To:
The California Air Resources Board
From: California Ocean Science Trust
(on behalf of the signatories below including members of the Ocean
Protection Council Science Advisory Team and additional scientific
experts)
Subject:
Recommending inclusion of best available science on
Blue Carbon habitats in the 2022 Climate Change Scoping Plan
This memo was developed by the California
Ocean Science Trust (OST) in consultation with members of the Ocean
Protection Council (OPC) Science Advisory Team and leading coastal
scientists listed below. OST is a legislatively mandated non-profit
organization dedicated to accelerating progress towards a healthy,
equitable and productive coast and ocean, formally bridging the gap
between cutting edge scientific research and sound ocean and
coastal management. OST’s Executive Director serves as
co-chair of the OPC Science Advisory Team, an interdisciplinary
team of experts who work to ensure that the best available science
supports OPC policy and funding decisions. www.oceansciencetrust.org
Dear Chair Randolph and
Members of the California Air Resources Board,
We applaud the California
Air Resources Board (CARB) for their extensive efforts to prepare
the 2022 Climate Change Scoping Plan (Scoping Plan) with the aim of
building a robust and comprehensive strategy for meeting the goals
of the Global Warming Solutions Act of 2006 (AB/SB 32). This scale
of analysis is no small undertaking, and we commend the work of
CARB staff and Board to position California as a national and
global leader in developing science-based climate mitigation
policies.
The magnitude of the
climate crisis, however, requires that we account for, manage,
conserve, and invest in all natural and working lands to
achieve carbon neutrality by mid-century. On behalf of
members of the OPC Science Advisory Team and the state’s
leading coastal scientists, we are writing to recommend that the
best available science on California’s coastal “blue
carbon” habitats be included in the natural and working lands
(NWL) modeling scenarios presented in the draft Scoping Plan.
We appreciate inclusion of new modeling of potential
emissions reduction opportunities from restoration activities in
Suisun Marsh and the Sacramento-San Joaquin Delta (the Delta).
However, a critical missing component of the wetland landscape in
the draft Scoping Plan includes the scientifically verifiable
carbon sequestered and stored within the biomass and soils of the
state’s coastal wetlands.
There
are now sufficient data and methods available for inventorying and
estimating GHG emissions and removals from coastal wetlands to
support their inclusion in the 2022 Scoping Plan.
Below, we reference some of the latest information and
resources that are contributing to our best estimates of carbon
stocks and GHG exchanges across California’s coastal wetland
habitats, a field of study which has rapidly advanced over the last
decade. We also offer our expertise and commitment to engaging in a
process to integrate these data into modeling of management
scenarios for coastal wetlands that could be included in the 2022
Scoping Plan and refined in future updates.
California’s blue carbon habitats -
also referred to here as coastal wetlands - include
tidally-influenced marshes, scrub/shrubs, and eelgrass habitats
that consist of organic and mineral soils that are covered or
saturated for all or part of the year by water. Coastal wetland
organic carbon is derived from above- and below-ground
photosynthetic production as well as inputs from coastal
watersheds. Based on spatially explicit land cover mapping
datasets, these habitats cover over 57,000 acres, including
approximately 43,000 acres of tidal marsh and scrub/shrub wetlands
and 13,000 acres of eelgrass. According to new analyses,
the inclusion of coastal wetlands has the potential to
increase the extent of existing wetlands evaluated in Scoping Plan
scenarios by nearly 70% (Vaughn, Plane, Harris, Robinson, and
Grenier, in prep).
With regards to estimating the
statewide standing stock of coastal wetland carbon, California has
ample spatial and temporal coverage of peer-reviewed (~140) and
unpublished (~250) soil core data that span a range of coastal
wetland types, salinity classes, and include restoration sites.
These data have been deemed sufficient for carbon
stock assessments and carbon sequestration modeling (Holmquist,
Wolfe, and Megonigal, 2021), many of which are publicly accessible
on the Coastal Carbon Atlas and have been standardized across the
Pacific coast. Radiometric dating of soil core profiles provides a
historic time series of carbon accumulation over the last 100+
years, thus it is not required to sample stocks
annually.
While
data are available for a statewide approach, a regional inventory
recently developed for the San Francisco Bay tidal Estuary provides
an “off-the-shelf” assessment that can inform the
Scoping Plan and serve as a template for expanding statewide (Beers
and Crooks, 2022). From the period of 1990 to 2020,
coastal wetlands in the San Francisco Estuary were a net carbon
sink, with GHG removals increasing through time attributable to
significant coastal wetland restoration in the region. In 2020,
these habitats sequestered approximately 43,600 metric tons
CO2 equivalent (CO2e).
