Little evidence of management change in California’s forest offset program

Abstract Carbon offsets are widely promoted as a strategy to lower the cost of emission reductions, but recent findings suggest that offsets may not causally reduce emissions by the amount claimed. In a compliance market, offsets increase net emissions if they do not reflect real emission reductions beyond the baseline scenario. Few studies have examined the additionality of forest carbon offsets within California’s U.S. Forest Projects compliance offset protocol, one of the largest forest offset programs in the world. Here we examine additionality in California’s offset protocol. Since 2012, most of California’s offset credits (84%) have been awarded to improved forest management projects. Using a database of improved forest management project characteristics, locations, and remotely sensed forest disturbance data indicative of management activity, we find that projects have been primarily allocated to forests with high carbon stocks (127% higher than regional averages) and low historical disturbance (28% less disturbance than regional averages since 1985). A matching and panel regression analysis failed to show additionality, as project creation did not significantly lower disturbance rates 3 and 5 years after project implementation relative to similar non-project lands. These results indicate that California’s forest offset protocol may contribute to an increasingly large carbon debt.