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短日照作物[3分]

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一般起源于低纬度地带，在其生长发育过程中，只有当某一时期的日长短于临界日长时才能开花，在一定范围内，缩短日照时间能促进开......

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Last Friday an advisory panel to the European Environment Agency issued an extraordinary scientific opinion: The European Union should suspend its goal of having 10 percent of transportation fuel made from biofuel by 2020.The European Union&39;s biofuel targets were increased and extended from 5.75 percent by 2010 to 10 percent by 2020 just last year. Still, Europe&39;s well-meaning rush to biofuels, the scientists concluded, had produced a slew of harmful ripple effects - from deforestation in Southeast Asia to higher prices for grains.In a recommendation released last weekend, the 20-member panel, made up of some of Europe&39;s most distinguished climate scientists, called the 10 percent target overambitious and an experiment whose unintended effects are difficult to predict and difficult to control. The idea was that we felt we needed to slow down, to analyze the issue carefully and then come back at the problem, Laszlo Somlyody, the panel&39;s chairman and a professor at the Budapest University of Technology and Economics, said in a telephone interview.He said that part of the problem was that when it set the targets, the European Union was trying desperately to solve the problem of rising transportation emissions in isolation, without adequately studying the effects of other sectors like land use and food supply. The starting point was correct: I&39;m happy that the European Union took the lead in cutting greenhouse gasses and we need to control traffic emissions, Somlyody saiD. But the basic problem is it thought of transport alone, without considering all these other effects. And we don&39;t understand those very well yet. The panel&39;s advice is not binding and it is not clear whether the European Commission will follow the recommendation.It has become increasingly clear that the global pursuit of biofuels - encouraged by a rash of targets and subsides in both Europe and the United States - has not produced the desired effect.Investigations have shown, for example, rain forests and peat swamp are being cleared to make way for biofuel plantations, a process that produces more emissions than the biofuels can savE.Equally concerning, land needed to produce food forpeople to eat is planted with more profitable biofuel crops, and water is diverted from the drinking supply.In Europe and the United States, food prices for items like pizza and bread have increased significantly as grain stores shrink and wheat prices risE.The price of wheat and rice are double those of a year ago, and corn is a third higher, the UN Food and Agriculture Organization said this week. Food price inflation hits the poor hardest, as the share of food in their total expenditures is much higher than that of wealthier populations, said Henri Josserand of the Food and Agriculture OrganizationFor example, the European Environment Agency advisory panel suggests that the best use of plant biomass is not for transport fuel but to heat homes and generate electricity.To be useful for vehicles, plant matter must be distilled to a fuel and often transported long distances. To heat a home, it can often be used raw or with minimal processing, and moved just a short distance away.
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即使遇到丰收年景，对中国来说，要用世界百分之七的耕地养活全球五分之一的人口仍是一项艰巨的任务。中国政府面临许多挑战，最严峻的挑战之一就是耕地流失。过去几年中，平均每年有66.7万公顷耕地被城市扩建、工业发展以及公路建设工程占用，另有1万平方公里的耕地被沙漠吞噬。中国北方地区地下水位下降，农民不得不改种耐旱、地产作物，甚至撂荒。同时，农业基础设施损耗严重，三分之二的灌溉设施需要整修。由于农民为增加收入而改种经济作物，农业生产方式正在转变。过去十几年，全国水果和蔬菜种植面积平均每年增加130万公顷。因此，水稻、玉米及小麦产量急剧下降。中国已由粮食净出口国变为粮食净进口国。中国政府把农业改革视为头等大事，投入大量资金用于提高小麦和稻米的收购价以及改进农田灌溉基础设施。近年来，农产品的价格稳步上升，中国政府采取此项措施以提高农民种粮的积极性。
A.7万公顷耕地被城市扩建、工业发展以及公路建设工程占用，另有1万平方公里的耕地被沙漠吞噬。
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