by Peter Moyle, Carson Jeffres, John Durand

Cache Slough sunrise. Photo by Matt Young

The Delta is described in many ways.  When extolling the Delta as a tourist destination, it is described as a place of bucolic beauty; islands of productive farmland are threaded by meandering channels of sparkling water, a place to boat, fish, view wildlife, and grow cherries and pears.

But when its future is discussed, especially in relation to big water projects, this heavenly place is often portrayed as being on its way to an aquatic Hellscape.

The Sacramento Bee recently (April 8, 2008) published a reasonable editorial advocating a holistic approach to solving Delta problems.  But the editors chose language to describe the Delta such as:  it is “dying as the planet warms” and it is on the verge of “ecosystem collapse.” This language tracks that of groups that want to “save the Delta,” especially from proposed changes to its human-dominated plumbing system.

At the risk being labeled heretics, we say the Delta is not dying, and its ecosystem is not on the verge of collapse, but that it is changing.

The last time California faced real collapse of aquatic ecosystems was before the passage of the state and federal clean water acts in the 1970s, which eliminated or greatly reduced the dumping of huge volumes of toxic material into the estuary.  The present Delta, as measured by total fish populations, species diversity, navigability, migratory waterfowl abundance, and other measures, even water quality, is a ‘healthy’ ecosystem in many ways.

The most likely future Delta, even after widespread levee failure, will not feature a collapsed ecosystem (whatever that may be) or even a particularly unhealthy Delta ecosystem.  No matter what happens, there will still be fish and fisheries in the Delta, as well as boating, abundant wildlife, complex food webs and prosperous farms. But the future ecosystem may not have many of the species we find desirable today, especially endangered species such as delta smelt and winter-run Chinook salmon. Current land use patterns are also likely to change, away from urbanization and low-value agriculture.

If present trends continue, native fishes in the Delta will be replaced largely by alien species such as wakasagi smelt, Mississippi silversides, and largemouth bass. Deeply  subsided islands will be transformed via levee collapses to large open areas of tidal brackish water. These habitats will favor salt-tolerant species such as striped bass, starry flounder, crangon shrimp, splittail and various species of Japanese gobies.  In short, at least in the water, the fishes tell us that, no matter what happens, there will be thriving novel ecosystems that will support many of the same functions as today. The present ecosystem is already quite different from earlier manifestations of the ecosystem, especially the original historic ecosystem. Native species disappear while non-native species increase.

But we don’t have to accept whatever Delta ecosystem comes our way. To some extent, we can choose the species making up the future Delta ecosystem as well as many of its physical features, if we make some tough management decisions and accept that ecosystem changes will continue, some beyond our control.  Today’s somewhat foggy general vision of the Delta’s future seems to be that it will remain in its present configuration forever, with levees and channels maintained despite continual land subsidence, bigger storms, higher tides, and changing habitats and economies.  This Delta is assumed to continue as a freshwater system, thanks to large pulses of water from dams.  Despite these pulses, native fishes will gradually disappear, although fall-run Chinook salmon runs may continue due to hatcheries and trucking operations.  Delta smelt and longfin smelt will likely be extinct; they will no longer drive water decisions unless maintained by artificial propagation, like salmon. Fisheries for largemouth bass and other warm-water fishes will expand, dominating the system even more than today.

This vision does not have to prevail in all of the Delta.  We recently wrote a report that provides an alternative vision (Moyle et al. 2018, Making the Delta a Better Place for Native Fishes (https://www.coastkeeper.org/wp-content/uploads/2018/03/Delta-White-Paper_completed-3.6.pdf).   The vision we present is a modified version of some earlier thoughts (Moyle et al. 2013, and other references listed below).  The key to this vision is that management for native species and related values focuses on the North Delta Arc, a string of habitats connected by the Sacramento River.  The  Arc starts in the Yolo Bypass, continues through the Cache Slough region, then down the river past Rio Vista and into Suisun Marsh.  It also includes the Cosumnes-Mokelumne river corridor, to the Sacramento River.

Under this vision, the central and south Delta are treated as habitat that is, in fact, inhospitable for native fishes.  Indeed, native fishes may need to be excluded from these parts of the Delta, especially in summer.  The main issue for the central and south Delta is creation of a corridor for safe passage of adult and juvenile salmon and steelhead between San Francisco Bay and the San Joaquin, Tuolumne, Merced, and Stanislaus rivers.  This division of the Delta into two ecosystems is tacitly recognized already by most restoration projects (e.g., EcoRestore) as being located in the Arc.  This area provides the best opportunities because of habitat diversity and the fact that the Sacramento River connects these diverse habitats. The river also serves as the major migration corridor for fishes.

Our paper recommends 17 actions, listed below. Collectively, these actions could significantly improve habitat for native fishes, either directly or indirectly through stressor reduction and through development of new approaches via research. They at least will slow the ecosystem shift now occurring in favor of native species, floodplains, and wetlands.

