A scenic view of the Grizzly Island Wildlife Area in Solano County, California, April 20, 2023. Fred Greaves/California Department of Water Resources

FEATURE: Ecosystem Restoration Progress Review for the Delta and Suisun Marsh

The Delta and Suisun Marsh are among the most important ecosystems in the state, providing vital habitat for a variety of plant and animal species, supporting numerous recreational activities, and supplying drinking water for millions of people.  However, the Delta’s ecosystem and native species have been declining for decades, with loss of habitat among the numerous factors.  In recent years, significant efforts have been made to restore habitat.  At the 2023 Interagency Ecological Program Annual Meeting, Daniel Constable, environmental program manager with the Delta Stewardship Council, reviewed the restoration progress made in the Delta and Suisun Marsh.

At the Delta Stewardship Council, the guiding document is the Delta Plan, which articulates a vision for the Delta and Suisun Marsh.  The Delta Reform Act of 2009 established the Delta Stewardship Council and directed the Council to develop a comprehensive plan for managing the Delta.  The Delta Plan includes 17 regulations, as well as several non-regulatory performance measures and recommendations to other agencies to achieve the coequal goals.  Since the development of the Delta Plan in 2013, several parts have been updated and amended to reflect new science and changing conditions.

The habitat surrounding the future location of the Lookout Slough Tidal Restoration Project. Photo by Florence Low / DWR

When the first Delta Plan was finalized in 2013, it was envisioned that the Bay Delta Conservation Plan or BDCP would become part of the Delta Plan and form the approach to ecosystem restoration.  The Bay Delta Conservation Plan laid out a vision of around 100,000 acres of restoration.  The Delta Reform Act said that if the Bay Delta Conservation Plan came forward as a Habitat Conservation Plan or Natural Communities Conservation Plan, it would become part of the Delta Plan.

In 2015, the state pivoted away from BDCP and divided the restoration actions into the Eco Restore initiative and the conveyance infrastructure into WaterFix.   When that occurred, the Council started considering an amendment to the ecosystem chapter.

“We suddenly had a gap in the Delta Plan,” said Mr. Constable.  “So in 2016, we started working on an amendment to develop a plan chapter focused on ecosystem restoration.  And in June of 2022, that became part of the Delta Plan.”

The ecosystem chapter, chapter 4, reflects a lot of new science and changing conditions on the ground that have changed since 2013.  It was informed by synthesizing research conducted over the last nearly 20 years, including 14 recovery plans, conservation strategies, and other species-specific resiliency plans.  The targets in the ecosystem chapter are based on the targets identified in those documents.

The new ecosystem chapter sets a goal of 60-80,000 acres of restoration by 2050 above the 2007 baseline.  These restoration targets are non-regulatory; they set a vision but are not required.

The amendment has five core strategies:

  • More natural, functional flows
  • Restore ecosystem function
  • Protect land for restoration
  • Protect native species, reduce the impact of nonnative invasive species
  • Improve institutional coordination

There are other considerations, such as following the ‘good neighbor checklist’ and ensuring restoration is compatible with adjacent land uses.  Tribal consultation is also required; Mr. Constable noted they received highly useful feedback from Tribes, and the recommendation is to do so before finishing the project design.

The slide below shows the breakdown of the restoration targets for 2050.  The targets in blue are highlighted because there is more data available, and there’s been progress; the targets shown in gray have not made much progress, and there isn’t much data.  The baseline is 2007 because that is when the most land use data was available.

The column on the left shows the historical acreage based on work by the San Francisco Estuary Institute.  Historically, there were about 116,000 acres of non-tidal wetlands; as of 2007, there were 5800 acres, as wetlands were converted to farmland, urban, and other non-wetland land uses.  The target is to increase non-tidal wetlands by 19,000 acres for about 25,000 total acres of non-tidal wetlands by 2050.

The vast majority of the historical Delta was tidal wetlands; the San Francisco Estuary Institute study estimated over half a million acres.  In 2007, there were 20,000 acres, a small fraction of what used to exist.  The target is to add another 32,000 acres, which would bring the total tidal wetland acreage to 52,000 acres, about 10% of its historic level.

Riparian and floodplain habitat historically occupied over 50,000 acres; in 2007, there were 14,200 acres remaining.  The target is to add 16,300 by 2050 for about 30,000 acres total.

The intent of the project was to synthesize the progress made since 2007.  So for this project, only projects that occurred within the Council’s jurisdictional boundaries, the legal Delta and Suisun Marsh, were included.  Also, only projects that had a spatially explicit component were included.

Projects were categorized depending on their status: Completed projects where something has been constructed, although perhaps not completely functional; in progress are those under construction; and planned projects are projects that are far enough along in the environmental documentation process that it looks likely the project will go ahead.  A literature review was also done to examine various restoration and management options for the landscape.

Mr. Constable also noted that this does not include any flow or related actions; the study only looks at projects with a physical acreage footprint.

The starting point for the project data was Eco Atlas.  178 projects were initially found; those were narrowed down to only those within the spatial boundaries, so those projects outside the Council’s jurisdiction were removed.  If the project intent was acquisition or preservation, those were removed.  That left 63 projects; interviews and input from others added 18 additional projects.  Mr. Constable pointed out that the numbers were tabulated from project documents and not estimations.

Since 2007, 5700 acres of tidal wetlands, 2700 acres of non-tidal, and 940 acres of riparian and floodplain have been constructed.

If in-progress and planned acres are included, there are about 14,000 additional acres of tidal wetlands, almost 5000 acres of non-tidal, and 2500 acres of riparian and floodplain.  A lot of this has been just since 2017.

Although much progress has been made, compared to the targets identified in the Delta Plan, there’s still a lot of restoration work to be done: 18,000 acres of tidal wetlands, almost 15,000 acres of non-tidal, and about 13,000 acres of riparian and floodplain habitat.

“There’s both a positive and sobering aspect to this because it shows how much has been done, yet how much is also needed,” said Mr. Constable.  “On the positive spin, some of these targets are within striking distance … it actually may be achievable, which is really good news.”

The slide shows a breakdown of the motivation for constructing these restoration projects.  The vast majority (38%) of restoration projects have resulted from water project mitigation; the Delta Levees Program and ecosystem services contributed about 20% each, and other CEQA/NEPA mitigation and voluntary restoration efforts make up the remainder.

Looking to the future …

“These results give us a picture of what is out there and what is planned, but it’s by no means comprehensive, and a lot more work needs to be done,” said Mr. Constable.  “As new projects are added, there’s a need to track those and keep this up to date.”

He noted that there is a Delta Plan performance measure to track progress.

The majority of the tidal wetland restoration has been completed since 2017, so it is relatively recent, and we don’t know yet how well it functions—tracking how projects actually function will be important as future projects will need to be adaptively managed based on what is added and how they’re functioning.

There is a potential to expand the boundaries beyond just the legal Delta and Suisun Marsh; they only considered projects within the Council’s jurisdiction.  However, the Big Notch Project and Lower Elkhorn Basin Levee Setback Project are just outside of the Delta yet still very important, he said.  Similarly, targets for oak woodland and vernal pools might actually make more sense partially outside of the Delta, so we might want to track those as well.

“We need to consider how climate is going to affect these ecosystems – everything from the physical impacts of sea level rise to things like heat stress and food web impacts,” said Mr. Constable.  “I want to highlight that the Council is working on a separate initiative, Delta Adapts, which is our climate change initiative.  And one of the aspects of that is looking at ecosystem adaptation, so we are trying to address that and would certainly welcome more feedback on that from all of you as well.”

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