CO2 Mitigation by Agriculture: An Overview

Agriculture currently contributes significantly to the increase of CO2 in the atmosphere, primarily through the conversion of native ecosystems to agricultural uses in the tropics. Yet there are major opportunities for mitigation of CO2 and other greenhouse gas emissions through changes in the use and management of agricultural lands. Agricultural mitigation options can be broadly divided into two categories: (I) strategies to maintain and increase stocks of organic C in soils (and biomass), and (ii) reductions in fossil C consumption, including reduced emissions by the agricultural sector itself and through agricultural production of biofuels to substitute for fossil fuels.Reducing the conversion of new land to agriculture in the tropics could substantially reduce CO2 emissions, but this option faces several difficult issues including population increase, land tenure and other socio-political factors in developing countries. The most significant opportunities for reducing tropical land conversions are in the humid tropics and in tropical wetlands. An important linkage is to improve the productivity and sustainability of existing agricultural lands in these regions.Globally, we estimate potential agricultural CO2 mitigation through soil C sequestration to be 0.4-0.9 Pg C y-1, through better management of existing agricultural soils, restoration of degraded lands, permanent "set-asides" of surplus agricultural lands in temperate developed countries and restoration of 10-20% of former wetlands now being used for agriculture. However, soils have a finite capacity to store additional C and therefore any increases in C stocks following changes in management would be largely realized within 50-100 years.Mitigation potential through reducing direct agricultural emissions is modest, 0.01-0.05 Pg C y-1. However, the potential to offset fossil C consumption through the use of biofuels produced by agriculture is substantial, 0.5-1.6 Pg C y-1, mainly through the production of dedicated biofuel crops with a smaller contribution (0.2-0.3 Pg C y-1) from crop residues.Many agricultural mitigation options represent "win-win" situations, in that there are important side benefits, in addition to CO2 mitigation, that could be achieved, e.g. improved soil fertility with higher soil organic matter, protection of lands poorly suited for permanent agriculture, cost saving for fossil fuel inputs and diversification of agricultural production (e.g. biofuels). However, the needs for global food production and farmer/societal acceptability suggest that mitigation technologies should conform to: (I) the enhancement of agricultural production levels in parts of the world where food production and population demand are in delicate balance and (ii) the accrual of additional benefits to the farmer (e.g., reduced labor, reduced or more efficient use of inputs) and society at large.     

Monitoring and reducing greenhouse gas emissions from agricultural,forestry and other human activities

Agriculture and forestry are significant sources and sinks of greenhouse gases. A holistic systems approach to estimating and reducing greenhouse gas emissions from agricultural, forestry and other systems requires that the major inputs, components and outputs of the production system are defined. Fluxes of greenhouse gases in natural systems may be estimated by mathematical modelling of the major biological processes and activities. Field and laboratory experiments and information from satellites provide the raw data on which such models are based. Such an approach can have a significant role in guiding key decision makers and policy analysts. We conclude that management strategies that reduce greenhouse gas emissions from agriculture and forestry are likely to be strategies that will also contribute to ecologically sustainable development.     

Carbon Dioxide Fluxes and Potential Mitigation in Agriculture and Forestry of Tropical and Subtropical China

Tropical and subtropical areas comprise about 23% of the total land area (960 Mha) of China. Of this, about 40% is in forests, 20% is in cropland and another 20% is wasteland. Preliminary estimates of overall sources and sinks of carbon dioxide indicate that current agricultural activities probably constitute a net sink. We estimate that improved agricultural management and wasteland reclamation have the potential to sequester an additional 1.9 Tg CO2-C y-1 or more, largely through increasing productivity and C inputs to soils and conversion of wasteland to agricultural production. We estimate that current forestry activities in the region could sequester about 7 Tg CO2-C y-1. There is also a large potential for increased C sequestration and fossil fuel offsets by conversion of wasteland to fuel wood plantations, on the order of 30-70 Tg C y-1. A number of practices for increasing mitigation of CO2 emissions in the forestry and agricultural sectors are presented.     

