbon emissions and the limited coverage of existing data to monitor their climate pledges. By linking household-level consumer surveys to a global supply chain database, spatially-explicit CF assessment is possible at a district and household scale. To date, such technique has exposed otherwise unforeseen differences in consumer carbon footprints in developed countries. Within this study we calculate and compare the household carbon footprints 623 districts in India, based on micro consumption data from 203,313 households and explain their variation by economic, cultural and demographic factors. We show the eradication of extreme poverty does not conflict with ambitious climate change mitigation in India. However, our analysis suggests CF reduction policies within India need to target high-expenditure households which are responsible for nearly seven times the carbon emissions than low-expenditure households (living on $1.9 consumption a day). These vast disparities between the carbon footprint of citizens in India highlights the need to differentiate individual responsibilities for climate change in national and global climate policy.     

Influence of soil C, N2O and fuel use on GHG mitigation with no-till adoption

Previous research has demonstrated that soil carbon sequestration through adoption of conservation tillage can be economically profitable depending on the value of a carbon offset in a greenhouse gas (GHG) emissions market. However adoption of conservation tillage also influences two other potentially important factors, changes in soil N₂O emissions and CO₂ emissions attributed to changes in fuel use. In this article we evaluate the supply of GHG offsets associated with conservation tillage adoption for corn-soy-hay and wheat-pasture systems of the central United States, taking into account not only the amount of carbon sequestration but also the changes in soil N₂O emission and CO₂ emissions from fuel use in tillage operations. The changes in N₂O emissions are derived from a meta-analysis of published studies, and changes in fuel use are based on USDA data. These are used to estimate changes in global warming potential (GWP) associated with adoption of no-till practices, and the changes in GWP are then used in an economic analysis of the potential supply of GHG offsets from the region. Simulation results demonstrate that taking N₂O emissions into account could result in substantial underestimation of the potential for GHG mitigation in the central U.S. wheat pasture systems, and large over-estimation in the corn-soy-hay systems. Fuel use also has quantitatively important effects, although generally smaller than N₂O. These findings suggest that it is important to incorporate these two effects in estimates of GHG offset potential from agricultural lands, as well as in the design of GHG offset contracts for more complete accounting of the effect that no-till adoption will have on greenhouse gas emissions.     

中国新能源发电生命周期温室气体减排潜力比较和分析

从生命周期的角度分析,各类新能源发电技术的开发、建设、运行过程,也会带来一定的温室气体排放,这引发了人们对于新能源发电技术“低碳”属性的担忧。遵循生命周期评价方法,在对国内外大量资料文献进行收集整理的基础上,对中国传统火电和主要新能源发电技术的温室气体排放系数进行了对比分析;并根据国家发展规划目标,对新能源发电替代火电的温室气体减排潜力进行了估算。分析结果表明,即使考虑生命周期内的排放,新能源发电技术的温室气体排放系数仍远远低于火电,新能源发电技术替代火电的温室气体减排潜力巨大。     

基于多区域投入产出模型中美贸易隐含能源、碳排放的测算

采用多区域投入产出模型（MRIO）,利用欧盟资助开发的世界投入产出表和环境账户数据,测算了1995—2009年中国与美国的增加值贸易规模及净值,在此基础上利用环境账户中的能源消耗和碳排放数据测算出中美外贸隐含能源和隐含碳排放总体水平及其行业结构。研究表明：1995—2009年,中国对美国的增加值出口保持持续增长的态势,尤其是在中国加入世界贸易组织（WTO）后,但随后受2008年全球经济危机的影响,中国增加值出口规模有所减小;相比于美国,中国单位增加值能耗和碳排放水平较高,从而导致较大规模的隐含能源和隐含碳出口,长期处于隐含能源和隐含碳净输出国地位,且净输出规模呈现出上升的趋势;从行业结构来看,电力、燃气及水的供应业等能源行业是中国出口隐含能源和隐含碳排放的主要行业来源。     

China's carbon emissions and international trade: implications for post-2012 policy

Growing international trade has been one of the most important drivers for China's recent economic growth. This growth has fed rapid increases in energy demand and carbon emissions since 2000. China is now the world's largest emitter of carbon dioxide. There is mounting pressure from some in the international community for China to take specific actions to mitigate its emissions as part of a post-2012 climate regime. However, emissions embodied in internationally traded goods have not been given enough attention in this debate. This article discusses the results of research to quantify the emissions stemming from goods that are exported from China to other countries. It finds that these emissions accounted for 23% of China's national total in 2004. The article sets out how this result has been obtained and compares it to the results of several other pieces of research to demonstrate the importance of this issue. Some pointers for international climate policy are then discussed, including the advantages and difficulties of moving to consumption-based emissions accounting, and implications for international trade rules.     

