This paper reviews the knowledge on effects of climate change on agricultural productivity in Europe and the consequences for policy and research. Warming is expected to lead to a northward expansion of suitable cropping areas and a reduction of the growing period of determinate crops (e.g. cereals), but an increase for indeterminate crops (e.g. root crops). Increasing atmospheric CO2 concentrations will directly enhance plant productivity and also increase resource use efficiencies.
In northern areas climate change may produce positive effects on agriculture through introduction of new crop species and varieties, higher crop production and expansion of suitable areas for crop cultivation. Disadvantages may be an increase in the need for plant protection, the risk of nutrient leaching and the turnover of soil organic matter. In southern areas the disadvantages will predominate. The possible increase in water shortage and extreme weather events may cause lower harvestable yields, higher yield variability and a reduction in suitable areas for traditional crops. These effects may reinforce the current trends of intensification of agriculture in northern and western Europe and extensification in the Mediterranean and southeastern parts of Europe.
Policy will have to support the adaptation of European agriculture to climate change by encouraging the flexibility of land use, crop production, farming systems etc. In doing so, it is necessary to consider the multifunctional role of agriculture, and to strike a variable balance between economic, environmental and social functions in different European regions. Policy will also need to be concerned with agricultural strategies to mitigate climate change through a reduction in emissions of methane and nitrous oxide, an increase in carbon sequestration in agricultural soils and the growing of energy crops to substitute fossil energy use. The policies to support adaptation and mitigation to climate change will need to be linked closely to the development of agri-environmental schemes in the European Union Common Agricultural Policy.
Research will have further to deal with the effect on secondary factors of agricultural production, on the quality of crop and animal production, of changes in frequency of isolated and extreme weather events on agricultural production, and the interaction with the surrounding natural ecosystems. There is also a need to study combined effects of adaptation and mitigation strategies, and include assessments of the consequences on current efforts in agricultural policy to develop a sustainable agriculture that also preserves environmental and social values in the rural society. 相似文献
Drought response of three Douglas-fir clones (slow, intermediate and fast growing) inhabiting two different climatic regimes in France was examined. We used the hydraulic conductivity and the percent loss of conductivity due to embolism from stems and branches as well as wood microdensity measurements to determine the role of genetics in the control of embolism in this species. Conductivity and tree-ring’s microdensity variables (ring width: RW, mean ring density: MRD, minimum ring density: MID and maximum ring density: MAD) were compared in growth rings in all three clones during a typical year (2002) vs. an extremely dry year (2003). A new method was developed in order to assess axial hydraulic specific conductivity (Ks) within tree rings. The results show that branches are more resistant to embolism than stems, and that there are significant differences in embolism resistance among the clones between the two sites. Ks varied between years, sites and clones but the site exerted the most significant effect. Lartimache (more humid site during 2003) trees showed substantially higher Ks than those inhabiting Chassenoix (strongly affected by the 2003 heat and drought wave site). Wood analysis showed a significant year effect for all ring variables and a significant clone effect for all ring variables except for MAD, while the site effect was significant for MRD and MAD. The existence of a genetic control for the study traits indicates that Douglas-fir populations introduced in France may have a selection potential to face extreme climate events like the 2003 heat and drought wave. 相似文献
There is limited documentation of soil and water management technologies that enhance adaptation to climate change in drylands of Kenya. Rainfall patterns were analyzed in the semi-arid Machakos and Makueni counties of eastern Kenya using historical data. A total of forty-three smallholder farmers implementing soil water management practices were sampled, and an estimate of the seasonal water budget for current crop and livestock production systems computed. Analysis of rainfall amounts and distribution shows increasing variability, with the average annual total amounts decreasing over the past 50 years. Furthermore, the number of rainy days within the March-April-May season that can support crop growth is gradually decreasing. These decreases are however not significant at P < 0.05. There were more seasons with low rainfall amounts compared to those with high rainfall amounts. All these subject the smallholder crop and livestock production system to limited soil moisture. Farmers address the risk by harnessing and utilizing green (rainfall stored in soil) and blue (rainfall collected into storage tanks) water technologies. The study found that farmers in these semi-arid counties practice fifteen diverse soil and water management interventions on their farms. The most popular practices are cut-off drains, retention ditches, terracing, run-off harvesting, and agroforestry. The estimated seasonal water budget indicates the need for integrated soil and water management interventions to address the crop and livestock production constraints. 相似文献