Estimation of Soil Carbon Gains Upon Improved Management within Croplands and Grasslands of Africa

Many agro(eco)systems in Africa have been degraded as a result of past disturbances, including deforestation, overgrazing, and over exploitation. These systems can be managed to reduce carbon emissions and increase carbon sinks in vegetation and soil. The scope for soil organic carbon gains from improved management and restoration within degraded and non-degraded croplands and grasslands in Africa is estimated at 20–43 Tg C year^?1, assuming that 'best' management practices can be introduced on 20% of croplands and 10% of grasslands. Under the assumption that new steady state levels will be reached after 25 years of sustained management, this would correspond with a mitigation potential of 4–9% of annual CO₂ emissions in Africa. The mechanisms that are being put in place to implement the Kyoto Protocol - through C emission trading - and prevailing agricultural policies will largely determine whether farmers can engage in activities that enhance C sequestration in Africa. Mitigation of climate change by increased carbon sequestration in the soil appears particularly useful when addressed in combination with other pressing regional challenges that affect the livelihood of the people, such as combating land degradation and ensuring food security, while at the same time curtailing global anthropogenic emissions.     

农田固碳措施对温室气体减排影响的研究进展

农田是CO2,CH4和N2O三种温室气体的重要排放源,在全球范围内农业生产活动贡献了约14%的人为温室气体排放量,以及58%的人为非CO2排放,不合理的农田管理措施强化了农田温室气体排放源特征,弱化了农田固碳作用。土壤碳库作为地球生态系统中最活跃的碳库之一,同时也是温室气体的重要源/汇。研究表明通过采取合理的农田管理措施,既可起到增加土壤碳库、减少温室气体排放的目的,又能提高土壤质量。农田土壤碳库除受温度、降水和植被类型的影响外,还在很大程度上受施肥量、肥料类型、秸秆还田量、耕作措施和灌溉等农田管理措施的影响。本文通过总结保护性耕作/免耕,秸秆还田,氮肥管理,水分管理,农学及土地利用变化等农田管理措施,探寻增强农田土壤固碳作用,减少农田温室气体排放的合理途径。农田碳库的稳定/增加,对于保证全球粮食安全与缓解气候变化趋势具有双重的积极意义。在我国许多有关土壤固碳与温室气体排放的研究尚不系统或仅限于短期研究,这也为正确评价各种固碳措施对温室气体排放的影响增加了不确定性。     

The potential for adoption of climate smart agricultural practices in Sub-Saharan livestock systems

Livestock systems play an important role in the livelihoods of many rural communities in Sub-Saharan Africa while being responsible for an important share of human-induced greenhouse gas emissions. This study aimed to evaluate the potential for adoption of climate smart agricultural practices in Sub-Saharan livestock systems, related to the improvement in feed, animal husbandry, and grassland management. These practices present productivity and mitigation benefits and in some cases may also contribute to enhance resilience. In this study, we used a data set of 1538 farm households across nine Sub-Saharan countries. A mixed logit model was used to assess the influence on adoption and to estimate the probability of adoption. Our results show that there seems to be stronger influence of physical and financial capitals on adoption than the other capitals. Different types of capitals influence the uptake of different agricultural practices. Yet the probability of adoption would change across countries. The results of this study could help to refine adoption estimates calculated through global or regional modelling approaches and to inform the design of policies to better target investments in order to foster adoption.     

Mitigating Greenhouse Gas Emissions from Tropical Agriculture: Scope and Research Priorities

The scope of mitigation options in tropical agriculture is discussed for three different activities (a) agroforestry, (b) rice-based production systems and (c) pasture/animal husbandry. The prevention of deforestation - and the re-forestation of degraded land - could become a key elements to national climate protection programs of some developing countries. Agroforestry may offer economically viable windows of opportunity for sustainable use of tropical forests whereas additional funds (e.g. through “Clean Development Mechanism”) will be required to make re-forestation programs profitable. Alternative management practices in rice-based systems may offer win-win options to reduce emissions and - at the same time - to obtain another improvement in the production system, namely through optimized timing of nitrogen fertilizer, temporary drainage in irrigated rice fields and integrated residue management. Introducing pasture in degraded land can sequester substantial amounts of carbon (similar to re-forestation). Future research has to include participation of stakeholders from all conceivable levels, i.e. farmers' cooperatives, non-governmental organizations, national agricultural research centers and extension services, to devise simple and financially interesting incentives for reducing emissions. The feasibility of environmentally friendly production techniques has to be disseminated to the public through ‘success stories’ (documented in public media) and demonstration farms.     

