CA AB6

Requires the State Air Resources Board to update regional greenhouse gas emission reduction targets indefinitely (rather than only until 2050) and authorizes updating the target years themselves, subject to constraints that no more than two target years are in effect at any time and target years must be at least 10 years apart.

Requires metropolitan planning organizations to quantify greenhouse gas reductions from amendments to regional transportation plans and maintain emission reductions throughout the 20-year or longer life of the plan, and requires identification and analysis of wildlife connectivity areas and natural landscape features.

Expands the State Air Resources Board's authority to reject a sustainable communities strategy not only if it fails to achieve targets, but also if the board determines the strategy is unlikely to be implemented.

Prohibits environmental review under CEQA from relying on a certified environmental impact report for a regional transportation plan if that plan lacks a sustainable communities strategy determined by the state board to achieve regional greenhouse gas reduction targets.

Imposes state-mandated local program requirements on transportation planning agencies and metropolitan planning organizations, with reimbursement provisions through existing statutory procedures.