Pesticides, Severe Weather, Land Development Threaten Butterfly Migration

Newswise — Clinton, N.Y. - “This is the first time we have the data that we can analyze statistically that shows there’s a downward trend [in monarch butterfly populations],” said Hamilton College Professor of Biology Ernest H. Williams, co-author of “Decline of monarch butterflies overwintering in Mexico: is the migratory phenomenon at risk?” recently published in the journal Insect Conservation and Diversity. Williams attributes the decrease in monarchs to the loss of milkweed from use of “Roundup Ready” crops, land development, illegal logging at the wintering sites in Mexico and severe weather.

The article presents the results of a study showing that the number of monarchs overwintering on the mountains in Mexico - representing the population of monarchs east of the Rocky Mountains - has declined significantly over the past 17 years. Williams and his co-authors feel that this decline calls into question the long-term survival of the monarchs’ migratory phenomenon.

Williams, Hamilton College’s Christian A. Johnson Excellence in Teaching Professor of Biology, studies population biology, chemical ecology and conservation of butterflies. His most recent book is The Nature Handbook: A Guide to Observing the Great Outdoors, a field guide to patterns in nature and was released in 2005 by Oxford University Press. He is also co-author of The Stokes Butterfly Book, published by Little, Brown and Co., and editor and co-author of A Marsh for all Seasons, published locally by the Utica Marsh Council. His recent publications have appeared in Journal of Insect Conservation, Journal of the Lepidopterists' Society, the Journal of Animal Ecology, Restoration Ecology, The Journal of Biogeography, and American Butterflies. Williams currently works with Associate Professor of Biology Bill Pfitsch on habitat restoration and management in the Rome Sand Plains of central New York.

Williams’ article is available at: http://onlinelibrary.wiley.com/doi/10.1111/j.1752-4598.2011.00142.x/abstract.