(CBS) — In the Woody Wickham Butterfly Garden in the back of the Peggy Notebaert Nature museum, you can see them flying about. But over the past 20 years, the monarch butterfly population has declined by 90 percent.

“The main reason is the destruction of their habitat. Monarch butterflies literally cannot survive without milkweed,” says Sen. Melinda Bush, D-Grayslake. “It’s the only plant they lay their eggs on and the caterpillars grow.”

House Bill 6182 was signed into law on Friday. The legislation would create a specialty license plate. Fees would go toward a highway program to plant milkweed along the median strips of Illinois highways.

“Once a prolific native plant, the use of pesticides and herbicides nearly eradicated milkweed from the state of Illinois, so we are proposing we replant this along the state’s roadways, Bush says.

The median strips provide land that is easy for the butterflies to reach but hard for humans to disturb.

“At the nature museum, education is at the heart of everything we do. One of our passions is teaching children about the monarch’s life cycle,” says Doug Taron, chief curator at Peggy Notebaert Nature Museum.

“The monarch butterfly that weighs less than a gram takes a 2,500-mile flight from Canada through Chicago in the U.S. before finally finding sanctuary in the Fir Forest of the Butterfly Sanctuary in Michoacan, Mexico, where monarchs spend the winter,” Taron says.

Woody Wickham Butterfly Garden (WBBM/Lisa Fielding)

Woody Wickham Butterfly Garden (WBBM/Lisa Fielding)

The monarch, along with bees and other butterflies, play a critical role in our ecosystem.

“Pollinators are essential to our food supply. Without their contribution, we would not enjoy many of the foods we take for granted. Unfortunately, pollinator populations are in decline. For monarchs, habitat destruction has resulted in fewer places to grow milkweed, which means fewer monarchs. That’s why preserving the pollinator food supply, in this case, planting more milkweed, is critical,” Taron says.

The conservancy program is looking for volunteer sign-ups, first. Motorists would pay a surcharge for stickers to indicate their support for the monarch.

“I’m encouraging people to voluntarily sign up for the sticker. We need 2,000 people to sign up for the sticker before it actually becomes part of the new universal plate. After the 2,000, you will pay $25 for the monarch decal and then people who want to participate, it’ll be $29 to replace their current license plate with the universal plate and the decal,” Bush says.

You can call or stop in any Illinois Secretary of State’s office to reserve the monarch sticker.