Monarch butterflies rest on a rock at the Sierra Chincua Butterfly Sanctuary near Angangueo in the state of Michoacan, Mexico, on Friday, Jan. 16, 2015. Climate change and increased use of herbicides are threatening the monarch migration as well as eco-tourism in the region which attracts 120,000 visitors annually, according to scientists at the World Wildlife Fund in Mexico. Photographer: Susana Gonzalez/Bloomberg via Getty Images
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