You are here

Delta ISB to Council: Science Alone Cant Rank Stressors - Stressors on the Delta are interactive and complex

February 2011

Despite hope that best available science would provide a ranking system for stressors, the Delta Independent Science Board found that prioritization cannot be done using science alone.

Examples of stressors in the Delta include: wastewater pollution, agricultural run-off, federal, state and local pumping diversions, competition from non-native fish and plant species, temperature change and sea level rise due to the effects of climate change, and other pollutants.

Responding to a request from some members of the California Legislature and the Delta Stewardship Council, the Delta ISB recently released its report on stressors in the Delta, and reported its findings at the Council’s January meeting.

“There is no objective, scientifically agreed upon method for prioritizing multiple stressors,” Delta ISB Chair Dr. Richard Norgaard told the Council. “Stressors and the objectives we are trying to reach have to be thought about together.”

Delta Stressors

Norgaard asked the Council not to think of the report as a list, but rather as a “Mobius strip,” with no one stressor, or group of stressors, more important than another.

“The stressors are interactive and complex. [Ranking stressors] is going to be a judgment call on the political side and on the scientific side,” Norgaard said. “The importance of the objectives will tell us about the importance of the stressors.”

Norgaard also said that the state of the research is not advanced enough to accurately rank the most harmful stressors in the Delta.

“We are not in a position now to say that these three stressors are causing 90 percent of the problem, or it’s this one stressor that is causing 45 percent of the problem,” Norgaard said. “At the present state of the knowledge we just think there are a lot of interactive stressors.”

Even though the Delta ISB was unable to provide a cut-and-dried, ranked list, it did provide the Council with a way to think about the subject. The Delta ISB’s report organized stressors into four categories: global stressors, legacy stressors, anticipated stressors and current stressors.

According to the report, global stressors are those that have to be adapted to, like climate change and population growth. Legacy stressors are human-caused actions, such as the continuing effects of sediment and mercury discharge from the gold mining era. Anticipated stressors are stressors that can be anticipated and will result from present or future activities.

Current stressors are ongoing activities like water management practices, agricultural practices and waste discharges that can be changed or steps taken to reduce their effects on the Delta, or both.

While the natural conclusion would be to concentrate on the current stressors, Norgaard warned the Council not to get too bogged down by focusing on the next few years alone. “It is worrisome to me that the Council will feel pressure to address current stressors rather than to think out into your second and third timeframe and that [current stressors] will absorb too much of your time,” Norgaard said. “Keep your mind on 30 to 50 years out.”

Council Vice Chair Randy Fiorini was complimentary of the Delta ISB’s report.


“This is very useful. It’s written in terms we all understand and it outlines how complex the issues that we’re dealing with are,” Fiorini said.

The Council also asked the Delta ISB to weigh in on parts of the Delta Plan that require the best available scientific advice.

“It will be valuable to us if you look at the Delta Plan and see if it is focused on the stressors that [the Delta ISB] thinks are appropriate,” Council Executive Officer Joe Grindstaff said, “and tell us what needs to be added in to restore the ecosystem.”

Councilmember Felicia Marcus took her request a step further.

“We need to get our scientists to a place where they can say ‘On balance, this package of things will be better,’ and articulate how we can get in front of the curve,” Marcus said. “We need [the Delta ISB] to step out and help us a little more than saying ‘no this, not that, no that’s too hard,’ because then it becomes an interesting intellectual exercise that’s really expensive and not that useful.”

Norgaard promised that the Delta ISB would continue to interact with the Council by reviewing the upcoming drafts of the Delta Plan as they are released.

“The blending of science and politics will come from the iterations of the Plan rather than us sitting in a backroom debating,” Norgaard said.

To view the full Delta ISB report on stressors, please visit the Council’s website here.

Coequal goals

The Delta Stewardship Council was created in legislation to achieve the state mandated coequal goals for the Delta. "'Coequal goals' means the two goals of providing a more reliable water supply for California and protecting, restoring, and enhancing the Delta ecosystem. The coequal goals shall be achieved in a manner that protects and enhances the unique cultural, recreational, natural resource, and agricultural values of the Delta as an evolving place." (CA Water Code §85054)