A bioregion is a geographic area defined by its unique characteristics, such as flora and fauna species, landforms, hydrology, and climate. Two California examples: the Bay Delta and the Central Valley both have distinctive features, including water bodies, major rivers, subregions, and land use. A bioregion can be scaled up and scaled down, for our purpose we focus on the bioregional scale known to the US EPA as Level 3 ecoregions, divided based on physical characteristics, such as climate, soil, and vegetation.