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Science:墨西哥帝王蝶数量正从历史低值中恢复

摘要 : 在墨西哥越冬的帝王蝶数量连续第二年出现上升,但它们著名的大迁徙仍因此岌岌可危,研究人员今天在墨西哥城的一场新闻发布会上报告了这一信息。

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在墨西哥越冬的帝王蝶数量连续第二年出现上升,但它们著名的大迁徙仍因此岌岌可危,研究人员今天在墨西哥城的一场新闻发布会上报告了这一信息。每年,数以百万计的蝴蝶从它们位于美国中西部和加拿大的繁殖地出发,长途跋涉到它们在墨西哥中部欧亚美尔杉和松树树林的冬季栖息地。从1993年开始,研究人员深入到这些森林并测量了帝王蝶覆盖的整体面积,用以作为确定其数量的基础。根据今天发布的最近的一份于2015年12月进行的调查,帝王蝶今冬占领了4公顷森林。这比去年帝王蝶占领的1.13公顷大了三倍还多,说明帝王蝶群的数量正从2013年至2014冬季的历史最低记录0.67公顷开始持续反弹。但同20世纪90年代末和21世纪初相比,帝王蝶的数量还是很低,当年帝王蝶往往可以覆盖8公顷以上的面积。世界野生动物基金会墨西哥地区的总干事Omar Vidal说,对帝王蝶4000公里的迁徙形程造成主要威胁的还是美国境内乳草的匮乏; 而该组织记录着乳草每年的数量。帝王蝶只将卵产在乳草上,而乳草曾经蓬勃生长在农田的作物间。但自从农民种植了抗除草剂的玉米和大豆,他们就能够在农田上喷洒强劲有效的农药,清除了害虫,却也将帝王蝶最需要的乳草全毁了。

原文链接:

Monarchs in Mexico recovering from record low numbers

原文摘要:

The number of monarch butterflies wintering in Mexico is up for the second year in a row but their famous migration remains imperiled, researchers said in a press conference in Mexico City today. Every year, millions of butterflies journey from their breeding grounds in the U.S. Midwest and Canada to their winter habitat in the oyamel fir and pine forests of central Mexico. Beginning in 1993, researchers have ventured into those forests and measured the total area covered by the butterflies, the established proxy for their numbers. According to the most recent survey, conducted in December 2015 and released today, monarchs covered 4 hectares of forest this winter. That’s nearly four times more area than the 1.13 hectares the butterflies occupied last year, indicating that the population continues to rebound from the all-time recorded low of 0.67 hectares in the winter of 2013–14. But monarch numbers remain low compared with the late 1990s and early 2000s, when the butterflies often covered 8 hectares or more. The main threat to the butterflies’ 4000-kilometer journey continues to be the loss of milkweed in the United States, says Omar Vidal, the director general of the World Wildlife Fund Mexico, which administers the annual count. Monarchs lay their eggs exclusively on milkweed, which used to thrive in between rows of crops in farmers’ fields. But since farmers have adopted herbicide-resistant corn and soybeans, they have been able to spray their fields with powerful chemicals that have all but wiped out milkweed wher the monarchs need it most.

来源: Science 浏览次数:0

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