畜牧业“碳排放”到“碳足迹”核算方法的研究进展

全球变暖趋势日益加剧,不仅影响农业可持续发展,而且威胁到人类生存。畜牧业碳排放因其在农业碳排放中乃至全球碳排放中占比较大而日益备受关注。准确核算畜牧业碳排放是制定切实可行的碳减排政策的前提,也为我国在气候变化下承担共同但有差别的减排责任提供话语权。本文基于研究范式的演进,对畜牧业碳排放到碳足迹核算方法的研究发展进行了系统梳理,研究表明,在学者的不断研究与质疑下,畜牧业碳排放到碳足迹的核算方法经历了从OECD核算法、IPCC系数法到生命周期法与投入-产出法的演变与完善,学术界认为区域异质性、养殖规模与管理方式均影响碳足迹;散养比规模化养殖产生更多的碳排放,舍饲比户外放牧排放更多的碳。畜牧业碳足迹核算能够更加全面地反映畜牧业全生命周期的碳排放情况,但由于研究假设、研究方法及研究样本等差异导致不同区域、不同畜产品的碳排放核算结果存在不确定性。运用生命周期法和投入-产出法对欧盟成员国畜牧业碳排放的核算结果基本一致,但运用IPCC系数法和全生命周期法对中国畜牧业碳排放核算中,牛、猪和羊的碳排放量排序结果不尽一致。鉴于核算结果的差异性,本研究对不同核算方法的起源、最早采用时间、特点、局限性等方面进行了归纳总结,并建议后续研究探讨基于生命周期评价的畜牧业碳足迹研究边界的延伸性,标准化畜牧业碳排放或碳足迹核算,避免学者重复核算畜牧业碳排放,以便深入展开畜牧业碳排放其他方面的研究。     

Mitigating Greenhouse Gas Emissions from Rice-Wheat Cropping Systems in Asia

The rice-wheat belt comprises nearly 24–27 million ha in South and East Asia. Rice is generally grown in flooded fields whereas the ensuing wheat crop requires well-drained soil conditions. Consequently, both crops differ markedly in nature and intensity of greenhouse gas (GHG) fluxes, namely emission of (1) methane (CH₄) and (2) nitrous oxide (N_2O) as well as the sequestration of (3) carbon dioxide. Wetland rice emits large quantities of CH₄; strategies to CH₄ emissions include proper management of organic inputs, temporary (mid-season) field drainage and direct seeding. As for the wheat crop, the major GHG is N_2O that is emitted in short-term pulses after fertilization, heavy rainfall and irrigation events. However, N_2O is also emitted in larger quantities during fallow periods and during the rice crop as long as episodic irrigation or rainfall result in aerobic-anaerobic cycles. Wetland rice ensures a relatively high content of soil organic matter in the rice-wheat system as compared to permanent upland conditions. In terms of global warming potential, baseline emissions of the rice-wheat system primarily depend on the management practices during the rice crop while emissions from the wheat crop remain less sensitive to different management practices. The antagonism between CH₄ and N_2O emissions is a major impediment for devising effective mitigation strategies in rice-wheat system - measures to reduce the emission of one GHG often intensify the emission of the other GHG.     