Deforestation in Russia and its contribution to the anthropogenic emission of carbon dioxide in 1990–2013

The contribution of deforestation in Russia to the anthropogenic emission of carbon dioxide (CO₂) in 1990–2013 is estimated using the methods of computational monitoring. It is found that since 1990 the area of deforestation and forest conversion to other land-use categories is equal to 628.4 x 10³ ha. The respective CO₂ emissions from deforestation in Russia for the whole analyzed period are estimated at 142200 kt CO₂ with the average annual value of 5900 + 2270 kt CO₂/year. The largest contribution to the total losses is made by the changes in soil carbon stock (41.6%) and biomass carbon losses (28.8%). CO₂ emissions from deforestation make an insignificant contribution to the total anthropogenic CO₂ emission in the country (0.2%). Among the CO₂ sources in the land use, land-use change, and forestry sector (LULUCF), the emission from deforestation is the lowest with the average for 1990–2013 contribution of about 0.6%.     

Carbon prices and greenhouse gases abatement from agriculture,forestry and land use in Nepal

The Agriculture, forestry and other land use (AFOLU) sector as a whole accounts for more than 80% of the total greenhouse gas (GHG) emission in Nepal. This study estimates the GHG emissions from the AFOLU sector in the business as usual (BAU) case during 2010–2050 and identifies the economically attractive countermeasures to abate GHG emissions from the sector at different carbon prices. It also estimates the carbon price elasticity of GHG abatement from the sector. The study finds that enteric fermentation processes in the livestock and emissions from agricultural soils are the two major contributors of GHG emission in AFOLU sector. It identifies no-regret abatement options in the AFOLU sector that could mitigate about 41.5% of the total GHG emission during 2016–2050 in the BAU scenario. There would be a net cumulative carbon sequestration of 16 million tonnes of carbon dioxide equivalent (MtCO₂e) at $10 per tonne of carbon dioxide equivalent (tCO₂e) during the period. Carbon price above $75/tCO₂e is not found to be much effective in achieving significant additional reduction in GHG emissions from the AFOLU sector.     

Agricultural production and greenhouse gas emissions from world regions—The major trends over 40 years

Since 1970, global agricultural production has more than doubled with agriculture and land-use change now responsible for ∼1/4 of greenhouse gas emissions from human activities. Yet, while greenhouse gas (GHG) emissions per unit of agricultural product have been reduced at a global level, trends in world regions have been quantified less thoroughly. The KPI (Kaya-Porter Identity) is a novel framework for analysing trends in agricultural production and land-use change and related GHG emissions. We apply this to assess trends and differences in nine world regions over the period 1970–2007. We use a deconstructed analysis of emissions from the mix of multiple sources, and show how each is changing in terms of absolute emissions on a per area and per produced unit basis, and how the change of emissions from each source contributes to the change in total emissions over time. The doubling of global agricultural production has mainly been delivered by developing and transitional countries, and this has been mirrored by increased GHG emissions. The decoupling of emissions from production shows vast regional differences. Our estimates show that emissions per unit crop (as kg CO₂-equivalents per Giga Joule crop product), in Oceania, have been reduced by 94% from 1093 to 69; in Central & South America by 57% from 849 to 362; in sub-Saharan Africa by 27% from 421 to 309, and in Europe by 56% from 86 to 38. Emissions per unit livestock (as kg CO₂-eq. GJ⁻¹ livestock product) have reduced; in sub-Saharan Africa by 24% from 6001 to 4580; in Central & South America by 61% from 3742 to 1448; in Central & Eastern Asia by 82% from 3,205 to 591, and; in North America by 28% from 878 to 632. In general, intensive and industrialised systems show the lowest emissions per unit of agricultural production.     

Closing yield gap is crucial to avoid potential surge in global carbon emissions

Global greenhouse gas (GHG) emissions models generally project a downward trend in CO₂ emissions from land use change, assuming significant crop yield improvements. For some crops, however, significant yield gaps persist whilst demand continues to rise. Here we examine the land use change and GHG implications of meeting growing demand for maize. Integrating economic and biophysical models at an unprecedented spatial resolution, we show that CO₂ emissions from land conversion may rise sharply if future yield growth follows historical trends. Our results show that ~4.0 Gt of additional CO₂ would be emitted from ~23 Mha agricultural expansion from 2015 to 2026, under historical yield improvement trends. If yield gaps are closed expeditiously, however, GHG emissions can be reduced to ~1.1 Gt CO₂ during the period. Our results highlight the urgent need to close global yield gaps to minimize agricultural expansion and for continued efforts to constrain agricultural expansion in carbon-rich lands and forests.