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加州蝴蝶数量近40年来最低

2006-05-12 08:52王高山,CRI

California Butterfly Numbers Near 40-year Low

  The number of butterflies migrating through California has fallen to a nearly 40-year low as populations already hurt by habitat loss and climate change encountered a cold, wet spring, researchers said.

    "Some of them were already in decline, but this weather really added insult to injury, kicking them when they were down," said Arthur Shapiro, an entomologist with the University of California, Davis.

    Shapiro, who over 35 years of tracking the insects has developed one of the world's two largest butterfly databases, monitors 10 observation stations from the Suisun Marsh, in the San Francisco Bay Area, to the eastern slopes of the Sierra Nevada.

    About half of the usual species haven't shown up, while others — such as the drab-colored sooty wing or the iridescent eastern tailed-blue — are fluttering in at one-fourth or less of their usual numbers, he said.

    The change was particularly dramatic for the red and black painted ladies, which last year enjoyed a possibly record-breaking migration after feeding on the vegetation nurtured by abundant rain in Southern California's deserts.

    Last spring, millions of them migrated through the state and into Oregon, passing Shapiro's Sacramento site at a rate of four per second. This spring, he had reports of four painted ladies a month in the same area.

    Part of the problem was that the erratic weather — a mild winter, warm February and wet March — upset the usual cues that tell butterflies when to emerge from dormancy, Shapiro said.

    Long-term changes in rain patterns linked to global warming and the paving over of habitat could be playing a role, said Jessica Hellmann, an entomologist with the University of Notre Dame who has examined Shapiro's data.



美国科学家日前表示,寒冷潮湿的环境已经使得加利福尼亚今年的蝴蝶季节变得一去不返,还会导致某些种类的蝴蝶从该州境内完全消失。

据美国“生活科学网”5月8日报道,加州大学进化及生态学教授阿特·夏皮洛表示,对于生活在加州的蝴蝶来说,今年春天是35年来最糟的一个季节。他说:“这可能将造成一些长期的不利影响,对于那些数量本来就已经严重下降的某些种类的蝴蝶来说,更是如此。”

在夏皮洛进行监控的大部分观测点,蝴蝶数量只达到了每年这个时候正常数量的一半。4月18日,在瓦卡维尔附近的盖茨·坎宁,夏皮洛共监测到10个种类的48只蝴蝶。与此形成鲜明对比的是,去年的4月19日,在同一个监测点,他曾发现了21个种类的378只蝴蝶。

夏皮洛解释说,去年初冬气候相对较温和,不够寒冷的环境破坏了蝴蝶的休眠期,因此在今年较暖和的2月份里,蝴蝶并没有破茧而出。到了3月份,气候变得寒冷且潮湿,而这种天气状况对已经破茧而出的蝴蝶的繁殖又造成了非常大的破坏。

同时,由于西南部沙漠地区气候干燥,苎胥(蝴蝶的一种)毛虫的食物来源不足。因此,最近的数周内,夏皮洛和他的学生在戴维斯地区只观测到了一只苎胥。而通常情况下,现在应该有很多苎胥出现才对。夏皮洛还说,其他一些种类的蝴蝶的数量自1999年大幅减少后,至今仍没有得到恢复。另外,加州蝴蝶数量持续减少的同时,青蛙和其他一些两栖类动物的数量也在减少。

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