中部六省低碳发展水平测度及发展潜力分析

人为的碳排放导致气候变化的加剧，低碳经济已成为人类的共识，向低能耗、低污染、低排放的低碳发展模式转型已成为世界各国可持续发展的必经之路。以我国中部六省作为研究区域，通过碳排放总量、人均碳排放量、地均碳排放量、碳生产率、碳能源排放系数等一系列指标对中部地区的低碳发展水平进行测度，对比各指标空间差异，认为中部地区目前还处于高碳发展阶段，碳排放总量大，碳生产率低，碳能源排放系数高，山西、河南尤为严重；在此基础上，采用产业 能源关联模型和能源 碳排放关联模型分析中部地区的低碳发展潜力，认为中部地区产业结构多元化水平和能源结构多元化水平低，且演化速率极其缓慢，致使碳排放增长速率无法减缓；中部地区虽然碳减排难度大，但减排潜力也大。〖     

Uncovering blind spots in urban carbon management: the role of consumption-based carbon accounting in Bristol,UK

The rapid urbanisation of the twentieth century, along with the spread of high-consumption urban lifestyles, has led to cities becoming the dominant drivers of global anthropogenic greenhouse gas emissions. Reducing these impacts is crucial, but production-based frameworks of carbon measurement and mitigation—which encompass only a limited part of cities’ carbon footprints—are much more developed and widely applied than consumption-based approaches that consider the embedded carbon effectively imported into a city. Frequently, therefore, cities are left blind to the importance of their wider consumption-related climate impacts, while at the same time left lacking effective tools to reduce them. To explore the relevance of these issues, we implement methodologies for assessing production- and consumption-based emissions at the city-level and estimate the associated emissions trajectories for Bristol, a major UK city, from 2000 to 2035. We develop mitigation scenarios targeted at reducing the former, considering potential energy, carbon and financial savings in each case. We then compare these mitigation potentials with local government ambitions and Bristol’s consumption-based emissions trajectory. Our results suggest that the city’s consumption-based emissions are three times the production-based emissions, largely due to the impacts of imported food and drink. We find that low-carbon investments of circa £3 billion could reduce production-based emissions by 25% in 2035. However, we also find that this represents <10% of Bristol’s forecast consumption-based emissions for 2035 and is approximately equal to the mitigation achievable by eliminating the city’s current levels of food waste. Such observations suggest that incorporating consumption-based emission statistics into cities’ accounting and decision-making processes could uncover largely unrecognised opportunities for mitigation that are likely to be essential for achieving deep decarbonisation.

     

Greenhouse Gas Fluxes in Tropical and Temperate Agriculture: The need for a Full-Cost accounting of Global Warming Potentials

Agriculture's contribution to radiative forcing is principally through its historical release of carbon in soil and vegetation to the atmosphere and through its contemporary release of nitrous oxide (N_2O) and methane (CHM₄). The sequestration of soil carbon in soils now depleted in soil organic matter is a well-known strategy for mitigating the buildup of CO₂ in the atmosphere. Less well-recognized are other mitigation potentials. A full-cost accounting of the effects of agriculture on greenhouse gas emissions is necessary to quantify the relative importance of all mitigation options. Such an analysis shows nitrogen fertilizer, agricultural liming, fuel use, N_2O emissions, and CH₄ fluxes to have additional significant potential for mitigation. By evaluating all sources in terms of their global warming potential it becomes possible to directly evaluate greenhouse policy options for agriculture. A comparison of temperate and tropical systems illustrates some of these options.     

