August 2007 Watershed Highlight of the Month

Southern California Coastal Water Research Group

The Southern California Coastal Water Research Group in collaboration with the Los Angeles and San Gabriel River Watershed Council and others, and led by biologist Eric Stein, is pioneering a new field called "historical ecology" that combines the skills of historians and scientists. In February 2007, they completed a study of the San Gabriel River and Floodplain that shows how plants, animals and their habitats have changed. They drew on sources such as Spanish land-grant maps from the 1830s, surveyor’s maps from the 19th Century, 90-year old soils maps and aerial photos from the 1920s along with written and oral histories. This was matched with geographic information system maps and other modern data sources and cross-checked until a clear picture of the river’s past emerged, showing a much wetter system that generally thought.

The study shows how the acreage, type, and distribution of wetlands have changed, what species were lost, how the plant composition has been modified, and what types of plants might best be used for restoration. "We're not trying to recreate the past," Stein said. "There's been too much change. But we can use our understanding of the past to make smarter decisions." For example, the most common freshwater wetlands were alkali wetlands, known as cienegasin Spanish, which have almost disappeared. One of the best remaining is by the Emo Mall in Torrance. That knowledge could influence future restoration work.

The San Gabriel River Historical Wetlands Projects represents a “proof of concept.” An exhibit based in part on this work is being developed at the Aquarium of the Pacific in Long Beach. With the value and methodology established on the San Gabriel River, another historical ecology project has begun in Ventura County. Stein hopes to perform similar studies for rivers up and down California’s coast.

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