Evaluating bundles of interventions to prevent peat-fires in Indonesia

The carbon-dense peatlands of Indonesia are a landscape of global importance undergoing rapid land-use change. Here, peat drained for agricultural expansion increases the risk of large-scale uncontrolled fires. Several solutions to this complex environmental, humanitarian and economic crisis have been proposed, such as forest protection measures and agricultural support. However, numerous programmes have largely failed. Bundles of interventions are proposed as promising strategies in integrated approaches, but what policy interventions to combine and how to align such bundles to local conditions remains unclear. We evaluate the impact of two types of interventions and of their combinations, in reducing fire occurrence through driving behavioural change: incentives (i.e. rewards that are conditional on environmental performance), and deterrents (e.g. sanction, soliciting concerns for health). We look at the impact of these interventions in 10 villages with varying landscape and fire-risk contexts in Sumatra, Indonesia. A private-led implementation of a standardised programme allows us to study outcome variability through a natural experiment design. We conduct a systematic cross-case comparison to identify the most effective combinations of interventions, using two-step qualitative comparative analysis (QCA) and geospatial and socio-economic survey data (n = 303). We analysed the combined influence of proximate conditions (interventions, e.g. fear of sanction) and remote ones (context; e.g. extent of peat soil) on fire outcomes. We show how, depending on the level of risk in the pre-existing context, certain bundles of interventions are needed to succeed. We found that, despite the programme being framed as rewards-based, people were not responding to the reward alone. Rather sanctions and soliciting concern appeared central to fire prevention, raising important equity implications. Our results contribute to the emerging global interest in peat fire mitigation, and the rapidly developing literature on PES performance.     

Farm-scale adaptation and vulnerability to environmental stresses: Insights from winegrowing in Northern California

The wine industry is increasingly recognized as especially vulnerable to climate change due to the climate sensitivity of both winegrape yields and quality, making it an important model system for the agricultural impacts of global changes. However, agricultural production is strongly influenced by the management decisions of growers, including their practices to modify the microclimate experienced by the growing crop; these adaptations have not been studied at the vineyard level, where managers on the ground are on the front lines of responding to global change.We conducted 20 in-depth interviews with winegrowers to examine farm-scale adaptive responses to environmental stresses, to understand the views and motivations of agricultural managers, and to explore adaptive capacity in practice. We found that growers tend to respond to stresses individually rather than collectively, except when facing severe, unfamiliar pests and diseases. Responses may be reactive or anticipatory; most anticipatory strategies have been short-term, in response to imminent threats. Growers tend to rely on their own experience to guide their management decisions, which may offer poor guidance under novel climate regimes. From using a Vulnerability Scoping Diagram, we find that changing exposure (vineyard location) and sensitivity (planting choices such as vine variety) have the biggest impact on reducing vulnerability, but that adaptations in growing or processing the crop in the vineyard and winery are easier to implement, much more commonly undertaken, and may also offer substantial adaptive capacity. Understanding the context of adaptations, as well as the decision-making processes motivating them, is important for understanding responses to global change.These findings highlight some innovations in adapting to global change, as well as some of the barriers, and point to the need for strategic investments to enhance agricultural resilience to climate change. In particular, strategies to enhance both effective and easy to implement farming adaptations, as well as broader-scale anticipatory, collective responses, could reduce vulnerability in the context of climate change.     

Adaptation to climate change in Uganda: Evidence from micro level data

This study employed data from the 2005/06 Uganda national household survey to identify adaptation strategies and factors governing their choice in Uganda's agricultural production. Factors that mediate or hinder adaptation across different shocks and strategies include age of the household head, access to credit and extension facilities and security of land tenure. There are also differences in choice of adaptation strategies by agro-climatic zone. The appropriate policy level responses should complement the autonomous adaptation strategies by facilitating technology adoption and availing information to farmers not only with regard to climate related forecasts but available weather and pest resistant varieties.     

The adaptation and mitigation potential of traditional agriculture in a changing climate

The threat of global climate change has caused concern among scientists because crop production could be severely affected by changes in key climatic variables that could compromise food security both globally and locally. Although it is true that extreme climatic events can severely impact small farmers, available data is just a gross approximation at understanding the heterogeneity of small scale agriculture ignoring the myriad of strategies that thousands of traditional farmers have used and still use to deal with climatic variability. Scientists have now realized that many small farmers cope with and even prepare for climate change, minimizing crop failure through a series of agroecological practices. Observations of agricultural performance after extreme climatic events in the last two decades have revealed that resiliency to climate disasters is closely linked to the high level of on-farm biodiversity, a typical feature of traditional farming systems.Based on this evidence, various experts have suggested that rescuing traditional management systems combined with the use of agroecologically based management strategies may represent the only viable and robust path to increase the productivity, sustainability and resilience of peasant-based agricultural production under predicted climate scenarios. In this paper we explore a number of ways in which three key traditional agroecological strategies (biodiversification, soil management and water harvesting) can be implemented in the design and management of agroecosystems allowing farmers to adopt a strategy that both increases resilience and provides economic benefits, including mitigation of global warming.     

