The strike could impact non-urgent health clinics, libraries, wildfire debris removal, homeless encampment enforcement and trash pickup services, the union said.

Leaders of SEIU Local 721 said the two-day strike started at 7 p.m. Monday, sparked by what they characterized as a failure by the county to fairly negotiate a new contract.

The nation’s most populous county was already juggling legal liabilities, wildfire costs and threats to federal funding. Now its largest union is holding a 48-hour strike.