This is The Fifth Sacred Thing by Starhawk (you almost nailed the author!)
The novel describes a world set in the year 2048 after a catastrophe which has fractured the United States into several nations. The protagonists live in San Francisco and have evolved in the direction of Ecotopia, reverting to a sustainable economy, using wind power, local agriculture, and the like.
San Francisco is presented as a mostly pagan city where the streets have been torn up for gardens and streams, no one starves or is homeless, and the city's defense council consists primarily of nine elderly women who "listen and dream". The novel describes "a utopia where women are leading societies but are doing so with the consent of men."
To the south, an overtly-theocratic Christian fundamentalist nation has evolved and plans to wage war against the San Franciscans. The novel explores the events before and during the ensuing struggle between the two nations, pitting utopia and dystopia against each other