Mechanisms of Basin-Scale Nitrogen Load Reductions under Intensified Irrigated Agriculture

Irrigated agriculture can modify the cycling and transport of nitrogen (N), due to associated water diversions, water losses, and changes in transport flow-paths. We investigate dominant processes behind observed long-term changes in dissolved inorganic nitrogen (DIN) concentrations and loads of the extensive (465,000 km2) semi-arid Amu Darya River basin (ADRB) in Central Asia. We specifically considered a 40-year period (1960–2000) of large irrigation expansion, reduced river water flows, increased fertilizer application and net increase of N input into the soil-water system. Results showed that observed decreases in riverine DIN concentration near the Aral Sea outlet of ADRB primarily were due to increased recirculation of irrigation water, which extends the flow-path lengths and enhances N attenuation. The observed DIN concentrations matched a developed analytical relation between concentration attenuation and recirculation ratio, showing that a fourfold increase in basin-scale recirculation can increase DIN attenuation from 85 to 99%. Such effects have previously only been observed at small scales, in laboratory experiments and at individual agricultural plots. These results imply that increased recirculation can have contributed to observed increases in N attenuation in agriculturally dominated drainage basins in different parts of the world. Additionally, it can be important for basin scale attenuation of other pollutants, including phosphorous, metals and organic matter. A six-fold lower DIN export from ADRB during the period 1981–2000, compared to the period 1960–1980, was due to the combined result of drastic river flow reduction of almost 70%, and decreased DIN concentrations at the basin outlet. Several arid and semi-arid regions around the world are projected to undergo similar reductions in discharge as the ADRB due to climate change and agricultural intensification, and may therefore undergo comparable shifts in DIN export as shown here for the ADRB. For example, projected future increases of irrigation water withdrawals between 2005 and 2050 may decrease the DIN export from arid world regions by 40%.     

Flexible Strategies for Coping with Rainfall Variability: Seasonal Adjustments in Cropped Area in the Ganges Basin

One of the main manifestations of climate change will be increased rainfall variability. How to deal with this in agriculture will be a major societal challenge. In this paper we explore flexibility in land use, through deliberate seasonal adjustments in cropped area, as a specific strategy for coping with rainfall variability. Such adjustments are not incorporated in hydro-meteorological crop models commonly used for food security analyses. Our paper contributes to the literature by making a comprehensive model assessment of inter-annual variability in crop production, including both variations in crop yield and cropped area. The Ganges basin is used as a case study. First, we assessed the contribution of cropped area variability to overall variability in rice and wheat production by applying hierarchical partitioning on time-series of agricultural statistics. We then introduced cropped area as an endogenous decision variable in a hydro-economic optimization model (WaterWise), coupled to a hydrology-vegetation model (LPJmL), and analyzed to what extent its performance in the estimation of inter-annual variability in crop production improved. From the statistics, we found that in the period 1999–2009 seasonal adjustment in cropped area can explain almost 50% of variability in wheat production and 40% of variability in rice production in the Indian part of the Ganges basin. Our improved model was well capable of mimicking existing variability at different spatial aggregation levels, especially for wheat. The value of flexibility, i.e. the foregone costs of choosing not to crop in years when water is scarce, was quantified at 4% of gross margin of wheat in the Indian part of the Ganges basin and as high as 34% of gross margin of wheat in the drought-prone state of Rajasthan. We argue that flexibility in land use is an important coping strategy to rainfall variability in water stressed regions.     

Coping Strategies among Urban Poor: Evidence from Nairobi,Kenya

Aims

In Kenya, it is estimated that 60 to 80% of urban residents live in slum or slum-like conditions. This study investigates expenditures patterns of slum dwellers in Nairobi, their coping strategies and the determinants of those coping strategies.

Method

We use a dataset from the Indicator Development for Surveillance of Urban Emergencies (IDSUE) research study conducted in four Nairobi slums from April 2012 to September 2012. The dataset includes information related to household livelihoods, earned incomes of household members, expenditures, shocks, and coping strategies.

