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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.
Building Ecological Resilience in Highly Modified Landscapes.2018. (4.93 MB)
Ecological resilience is a powerful heuristic for ecosystem management in the context of rapid environmental change. Significant efforts are underway to improve the resilience of biodiversity and ecological function to extreme events and directional change across all types of landscapes, from intact natural systems to highly modified landscapes such as cities and agricultural regions. However, identifying management strategies likely to promote ecological resilience remains a challenge. In this article, we present seven core dimensions to guide long-term and large-scale resilience planning in highly modified landscapes, with the objective of providing a structure and shared vocabulary for recognizing opportunities and actions likely to increase resilience across the whole landscape. We illustrate application of our approach to landscape-scale ecosystem management through case studies from two highly modified California landscapes, Silicon Valley and the Sacramento–San Joaquin Delta. We propose that resilience-based management is best implemented at large spatial scales and through collaborative, cross-sector partnerships.
Creating Landscape Profiles of Aquatic Resource Abundance, Diversity and Condition. SFEI Contribution No. 725. San Francisco Estuary Institute - Aquatic Science Center: Richmond, CA. p 21.2014. (651.67 KB)
Delta Landscapes: A Delta Renewed User Guide. SFEI Contribution No. 854.2017. (28.86 MB)
A Delta Renewed User Guide aims to increase the accessibility of the technical findings in A Delta Renewed for easier application to restoration and conservation efforts across the Delta. The recommendations in A Delta Renewed focus on landscape-scale ecological guidance. We present three examples of how the information in A Delta Renewed might be used to address different management and restoration questions. Because of the complexity of the Delta system, this guide does not address all possible questions and does not replace the need for detailed, site-specific data and expertise. Rather, it shows how the information in A Delta Renewed might provide a common foundation for restoration planning.
The User Guide was written for a broad audience, including restoration practitioners, landowners, and local, state and federal agencies. The guide provides a step-by-step path through A Delta Renewed; a user is walked through how to apply the findings of the report via a series of steps to address each of the three restoration and management questions. This process is intended to help the user access regionally-specific recommendations and strategies to plan and manage future Delta landscapes that can support desired ecological functions over the long term.
The goal of A Delta Renewed and this guide is not to recreate the Delta of the past. Rather, the objective is to understand how we can re-establish or mimic important natural processes and patterns within this altered system to support desirable ecological functions (such as healthy native fish populations, a productive food web, and support for endangered species), now and into the future.
Delta Landscapes Executive Summary. SFEI Contribution No. 853.2017. (23.99 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.
A Delta Renewed: A Guide to Science-Based Ecological Restoration in the Sacramento-San Joaquin Delta. Delta Landscapes Project. Prepared for the California Department of Fish and Wildlife and Ecosystem Restoration Program. A Report of SFEI-ASC’s Resilient Landscapes Program. SFEI Contribution No. 799. San Francisco Estuary Institute - Aquatic Science Center: Richmond, CA.2016. (121.28 MB) (17.67 MB)
This report offers guidance for creating and maintaining landscapes in the Sacramento-San Joaquin Delta that support desired ecological functions, while retaining the overall agricultural character and water-supply service of the region. Based on extensive research into how the Delta functioned historically, how it has changed, and how it is likely to evolve, we discuss where and how to re-establish the dynamic natural processes that can sustain native Delta habitats and wildlife into the future. The approach, building on work others have piloted and championed, is to restore or emulate natural processes where possible, establish an appropriate mosaic of habitat types at the landscape scale, use multi-benefit management strategies to increase support for native species in agricultural and urban areas, and allow the Delta to adapt to future uncertainties of climate change, levee failure, and human population growth. With this approach, it will be critical to integrate ecological improvements with the human landscape: a robust agricultural economy, water infrastructure and diversions, and urbanized areas. Strategic restoration that builds on the history and ecology of the region can contribute to the strong sense of place and recreational value of the Delta.
Printed copies of the report are available for purchase.
