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
The effect of fertilizers on methane emission rates was investigated using an automated closed chamber system in Chinese rice fields (Human Province). Each of three experiments compared two fields treated with a first uniform fertilizer dose and a second fertilizer dose which was different for each of the two fields. The uniform fertilizer doses for both fields in each experiment comprised mineral (experiment 1), organic (experiment 2) and combined mineral plus organic components (experiment 3). In all three experiments the second fertilizer dose comprised organic amendments for field 1 and no organic amendments for field 2. The rate of increase in methane emission with a given amount of organic manure was found to depend on the total amount of organic manure applied. A single dose of organic manure increased the emission rates by factors of 2.7 to 4.1 as compared to fields without organic manure (experiment 1). In rice fields that had already been treated with organic manure, the application of a second dose of organic manure only slightly enhanced the emission rates in experiment 2 by factors of 1.1 to 1.5 and showed no detectable increase in experiment 3. The net reduction achieved by separation of organic and mineral fertilizers was maximized by concentrating the organic amendments in the season with low emission rates, i.e. early rice, and using exclusively mineral fertilizers on late rice when emission rates were generally higher. This distribution pattern, which was not associated with significant yield losses, resulted in an annual methane emission corresponding to only 56% of the methane emitted from fields treated with blended fertilizers. 相似文献
The usual treatment of dogs with inflammatory bowel disease (IBD) consists of administration of immunosuppressive doses of steroids. However, some dogs are refractory to steroid treatment and pose a significant challenge to the veterinarian. Because cyclosporine A (cyA) has been shown to be effective in steroid-resistant IBD in humans, the purpose of this study was to investigate the pharmacokinetics and clinical efficacy of PO cyA treatment in dogs with steroid-refractory IBD (n = 14). All dogs were treated with cyA 5 mg/kg PO q24h for a period of 10 weeks. A clinical activity score was assigned to assess severity of clinical signs before and after treatment. The total number of infiltrating lymphocytes and T cells in duodenal biopsies were assessed before and after treatment in 9 dogs. In addition, serum concentration of cyA was measured in 8 dogs over a 24-hour period. Pharmacokinetic profiles in dogs with IBD were similar to those of healthy dogs. Improvement of clinical signs was observed in 12 of 14 dogs with IBD. Median clinical activity score after treatment with cyA was significantly reduced from a median score of 9 to a median score of 5 (P = 0.001). T cell numbers in duodenal biopsies were significantly decreased after treatment from a median +/- 95% range in the villous region of 28 (19-30) cells/10,000 microm2 before versus 7 (0-10)/10,000 microm2 after treatment, P = 0.01; and from a median +/- 95% range number in the crypt region of 15 (6-23) cells/10,000 microm2 before versus 4 (0-9)/10,000 microm2 after treatment, P = 0.02, implying T cell lysis as a possible mechanism of action. In conclusion, based on this small study, cyA appears to be an effective alternative drug in dogs with IBD that are refractory to immunosuppressive doses of steroids. 相似文献
Counts of bushbuck tracks were used to estimate their population densities. Good correlations were obtained between various indices of track frequency and estimated absolute population density. The technique is therefore recommended for assessing the absolute density of a population. High sampling costs, however, disqualify the technique for detecting small changes in density. 相似文献
Critical source areas (CSAs) define areas of a farm or catchment that emit the majority of water quality contaminants but account for a minority of the area at a field, farm or catchment scale. Using process based modelling we tested the hypothesis that the definition and management of CSAs would decrease losses of phosphorus (P) in two New Zealand catchments and nitrogen (N) in a French catchment. In the New Zealand catchment, CSAs of P loss were isolated to small areas within fields commensurate with surface flow pathways, while in the French catchment, CSAs for N loss were influenced by factors (inputs and land use) relevant at a field (or multiple field) scale. Scenarios were tested that examined the management of CSAs versus whole field management for P, and decreasing N loss within CSAs by increasing the proportion of grassland fields and changing their location relative to cropland. The results showed that N losses decreased by up to 25% as more grassland was incorporated into the catchment, especially in wet areas near valley bottoms due to a longer growth period and better utilisation/storage of N than cropland. For P, focusing mitigation on CSAs decreased catchment losses to a similar degree as mitigations applied across the whole catchment, but was on average 6–7 times more cost-effective. Therefore, the definition and management of CSAs at an appropriate scale is recommended to improve water quality and minimise the impact on farm profitability. 相似文献