Elkhorn Slough: The Estuary That Has No Right to Exist

Elkhorn Slough should not be what it is. By every measure of twentieth-century industrial and agricultural impact, it should be a degraded drainage ditch, not one of the most ecologically significant estuaries in California.

The slough cuts seven miles east from Moss Landing into the agricultural flatlands of Monterey County. It was diked for farming. It was drained, channeled, and surrounded by strawberry and artichoke fields that applied pesticides and fertilizer for decades. In nineteen forty-six, when engineers cut the new Moss Landing harbor entrance, they altered the tidal flows that the slough had operated on for thousands of years. The change accelerated erosion and complicated the salinity balance. The ecology should have collapsed.

Instead, something else happened. The altered tidal flushing brought in more seawater, which turned out to benefit the marsh grasses and the animals that depended on them. Sea otters moved in from the bay. Leopard sharks found the warmer, shallow water ideal for pupping. Three hundred and forty species of birds use the slough as migratory stopover, wintering ground, or breeding site. The slough became a National Estuarine Research Reserve, one of twenty-eight designated nationally. In two thousand and eighteen it was designated a Ramsar site, an internationally protected wetland of global ecological importance.

The largest tract of tidal salt marsh in California outside San Francisco Bay is here, in the middle of a vegetable-growing region, bordered on one side by a decommissioned power plant and on the other by a state highway. The biology declined to follow the engineering.

You can see sea otters on calm mornings. They are floating on their backs, as if the twentieth century never happened here.