And the cause is the human hunger for water.
From an ominous report in the San Francisco Chronicle:
Evidence of what scientists are calling the planet’s Sixth Mass Extinction is appearing in San Francisco Bay and its estuary, the largest on the Pacific Coast of North and South America, according to a major new study.
So little water is flowing from the rivers that feed the estuary, which includes the Sacramento-San Joaquin River Delta, Suisun Marsh and the bay, that its ecosystem is collapsing, scientists who conducted the study say.
Human extraction of water from the rivers is not only pushing the delta smelt toward extinction, they say, but also threatening dozens more fish species and many birds and marine mammals, including orca whales, that depend on the estuary’s complex food web.
The findings by scientists at the Bay Institute, an environmental group, underline conclusions already reached by state regulators and are intended to buttress the environmental case for potentially drastic water restrictions in San Francisco and other parts of the Bay Area, and among farmers in the northern San Joaquin Valley.
From the report itself, a graphic revelation [the white line is a reproduction artifact — esnl]:
Key findings summarized
From the Bay Institute website, a summary of significant findings:
The report’s major findings include:
- On average, since 1975 more than half (53%) of runoff from the Central Valley watershed has been diverted, stored, or exported before it can reach the Bay – and in many years two-thirds or more of the Bay’s inflow is captured;
- As a result of intensive water diversions, the Bay experiences catastrophically dry years almost half the time (only one “supercritically dry” year occurred naturally between 1975-2014, but the Bay experienced nineteen supercritical years during that period);
- Numerous unrelated fish species – from sharks to salmon, from sturgeon to smelt – show strong positive correlations with Bay Inflow; many of these species are now endangered, and even commercially viable fisheries are in decline;
- Predators that feed on flow-dependent fish and shrimp are feeling the pinch – for example, dwindling supplies of Central Valley Chinook salmon may restrict the recovery of the local Orca whale population;
- Blooms of toxic “algae” (cyanobacteria) are becoming more frequent, and other pollutants are becoming more concentrated, as a result of reductions in freshwater flows from the Bay’s watershed;
- Bay Area beaches and tidal wetlands are deprived of sediment that was once transported by high river flows.