Biodiversity: Our Precious Heritage

Unusually heavy rains in the winter of 1969 transformed California’s normally dry Owens Valley, causing an explosion of grasses and reeds along the edge of the Owens River. Lying in the eastern rain shadow of the Sierra Nevada, not far from Death Valley, the river flows south down the valley before disappearing into a dry lake bed. By summer the heavy vegetation along the river and its adjacent spring-fed marshes was sucking up moisture and releasing it into the hot, dry air. At the same time, the flow from one of these springs suddenly and mysteriously dropped, and parts of a wetland called Fish Slough began to dry up fast. The disappearance of the small pools that make up Fish Slough would have gone unnoticed in a world not reshaped by human hands. Desert springs and marshes can be verdant one year, parched the next. Human activity, however, had made Fish Slough a vital place. The need for water to support Los Angeles and other cities has led to all manner of water projects, including dams, reservoirs, canals, and aqueducts. One of those projects, the Los Angeles Aqueduct, diverted nearly all the water from the Owens River beginning in 1913, greatly reducing the flows that once created seasonally flooded shallows along the river’s edge. Those shallow, warm waters provided ideal habitat for a unique species offish, the Owens pupfish (Cyprinodon radiosus). The loss of habitat, along with the introduction of exotic species like largemouth bass, gradually eliminated the pupfish from most of its relatively limited range, until the species remained only in Fish Slough. If the marsh disappeared, so would the Owens pupfish. Alerted to the potential disaster, Phil Pister, a fishery biologist working nearby with the California Department of Fish and Game, and two colleagues grabbed nets, buckets, and aerators and raced for the pond (Pister 1993). They removed the last 800 of the two-inch-long pupfish to wire mesh cages in the main channel of the slough. As his colleagues drove off, thinking the pupfish at least temporarily secure, Pister realized that the cages were in eddies out of the main current and that the water in the eddies was not carrying enough dissolved oxygen.