by Lisa Song, ProPublica, and James Temple, MIT Technology Review
April 29, 2021
All trees consume carbon dioxide, releasing the oxygen and storing the carbon in their trunks, branches and roots. Every ton of carbon sequestered in a living tree is a ton that isn’t contributing to climate change. And that thick coastal forest can easily store twice as much carbon per acre as the trees deeper inland.
This math is crucial to determining the success of California’s forest offset program, which seeks to reduce carbon emissions by preserving trees. The state established the program a decade ago as part of its efforts to combat climate change.
But ecology is messy. The boundaries between forest types are nebulous, and the actual amount of carbon on any given acre depends on local climate conditions, conservation efforts, logging history and more.
California’s top climate regulator, the Air Resources Board, glossed over much of this complexity in implementing the state’s program. The agency established fixed boundaries around giant regions, boiling down the carbon stored in a wide mix of tree species into simplified, regional averages.
That decision has generated tens of millions of carbon credits with dubious climate value, according to a new analysis by CarbonPlan, a San Francisco nonprofit that analyzes the scientific integrity of carbon removal efforts.