A slide in a long term decline can be North America's beloved monarch butterfly. During monarch numbers fluttered to the top and bottom in the last decades, a research group says now, enough data there, a downward trend on the ground.
In the last 17 years, area the Mexican forest of patches covered by wintering butterflies has been shrinking overall, biologist Ernest of Williams of Hamilton College in Clinton, New York conservation says he and his colleagues use the area since late 1994 occupied,, as gross index winter monarch population size has 7.24 hectares on average.
Several threats, including loss of Habitat, confront monarch, but the researchers focused on the assessment of the trends in the human populations instead of the confirmation of the causes.
Within the general downward trend followed below-average seven each other of 10 years in the study in a disturbing slice through the winter of expectations, the researchers say. The downward trend appeared no fluke based on a few years be good or bad; It showed up even if researchers the most area (20.97 hectares in 1996 / 97 removed) or the smallest (1.92 hectares in 2009 / 10) from the data, Williams and his colleagues online March 21 in insect conservation and diversity report.
"We have enough data now to to say that we see a long-term decline," says Williams.
This trend in winter may be statistically significant, the monarch says researchers Karen Oberhauser of the University of Minnesota in St. Paul, but they and other researchers working populations to a further analysis of the monarch and treated the insects to get a better challenges in the course of the year whether the population is declining and, if so, why. "I do not argue am, am that monarch population not threats face, or I say, I'm not concerned,", she says. "I don't think the [wintering] trend data to clarify the situation."
This situation affects the long-term health of the Williams is the best known species in the world. DART-orange black search coast to coast and as far north as Canada, milkweed plants as sites for eggs monarchs and waver North American summer landscapes. The species annual migration his dramatic feat is perhaps. Butterflies, which schlüpfen-in the summer and autumn - depending on the Mexico been without - find their way to the same patches of forest, their predecessor Act.
In the places ceiling monarch the forest. "It is stunning," Williams says. "Sometimes the bark does not see a look at a tree trunk and you." If sunlight is a burst of the monarchs in the escape, "you will hear a large sound of their wings."
For butterflies in Mexico and in their summer range "We see a confluence of threats," says Williams. Winter monarch retreats are officially protected, but illegal logging of chews entferntgelegene Mexico's forests. Plus, emerging climate change can bring more episodes of severe weather that may the butterflies of hammers. And monarch in North America will find fewer breeding ground than in the past. Open land for Milkweeds is on development and researchers warn that a boom in genetically cultures pattern change herbicide and the ranks of the Milkweeds thinning.
Sparser Milkweeds for breeding could theoretically have significant impact on monarch wealth, Myron Zalucki ecologist from the University of Queensland in Brisbane, Australia, "The big problem," says insect he says, "disentangling the effects of all threatening processes."
没有评论:
发表评论