Climate change and the transgenic adaptation strategy: Smallholder livelihoods,climate justice,and maize landraces in Mexico

Climate change will affect agricultural production by subsistence farms in crop centers of origin, where landraces are conserved in situ. Various strategies for adaptation to climate change have been proposed. In this paper we examine the prospects of what we call the ‘transgenic adaptation strategy’, i.e. the appeal to use transgenic seeds to adapt to climate change, through the lens of smallholder maize farming in Mexico. Landraces are the bedrock of maize production in Mexico. We consider how maize farmers may respond to climate change and the effects of those responses on crop diversity. In this paper, we argue that the promotion of the transgenic adaptation strategy is problematic for biological and social reasons. Smallholder livelihoods in southern Mexico could suffer a disproportionate negative impact if transgenic technology is privileged as a response to climate change. Agroecological and evolutionary approaches to addressing the effects of climate change on smallholder agriculture provides an alternative adaptive strategy.     

Reevaluating suitability estimates based on dynamics of cropland expansion in the Brazilian Amazon

Agricultural suitability maps are a key input for land use zoning and projections of cropland expansion. Suitability assessments typically consider edaphic conditions, climate, crop characteristics, and sometimes incorporate accessibility to transportation and market infrastructure. However, correct weighting among these disparate factors is challenging, given rapid development of new crop varieties, irrigation, and road networks, as well as changing global demand for agricultural commodities. Here, we compared three independent assessments of cropland suitability to spatial and temporal dynamics of agricultural expansion in the Brazilian state of Mato Grosso during 2001–2012. We found that areas of recent cropland expansion identified using satellite data were generally designated as low to moderate suitability for rainfed crop production. Our analysis highlighted the abrupt nature of suitability boundaries, rather than smooth gradients of agricultural potential, with little additional cropland expansion beyond the extent of the flattest areas (0–2% slope). Satellite-based estimates of the interannual variability in the use of existing crop areas also provided an alternate means to assess suitability. On average, cropland areas in the Cerrado biome had higher utilization (84%) than croplands in the Amazon region of northern Mato Grosso (74%). Areas of more recent expansion had lower utilization than croplands established before 2002, providing empirical evidence for lower suitability or alternative management strategies (e.g., pasture–soya rotations) for lands undergoing more recent land use transitions. This unplanted reserve constitutes a large area of potentially available cropland (PAC) without further expansion, within the management limits imposed for pest management and fallow cycles. Using two key constraints on future cropland expansion, slope and restrictions on further deforestation of Amazon or Cerrado vegetation, we found little available flat land for further legal expansion of crop production in Mato Grosso. Dynamics of cropland expansion from more than a decade of satellite observations indicated narrow ranges of suitability criteria, restricting PAC under current policy conditions, and emphasizing the advantages of field-scale information to assess suitability and utilization.     

Rural livelihoods and climate variability in Ningxia, Northwest China

This study addresses the role of climate variability in the livelihoods of agricultural communities in Ningxia, Northwest China. Data sources comprise meteorological observations and official reports, complemented by questionnaires and focus group discussions designed around a livelihoods framework. Sample villages were located in three different agricultural systems: irrigated, mixed irrigated/grazing, and rainfed. Much of Ningxia is perennially dry and this is a significant limiting factor to agricultural production in the region, exacerbated by drought and buffered by irrigation mainly supplied from the Yellow River. Climate observations show stable temperatures from the 1950s to the 1980s followed by a positive trend (0.38°C/decade 1961–2010). Precipitation shows very modest trends and low decadal variability. Recent climate variability, particularly a drought from 2004–2006, was perceived to have had a significant effect on agricultural production and access to water, but it was not the only challenge respondents had faced. Susceptibility to drought was higher in the mixed irrigated and grazing and rainfed areas, due to farmers’ greater exposure to climatic hazards and because a higher proportion of their income originated from farming activities. Respondents were using a wide range of measures to retain and enhance soil moisture and maintain agricultural production. The discussion examines challenges in disentangling the role of climate within rapidly changing livelihood systems.     

