Weather and Milkweed Shortage Lead to Monarch Butterfly Declines


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The same combination of habitat loss and bad weather that has devastated pheasant populations in the Great Plains states has affected many other species as well, including the Monarch butterfly.

Bad weather and a shortage of milkweed, one of their most important foods, has driven Monarch butterfly populations to record lows, reports The New York Times. This year biologists estimate the migrating population of monarchs numbered about 35 million out of a population once estimated around a billion. The monarch makes one of nature's more remarkable migrations, an annual flight from the northern plains to Mexico begun by one generation of butterflies and completed by their descendants.

Heat in 2012 and wet weather last spring threw the migration off schedule, stressing the butterflies. And the last few years have seen widespread conversion of CRP grasses to rowcrops as well as clearing and planting of marginal lands driven by record commodity prices. The habitat loss has reduced the amount of flowering plants and milkweed on the monarch's migratory route, which stresses the butterflies by making them fly farther to find food. Monarchs lay their eggs on milkweed and it's the only food the larva can eat.