A group of environmental advocates has qualified enough signatures to qualify a parcel tax that would raise roughly $17 million a year for the Santa Clara Valley Open Space Authority, a government agency based in San Jose, to acquire land, hire more rangers and maintenance staff, and build new trails, parking lots, restrooms, and other facilities. The measure would impose an annual tax of 2 cents per square foot of buildings on property owners within the district’s boundaries, which include San Jose and Milpitas. The owner of a typical 1,600-square foot home would pay $32 a year, while a 2,500 square-foot home would cost $50 a year. Supporters argue that the money is needed to provide more public access as the agency expands its open space preserves. Critics argue that living costs in the high-cost Silicon Valley are already too high.