Climate change is causing heat waves, drought, fires, and other impacts across California. We must address these life-threatening issues by decreasing emissions and increasing removal of carbon dioxide from the atmosphere.
While California can lead on technological solutions, we should also immediately adopt low-cost and environmentally beneficial nature-based solutions while other methods are brought on-line.
Adapting how California manages its forests, grasslands and farmlands can increase carbon sequestration. But no other ecosystem in the state can, on an acre-for-acre basis, soak up more carbon than coastal wetlands and seagrass beds (more than 10 times faster than terrestrial forests).
These “blue carbon ecosystems,” though lacking the stature of the redwoods and the area of other terrestrial landscapes, sequester organic matter in their sediments, building centuries-old carbon stockpiles. This carbon trapping efficiency, and the fact that California has already lost most of its tidal wetlands, should put the remaining blue carbon ecosystems first among environments to enlist in the fight against climate change.
Up to now, unfortunately, the state has not incorporated them into most of its plans to use natural landscapes to mitigate carbon emissions. It’s time to change that.
The California Air Resources Board (CARB) just released its draft 2022 scoping plan. This plan identifies the actions and investments that the state can make to reach carbon neutrality by 2045. It recognizes the management of California’s natural and working lands, including forests, farmlands and some wetlands, as essential to reaching neutrality. Beneficially, the draft plan aims to restore 60,000 acres of wetlands in the Sacramento-San Joaquin River Delta.
However, coastal wetlands in general and seagrass beds have not been incorporated into CARB’s scoping plan, meaning that the most efficient carbon sinks in the state are not formally included in our plans to mitigate climate change. With intensifying wildfires, the risk of losing forest carbon is increasing, a negligible risk for waterlogged blue carbon stocks.
The scoping plan indicates a lack of blue carbon data and insufficient guidelines on incorporating them into carbon inventories. While data gaps should be filled, especially in the smaller, urbanized estuaries of Southern California, several extensive datasets of California blue carbon already exist, and recent mapping efforts provide good data on the coverage of these habitats.
Moreover, the United Nation’s Intergovernmental Panel on Climate Change already has explicit blue carbon guidelines, and existing models can be leveraged now to include blue carbon in California’s carbon inventories.
Beyond their carbon value, blue carbon habitats benefit the state’s fisheries, improve water quality and protect shorelines, resisting the effects of sea-level rise. For these reasons, many agencies such as the California Ocean Protection Council already have goals to increase the acreage of these habitats. CARB acknowledges these co-benefits, and we encourage their full assessment to inform prioritization of projects likely to achieve diverse co-benefits.
By overlooking formal inclusion of blue carbon in the scoping plan, we miss out on a mitigation strategy that can vastly outpace forest projects on a per-area basis while simultaneously providing value to California’s people, economies and ecosystems.
As climate change costs California more lives and resources every year, we cannot afford to leave out any solution, least of all the most efficient natural carbon sinks in the state. While we continue to gather important data, we know more than enough to move forward with leveraging blue carbon to mitigate climate change.
We recommend that CARB, and other relevant state agencies, include blue carbon habitats in their current and future scoping plans and guidance documents on reaching carbon neutrality. There is no time to waste.
Matthew Costa is a postdoctoral scholar at Scripps Institution of Oceanography at UC San Diego. Melissa Ward is a research scientist at the University of Oxford and San Diego State University.
