Brian Yearout, president of the Washington Federation of State Employees Local 1466, says the Discover Pass program isn't raising enough money to keep parks open.
The passes were created in 2011 after funding for state parks was cut from the budget.
Yearout says without more funding, it's estimated that about half of the state's parks would have to close.
He says parks are money generators, so fully closing any state parks would be a bad idea.
The state has 116 state parks, including Larrabee State Park and Birch Bay State Park here in Whatcom County.
Outgoing Governor Chris Gregoire has recommended taking $19 million from the state's general fund to help pay for parks.
The incoming legislature will have to decide on Gregoire's proposal.