Ecosystem carbon budgeting and soil carbon sequestration in reclaimed mine soil

Global warming risks from emissions of green house gases (GHGs) by anthropogenic activities, and possible mitigation strategies of terrestrial carbon (C) sequestration have increased the need for the identification of ecosystems with high C sink capacity. Depleted soil organic C (SOC) pools of reclaimed mine soil (RMS) ecosystems can be restored through conversion to an appropriate land use and adoption of recommended management practices (RMPs). The objectives of this paper are to (1) synthesize available information on carbon dioxide (CO2) emissions from coal mining and combustion activities, (2) understand mechanisms of SOC sequestration and its protection, (3) identify factors affecting C sequestration potential in RMSs, (4) review available methods for the estimation of ecosystem C budget (ECB), and (5) identify knowledge gaps to enhance C sink capacity of RMS ecosystems and prioritize research issues. The drastic perturbations of soil by mining activities can accentuate CO2 emission through mineralization, erosion, leaching, changes in soil moisture and temperature regimes, and reduction in biomass returned to the soil. The reclamation of drastically disturbed soils leads to improvement in soil quality and development of soil pedogenic processes accruing the benefit of SOC sequestration and additional income from trading SOC credits. The SOC sequestration potential in RMS depends on amount of biomass production and return to soil, and mechanisms of C protection. The rate of SOC sequestration ranges from 0.1 to 3.1 Mg ha(-1) yr(-1) and 0.7 to 4 Mg ha(-1) yr(-1) in grass and forest RMS ecosystem, respectively. Proper land restoration alone could off-set 16 Tg CO2 in the U.S. annually. However, the factors affecting C sequestration and protection in RMS leading to increase in microbial activity, nutrient availability, soil aggregation, C build up, and soil profile development must be better understood in order to formulate guidelines for development of an holistic approach to sustainable management of these ecosystems. The ECBs of RMS ecosystems are not well understood. An ecosystem method of evaluating ECB of RMS ecosystems is proposed.     

Soil management practices for sustainable agro-ecosystems

A doubling of the global food demand projected for the next 50 years poses a huge challenge for the sustainability of both food production and global and local environments. Today’s agricultural technologies may be increasing productivity to meet world food demand, but they may also be threatening agricultural ecosystems. For the global environment, agricultural systems provide both sources and sinks of greenhouse gases (GHGs), which include carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O). This paper addresses the importance of soil organic carbon (SOC) for agro-ecosystems and GHG uptake and emission in agriculture, especially SOC changes associated with soil management. Soil management strategies have great potential to contribute to carbon sequestration, since the carbon sink capacity of the world’s agricultural and degraded soil is 50–66% of the historic carbon loss of 42–72 Pg (1 Pg=10¹⁵ g), although the actual carbon storage in cultivated soil may be smaller if climate changes lead to increasing mineralization. The importance of SOC in agricultural soil is, however, not controversial, as SOC helps to sustain soil fertility and conserve soil and water quality, and organic carbon compounds play a variety of roles in the nutrient, water, and biological cycles. No-tillage practices, cover crop management, and manure application are recommended to enhance SOC storage and to contribute to sustainable food production, which also improves soil quality. SOC sequestration could be increased at the expense of increasing the amount of non-CO₂ GHG emissions; however, soil testing, synchronized fertilization techniques, and optimum water control for flooding paddy fields, among other things, can reduce these emissions. Since increasing SOC may also be able to mitigate some local environmental problems, it will be necessary to have integrated soil management practices that are compatible with increasing SOM management and controlling soil residual nutrients. Cover crops would be a critical tool for sustainable soil management because they can scavenge soil residual nitrogen and their ecological functions can be utilized to establish an optimal nitrogen cycle. In addition to developing soil management strategies for sustainable agro-ecosystems, some political and social approaches will be needed, based on a common understanding that soil and agro-ecosystems are essential for a sustainable society.     

Evaluation of food industry by-products as feed in semi-arid dairy farming systems: the case of Jordan

Dairy feeding systems in many semi-arid countries are based on imported concentrates and forages. This has economic and ecological implications given the increase in global feed prices and greenhouse gas (GHG) emissions from land use change. This paper aims to explore alternative dairy feeding systems under semi-arid conditions, using Jordan as an example. The feedings systems under investigation vary in their share of food industry by-products (replacing concentrates in the diet) and are compared against the current concentrate-based feeding systems. The systems are evaluated against three criteria: their nutritional value, their impact on the cost of milk production, and their GHG mitigation potential. Feed samples from eleven food industry by-products and ten conventional feeds were collected from food factories and from three typical dairy farms, representing the typical large-, medium- and small-scale farm types, respectively. Feed samples were analysed for their chemical composition and metabolisable energy contents. In addition, economic and production farm data were collected and entered into a model for GHGs calculation and economic evaluation. The results suggest that inclusion of locally available food industry by-products in the rations of milk cows in semi-arid production systems can be instrumental in reducing production costs and mitigating GHG emissions. Cost of milk production in the model farms can be lowered by up to 14 %; mitigation of CO₂ eq. emission ranged between 70 and 290 g CO₂ eq./kg milk. The degree to which these benefits can be reaped is positively related to the level of inclusion of by-product feeds in lactating cows’ diets.     

