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Monarch Butterfly Population Plummets: Is the Drought to Blame?

First Posted: Mar 19, 2013 10:44 AM EDT

The massive drought which has affected areas of the southwest, including Texas, isn't just affecting people; it's also affecting monarch butterfly populations. New research shows that the insect numbers are dropping rapidly--partly due to the dry weather.

This last December, scientists surveyed monarch habitat in Mexico's Monarch Butterfly Biosphere Reserve. Yet in contrast to previous years, the researchers noted that the populations had severely declined. The insects occupied 59 percent less land than the previous year--the smallest area recorded in the 20 years of comparable record keeping. Essentially, fewer butterflies are arriving in Mexico during their winter migration, indicating that many of them have died off beforehand.

"The severe drought in Texas and much of the Southwest continues to wreak havoc with the number of monarchs," said Craig Wilson, a Texas A&M University researcher, in an interview with My San Antonio.

In fact, temperatures higher than 95 degrees can be lethal for the butterfly larvae. In addition, monarch eggs can dry out in hot, arid conditions, which means fewer of them hatch.

It's not only the temperatures that are affecting them, though. Monarch butterflies rely on a plant called milkweed, which their young eat for food. Unfortunately, milkweed habitat has declined, and herbicides used in farming have largely decimated milkweed numbers. This means less food for the monarch.

Monarch butterflies have one of the most astounding migration patterns in nature when it comes to insects. Every year, they journey hundreds of miles to winter in Mexico in vast clusters. While most monarchs live only about a month, the migrating generation lives about seven to eight months--long enough to accomplish the journey that can range from Canada to central Mexico.

Yet this migration may not happen for much longer. The combination of milkweed decline and rising temperatures has continued to affect monarch butterfly populations. Yet the drought in particular may cause catastrophic effects.

According to Chip Taylor, founder and direct of Monarch Watch, in an interview with National Geographic, extreme weather events such as drought or heat could potentially wipe out all Mexican butterfly colonies.

Whether there's a way to halt the monarch butterfly decline remains to be seen. Yet with the effects of drought and rising temperatures in full force, it's unlikely that numbers will rise until a little rain falls.

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