Role of Education and Training in Agricultural Meteorology to Reduce Vulnerability to Climate Variability

Agricultural meteorologists are concerned with many operational aspects of the effects of climate on crop production, livestock, and natural resource management. For them to continue to make a contribution to the economy of a country they must continually sharpen their skills and remain updated on the latest available information. Training should include a variety of skills, including transferable skills (e.g. communication, numeracy), professional skills (including cognitive skills) and information technology skills. Problem-based learning can be used to promote critical thinking, decision making and analytical skills. More use should be made of computer-aided learning for agricultural meteorologists’ in-service training. In particular, the Internet or CDs could be used to disseminate specific recently developed techniques and applications to improve the understanding of the variability in climate and its effect on agricultural production and natural resource management. Examples that can address the vulnerability of farmers include crop–climate matching, the use of indices, crop modelling and risk assessment together with seasonal outlooks. A strategy needs to be formulated to address these needs and implement changes in the education and training of agricultural meteorologists. These training needs must be constantly updated to meet the changing demands of new technology to cope with climate change and climate variability.     

东北农业区降水年内分配的不均匀性及对区域增暖的响应

水热的合理配置为农业生产提供了有利的气候条件,明确热量和水分的匹配及变异规律对指导农业生产具有重要意义。本文利用东北农业区1961—2014年的逐日降水和气温资料,分析了东北农业区降水年内分配不均匀性的变异规律及其对区域增暖的响应,结果表明：(1)近54年来,该区表现为全区一致性的降水年内分配不均匀性降低、年际变化幅度增大和降水集中期提前的变化趋势;(2)降水年内分配不均匀性降低速率表现为中间大,南、北小的区域间差异;(3)降水年内分配不均匀性对气温具有很强的响应,表现出明显的不同步和区域间差异性,大致表现为在短周期上降水集中度落后气温、而长周期上超前气温的响应特征。气候增暖背景下,降水集中期的提前使得该区雨热同期的气候要素匹配关系保持稳定,但降水年内分配不均匀性的降低及年际间变化幅度的增大可能会增加该区夏季发生干旱的风险。研究结果可为制定科学的农田水管理策略提供参考。     

Effects of ozone air pollution on crop pollinators and pollination

Human driven environmental changes increase the concentrations of polluting reactive compounds in the troposphere, such as ozone and nitrogen oxides. These changes lead to biodiversity losses and alter plant physiology and plant-pollinator interactions, essential for pollination services, with potential consequences for agricultural production. Here we used 133 unique sampling events from NW Europe to investigate how air pollution (ozone and nitrogen oxides) and other sources of nitrogen is related to pollinator visitation rate and their contribution to agricultural production, also considering possible interactive effects with landscape quality and pesticide input. We showed that ozone modulates the effect of pesticide exposure and temperature on crop pollinators, increasing the probability of negative impacts on crop pollination. Indeed, when ozone levels are highest, the strength of the effect of pesticide on pollinators is more than double then when ozone levels are intermediate. This indicates that air pollution should be considered in management plans and policies aiming to safeguard biodiversity and promote more sustainable food production practices.     

Effects of Greenhouse Gas Emissions on World Agriculture, Food Consumption, and Economic Welfare

