The Great Salt Lake, Ancient, Shrinking, Irreplaceable

Drive west from Salt Lake City in the afternoon and the light changes before you reach the water. It flattens, whitens, loses its edges. The lake itself is hard to locate at first, it merges with the salt flats, with the sky, with the haze. Then you are on the causeway and the smell arrives: brine, mud, something alive and ancient. The Great Salt Lake is the largest saltwater lake in the Western Hemisphere. It is a remnant of Lake Bonneville, the ice-age sea, and it has been here in various forms for many thousands of years.

The lake has no outlet. Water flows in from three rivers and from hundreds of smaller streams draining the Wasatch Mountains; it leaves only by evaporation. Everything dissolved in those inflows accumulates. The salt content varies by location but averages several times that of the ocean. Nothing lives in the lake except brine shrimp and brine flies, both in staggering abundance: brine shrimp by the billions, brine flies in mats thick enough to darken the shore. Those populations feed millions of migratory birds, phalaropes, avocets, snowy plovers, and eared grebes by the hundreds of thousands, making the lake one of the most critical shorebird stopover sites in the Western Hemisphere.

The lake is shrinking. Since the mid-nineteenth century, diversions of its feeder rivers for agriculture and municipal use have sharply reduced its surface area and volume. The exposed lakebed is a powder of arsenic, mercury, and other heavy metals, accumulated over millennia, that winds pick up and carry into the Wasatch Front's valley air. Scientists have named this a public health crisis in the making.

A lake that has lasted for thousands of years could, by some projections, be functionally gone within decades. Utah's legislature has passed emergency measures to increase flows. Whether those flows will be sufficient, and whether they will arrive in time, remains genuinely uncertain.