DELTA-WIDE ACTIONS

1. Four Easy Fixes (Fremont Weir, McCormick –Williams Tract, Delta smelt beaches, Putah Creek restoration).
2. Expand Monitoring for Estuarine Health
3. Provide a Water Right for the Environment
4. Develop a Functional Flow Regime for the Delta
5. Expedite Permitting and Implementation of Habitat Restoration Projects

REGIONAL INITIATIVES

6. Expand EcoRestore and Learn from First 30,000 Acres
7. Expand Restoration Projects in the North Delta Habitat Arc
8. Establish Suisun Marsh as a Horizontal Levee
9. Eliminate Predation Problems at Clifton Court Forebay
10. Improve Delta Passage for Juvenile Salmon from the San Joaquin River and Tributaries.

REDUCING STRESSORS ON DELTA FISHES

11. Reversing Subsidence in the Delta
12. Accommodating Climate Change
13. Reducing Impacts of Invasive species
14. Reducing Impacts of Pesticides, Micro-contaminants, and Other Toxic Materials

PROBLEM-SOLVING RESEARCH

15. Experimenting with Island Flooding
16. Evaluating Restoration Projects
17. Developing a Stable Source of Innovative Research Funding.

As the report states: “The alternative to taking these and other actions is to continue on our present path, which is leading to the extinction of native fishes and the loss of significant fisheries for Chinook salmon, steelhead, striped bass and other fishes. It is important to remember that the Delta will always support a complex ecosystem. But whether that ecosystem is one that is desirable and consistent with our needs is up to us.”

The vision expressed by our report accepts that changes to the Delta ecosystem are inevitable but that, optimistically, we can collectively direct some of the change towards a more desirable state than will exist without high levels of additional activity. This vision can encompass actions favored by those who want to “save” the Delta, as well as those who envision a managed ecosystem that includes most of the remaining native fish fauna, as well as many other desirable elements, native and non-native.  It is not a vision that supports the rhetoric of a dying Delta or the Delta as a collapsed ecosystem, a rhetoric which does not lead to plausible actions to improve reality.

Peter B. Moyle is a UC Davis Professor Emeritus of fish biology and an associate director of the Center for Watershed Sciences. John Durand is a researcher specializing in estuarine ecology and restoration at the Center for Watershed Sciences.  Carson Jeffres is a researcher specializing in fish ecology at the Center for Watershed Sciences.

Further reading

Durand, J., P. Moyle, and A. Manfree. 2017. Reconciling conservation and human use in the Delta. UCD California Water Blog, February 12, 2017.

Hanak, E., J. Lund, J. Durand, W. Fleenor, B. Gray, J. Medellín-Azuara, J. Mount, P. Moyle, C. Phillips, and B. Thompson. 2013. Stress Relief: Prescriptions for a Healthier Delta Ecosystem. San Francisco: Public Policy Institute of California. Available at www.ppic.org/main/publication.asp?i=1051

Hobbs, J.A, P.B. Moyle, N. Fangue and R. E. Connon. 2017. Is extinction inevitable for Delta Smelt and Longfin Smelt? An opinion and recommendations for recovery.  San Francisco Estuary and Watershed Science 15 (2):  San Francisco Estuary and Watershed Science 15(2). jmie_sfews_35759. Retrieved from: http://escholarship.org/uc/item/2k06n13x

Lund, J., E. Hanak, W. Fleenor, W. Bennett, R. Howitt, J. Mount, and P. B. Moyle.  2010. Comparing futures for the Sacramento-San Joaquin Delta. Berkeley University of California Press. 230 pp.

Moyle. P.B. W. Bennett, J. Durand, W. Fleenor, J. Lund, J. Mount, E. Hanak, and B. Gray. 2012. Reconciling wild things with tamed species- a future for native fish species in the Delta. California Water Blog. Center for Watershed Sciences, June 15, 2012. http://californiawaterblog.com

Moyle, P. B., W. Bennett, J. Durand, W. Fleenor, B. Gray, E. Hanak, J. Lund, J. Mount. 2012. Where the wild things aren’t: making the Delta a better place for native species. San Francisco: Public Policy Institute of California. 53 pages.

Moyle, P. B., W. A. Bennett, W. E. Fleenor, and Jay R. Lund. 2010. Habitat variability and complexity in the upper San Francisco Estuary. San Francisco Estuary and Watershed Science  8(3): 1-24. http://repositories.cdlib.org/jmie/sfews/vol8/iss3

 Moyle, P., J. Durand, A. Manfree. 2016. The North Delta habitat arc: an ecosystem strategy for saving fish. UCD Center for Watershed Sciences California WaterBlog. November 6. 2016.

Moyle, P.B., J. A. Hobbs, and J. R. Durand. 2018.  Delta smelt and the politics of water in California.  Fisheries 43:42-51.

Moyle, P.B., A. D.  Manfree, and P. L. Fiedler. 2014. Suisun Marsh: Ecological History and Possible Futures.  Berkeley: University of California Press.

Moyle, P.B., C. Jeffres, and J. Durand. 2018, Making the Delta a Better Place for Native Fishes (https://www.coastkeeper.org/wp-content/uploads/2018/03/Delta-White-Paper_completed-3.6.pdf)

Opperman, J.J, P.B. Moyle, E.W. Larsen, J.L. Florsheim, and A.D. Manfree. 2017 Floodplains: Processes, Ecosystems, and Services in Temperate Regions. Berkeley: University of California Press.