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The term pollinator decline refers to the reduction in abundance of insect and other animal pollinators in many ecosystems worldwide beginning at the end of the twentieth century, and continuing into the present day. Pollinators participate in sexual reproduction of many plants, by ensuring cross-pollination, essential for some species, or a major factor in ensuring genetic diversity for others. Since plants are the primary food source for animals, the reduction of one of the primary pollination agents, or even their possible disappearance, has raised concern, and the conservation of pollinators has become part of biodiversity conservation efforts. == Consequences == The value of bee pollination in human nutrition and food for wildlife is immense and difficult to quantify. 60 to 80% of the world’s flowering plant species are animal pollinated, and 35% of crop production〔 and 60% of crop plant species〔Roubik, D.W., 1995. "Pollination of Cultivated Plants in the Tropics". In: Agricultural Services Bulletin 118. Food Agriculture Organization of the United Nations, Rome, Italy. Pages 142–148〕 depend on animal pollinators. It is commonly said that about one third of human nutrition is due to bee pollination. This includes the majority of fruits, many vegetables (or their seed crop) and secondary effects from legumes such as alfalfa and clover fed to livestock. In 2000, Drs. Roger Morse and Nicholas Calderone of Cornell University attempted to quantify the effects of just one pollinator, the Western honey bee, on only US food crops. Their calculations came up with a figure of US $14.6 billion in food crop value.〔''The Value of Honey Bees As Pollinators of U.S. Crops in 2000'', Drs. Roger Morse and Nicholas Calderone of Cornell University (2000) : ()〕 In 2009, another study calculated the worldwide value of pollination to agriculture. They calculated the costs using the proportion of each of 100 crops that need pollinators that would not be produced in case insect pollinators disappeared completely. The economic value of insect pollination was then of €153 billion.〔Gallai, N., Salles, J. M., Settele, J., & Vaissière, B. E. (2009). Economic valuation of the vulnerability of world agriculture confronted with pollinator decline. Ecological Economics, 68(3), 810-821〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Pollinator decline」の詳細全文を読む スポンサード リンク
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