Historical ecologists are “ecological detectives,” scouring archives for clues about the past landscape and piecing them together. Information about the past landscape comes from diverse and sometimes unexpected sources. These are some tools in the historical ecologist’s toolkit:
The earliest written descriptions of San Francisco come from the Spanish missionaries, who made overland expeditions through California in the 18th century in search of suitable mission sites. Though limited in spatial detail, these accounts provide crucial information about landscape conditions prior to major social and environmental changes. Later accounts provide information about a wide range of topics, from plant species presence to the dimensions of stream channels to disturbances such as fires and floods. Botanical records from early collectors offer invaluable information about the makeup of early habitats. Newspaper articles, county histories, travelogues, and many other sources give rich perspectives from early visitors and residents.
photographs and drawings
Early photographs provide extremely localized, accurate information, often with substantial detail about vegetation structure and composition. For example, a circa 1910 photo, probably in the Sunset District (below right), depicts the sand dunes and dune vegetation that characterized much of western San Francisco prior to development. A circa 1860 photo of Black Point (below left) shows the coastal scrub vegetation that covered much of the bluff.
Early maps of San Francisco, like this circa 1840 diseño (or sketch) of Rancho San Miguel (right), show many interesting features of the landscape, but are limited in spatial accuracy. Later maps, such as the 1859 U.S. Coast Survey chart (right, middle) or the 1908 geological map (right, bottom), are much more accurate, but reflect a landscape already in transformation. Maps were created for many different purposes, and often show very different aspects of the same landscape: individual maps may provide information about topography, waterways, vegetation cover, land use, property ownership, or other topics.