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They are icons of the skies: in huge swarms the orange-black monarch butterflies flutter from North America to Mexico every year. There, the big butterflies then move into their warm winter quarters. The swarms provide an impressive picture that may not be that long before. The populations east of the Rocky Mountains have declined by more than 80 percent in the last two decades, part of which is threatened with extinction. Because the survival of the moths depends on certain plants, which are getting less and less: silk plants. They serve as a breeding ground for the butterflies and are the only food source of the caterpillars.

In a new study by the US Geological Survey (USGS) and the University of Arizona, researchers are developing possible scenarios to resettle silk plants in the Midwestern United States. They included not only agricultural land, but also protected areas and urban areas. According to the USGS, 1.6 billion silk plants are needed in North America to re-stabilize the butterfly populations. A resettlement of this magnitude can only be achieved through the cooperation of all sides, explains Wane Thogmartin, USGS scientist and lead author of the study.

Photo: Karen Oberhauser, University of Minnesota, provided by Fred Ormand and Joyce Pearsall

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