Results

Food spending is the single most important component, accounting for 52% of total households'' income and 42% of total expenditures. Households report a variety of coping strategies over the last four weeks preceding the interview. The most frequently used strategy is related to reduction in food consumption, followed by the use of credit, with 69% and 52% of households reporting using these strategies respectively. A substantial proportion of households also report removing children from school to manage spending shortfalls. Formal employment, owning a business, rent-free housing, belonging to the two top tiers of income brackets, and being a member of social safety net reduced the likelihood of using any coping strategy. Exposure to shocks and larger number of children under 15 years increased the probability of using a coping strategy.

Policy Implications

Policies that contain food price inflation, improve decent-paying job opportunities for the urban poor are likely to reduce the use of negative coping strategies by providing urban slum dwellers with steady and reliable sources of income. In addition, enhancing access to free primary schooling in the slums would help limit the need to use detrimental strategies like “removing” children from school.     

Coping with Uncertainty and Variability: The Influence of Protected Areas on Pastoral Herding Strategies in East Africa

A large number of East African pastoralists reside around protected areas (PAs). Over the last few decades pastoralists have been affected by the loss of grazing lands and increasing climatic variability. Many pastoralists who reside around PAs have resorted to grazing inside PAs to counter environmental variability. However, there is little information on how PAs influence the herding strategies of pastoralists. This case study from southern Kenya employs a spatially and temporally explicit mixed-methods approach to understand and evaluate the herding strategies of pastoralists around a PA. The results find that pastoralists access PAs on a regular basis, regardless of seasonality or herd size. Movement into PAs was partly driven by the loss of grazing land to conservancies. PAs affected pastoral herding by presenting differential opportunity costs to disparate groups. However, households with large herd sizes utilized the most flexible strategies to counter environmental variability and uncertainty.     

转基因植物中外源基因的沉默及应对策略

随着转基因技术在作物育种领域的应用,转基因植物中外源基因表达量低的现象较为普遍。导致外源基因表达量低的主要原因是基因沉默。外源基因沉默可分为转录水平的基因沉默和转录后水平的基因沉默。如何应对基因沉默,提高外源基因的表达量,是转基因技术发展亟待解决的问题。     

广东省生态农业建设及其发展对策

介绍了广东生态农业的产生和发展的背景及生态农业建设的基本情况,并着重对目前广东省生态农业建设的9种主要模式及其经济和生态效益以及存在的问题进行了较详细的分析,在此基础上提出了广东生态农业发展的主要对策。     

Coping Strategies in Livestock-dependent Households in East and Southern Africa: A Synthesis of Four Case Studies

Integrated assessment seeks to combine models of the ecological as well as the social system to allow different scenarios to be tested in terms of their likely impacts on ecological functioning and household well-being. We outline such work undertaken in four case studies in East and southern Africa: pastoralist communities in northern Tanzania, agro-pastoralists in southern Kenya, communal and commercial ranchers in South Africa, and mixed crop-livestock farmers in western Kenya. Results from these case studies are synthesised to test the hypothesis that households’ capacity to adapt in the face of increasing external stresses is governed by flexibility in livelihood options. The results support this hypothesis. There is considerable variation in how households in these places cope with external stresses. Options include intensification, diversification, and increasing off-farm economic activities, and these depend on household objectives and attitudes as well as on access to natural resources, inputs and output markets. The results also indicate that generally it is the poorer households that can gain the most from implementing such options for coping and managing risk. Quantifying likely household and ecosystem impacts of different options is a crucial step in targeting appropriate technology, policy and adaptation interventions in the face of considerable system changes. We conclude with some research needs to improve integrated assessment tools that may allow us to represent more realistically the highly complex decision-making milieu of householders in sub-Saharan Africa who are dependent on ecosystem goods and services for a large part of their livelihoods.     

广东省生态农业建设及其发展对策

介绍了广东生态农业的产生和发展的背景及生态农业建设的基本情况,并着重对目前广东省生态农业建设的9种主要模式及其经济和生态效益以及存在问题进行了较详细的分析,在此基础上提出了广东生态农业发展的主要对策。