A Delta Transformed: Ecological Functions, Spatial Metrics, and Landscape Change in the Sacramento-San Joaquin Delta. SFEI Contribution No. 729. San Francisco Estuary Institute - Aquatic Science Center: Richmond, CA.2014. (58.56 MB) (11.76 MB)
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)
ELEVATION AND OPPORTUNITY IN THE DELTA: Restoring the right thing in the right place. SFEI Contribution No. 1082. San Francisco Estuary Institute: Richmond, Ca.2022. (11.1 MB) (1.24 MB)
A future Sacramento-San Joaquin Delta and Suisun Marsh (“Delta” herein) that supports healthy ecosystems and native species, while also meeting flood risk reduction, water supply, water quality, carbon sequestration, economic, and cultural objectives, requires that appropriate restoration and management actions be taken in the right place at the right time. Geographic setting affects the potential opportunities available—not all actions are suitable everywhere. Physical factors determining what types of activities are appropriate now and in the future include a site’s elevation, degree of tidal and fluvial influence, salinity, soil type, and local effects of climate change, which all vary spatially across the Delta. While there has been considerable progress over the last several decades, continued acceleration of the pace and scale of enhancement actions appropriate to landscape position is needed. Understanding the physical template is necessary for developing strategies that move beyond opportunistic restoration, support resilience over time, and have the potential to connect and magnify benefits across the larger landscape.
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.
Landscape Resilience Framework: Operationalizing Ecological Resilience at the Landscape Scale. SFEI Contribution No. 752. San Francisco Estuary Institute - Aquatic Science Center: Richmond, CA.. 2015. (5.18 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.
North Bay Mercury Biosentinel Project: 2016 - 2017. SFEI Contribution No. 868.2018. (1.59 MB)
North Bay Mercury Biosentinel Project (December 2014 Report). SFEI Contribution No. 738. San Francisco Estuary Institute: Richmond, CA.2014. (2.88 MB)
Primary Production in the Delta: Then and Now. San Francisco Estuary and Watershed Science 14 (3).2016. (864.19 KB)
To evaluate the role of restoration in the recovery of the Delta ecosystem, we need to have clear targets and performance measures that directly assess ecosystem function. Primary production is a crucial ecosystem process, which directly limits the quality and quantity of food available for secondary consumers such as invertebrates and fish. The Delta has a low rate of primary production, but it is unclear whether this was always the case. Recent analyses from the Historical Ecology Team and Delta Landscapes Project provide quantitative comparisons of the areal extent of 14 habitat types in the modern Delta versus the historical Delta (pre-1850). Here we describe an approach for using these metrics of land use change to: (1) produce the first quantitative estimates of how Delta primary production and the relative contributions from five different producer groups have been altered by large-scale drainage and conversion to agriculture; (2) convert these production estimates into a common currency so the contributions of each producer group reflect their food quality and efficiency of transfer to consumers; and (3) use simple models to discover how tidal exchange between marshes and open water influences primary production and its consumption. Application of this approach could inform Delta management in two ways. First, it would provide a quantitative estimate of how large-scale conversion to agriculture has altered the Delta's capacity to produce food for native biota. Second, it would provide restoration practitioners with a new approach—based on ecosystem function—to evaluate the success of restoration projects and gauge the trajectory of ecological recovery in the Delta region.
Primary Production in the Sacramento-San Joaquin Delta: A Science Strategy to Quantify Change and Identify Future Potential. SFEI Contribution No. 781.2016. (4.26 MB)
Selenium in White Sturgeon Tissues: 2015 Sturgeon Derby. SFEI Contribution No. 834.2017. (1.85 MB)
Shoreline Resilience Framework for San Francisco Bay: Wildlife Support. SFEI Contribution No. 1115. San Francisco Estuary Institute: Richmond, CA.2023. (9.99 MB)
Translating Science-Based Restoration Strategies into Spatially-Explicit Restoration Opportunities in the Delta (2018 Bay-Delta Science Conference Presentation).2018. (3.78 MB)
In a previous report titled “A Delta Renewed” we offered a collection of guidelines for science-based ecological restoration in the Sacramento-San Joaquin Delta that emphasized restoring or emulating natural processes, anticipating future changes associated with climate change, establishing appropriate configurations of habitat types at the landscape scale, and utilizing a variety multi-benefit management strategies. In this talk, we present on our recent work to support regional restoration planning efforts by developing a repeatable process for using these guidelines to identify spatially-explicit restoration opportunities. The process is largely GIS-based and utilizes spatial data on existing land cover and conservation status, habitat configuration (including patch sizes and distances), surface elevations (including depth of subsidence), and future changes in tidal elevations associated with sea-level rise. By distilling generalized guidelines into spatially-explicit opportunities, we hope to provide a practical tool for incorporating science into planning. To that end, these new methods are currently being piloted through planning efforts focused on the Central Delta Corridor and the McCormack Williamson Tract, and are also being used to assist with the quantification of ecological restoration potential in the Delta Plan Ecosystem Amendment.
Presentation recording: available here.
Vision for a Resilient Silicon Valley Landscape. SFEI Contribution No. 753.. 2015. (21.78 MB)