Managing Open Space in Support of Net Zero: Carbon sequestration opportunities and tradeoffs in the Alameda Watershed. San Francisco Estuary Institute: Richmond, CA. p 120.2023. (7.01 MB)
An assessment of future tidal marsh resilience in the San Francisco Estuary through modeling and quantifiable metrics of sustainability. Frontiers in Environmental Science 10.2022.
Quantitative, broadly applicable metrics of resilience are needed to effectively manage tidal marshes into the future. Here we quantified three metrics of temporal marsh resilience: time to marsh drowning, time to marsh tipping point, and the probability of a regime shift, defined as the conditional probability of a transition to an alternative super-optimal, suboptimal, or drowned state. We used organic matter content (loss on ignition, LOI) and peat age combined with the Coastal Wetland Equilibrium Model (CWEM) to track wetland development and resilience under different sea-level rise scenarios in the Sacramento-San Joaquin Delta (Delta) of California. A 100-year hindcast of the model showed excellent agreement (R2 = 0.96) between observed (2.86 mm/year) and predicted vertical accretion rates (2.98 mm/year) and correctly predicted a recovery in LOI (R2 = 0.76) after the California Gold Rush. Vertical accretion in the tidal freshwater marshes of the Delta is dominated by organic production. The large elevation range of the vegetation combined with high relative marsh elevation provides Delta marshes with resilience and elevation capital sufficiently great to tolerate centenary sea-level rise (CLSR) as high as 200 cm. The initial relative elevation of a marsh was a strong determinant of marsh survival time and tipping point. For a Delta marsh of average elevation, the tipping point at which vertical accretion no longer keeps up with the rate of sea-level rise is 50 years or more. Simulated, triennial additions of 6 mm of sediment via episodic atmospheric rivers increased the proportion of marshes surviving from 51% to 72% and decreased the proportion drowning from 49% to 28%. Our temporal metrics provide critical time frames for adaptively managing marshes, restoring marshes with the best chance of survival, and seizing opportunities for establishing migration corridors, which are all essential for safeguarding future habitats for sensitive species.
Delta Wetland Futures: Blue Carbon and Elevation Change. SFEI Contribution No. 1105. San Francisco Estuary Institute: Richmond, CA.2022. (13.45 MB)
Delta Wetland Futures: Tidal Marsh Resilience to Sea Level Rise. SFEI Contribution No. 1106. San Francisco Estuary Institute: Richmond, CA.2022. (16.65 MB)
Leveraging Wetlands for a Better Climate Future: Incorporating Blue Carbon into California's Climate Planning. SFEI Contribution No. 1084. San Francisco Estuary Institute: Richmond, CA. p 31.2022. (9.61 MB)
The 2022 update to California’s climate change Scoping Plan incorporates management actions in the state’s forests, shrublands/chaparral, grasslands, croplands, developed lands, deltaic wetlands, and sparsely vegetated lands. Missing from this list are the tidally-influenced coastal ecosystems outside the Sacramento-San Joaquin Delta. These blue carbon ecosystems support high rates of carbon storage and sequestration while providing many co-benefits that can enhance coastal climate change resilience. With sufficient data and robust modeling approaches, California has the opportunity to incorporate blue carbon in future Scoping Plan updates and set actionable targets for restoration, migration space conservation, and other management activities that promote long-term survival of the state’s coastal wetlands. To support this goal, this report offers a high-level overview of the state of the science for blue carbon quantification in California. This summary, which covers datasets and quantification approaches, key focus areas for additional science investment, and example scenarios for coastal wetland restoration, is intended to facilitate broader inclusion of blue carbon in future Scoping Plan updates and other state-level climate-planning documents.
On the human appropriation of wetland primary production. Science of the Total Environment 785.2021.
Humans are changing the Earth's surface at an accelerating pace, with significant consequences for ecosystems and their biodiversity. Landscape transformation has far-reaching implications including reduced net primary production (NPP) available to support ecosystems, reduced energy supplies to consumers, and disruption of ecosystem services such as carbon storage. Anthropogenic activities have reduced global NPP available to terrestrial ecosystems by nearly 25%, but the loss of NPP from wetland ecosystems is unknown. We used a simple approach to estimate aquatic NPP from measured habitat areas and habitat-specific areal productivity in the largest wetland complex on the USA west coast, comparing historical and modern landscapes and a scenario of wetland restoration. Results show that a 77% loss of wetland habitats (primarily marshes) has reduced ecosystem NPP by 94%, C (energy) flow to herbivores by 89%, and detritus production by 94%. Our results also show that attainment of habitat restoration goals could recover 12% of lost NPP and measurably increase carbon flow to consumers, including at-risk species and their food resources. This case study illustrates how a simple approach for quantifying the loss of NPP from measured habitat losses can guide wetland conservation plans by establishing historical baselines, projecting functional outcomes of different restoration scenarios, and establishing performance metrics to gauge success.
Peninsula Watershed Historical Ecology Study. SFEI Contribution No. 1029. San Francisco Estuary Institute: Richmond, Ca.2021. (204.95 MB) (21.97 MB)
Delta Landscapes Primary Production: Past, Present, Future. SFEI Contribution No. 988. San Francisco Estuary Institute: Richmond, CA.2020. (9.73 MB) (23.17 MB) (694.54 KB)
This report describes the Delta Landscapes Primary Production project, which quantifies how landscape change in the Delta has altered the quantity and character of primary production. Combining historical and modern maps with simple models of production for five dominant plant and algae groups, we estimate primary production across the hydrologically connected Delta. We evaluate changes in primary production over time (between the early 1800s and early 2000s), between wet and dry years, and with future targets for landscape-scale restoration. For managers in the Delta, restoring historical patterns of primary productivity is a means to better support native fish and other wildlife. To better equip decision makers in managing for improved primary production, this study offers historical context and the best available science on the relative production value of habitat types and their configurations.
Livestock grazing and its effects on ecosystem structure, processes, and conservation. SFEI Contribution No. 1011. San Francisco Estuary Institute: Richmond, CA.2020. (1.75 MB)