Death Valley, the hottest and driest place in America, sits atop a sprawling system of underground water.

In many places, it burbles toward the surface in support of oases and strange, watery cradles of life like Devils Hole, a deep limestone cavern just over the Nevada border that’s home to perhaps the world’s rarest fish. The Devils Hole pupfish has existed in a hellishly hot geothermal spring there — and only there — since the last Ice Age.

The luminous blue fish was among the first to be protected under the Endangered Species Act in 1967. Yet generations later, its survival remains tenuous. The pupfish population hovered in the 200-300 range for decades, then plummeted to a low of 35 in 2013.

Scientists have linked its struggle at least in part to human disruption of an exquisitely calibrated ecosystem, making the fish something of a canary in a coal mine for climate change.

As a last resort, the government created a 110,000-gallon replica of Devils Hole at a nearby facility where they have nurtured a “lifeboat population” of pupfish that could be used to replenish the wild population if needed. The project has consumed millions of dollars and years of attention from a team of federal biologists, prompting some people to ask: Why go to such lengths to rescue a tiny fish in the middle of the desert?

One answer from pupfish supporters was articulated in a N.Y. Times opinion by the nature writer Richard Conniff. Wildlife should be useless in the same way that art is useless, he wrote.

“They are useless in the sense that they do nothing more than raise our spirits, make us laugh or cry, frighten, disturb and delight us. They connect us not just to what’s weird, different, other, but to a world where we humans do not matter nearly as much as we like to think.

And that should be enough.”

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