甲烷排放与应对气候变化国家战略探析

甲烷的全球变暖潜势是二氧化碳的72倍(20年水平),但其在大气中的寿命短于二氧化碳,可以作为优先减排对象。中国的甲烷排放十分突出,甲烷减排在应对气候变化国家战略中具有重要的基础性地位,然而在政策研究中,甲烷受到的关注程度远低于二氧化碳。本文基于甲烷排放研究的相关进展,首次系统性地论述了中国甲烷排放与应对气候变化国家战略之间的关系。主要结论是:甲烷排放的有效控制和减缓可以成为中国温室气体减排的重要组成部分,甲烷等温室气体的减排战略要用"系统减排"思路替代传统的"末端减排"思路;甲烷系统减排的策略和实施措施不仅需要重视主要排放部门(如煤炭开采与洗选业,农业)的直接末端减排,更需要突出强调建设活动、城市消费、资本投资和出口贸易等消费端的间接体现减排;在国际气候谈判中通过纳入甲烷排放,可以至少在五个方面丰富和支撑中国的国家立场,如从承诺"单位GDP二氧化碳减排"向承诺"单位GDP温室气体减排"转变。     

Potential synergies of the main current forestry efforts and climate change mitigation in Central Africa

In Central Africa, important carbon stocks are stored in natural forest stands, while activities that modify the carbon storage occur in the forest landscape. Besides clean development mechanisms, the reduction of emission through deforestation and degradation (REDD) initiative is viewed as one way to mitigate climate change. Important forest habitat protection activities have already been implemented with the aim of conserving the biodiversity of the region in a sustainable manner. The main causes of land use changes in the region are small holder subsistence practices and logging activities. Agricultural production has low productivity levels and therefore investments in improved agricultural techniques can both reduce pressure on existing forests and perhaps allow for the reforestation of existing degraded lands. The logging industry is dominated by large, industrial scale, logging operations performing selective logging of specific species and large trees. The adoption of improved forest management practices can reduce the impact of such logging on the ecological integrity and carbon stocks. Some efforts to engage in the carbon market have begun in the region. Further research is needed into the types of projects that will most likely become successful in the region and what locations will offer the greatest benefits.     

中国省际碳排放极化格局研究

温室气体减排是减缓气候变化的重要途径.由于资源、劳动力、资本和技术等要素的差异,我国社会经济发展不平衡,碳减排的潜力也各不同.文章在计算中国雀际碳排放的基础上,运用基尼系数和空间自相关的方法,刻画了1990年到2007年中国省际碳排放时空分布格局和聚集程度,有利于设立合理的长期减排目标和战略,实现碳排放空间的公平分配,促进区域协调发展.研究表明,碳总量和碳强度都呈现正的空间自相关性,在局部空间上出现了高值的聚集现象.碳强度的极化现象比碳总量更加严重.文章最后根据区域经济发展,资源禀赋,碳排放聚集等,因地制宜地提出了碳排放区划方案.区划结果显示出资源丰裕程度与碳强度的关系,有利于实施差异化的减排战略,实现经济发展与碳排放脱钩.     

Mitigating GHG Emissions in the Humid Tropics: Case Studies from the Alternatives to Slash-and-Burn Program (ASB)

Tropical forest conversion contributes as much as 25% of the net annual CO₂ emissions and up to 10% of the N_2O emissions to the atmosphere. The net effect on global warming potential (GWP) also depends on the net fluxes of greenhouse gases from land-use systems following deforestation. Efforts to mitigate these effects must take into account not only the greenhouse gas fluxes of alternative land-use systems but also the social and economic consequences that influence their widespread adoption. The global alternatives to slash-and-burn program (ASB) investigated the net greenhouse gas emissions and profitability of a range of land-use alternatives in the humid tropics. The analysis showed that many tree-based systems reduced net GWP compared to annual cropping and pasture systems. Some of these systems are also profitable in terms of returns to land and labor. The widespread adoption of these systems, however, can be limited by start-up costs, credit limitations, and number of years to positive cash flow, in addition to the higher labor requirements. Projects that offset carbon emissions through carbon sinks in land use in the tropics might be a means of overcoming these limitations. A synthesis of the findings from this program can provide guidelines for the selection and promotion of land-use practices that minimize net global warming effects of slash-and-burn.     