Because of many uncertainties, quantitative estimates of agriculturally related economic impacts of greenhouse gas emissions are often given low confidence. A major source of uncertainty is our inability to accurately project future changes in economic activity, emissions, and climate. This paper focuses on two issues. First, to what extent do variable projections of climate generate uncertainty in agriculturally related economic impacts? Second, to what extent do agriculturally related economic impacts of greenhouse gas emissions depend on economic conditions at the time of impacts? Results indicate that uncertainty due to variable projections of climate is fairly large for most of the economic effects evaluated in this analysis. Results also indicate that economic conditions at the time of impact influence the direction and size of as well as the confidence in the economic effects of identical projections of greenhouse gas impacts. The economic variable that behaves most consistently in this analysis is world crop production. Increases in mean global temperature, for example, cause world crop production to decrease on average under both 1990 and improved economic conditions and in both instances the confidence with respect to variable projections of climate is medium (e.g.,67%) or greater. In addition and as expected, CO₂ fertilization causesworld crop production to increase on average under 1990 and improved economic conditions. These results suggest that crop production may be a fairly robust indicator of the potential impacts of greenhouse gas emissions.A somewhat unexpected finding is that improved economic conditions are not necessarily a panacea to potential greenhouse-gas-induced damages, particularly at the region level. In fact, in some regions, impacts of climate change or CO₂ fertilization that are beneficial undercurrent economic conditions may be detrimental under improved economic conditions (relative to the new economic base). Australia plus New Zealand suffer from this effect in this analysis because under improved economic conditions they are assumed to obtain a relatively large share of income from agricultural exports. When the climate-change and CO₂-fertilization scenariosin this analysis are also included, agricultural exports from Australia plus New Zealand decline on average. The resultant declines in agricultural income in Australia plus New Zealand are too large to be completely offset by rising incomes in other sectors. This indicates that regions that rely on agricultural exports for relatively large shares of their income may be vulnerable not only to direct climate-induced agricultural damages, but also to positive impacts induced by greenhouse gas emissions elsewhere.     

利用条件植被指数评价西藏植被对气象干旱的响应

基于2000—2014年4—10月西藏气象站遥感干旱指数 (条件植被指数,VCI) 和气象干旱指数 (标准降水指数,SPI) 之间的相关性,评估植被对气象干旱的响应特征,通过分析气候环境要素对响应特征的影响并归纳相应规则,获取西藏地区植被对气象干旱有明显响应的区域分布。结果显示:VCI与12周时间尺度的SPI具有较强相关性,说明西藏地区植被生长对降水的响应大约滞后12周;植被对气象干旱响应不敏感的原因主要包括气候极度干燥或极度湿润、土地覆盖类型为森林、年平均归一化植被指数 (NDVI) 值过小、多年NDVI变化标准差过小、有降水之外的其他水源补给等;基于对区域气候环境要素特征的分析,可以得出西藏中部偏南地区植被对气象干旱有明显响应,主要包括拉萨地区、山南地区北部、日喀则地区东部、那曲地区中部和西南部、阿里地区的东南部。     

Mitigating Agricultural Emissions of Methane

Agricultural crop and animal production systems are important sources and sinks for atmospheric methane (CH4). The major CH4 sources from this sector are ruminant animals, flooded rice fields, animal waste and biomass burning which total about one third of all global emissions. This paper discusses the factors that influence CH4 production and emission from these sources and the aerobic soil sink for atmospheric CH4 and assesses the magnitude of each source. Potential methods of mitigating CH4 emissions from the major sources could lead to improved crop and animal productivity. The global impact of using the mitigation options suggested could potentially decrease agricultural CH4 emissions by about 30%.     

Climate change and agriculture in computable general equilibrium models: alternative modeling strategies and data needs

Agricultural sectors play a key role in the economics of climate change. Land as an input to agricultural production is one of the most important links between economy and the biosphere, representing a direct projection of human action on the natural environment. Agricultural management practices and cropping patterns exert an enormous effect on biogeochemical cycles, freshwater availability and soil quality. Agriculture also plays an important role in emitting and storing greenhouse gases. To consistently investigate climate policy and future pathways for the economic and natural environment, a realistic representation of agricultural land use is essential. Top—down Computable General Equilibrium (CGE) models have increasingly been used for this purpose. CGE models simulate the simultaneous equilibrium in a set of interdependent markets, and are especially suited to analyze agricultural markets from a global perspective. However, modeling agricultural sectors in CGE models is not a trivial task, mainly because of differences in temporal and geographic aggregation scales. This study surveys some proposed modeling strategies and highlights different tradeoffs involved in the various approaches. Coupling of top-down and bottom-up models is found to be the most applicable for comprehensive analysis of agriculture in prism of climate change. However, linking interdisciplinary data, methods and outputs is still the major obstacle to be solved for wide-scale implementation.     

