California Forum

Delta ecosystem is in a constant state of change

The Sacramento-San Joaquin Delta ecosystems will change with different species living in altered physical habitat. The Delta ecosystem of today will not be the Delta ecosystem of tomorrow. The only constant is change.
The Sacramento-San Joaquin Delta ecosystems will change with different species living in altered physical habitat. The Delta ecosystem of today will not be the Delta ecosystem of tomorrow. The only constant is change. Sacramento Bee file

The term “ecosystem collapse” should be expunged from any discussion of the Sacramento-San Joaquin Delta. Its continual, confrontational use only makes finding solutions more difficult. It should be replaced by “ecosystem change” or, if you prefer, “dramatic ecosystem change.”

Ecosystem collapse is typically mentioned in the context of some opposed action, as in, “If we increase water diversions, the Delta ecosystem will collapse.” The words immediately bring to mind a building suddenly caving into rubble or a bridge falling into a river.

The closest we have to collapsed aquatic ecosystems are the legendary “dead zones” in oceans off the mouths of polluted rivers or dry rivers below dams. The worst scenarios imaginable for the Delta ecosystem do not even approach such human indifference to the environment.

Three compelling realities of Delta ecosystems are rarely mentioned in today’s contentious dialogue.

First, the Delta will always have an ecosystem with diverse fish and wildlife supported by complex food webs. Major changes to the Delta will not cause its ecosystem to collapse. Rather, Delta ecosystems will change with different species living in altered physical habitat. The new ecosystem may have invasive species and other attributes we don’t like, but it will nevertheless be an ecosystem.

The Delta ecosystem of today will not be the Delta ecosystem of tomorrow. The only constant is change, which we are not good at anticipating or embracing.

Take the ecosystem found today in the south and central Delta. It hosts dense growths of Brazilian waterweed and exotic water hyacinth, beds of Asian clams and dense populations of non-native fishes from all over the country.

Most popular of the fishes is largemouth bass, which is so abundant and grows so large that the Delta is now home to dozens of bass fishing tournaments. The water is warm, green and often stagnant. This ecosystem and its recreational fishing are thriving, but the region is hostile to the relatively small populations of native fish, such as salmon and Delta smelt. The more western parts of the Delta, dominated by Sacramento River and tidal flows, have larger populations of native fish that are hanging on precariously.

The second overlooked reality about the Delta is that its ecosystem has always been changing, especially in the past 150 years. We tend to treat current ecosystems as if they have always been there. We also expect they will last forever unless we deliberately change them.

However, today’s Delta ecosystem is distinctly different from the one in the 1960s and ’70s. Back then, the south and central Delta was dominated by outflows of cool, fresh water, and the most abundant game fish was striped bass that shared their waters with abundant Delta smelt and young salmon.

Finally, the Delta ecosystem of today will not be the Delta ecosystem of tomorrow. The only constant is change, which we are not good at anticipating or embracing. For example, it seems inevitable that many dikes surrounding deeply subsided Delta islands will fail. This will create large open bodies of water of varying salinity.

Higher sea levels and temperatures from climate change will also alter today’s ecosystems. We don’t know exactly what fish, bugs and plants will dominate the different regions within the Delta, but diverse organisms of some sort will thrive in these new ecosystems. Quite likely many of the species will be a nuisance, such as quagga mussel and water hyacinth.

The bottom line is that we will keep messing with the Delta by building dikes and draining its landscape, diverting its water and importing alien species and contaminants.

We have dramatically changed the Delta ecosystem many times over, but we have not caused it to collapse. Nor are we likely to. So let’s work to guide change, to create an ecosystem with attributes that we want, such as sustainable populations of Delta smelt and salmon.

If we let it go on its present trajectory, Californians will be saddled with lots of small alien fish and a few big ones such as common carp. There will be little to distinguish the fish fauna of the Delta from that of reservoirs in Texas or even California.

We need to take charge of change and direct it toward desirable outcomes, knowing there will be unexpected outcomes as well. We can start by becoming less confrontational in our language. Invoking calamity and otherwise exaggerating outcomes of change will not help us find reasonable responses to ecosystem change.

Peter Moyle is a fish biologist at the University of California, Davis, and is associate director of the Center for Watershed Sciences at UC Davis. Jay Lund, a professor of civil and environmental engineering, is director of the Center for Watershed Sciences at UC Davis.

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