Suchergebnisse

When assessing soil organic carbon (SOC) sequestration and its climate change (CC) mitigation potential at global scale, the dynamic nature of soil carbon storage and interventions to foster it should be taken into account. Firstly, adoption of SOC-sequestration measures will take time, and reasonably such schemes could only be implemented gradually at large-scale. Secondly, if soils are managed as carbon sinks, then SOC will increase only over a limited time, up to the point when a new SOC equilibrium is reached. This paper combines these two processes and predicts potential SOC sequestration dynamics in agricultural land at global scale and the corresponding CC mitigation potential. Assuming that global governments would agree on a worldwide effort to gradually change land use practices towards turning agricultural soils into carbon sinks starting 2014, the projected 87-year (2014–2100) global SOC sequestration potential of agricultural land ranged between 31 and 64 Gt. This is equal to 1.9–3.9% of the SRES-A2 projected 87-year anthropogenic emissions. SOC sequestration would peak 2032–33, at that time reaching 4.3–8.9% of the projected annual SRES-A2 emission. About 30 years later the sequestration rate would have reduced by half. Thus, SOC sequestration is not a C wedge that could contribute increasingly to mitigating CC. Rather, the mitigation potential is limited, contributing very little to solving the climate problem of the coming decades. However, we deliberately did not elaborate on the importance of maintaining or increasing SOC for sustaining soil health, agro-ecosystem functioning and productivity; an issue of global significance that deserves proper consideration irrespectively of any potential additional sequestration of SOC.

The yield gap has arisen again as a focus for agricultural research to ensure food security and economic growth for farmers around the world. To examine this renewed interest, we carried out a review of key literature in the field of yield gap analysis to identify important gaps in research and analysis. In so doing, both the complexities in yield gap studies emerged along with some significant omissions. Much of the literature and research on the yield gap has been framed by larger concerns and initiatives to raise agricultural productivity. This focus has led to an emphasis on technical solutions such as crop breeding, fertilizer application and other methods to increase production. However, this concentration on the technical usually ignores the wider social, economic and political context that shapes farmer decision making about agricultural production. This context can either discourage or enable farmers to close their yield gap. Additionally, the impact of increased agricultural production through certain technical solutions also often overlooks the wider impact on the landscape and the ecosystem services which underpin agricultural production and livelihoods. We argue that increasing agricultural productivity, and closing the yield gap, must be addressed with this broader approach.

Rangelands occupy 25% of the total land surface globally. In Africa, rangelands are estimated to cover 66% of the land surface, although there are variations from country to country. In Eastern Africa, for example, land surface coverage of rangeland areas varies from 44% in Uganda and 65% in Ethiopia to 74% in Tanzania and over 80% in Kenya. Rangelands have environmental, social and economic benefits, including support to national economies through tourism and employment. In Kenya, tourism, much of which is attributed to rangelands, accounts for 13% of the gross domestic product. In Tanzania, tourism contributed 9.0% of the total GDP, supporting 26% of total exports, 8.2% of the total employment, and 8.7% of total investment in the year 2017. Despite their benefits, rangelands are under threat of continued degradation driven by anthropogenic and natural causes. Natural causes of rangeland degradation include climate change and variabilities, aridity and desertification, drought, as well as alien species invasion. Anthropogenic rangeland degradation can manifest through agricultural activities and associated developmental practices, overstocking and overgrazing, as well as breakdown of social structures and government policies/by-laws. Continuous overgrazing and overstocking not only affect soil physical (compaction, breakdown of aggregates) but also chemical (soil pH and salinization, nutrient leaching, diminishing organic matter content), and biological properties. These decrease rangeland production potentials. However, numerous strategies to arrest and remedy rangeland degradation, such as rangeland re-vegetation, water harvesting, soil surface scarification, and livestock grazing management are available. This report addresses rangeland degradation and potential control measures with a strong focus on soil aspects.

The active participation of the stakeholder community is viewed as a crucial consideration in the regional assessment of climate change in the Mediterranean. Each of the CIRCE integrating case studies has benefited from the real-life experience and expertise of local and regional stakeholders. The level of involvement has included stakeholder dialogue on an informal basis throughout the project, culminating in a series of more formal regional stakeholder workshops in the final year of the project. For each case study, stakeholders were chosen from the arena for which decisions are made at the regional-to-local level, and comprise local and regional decision and policy makers within government departments, agencies, and public/private sector entities. Regional stakeholders have contributed to the case-study assessments in six key areas: the conceptual framework and indicator selection, data and knowledge, identification of climate impact thresholds, risk assessment and management, strategies for adaptation, and guidance for policy. However, impediments to stakeholder participation have also been highlighted and include lack of motivation and resources commitment, stakeholder fatigue, and a need for targeted information. The CIRCE experience suggests that a more participatory approach, which involves sharing of 'best' practice and accessible targeted information, will be fundamental to successful adaptation planning in the Mediterranean region. This experience has also been used to develop a good practice checklist for facilitating stakeholder involvement in research projects.