We have a tendency when we talk about an ecosystem to try and draw a bright and distinct boundary around it. We want to define our terms clearly. The desert is the desert and the redwood forest is the redwood forest, and we try to ignore the blurry areas around the edges.
It doesn’t usually work, of course. Even if the boundary you draw encompasses the whole planet, there are still the small matters of sunlight and tides to consider, the sun and moon stepping right across your boundaries like you didn’t even go to the trouble of drawing them.
There’s a popular and often mangled aphorism penned by John Muir that reads “When we try to pick out anything by itself, we find it hitched to everything else in the Universe.” That interconnectedness is the basic lesson of the science of ecology, and it’s nowhere more true than in the ecosystem in which Muir sat when he wrote the quote: the Bay Delta.
You can draw a bright line around the Bay Delta, encompassing the Golden Gate and the sloughs between Sacramento and Stockton and Muir’s ranch in south Martinez and everything in between, and there will be plenty worth to study within those boundaries, just as there is plenty worth studying in a human heart that has been excised from its chest cavity and laid on a dissecting table. But to really know the true Bay Delta, one must consider it as part of a near-organismal whole, connected Muir-style to the High Sierra and the seabed of the Pacific Ocean — among other places.
That organism is immense, with nuanced boundaries. Upstream, two dozen major rivers and hundreds of small tributaries drain an area the size of Norway. Downstream the ecosystem’s border dissolves into and intermingles with the Pacific Ocean.
And between the headwaters and the sea lies the Bay Delta, a narrow funnel through which runoff from three major mountain ranges flows into the tide, and the tide flows right back.
It’s a heart all right, the heart of California, except instead of one pulse it’s got dozens.
There are the daily pulses: the tides, the cycle of daylight and dark that phytoplankton and plants follow as they turn sunlight into food. There are the annual cycles, snowmelt flood and fall drought, the runs of salmon and sturgeon up into the headwaters to spawn, and the drifts of smolts washing back downstream.
Some of the Bay Delta’s pulses are measured in multiple years. For instance, there are the big floods every few decades as strong El Niño storms pummel the mountains. Some, like the flood of 1862, were cataclysmic; others, like 1997, were merely catastrophic. Wildfire years send silt and nutrients down into the Delta every so often.
And some pulses reside on the geological time scale, or close to it. There was a pulse of sediment in the late 19th century, washed down off the Mother Lode by hydraulic miners, that will affect the Bay Delta for a few centuries to come. Paleontologists a few million years from now, perhaps the sentient descendants of river otters, will note a broad band of silt in semi-petrified sediments and hypothesize that some horrible cataclysm took place for a few years, and they will be right. They will pick over the subtle remains of the large and temporary dams we’ve built, perhaps arguing over the natural forces that put them there.
About those dams: The Bay Delta is about 6,000 years old right now, and it’s doubtful the dams will still be there in another 6,000 years except as rust-stained rubble. As far as the rivers are concerned, it’s another cycle. The dams have been devastating to the Bay Delta’s anadromous fish populations, as well as to the less-migratory species downstream that once depended on the silt and sediment and nutrients the dams now impound.
But despite their massive character, even the largest dams in the Bay Delta watershed are mere temporary encumbrances to the rivers’ passage. Most large dams’ life spans are measured in decades. Without constant and expensive maintenance, few would last 200 years. Eventually, the reservoirs behind them will silt up. Eventually a storm the size of the one in 1862 will flood those silted-up reservoirs, overtop the crumbling concrete, and that silted-up water will carve notches in the dams’ concrete within a geologic eyeblink.
Nature bats last, as the bumpersticker says. At some point, new kinds of anadromous fish — perhaps the descendants of present-day rainbow trout — will make the journey again from the headwaters of the Pit and Feather and San Joaquin through the Delta and the Bay, and out to sea. Or perhaps we’ll manage to keep what’s left of the chinook and sturgeon going until then.
Or perhaps that anadromous fish species of the future will be something wholly unexpected. Either way, there will be fish that spend much of their adult lives eating the bounty of the Pacific Ocean, then bringing some of that biomass into the Bay Delta and upstream as far as they can to spawn, there to be eaten by mountain animals. How does a Sierra Nevada black bear like its squid? Inside a salmon.
That Muirian hitch works in the other direction. The biological productivity of the Bay and Delta, as clearcut as it may have been by invasive species, feeds the next generation of those anadromous fish as they drift down from their parents’ spawning grounds. The fish grow and head out to sea, where some of them are eaten. As we reported earlier this year, our dams and water diversions in the Bay Delta watershed have a significant impact on the southern resident population of orcas. Those orcas subsist on chinook salmon, and they’re suffering because we’ve damaged a major source of those chinook salmon.
And that exchange of ecological wealth doesn’t just happen in the water. The Bay Delta is a crucial stop for birds migrating along the constantly shifting corridor popularly called the Pacific Flyway; a bit of vegetation or an insect or a crustacean ingested in the Bay Delta might reemerge from the bird some hundreds of miles to the north or south. Stopover conditions in the Delta can determine the success of the very risky behavior that is bird migration: a bad year for stopover habitat can affect bird populations in the Yukon, or in Central America.
The notion that a dam in the mountains might harm an oceangoing animal like the orca that never pokes its head past the Golden Gate may be a bit hard to fathom, just as is the notion that protein from the depths of the Pacific might find its way into the hungry gullets of wolverines and bobcats living at 7,000 or 8,000 feet above sea level, or determine the success of a nest of birds in the Arctic. But it’s true.
Muir wrote an earlier draft of his “hitched to everything” epithet, more floridly in keeping with his ninth century writing style, that suits the Bay Delta even better. In July 1869, Muir wrote in his journal “When we try to pick out anything by itself we find that it is bound fast by a thousand invisible cords that cannot be broken, to everything in the universe.”
Each run of chinook in each of the Bay Delta’s tributary streams is one of those invisible cords. Each storm that blows in off the ocean to dump snow or rain on the slopes above treeline in the Sierra: another cord. Our aqueducts and sloughs diverting water to feed trees that grow nuts to export to far-distant countries: another cord. An orca eating a chinook; an angler landing a prize striped bass; a flock of snow geese landing to eat plants and fertilize them: all these interactions are invisible cords. That’s the Bay Delta watershed for you: a skein of distinct relationships that weave themselves together in this heart of California.
Source: kcet.org ~ By Chris Clarke