| The Magazine of the CALIFORNIA ACADEMY OF SCIENCES |
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FEATURE STORY Past The Salt Images and text by Herb Lingl
Let me show you what the salt ponds look like,” said Ann Elsbach, my flying mentor, a little over ten years ago. We prepared her red, two-passenger Taylorcraft, and moments later were over a world of magnificent colors, shapes and reflections. So began a decade of exploring San Francisco Bay from the air. Changing seasons, tides, salinity, and other forces ensure that each visit to this world is a unique experience. So began a decade long project of exploring the ever changing Bay from the air. Water from the bay floods into the first pond in the system at high tide. Over the next five years, this water slowly moves through a network of ponds. Though the system relies primarily on gravity as the water moves around the edge of the bay, it is sometimes pumped under the varios creeks and sloughs. As the wind and sun gradually evaporate the surface, the salinity increases. Finally, the highly saline water is transferred to the bittern and crystallizer ponds. A network of salt ponds still producing commercial salt stretches from Mountain View around the southern part of the Bay to Newark. An additional system of ponds in the north Bay along the Napa river was conveyed to the US Fish and Wildlife Service which now manages both the ponds and the efforts to restore these areas to tidal wetlands.
The varying colors of the salt ponds are caused by changes in the the species as the salinity increases. Halophilic bacteria and brine shrimp thrive in ponds with high saline concentrations, so the higher the salinity, the redder the ponds appear. Dunaliella (Dunaliella salina) a single-cell alga, is the primary contributor to the red of the ponds. Dunaliella are unique in their ability to adapt to harsh conditions. Dunaliella antarctica, for example, thrives at sub-zero temperatures. The salina strain has an exceptional ability to eliminate positive sodium ions. As the water evaporates during the Bay Area's dry seaon, the ponds take on even more dramatic colors. They are at their most vivid when ready to harvest.
When the Spanish first came to San Francisco Bay, they discovered that the native Americans were producing and trading salt. A commercial salt evaporator was established in 1854, and soon a complex system of levees and ponds was dedicated to salt production. In 1942 over 20 salt companies were integrated into the Leslie Salt Company which owned approximatedly 50,000 acres of salt ponds. Cargill, the world's largest privately held corporation, purchased Leslie Salt and sold 11,430 acres to the San Francisco Bay National Wildlife Refuge, while retaining mineral rights to the lands. they sold another 10,000 acres of salt ponds in the north Bay to the State of California in 1994, and in 2002 Cargill sold or provided conservation easements to 16,500 acres of salt ponds, in a transaction which represents the largest and most ambitious wetland restoration effort in the Bay Area.
Herb Lingl is director of Aerial Archives, a library of current and historical aerial photography. The photographs and text in this essay are excerpts from his forthcoming book, High Over San Francisco Bay, and are availble at www.aerialarchives.com. |