Exploring global interregional food system's sustainability using the functional regions typology

Maintaining food security and environmental integrity over time requires a transition towards sustainable food systems. This paper analyzes different dimensions of national food supply sustainability on a global scale. By focusing on four food staples: wheat, rice, maize, and soybeans, the analysis identifies production regions that are more or less environmentally sustainable. It explores the dependence of different countries on calories supplied by these regions. These four staples' production requires 648 million hectares of cropland and about 559 cubic kilometers of irrigation water. It also leads to several environmental impacts, including potential soil loss and species loss. Yet, these impacts and pressures are spread unevenly across agricultural systems.We find that over one-third of the global calorie intake originates from regions with a high per ton environmental impacts. Although most consumed calories are from domestic sources, traded calories mostly originate from environmentally suitable production regions, increasing importing countries' food supply sustainability. This analysis also reveals interregional tradeoffs, where food imports into one region (increased food provision) is associated with high environmental impact in production regions. Further, this typology allows identifying an elusive, often overlooked interregional connection. That is the potential loss of future ecosystem service flow from countries with the lower gross domestic product per capita and high biodiversity. To date, those countries rely primarily on domestic staple production, which puts pressure on vulnerable local ecosystems. Species loss in those regions reduces the potential future interregional flows of genetic material. Alternatively, conservation combined with food imports can maintain diversity and the potential flow of genetic material from those regions. The functional regions typology provides a complete assessment of the interregional connections that make up the global food system. Therefore, it is useful for informing policy analysts and policymakers of a broader collection of stakeholders regarding the local environment. It also provides essential information about the suitability of different policy mechanisms to govern interregional systems. Future research shall expand the functional regions' typology to include additional environmental and human-related (e.g., technological), to cover more crops, and to account for other food categories, such as meat.     

Reconciling global sustainability targets and local action for food production and climate change mitigation

The Sustainable Development Goals (SDGs) imply country-led implementation. Yet, their achievement depends on sustainability targets compatible across different sectors and scales. Our study examines how the GHG emission intensity of agriculture (EIA) should evolve globally, regionally (Western Europe) and nationally (The Netherlands) under different socioeconomic pathways, so that two major aims of SDGs 2 and 13 (i.e. sufficient food production and climate change mitigation) are achieved simultaneously. Results show that, by 2050, relative to 2010 values, EIA should decrease at all three levels when measured on a product basis (GHG emissions per ton dry matter) and on a land basis (GHG emissions per ha). This indicates that, globally, agriculture should be intensified per unit area, while in Western Europe and even more so in the Netherlands additional emission reductions require increased production efficiency and lower production volumes. Projected reductions in methane and nitrous oxide emissions from enteric fermentation, manure management and fertilizer application in Dutch agriculture are much higher than what would be achieved through the extrapolation of current trends. Given the high costs of increasing production efficiency further, our analysis indicates the need for significantly more ambitious policy targets and systemic changes, including reduced consumption of animal-sourced food. Besides shedding light on the interaction between climate and agricultural strategies, our analysis illustrates the application of cross-scale thinking in the operationalization of the SDG agenda and underscores the need for concerted action amongst countries.     

Subnational institutions and power of landholders drive illegal deforestation in a major commodity production frontier

Deforestation is a main threat to the biosphere due to its contribution to biodiversity loss, carbon emissions, and land degradation. Most deforestation is illegal and continues unabated, representing around half of the total deforestation in the tropics and subtropics. Quantifying illegal deforestation is challenging, let alone assessing the social and institutional processes underlying its occurrence. We tackle this challenge by quantifying the relative influence of individual (i.e., landholders’ power, landholding size) and contextual (i.e., subnational institutions, agricultural suitability) factors on the type and size of illegal deforestation in the Argentine Dry Chaco, a major commodity production frontier and global deforestation hotspot. We build a Bayesian network fed with data of 244 illegal deforestation events, obtained from journalistic articles, grey literature, key informant interviews, and geospatial analyses. The results reveal that more powerful landholders were associated with larger illegal deforestation events. Policy simulations suggest that higher concentration of land in the hands of powerful landholders and more flexible subnational forest regulations would escalate illegal deforestation. This points to the need for a smart policy mix that integrates across economic, agricultural, and environmental sectors to halt illegal deforestation at commodity production frontiers. A land tenure reform can facilitate forest protection, while incentives to land-use diversification and the criminal prosecution of illegal deforestation are critical to shift landholder behavior towards more balanced production and conservation outcomes.