Regulating the pace of change is a valid goal. But the bill includes meaningful safeguards, added after similar concerns sank a version of the legislation last year. It would protect the existing stock of rental housing by excluding from the new development rules any property used as rental housing at any point in the previous seven years. It would give some lower-income communities five years to develop alternate plans for allowing increased construction. And it would require larger developments to include a specified share of subsidized units or to provide funding for affordable-housing construction .

Opponents of the legislation also seem confused about the mechanics of the marketplace. The spread of gentrification in California is driven by the lack of housing. The state’s population continues to grow; the question confronting policymakers is where to put those people. Under the current rules, the state’s effective plan is to cede urban areas to the wealthy while forcing less affluent families to live on the state’s ever-more-distant suburban fringes.

The alternative of concentrating density along transit lines would allow more people to live in the parts of California with better jobs and services — and shorter commutes. That would mitigate economic inequality.

Precisely because the bill rewrites the rules for so much California land, it is likely to facilitate development at a wide range of price points. But even if the new construction is disproportionately upscale, it could serve to reduce development pressures on communities outside the rezoned areas.

It is not, to be sure, a silver bullet. Even if the state can reduce rents and home prices by greatly increasing the amount of new housing, California still needs to find the means and will to subsidize housing for those who cannot afford market-rate units. But it would be a mistake to preserve some affordable housing by preventing the construction of more affordable housing.

The bill also is a necessary piece of the response to another crisis: climate change. Cities like San Francisco and Los Angeles — landscapes of tall buildings, concrete and traffic-clogged streets — are the most environmentally friendly places for human life on earth. The Harvard economist Edward Glaeser has calculated that the residents of California’s core cities use about one-fourth less carbon per year than the residents of the surrounding suburbs. Better yet, the residents of California’s cities use less carbon than the residents of any other large American cities because the temperate climate limits the use of air-conditioning and heating.

The paradox, as Mr. Glaeser notes, is that the California coast — the most environmentally friendly place in America for dense housing — is one of the hardest places to build such housing.

It is time to rewrite the rules: The solution to California’s housing crisis is more housing.