我国减缓碳排放的近期形势与远期趋势分析

近3年来我国面临GDP能源强度呈上升趋势，能源消费及相应CO2排放增长对世界减缓碳排放的形势产生了更大影响的新的形势，从长远发展趋势看，我国当前由于工业特别是重化工业在国民经济结构中急剧增加引起的GDP能源强度阶跃性增长将随产业结构的稳定两平缓，并且随产业结构的优化和产业技术升级及高附加值产品比例提高而再度呈持续稳定下降的趋势。我国在现代化道路中与发达国家的历程相比，可以走更为节约能源和减少CO2排放的道路。但由于中国人口众多，和平发展的规模大、速度快，而且时间比发达国家滞后半个世纪以上，我国为实现现代化所必需的能源消费和CO2排放的增长会对全球的碳排放增长产生重大影响。这将使我国未来经济发展面临极为不利的外部环境。     

中国深度脱碳路径及政策分析

《巴黎协定》开启了全球气候治理的新进程,进一步明确了全球应对气候变化的紧迫性和目标要求。对中国来说,如何尽快推动经济增长和碳排放的脱钩,不仅是实现应对气候变化中长期战略目标的核心任务,更是保障经济社会可持续发展的必然要求。为此,本文基于中国经济、社会、能源和重要的终端能源消费行业历史发展趋势的分析,通过"自下而上"的模型方法考察了能源、工业、建筑、交通等行业和领域的深度碳减排潜力,并基于详细的技术分析提出了中国中长期的深度脱碳路径。研究表明,在深度脱碳路径下,中国将顺利完成国家自主贡献提出的2030年左右碳排放达峰和碳强度较2005年下降60%—65%的目标;此后非化石能源发展进一步加速,到2050年非化石能源在一次能源中占比达到44%左右,工业、建筑、交通等终端耗能行业的低碳转型进一步加速,2050年碳排放回落至2005年前水平,碳强度较2005年下降90%以上。为实现深度脱碳,本文从强化碳排放总量约束和相关制度规范建设、完善产业低碳发展激励政策、加强相关市场机制作用、倡导低碳生活和消费等四方面提出了相应的政策建议,以供决策者参考。     

Regional carbon footprints of households: a German case study

Households are either directly or indirectly responsible for the highest share of global anthropogenic greenhouse gas emissions. Hence, programs helping to improve human consumption habits have been identified as a comparatively cost-effective way to reduce household emissions significantly. Recently, various studies have determined strong regional differences in household carbon footprints, yet a case study for Germany has not been conducted. Local information and policies directed at household consumption in Germany thus devoid of any foundation. In this paper, we analyze the impact of different criteria such as location, income and size on household carbon footprints in Germany and demonstrate how the impact of GHG mitigation opportunities varies for different population segments. We use a multi-region input output hybrid LCA approach to developing a regionalized household carbon footprint calculator for Germany that considers 16 sub-national regions, 15 different household sizes, and eight different income and age categories. The model reveals substantial regional differences in magnitude and composition of household carbon footprints, essentially influenced by two criteria: income and size. The highest income household is found to emit 4.25 times as much CO₂e than the lowest. We identify indirect emissions from consumption as the largest share of household carbon footprints, although this is subject to fluctuation based on household type. Due primarily to local differences in vehicle availability, income and nutrition, an average household in Baden-Wuerttemberg is found to have 25 % higher carbon footprint than its Mecklenburg-West Pomeranian counterpart. Based on the results of this study, we discuss policy options for household carbon mitigation in Germany.