On-line herbarium specimen databases are becoming an important tool for studies of plant biogeography. They will increasingly point directions for plant conservation. Specimen records are not equally distributed between areas, and many herbaria are not yet functionally digitized.. As pointed out before, the variance in herbarium specimen density between counties within California is high.
As of today, my data compilation of specimen records for for Yosemite National Park stands at 30,149 specimens, a density of 9.8 specimens/square kilometer – about twice the specimen density for the state as a whole.
Yosemite Valley is perhaps one of the most visited sites on Earth. A total of ca. 5,450 specimens can be directly or strongly attributed to Yosemite Valley. Allowing that the area of the Valley floor, and abutting vertical walls, is uncertain, the area of the Valley is about 20 square kilometers (8 miles long, one mile wide). Thus, a vascular plant herbarium specimen density for Yosemite Valley is about 272 specimens/square kilometer.
Comparative is San Francisco city and county, with ca. 7800 specimens at ca. 75 specimens/square kilometer. Also comparative is Bronx County, New York (via Consortium Northeast Herbaria) at 3479 specimens, at 24 specimens/square kilometer.
Yosemite Valley is the most highly collected location in North America. Moreover, in some respects, Yosemite Valley is functionally as urbanized as San Francisco and the Bronx.