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Monarch butterflies are already in danger. Their numbers have decreased by 80 percent in the past 20 years, and this year's count of the number of the black-and-orange butterflies wintering in Mexico was lower than 2017's.
Now, researched reported Tuesday in a Louisiana State University (LSU) press release reveals that two human-caused environmental concerns could combine to pose another deadly threat to monarchs in the future: climate change, and the spread of non-native species.