Biodiversity: Monarch butterflies in steep decline

Monarch butterflies during migration. PHOTO COURTESY GENE NEIMINEN/USFWS.

GMO crops blamed for significant 10-year drop in population numbers

By Summit Voice

SUMMIT COUNTY —A decades-long downward trend in Monarch butterfly numbers is expected to continue this year, with reports from the World Wildlife Fund and other sources indicating there may be almost one-third fewer butterflies making the northward flight from Mexico this spring and summer.

This year’s steep decline may, in part, be due to last summer’s severe drought in Texas, which resulted in less food for the showy insects as they traveled south. But year-to-year fluctuations don’t hide the overall long-term trend of population decline.

“The latest information shows that Monarchs will be down from 25 to 30 percent this year, and that has been part of a disturbing trend the last few years,” said Craig Wilson, a senior research associate in the Center for Mathematics and Science Education and a long-time butterfly enthusiast.

This year, according to the Texas Monarch Watch, Monarchs covered about 7.14 acres of forest in their Mexican breeding grounds compared to 9.9 acres last year, and it shows a continued long-term downward trend in Monarch population since official surveys began in 1994.

The figures show an alarming decades-long decline, Wilson said, adding that it is best “that we take the long view rather than yearly cycles.”

“Last year’s severe drought and fires in the region no doubt played a part, resulting in less nectar for the Monarchs as they migrated south,” he said. “But estimates show that each year, millions of acres of land are being lost that would support Monarchs, either by farmers converting dormant land for crop use — mainly to herbicide tolerant corn and soybeans. The overuse of herbicides and mowing is probably another factor. Milkweed is the key plant because it’s the only plant where the female will lay her eggs.”

The loss of such lands is a critical factor in the Monarchs’ survival, Wilson explained.

“Chip Taylor, who is the director of Monarch Watch at the University of Kansas, estimates that 100 million acres of land have already been lost that previously supported Monarchs,” he said.

The Monarch Watch website clearly states the problem, with data showing that the steep decline in recent years is linked with the growing prevalence of genetically modified corn and soybeans. Where those crops have been planted, milkweed has nearly disappeared.

From Monarch Watch:

“It is apparent that there has been a significant decline in the overwintering monarch population since 2003. This decline is related to the adoption of herbicide tolerant row crops that were first introduced in 1996 … Overall, the amount of habitat lost due to the adoption of these crops may exceed 100 million acres.”

Most of the Monarch reserves are in the Mexican state of Michoacan. It’s an area where Monarchs spend the winter and mate before heading north, Wilson points out.

In the spring, the butterflies leave Mexico and across Texas, and Wilson has noticed both eggs and young Monarch caterpillars feeding on milkweed in the Monarch Waystation, a butterfly garden outside his office. The adults will fly various routes through Texas, with the fourth generation eventually arriving in Canada.

Wilson said there has to be a national effort to save Monarchs or their declining numbers will reach the critical stage.

“We need a national priority of planting milkweed to assure there will be Monarchs in the future,” he said. “If we could get several states to collaborate, we might be able to promote a program where the north-south interstates were planted with milkweed, such as Lady Bird Johnson’s program to plant native seeds along Texas highways 35-40 years ago. This would provide a ‘feeding’ corridor right up to Canada for the Monarchs.”

 

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