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U Of M Biologist Studies Road Salt's Effect On Butterflies, Other Wildlife

MINNEAPOLIS (WCCO) --Minnesotans know the sand and salt used to clear the roads in the winter is helpful to drivers. For University of Minnesota biologist Emilie Snell-Rood, who didn't grow up here, the MnDOT trucks made her curious.

"I was kind of amazed by the amount of road salt and snow," she said. "I started wondering, as all this road salt is getting dumped everywhere, what is the effect of this on animals that might be living on the side of the road?"

The researchers looked at a county highway near Bethel. The plants near the side of the road had up to 30 percent more sodium than plants 100 meters away.

Sodium is an important micronutrient for animal and insect development. It affects brain and muscle growth. In small doses, it has positive effects on monarch butterflies and caterpillars.

"If they have larger flight muscle or bigger brains, it could have effects on how much they fly, how far they fly. Or how good they are at finding plants, where they lay their eggs," Snell-Rood said.

Too much salt can be deadly. There's a threshold where it becomes toxic. Snell-Rood said mortality rates increase from 40 to 50 percent to 90 percent.

Of the plants growing on the side of the highway, not all soaked up sodium the same. Oaks and milkweed had saturated levels, meaning they were extra salty, while grasses weren't affected.

Snell-Rood said more research is needed, not only about the effect on animals, but the effect on plants too.

Since some animals like deer are attracted to salt, the road run-off could be drawing more them near roadways.

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