Scientists at Iowa State University say they have a plan to save monarch butterflies.In the last two decades, the population of monarch butterflies has decreased by 80%. Extinction could be just around the corner.That’s bad news for Iowa State University butterfly expert Dr. John Pleasants."They're just a really cool species and lots of people really like them," Pleasants said.Pleasants and his team have been working for years to come up with a way to save the monarch. They have a special colony of butterflies in an ISU science building laboratory. New research shows there is one surefire way to help the iconic insect — more milkweed plants.The question Pleasants has been asking is: "What's the best way to get more milkweeds out there and help the monarch population?"Over the years, herbicides have destroyed much of Iowa's native milkweed — mostly near farm fields.Researchers have used computer modeling and even attached radio transmitters to monarch butterflies to discover their habits."You have to know how a female butterfly makes decisions. So, she comes to a patch of milkweed. How many eggs does she lay? How long does she stay there, how does she find the next patch?” Pleasants said.Bottom line? Scientists say the state of Iowa needs a huge increase in milkweed plants — both in rural areas and in your own backyard."Over a billion milkweed stems need to be added to the landscape and that doesn’t even get us back to where we were before but backs to a level that's a pretty decent level but that's a lot of milkweeds," Pleasants said.Researchers say 2023 is expected to be another bad year for the monarch population, so planting more milkweed can't happen soon enough.