The Sacramento-San Joaquin River Delta is formed at the western edge of the Central Valley by the confluence of the Sacramento and San Joaquin rivers. As the largest estuary in Western North America it serves a vital role in Pacific Flyaway. The Delta also serves as a critical water supply delivery hub conveying rainfall and snowmelt from mountain watersheds to 25 million Californians in the Bay Area and Southern California, tens of thousands of businesses and about 3 million acres of agricultural farmland in the Central Valley and beyond – or about 1/3 of all the irrigated land in the country’s highest producing agricultural state. Understanding the evolution of the Delta and its significant role in water policy will be critical for the next governor.

In its natural state, the Delta was a large tidal marsh. Hundreds of years of human activity have changed that. Leading scientific experts correctly recognize the Delta today as a continually evolving or “novel” ecosystem. The evolutionary forces include:

Evolutionary Forces Icons 2

Nearly all of the Delta’s tidal marsh habitat was lost with development of the estuary’s complex levee system. Increasing local development has also increased demand and stress on the estuary. Growing populations exacerbate pollution through contaminated stormwater runoff and municipal wastewater and industrial discharges. Warmer temperatures, changing patterns of precipitation and runoff and rising sea level are increasingly affecting the Delta ecosystem and ecology. Human induced changes to the ecosystem have also led to a rapid alteration of biodiversity in the Delta, including crippling invasions by non-native species.

Two simple statistics best characterize the immense evolution that has occurred in the Delta.

  • Ninety five percent (95%) of the Delta’s historic tidal marsh habitat has been lost.
  • Ninety five percent (95%) of the biomass (fish and plant species) is non-native.

Given these tremendous forces of change, it is not surprising to see a continuing decline of native species. The rapid decline of imperiled species such as salmon, delta smelt and steelhead continues even as state and federal regulators continue to take increasingly costly and socially disruptive resource management actions. We will never “restore” the Delta but we can, through smart investments in ecosystem projects, restore some of the ecosystem functions crucial to native fishes. Significant investment is also required if we are to have any hope of reducing the multiple major stressors faced by native species.

One thing virtually everyone agrees with is that the current system is not working well for the fish we “care” about or the communities that have flourished because of our amazing water infrastructure. Our next Governor must recognize the evolving nature of the Delta and find solutions that better balance human and ecological needs. The next Governor will play a leading role in continuing the progress toward these critical “co-equal” water policy goals. More time and resources will need to be spent to achieve the proper balance to ensure a strong and robust economy for the future while also improving the health of native species in the Delta.

“The Delta Today is what’s called a novel ecosystem: It’s an ecosystem unlike any that has ever existed before. It’s permanently altered by humans and it continues to be altered. It has a mixture of native and non-native species… and they’re all interacting and creating this new ecosystem.”

— Peter Moyle, Professor Emeritus, Center for Watershed Science, University of California – Davis