It’s small, but it’s a keeper

California is a thirsty state. You don’t mess with its water, even in a good year, unless you have an excellent reason. Which is why many Californians are shaking their heads in dismay over a federal judge’s recent decision to cut by as much as 30% the water sent south from the San Joaquin-Sacramento River Delta this winter. The judge’s reason: to save a French-fry-sized fish called the delta smelt.

The delta smelt makes no heroic journey across the ocean or up river rapids to reproduce. Once superabundant, Chinese fishermen used to harvest the fish by net, but the little thing, a weak swimmer, wouldn’t put up any fight at the end of a line. And a smelt would not even make a decent snack. Frankly, on first glance, the fish just isn’t much to look at either.

So why should millions of Californians who rely on water pumped south from the delta make economic and social sacrifices -- including the possibility of rationing -- for a basically unremarkable fish?

There are at least four good reasons.

First, it is the law. The Endangered Species Act prohibits the government from doing anything that jeopardizes the continued existence of endangered or threatened species, and it forbids any government agency, corporation or citizen from harming, harassing or killing endangered animals without a permit. It is a sound law, put in place by the Nixon administration in 1973 to protect imperiled plants and animals “from the consequences of economic growth and development untempered by adequate concern and conservation.”

By drawing a bright legal line this side of annihilating whole kinds of creatures, the law is to thank for saving the bald eagle, the gray whale, the California condor and the Pacific green sea turtle, among other animals. And it’s a law that will be especially important in California and beyond as climate change, human population growth, habitat conversion and invasive species increasingly degrade the natural world.

But obeying even a good law may seem unjustified when it comes time to make sacrifices for a ghostlike fish that conveys no clear benefits to mankind. That common perception brings us to the second reason to save the smelt: The goal of the Endangered Species Act is not just to protect single species but also the ecosystems on which they depend. The delta smelt is what Peter Moyle, a fisheries biologist at UC Davis, calls an indicator species: Its condition reflects the overall health of an ecosystem.

In the case of the delta, we’re talking about a once-magnificent place that is in serious trouble. It is 16,000 square miles of wetland and open water -- the West Coast’s largest estuary -- and the end point of about 40% of California’s precipitation. When the Spanish arrived centuries ago, it was teeming with fish, crawling with bears and beavers, its skies periodically darkened with migrating birds.

Twenty-nine known fish species once called the delta home. Twelve of those are either gone altogether or are threatened with extinction. The Sacramento perch, once one of the most abundant fish in the system, was last seen in the 1970s, Moyle says. The thicktail chub disappeared in the 1950s. Many other fish are in rapid decline too, victims of pollution, overfishing and habitat destruction as big portions of the delta were diked and drained for agriculture, and the natural exchange of fresh and salt water was altered by the huge, sucking pumps that send water south. As for the delta smelt, Moyle has been charting its decline for decades. But that decline turned into a nose-dive a couple of years ago because of increased water diversions from the delta. This year’s spring survey found 90% fewer fish than in 2006, the previous record low.

Reducing the amount of water sucked from the delta, increasing the release of fresh water upriver and controlling pollutants would help save the delta smelt and help protect spring- and winter-run Chinook, striped bass, steelhead trout, green sturgeon and the entire delta ecosystem. If we don’t take these steps, and if we let the delta smelt go down, the longfin smelt, the next most endangered species in the delta, will follow. Then maybe the striped bass and the Sacramento splittail.

Why care? The species in an ecosystem are woven together like characters in a Shakespeare play. Start pulling them out, and the play’s integrity is lost. Removing the delta smelt would be like pulling the ghost from “Macbeth.” Forever. You’d still have a play, but it wouldn’t work. Then pull, say, Banquo and the three witches and replace them with characters who don’t belong there. You’d have some kind of absurdist sitcom where you once had a masterpiece. Without the native fish and other species that populate the delta, it won’t work either.

A slightly closer look at the delta smelt shows us a third reason to rescue the fish from oblivion -- it’s actually pretty impressive. While most fish are hard-wired either for salt or fresh water, the delta smelt tolerates both, a talent that allows it to exploit the brackish zone where the waters meet. Before there were giant aquatic vacuum cleaners in its midst to send water south, it could afford to be a weak swimmer because it mastered the cyclical ebbs and flows of the estuary, exploiting the system’s inhalations and exhalations to get where it needed to go.

During the dry season, when the salt water moves up the estuary toward the Sacramento and San Joaquin rivers that feed it, the smelt would ride the tidal currents up into the delta’s river channels, where it laid its eggs. With the winter rains and consequent outflows, the fish would be carried out to what is called the entrapment zone, where fresh and salt water meet, a place where the zooplankton they feed on is most abundant. The delta smelt’s ghostly blue color makes it nearly invisible to predators. It is a triumph of evolution and, believers might say, of creation, as well adapted to the old delta as the bald eagle and the gray whale are to their natural habitats.

Finally, the Torah says that if you save an individual, you save an entire universe. How much truer that is for a whole kind of creature. Nothing else on Earth lives the way the delta smelt does, senses the world the way it does, looks like it, moves like it, fits into an ecosystem the way it does. If we drive it from existence, we will have obliterated an entire world, willingly, in order for a while longer to grow cotton, rice and alfalfa in the desert, to keep our swimming pools topped off and open, to keep the price of water cheap.

If we can face our growing need for water, and our diminishing supply of it, without driving whole species to extinction, it might be more expensive and inconvenient in the short term. But if it saves the fish, saves the delta and saves a world, it would be well worth the price.