EnviroAtlas, Percent Rare Ecosystems Protected per 12-digit HUC, California

These data are based on data generated by the U.S. Geological Survey (USGS) National Gap Analysis Program (GAP) landcover data. Open water and human use (ex. urban or agriculture) landcover types were removed. The systems were grouped into four spatial pattern types (i.e. matrix forming, linear, small patch and large patch), as defined by NatureServe. For example, riparian systems or shore lines tend to be linear and matrix forming ecosystems covering vast areas that provide critical habitat for large-area dependent fauna such as bison and prairie chickens. 

The relative uniqueness of the ecosystems was determined by using the National Vegetation Classification (NVC) system, which acts as an ecological taxonomy. A relative rarity index ranging from 0 to 100 was then calculated for each ecosystem based on area, spatial pattern, and relative uniqueness. Rare ecosystem was then defined as land with an index value greater than 75. The percentage of total land within a subwatershed (12-digit HUC) that is covered by rare ecosystem was estimated and displayed in this map. 

The Protected Area Database of the United States (PAD-US 1.3) was used to identify protected lands. The database was limited to GAP protection status levels 1 and 2, which specify these areas are under permanent protection with minimal extractive uses allowed. This means that logging, mining, and other activities that drastically diminish the natural state of the area are precluded.