For a statewide time
series of emissions and removals, the US EPA National Greenhouse
Gas Inventory (NGGI) of Emissions and Sinks provides state-level
estimates of carbon stock change and methane emissions going back
to 1990, indicating California’s coastal wetlands are a net
sink (EPA, 2022). These data, in combination with state-specific
carbon data and land cover mapping, can allow for a more accurate
accounting of greenhouse gas (GHG) emissions and removals in
coastal wetlands than what is currently included in CARB’s
2018 Natural and Working Lands GHG inventory.
Continued conservation and
restoration of saline tidal wetlands and eelgrass habitats can
promote additional carbon storage and further reduce GHG emissions.
Management actions can include restoring natural
hydrology, reducing nutrient inputs, limiting vulnerability to sea
level rise, and avoiding high levels of bioturbation, among others
(Macreadie et al., 2017; Moritsch at al. 2021).
Loss of wetlands can cause significant release of GHGs
like methane, and there is evidence to suggest that restored
wetlands can provide greater rates of carbon storage compared with
natural systems, particularly in the first decade (Poppe and
Rybczyk, 2021). A forthcoming report by Vaughn, Plane, Harris,
Robinson, and Grenier provides preliminary analyses and
recommendations for expanding existing Scoping Plan scenarios to
include management actions for saline tidal wetlands and eelgrass
beds based on regional targets and planning
efforts.
In
closing, we urge CARB to consider the best available science
referenced herein indicating that coastal wetlands can play a
critical role in helping achieve the state’s climate change
and GHG reduction goals. In addition to long-term
carbon storage, significant alternative benefits of restoring these
ecosystems have already been observed and quantified - including
shoreline protection in response to sea level rise, localized
amelioration of ocean acidification, and cultural significance
(Akema et al., 2013; Lead et al. 2011; Pinksy et al., 2013; Ricart
et al., 2021; Shepard et al., 2011).
We appreciate the work of
CARB staff and Board, and acknowledge the task ahead to continue
updating the 2022 Climate Change Scoping Plan. The California Ocean
Science Trust, members of the OPC Science Advisory Team, and the
state’s leading coastal experts stand at the ready to serve
as a resource for continued engagement on this issue to help ensure
these critical habitats are recognized in state
policy.
Sincerely,
Dr. Sean
Anderson, California State University
Channel Islands
Dr.
Richard Ambrose,* University of California, Los
Angeles
Dr. Lisa
Beers, Silvestrum Climate Associates
Dr.
Kathryn Beheshti, University of California,
Santa Barbara
Dr.
Kathy Boyer, Estuary & Ocean Science
Center, San Francisco State University
Dr. John
Callaway, University of San Francisco
Warner
Chabot, San Francisco Estuary Institute
Ross
Clark, Central Coast Wetlands Group, Moss Landing
Marine Labs
Craig
Cornu, Pacific Northwest Blue Carbon Working
Group
Dr.
Matthew T. Costa, Scripps Institution of
Oceanography, University of California San Diego
Dr.
Steve Crooks, Silvestrum Climate
Associates
Dr.
Timothy M. Davidson, California State University
Sacramento
Dr. Hany
Elwany, President of Coastal Environment
Inc
Dr. Matt
Ferner, San Francisco Bay National Estuarine
Research Reserve and San Francisco State University
Dr. Gary
Griggs,* University of California Santa
Cruz
Dr.
Madeleine Hall-Arber, Massachusetts Institute of
Technology (retired)
Dr.
James R. Holmquist, Smithsonian Environmental
Research Center
Dr.
Christopher N. Janousek, Oregon State
University
Dr.
Kristy Kroeker,* University of California,
Santa Cruz
Dr.
Janet Kübler, California State University,
Northridge
Dr.
Raphael Kudela, University of California Santa
Cruz
Dr.
Arielle Levine,* San Diego State
University
Dr.
Sarah Lummis, University of California,
Santa Cruz
Dr. Glen
MacDonald, University of California, Los
Angeles
Dr.
Monica Moritsch, University of California,
Santa Cruz
Dr.
Steven N. Murray,* California State University
Fullerton
Dr.
Kerry J. Nickols, California State University
Northridge
Kevin
O'Connor, Central Coast Wetlands Group, Moss Landing
Marine Labs
Dr.
Patty Y. Oikawa, California State University,
East Bay
Manuel
Oliva, Point Blue Conservation Science
Dr.
Aurora M. Ricart, Bodega Marine Laboratory,
University of California, Davis
Dr.
Laurie Richmond,* Cal Poly Humboldt
Dr. Jay
Stachowicz,* University of California,
Davis
Dr.
Aaron L. Strong, Hamilton College
Christina Toms, San Francisco Bay
Regional Water Quality Control Board and SF Estuary Wetland
Regional Monitoring Program
Dr.
