By John Durand, Peter Moyle, and Amber Manfree
In a previous blog, we presented a Grand Scheme for habitat conservation in the North Delta Arc (the Arc). This follows up on our earlier broad vision for recreating a Delta more friendly to its native species. In this essay, we give philosophical and historical reasons to approach habitat conservation on the regional scale of the Arc, using reconciliation ecology as our guide.
The Sacramento-San Joaquin Delta has been extensively altered over the past 150 years. Major changes include manipulation of river flows, alien species invasions, conversion of wetlands to agriculture and, most recently, climate change. Changes have been incremental and slow enough that successive generations of Delta residents, fishermen, scientists, and managers have not seen the full extent of transformation. Each generation assumes the conditions they encounter are not much different from those of the recent past. This problem of slowly shifting baselines means that our understanding of historical conditions shifts with changing conditions, because the change is difficult to accept and because we cannot directly observe what conditions were like in the more distant past (Pauly 1995; Papworth et al. 2009).
A recent review of anthropological studies, early travelogues, and scientific surveys of the Delta gives a better sense of the transformation. The Delta originally was a place where the sky darkened with migratory waterfowl in fall, where salmon runs crowded tributary rivers, tule elk browsed on oak-topped natural levees, and delta smelt were a common prey for fishes and birds. Flows in the Sacramento and San Joaquin Rivers were highly variable, but predictable in pattern, with winter floods and summer droughts. Such aspects of the historic landscape were gradually lost with marsh reclamation, damming, levee construction, water diversions and pollution from mining, agriculture, waste water and urban runoff. It is impossible to restore natural conditions—little quality habitat remains, connectivity among habitats has been lost, and many historically abundant species are extinct or their populations are greatly reduced in number. Native species have been largely replaced by alien plant and animal species such as largemouth bass, Mississippi silversides and Brazilian waterweed. These new arrivals are abundant because they are adapted to conditions created by the expanding human-altered landscape.
Governor Brown’s EcoRestore initiative aims to provide habitat restoration projects to reverse the decline of native species and create habitat that functions to support native species . We agree that it is imperative that some of our pre-19th century historic natural legacy be maintained. Given the depth of transformation, restoration to perceived “baseline conditions” is impracticable. That historic Delta is lost.
As a workable alternative, we promote the idea of reconciling current land uses with desirable ecological outcomes. A reconciliation approach to Delta conservation offers opportunities to recapture lost ecological functions that support threatened species. It involves creative management of the current landscape to balance benefits for fish, waterfowl, food webs, and human uses. This idea can help to manage the emergence of novel ecosystems globally, landscapes with new conditions and combinations of organisms with no historical analogue, but which provide valuable and viable species conservation opportunities, as well as human benefits (Rosenzweig 2003; Hobbs et al. 2006).
This approach may involve some dramatic and expensive actions that involve earth moving to recreate marshes and meandering channels. But more often, it involves working with farmers, duck club owners, anglers, and other stakeholders to adjust breaching of levees and the operation of tidal gates to facilitate the movement of water across the landscape.
The Nigiri project on the Yolo Bypass illustrates this concept. Here, young salmon are raised in rice fields before being released to the Delta and before farmers need to plant, with involvement of local farmers, state agencies, county government, CalTrout, and UC Davis. But Nigiri is not the only reconciliation project in the Delta. In Suisun Marsh, the Potrero Duck Club, historically operated as a private hunting club, is being managed to promote not only water fowl, but as an incubator to create food for the larger aquatic ecosystem. Although these sites differ from historical conditions, they effectively capture the ecological functions of an earlier Delta that are largely lost: they grow and disperse food, act as nursery habitat for young fish and provide food for nearby wildlife. While opportunities to re-create the Delta’s original habitats have faded, opportunities have arisen to create new habitats that serve human needs, provide ecosystem services, and support native fish and wildlife. We see wild lands being integrated with managed lands as the most productive way to create a reconciled Delta.
In future essays, we will explore the use of reconciliation ecology to several important sites in the Delta. These include: Meins Landing, Montezuma Wetlands, Potrero Club, Lindsey Slough, Denverton Slough, Blacklock Pond, Liberty Island, North Liberty Mitigation Bank and Beaver Ponds, Prospect Island and Roaring River.
John Durand is a researcher specializing in estuarine ecology and restoration at the UC Davis Center for Watershed Sciences. He oversees projects in the north Delta Arc of habitat including the Cache Lindsey complex and Suisun Marsh. Peter Moyle is a UC Davis Professor Emeritus of fish biology and an associate director of the Center for Watershed Sciences. Amber Manfree is a postdoctoral researcher with the UC Davis Center for Watershed Sciences.
Hobbs RJ, Arico S, Aronson J, Baron JS, Bridgewater P, Cramer VA, Epstein PR, Ewel JJ, Klink CA, Lugo AE, et al. 2006. Novel ecosystems: theoretical and management aspects of the new ecological world order. Glob. Ecol. Biogeogr. 15:1–7.
Mount J, Bennett W, Durand J, Fleenor W, Hanak E, Lund J, Moyle P. 2012. Aquatic ecosystem stressors in the Sacramento–San Joaquin Delta. Public Policy Inst. Calif.
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Sommer TR, Nobriga ML, Harrell WC, Batham W, Kimmerer WJ. 2001. Floodplain rearing of juvenile Chinook salmon: evidence of enhanced growth and survival. Can. J. Fish. Aquat. Sci. 58:325–333.
Whipple A, Grossinger RM, Rankin D, Stanford B, Askevold R. 2012. Sacramento-San Joaquin Delta historical ecology investigation: Exploring pattern and process. Richmond, CA: San Francisco Estuary Institute-Aquatic Science Center Historical Ecology Program Report No.: 672.
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