SPRINGFIELD, Ill. — Invasive weeds have long threatened to erode dunes on a portion of the Chicago lakefront, but the area recently had to contend with a virtual invasion: “Pokemon Go” characters.

The game sends players into the real world in search of digital monsters that appear on smartphone screens to be caught, and hundreds of people have been flocking to the Loyola Dunes restoration area to find the hard-to-get “Lapras.” But in their quest to find the rare creature, players have been walking over native grassland critical to protecting the dunes from erosion.

The heavy foot-traffic became so worrisome to environmentalists that proposed legislation seeks to get certain sites removed from the game so players are only disturbing the virtual Pokemon characters and not ecologically sensitive areas in their quest to catch them.

“It should not be trampled and stampeded in that way,” said state Rep. Kelly Cassidy, a Chicago Democrat who is sponsoring the bill.

Cassidy’s bill would require app developers to remove locations in augmented reality games within two days of receiving a request to do so or face a daily fine of $100.

“We just want to make sure that the imaginary animals can co-exist with the real wildlife in our parks and natural areas,” said Jack Darin, director of the Sierra Club’s Illinois chapter.

The proposal is one of the first of its kind in the country, according to the National Conference of State Legislatures. In New York, lawmakers are considering legislation to restrict sex offenders’ use of augmented reality games.

Chicago’s case is not the first time in-game locations, known as “Pokestops,” have disrupted the real world. Pokestops at the atomic bomb memorial park in Hiroshima, Japan, and the U.S. Holocaust Memorial Museum in Washington are among the sites that have been removed from the game after complaints.

Niantec, the San Francisco-based developer behind the game, has removed the PokeStop that was frustrating conservationists in Chicago, but Cassidy said it took several requests and the introduction of her bill last week.

“We regret the delay in removing the site which was due to the unusually high usage of the game and subsequent requests for both removal and addition of game locations,” Niantic founder and CEO John Hanke said in a statement. “We want to emphasize that we are supporters of public space and believe that our cities and communities are healthier when citizens make use of public space, bringing us into contact with the outdoors and with one another. Yes, even when that use is motivated by capturing Pokemon.”

The earliest the bill can be heard is November, when state lawmakers return to the Capitol for a brief fall session. One small-government group has already expressed opposition, saying it’s an instance of government interfering with innovation.

“It’s trying to tell people to who develop a brand new product how they have to design it,” said Jacob Huebert, senior attorney with the Chicago-based Liberty Justice Center.

Cassidy said she has nothing against the game, which she also plays, and she applauded the fact that it’s getting people to explore the city and the dunes. She even named her bill after “Pidgey,”one of the more common bird-like characters from the game.

But environmentalists say the area, which volunteers have spent years trying to restore by pulling weeds and planting indigenous plants, was not meant to handle the amount of traffic it has received.

“There’ll be a hundred or two hundred people there, just like rushing on to the site to get a rare Pokemon, and a lot of them at one time,” said Jen Walling, executive director of the Illinois Environmental Council. “The site can have visitors, but that many is just too much.”