The park draws roughly 2 million visitors a year, and for busy weekends and holidays, reservations can fill up six months in advance.
In a staff report issued last month, regulators wrote that the environmental impacts of all that activity "warrant elimination" of off-highway vehicle use and a transition to "other less intensive forms of public access and recreation."
Dan Carl, director of the Coastal Commission's Central Coast District, says off-road vehicles have been motoring through the dunes under a temporary permit issued in 1982, despite the fact that allowing such activity in environmentally sensitive habitat violates the 1976 Coastal Act.
Carl pointed to several vehicle-related problems that have grown in intensity in recent years, including public health effects from the dust, the killing of endangered birds "and then that age-old question of how is this even allowed in environmentally sensitive habitat under the law?"
To access riding areas, vehicles must cross Arroyo Grande Creek, a perennial stream that empties into the ocean and supports tidewater goby and steelhead trout, fish that are listed under the federal Endangered Species Act.
The park also cordons off some 300 acres for much of the year to protect endangered snowy plovers and California least terns during breeding season. The birds, however, keep getting killed outside those areas. Last year, 15 plovers were found dead, eight of them "crushed next to tire tracks," according to the Coastal Commission's staff report.
"We've tried every trick in the book. But even with our best efforts, it has happened," said Ronnie Glick, a senior environmental scientist for the state parks department, who argues that off-roading can effectively be balanced with habitat conservation. "You have intense recreation and intense conservation. And you have them side-by-side."
Coastal Commission staff wants state parks to impose a list of near-term restrictions it says are necessary to protect the environment and the public. Among them, reduce the number of vehicles allowed in the park, prohibit them from crossing Arroyo Grande Creek when it's flowing, and make permanent the seasonal area fenced off to protect endangered species.
In addition to effects on wildlife, Coastal Commission staff has highlighted riding areas' disproportionate impacts on neighboring towns.
"These adjacent communities, particularly less affluent communities of color, are forced to bear the problems and degradation associated with that use," staff wrote. "Unlike the more affluent, adjacent beach communities, such as Avila Beach and Pismo Beach, the residents of Oceano have no nonmotorized beach access options fronting their community, and the downwind, inland residents residing under the dust plume receive no benefit."