Melissa Ward, San Diego State University and
University of Oxford
Dr.
Kerstin Wasson, University of California,
Santa Cruz
Dr. Lisa
Wedding, University of Oxford
Jaxine
Wolfe, Smithsonian Environmental Research
Center
Dr. Liz
Whiteman,* OPC Science Advisory Team co-chair,
California Ocean Science Trust
*Denotes member of the
Ocean Protection Council Science Advisory Team, an
interdisciplinary body of experts who provide scientific advice to
the California Ocean Protection Council (OPC) and works to ensure
that OPC policy and funding decisions are informed by the best
available science. The OPC Science Advisory Team offers a critical
venue to bring state leaders and scientists together on a range of
topics with emphasis on state priorities to address issues
impacting coastal and marine ecosystems in California.
www.opc.ca.gov/science-advisory-team
Disclaimer: Institutional
affiliations are provided for informational purposes. The views and
science expressed in this letter represent the collective views of
individuals and not their institutions or
organizations.
References
Arkema KK, Guannel G,
Verutes G, Wood SA, Guerry A, Ruckelshaus M, Kareiva P, Lacayo M,
Silver JM, (2013). Coastal habitats shield people and property from
sea-level rise and storms. Nature climate change, 3(10),
pp.913-918. https://www.nature.com/articles/nclimate1944
Beers L, Crooks S (2022).
Coastal Wetland Greenhouse Gas Inventory for the San Francisco Bay
Estuary. Access PDF here
EPA (2022) Inventory of
U.S. Greenhouse Gas Emissions and Sinks: 1990-2020. U.S.
Environmental Protection Agency, EPA 430-R-22-003. https://www.epa.gov/ghgemissions/draft-inventory-us-greenhouse-gas-emissionsand-sinks-1990-2020
IPCC 2014, 2013 Supplement
to the 2006 IPCC Guidelines for National Greenhouse Gas
Inventories: Wetlands, Hiraishi, T., Krug, T., Tanabe, K.,
Srivastava, N., Baasansuren, J., Fukuda, M. and Troxler, T.G.
(eds). Published: IPCC, Switzerland. https://www.ipcc.ch/site/assets/uploads/2018/03/Wetlands_Supplement_Entire_Report.pdf
Holmquist J, Wolfe J,
Megonigal P (2021). CCRCN Blue Carbon Inventory. The Coastal Carbon
Network at the Smithsonian Environmental Research Center. Access
report here.
Lead C, Jones L, Stewart
Angus AC, Doody P, Everard M, Garbutt A, Gilchrist P, Hansom J,
Nicholls R, Pye K, Ravenscroft N (2012). Coastal Margins. https://www.researchgate.net/publication/313311284
Macreadie PI, Nielsen DA,
Kelleway JJ, Atwood TB, Seymour JR, Petrou K, Connolly RM, Thomson
ACG, Trevathan-Tackett SM, Ralph PJ (2017). Can we manage coastal
ecosystems to sequester more blue carbon? Frontiers in Ecology and
the Environment. https://doi.org/10.1002/fee.1484
Moritsch MM, Young M,
Carnell P, Macreadie PI, Lovelock C, Nicholson E, Raimondi
PT, Wedding LM, Ierodiaconou D (2021). Estimating blue carbon
sequestration under coastal management scenarios, Science of The
Total Environment. https://doi.org/10.1016/j.scitotenv.2021.145962
Pinsky ML, Guannel G,
Arkema KK. (2013). Quantifying wave attenuation to inform coastal
habitat conservation. Ecosphere 4(8), 1-16. https://doi.org/10.1890/ES13-00080.1
Poppe KL, Rybczyk JM
(2021). Tidal marsh restoration enhances sediment accretion and
carbon accumulation in the Stillaguamish River estuary, Washington.
PLoS ONE 16(9): e0257244. https://doi.org/10.1371/journal.pone.0257244
Ricart AM, Ward M, Hill
TM, Sanford E, Kroeker KJ, Takeshita Y, Merolla S, Shukla P,
Ninokawa AT, Elsmore K, Gaylord B (2021). Coast‐wide evidence
of low pH amelioration by seagrass ecosystems. Global Change
Biology, 27(11), 2580–2591. https://doi.org/10.1111/gcb.15594
Shepard CC, Crain CM, Beck
MW (2011). The Protective Role of Coastal Marshes: A Systematic
Review and Meta-analysis. PLOS ONE 6(11): e27374. https://doi.org/10.1371/journal.pone.0027374
Vaughn LS, Plane E, Harris K, Robinson A, Grenier L
(in prep). Blue Carbon Science in California: Memo to the
California Air Resources Board on coastal wetland data and methods
for the 2022 Scoping Plan Update.