OTTUMWA — If you enjoy watching the migration of the monarch butterfly, you might be out of luck.
Nature researchers say even everyday butterfly watchers are noticing a massive decrease in the number of monarchs they see.
Alicia Houk teaches environmental science at Indian Hills Community College.
"Last year was the biggest drop ever measured," Houk said, adding that this does not appear to be one of those natural fluctuations sometimes seen in statistics.
She said scientists worry that numbers of monarchs are dropping so fast, one of Iowa's favorites may be heading toward the endangered species list. And even if the species survives, their visits to Iowa may come to a halt.
Annette Wittrock, the naturalist for the Wapello County Conservation Board, has noticed the same thing.
"Their numbers are definitely dropping, and there's concern out there as to whether they'll recover," she said.
Houk said one of the most interesting parts of the monarch life is also contributing to the danger they face: a migration that can be more than 2,000 miles.
They start in the mountain forests of Mexico and fly north, to about Texas. They lay eggs on milkweed — and then die of old age. The generation born in Texas is the group that makes it to Iowa. In Iowa, again, those butterflies lay eggs on milkweed, then we see those brand-new butterflies head toward Canada. And though they haven't figured out how, those Iowa-born butterflies know to leave Canada and head to the same forest their great-grandparents left several generations earlier.
Houk's research has led her and others to believe the danger to monarchs comes from something Iowans consider positive: improved agriculture. As new plant hybrids come on the market, farmers can safely blast their fields with herbicide. And that herbicide is kind to beans, deadly to weeds.
The problem is that milkweed is, of course, a weed. Houk said in most fields, milkweed has practically been eliminated, millions of the plants.
"That's their sole source of food when they're in the caterpillar stage, and so it's where they lay their eggs," said Wittrock. "But that's not the only factor."
For example, she said, Ottumwans certainly became familiar with drought over the past two summers. That reduces the amount of water butterflies need. It also cuts down on the nectar producing flowers they like to sip at. Because while milkweed is all the caterpillar will eat, the transformation into a butterfly brings an appetite for nectar.
"There's also been deforestation in their wintering habitat, the mountains of Mexico," Wittrock said.
Houk knows of that situation, which becomes especially important when one realizes all the millions of butterflies in this part of the country come from 12 wooded breeding areas. In the past, she said, the forests would become orange with butterflies. In fact, she said, that's what allowed researchers to count the population of monarch butterflies.
"This is a classic example of 'unintended consequences' that we see in environmental science," Houk said.
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