Four adjacent ranges define the western edge of the Avra and Altar valleys. Even though desert ironwood has dark green, lush foliage much of the year, this tree is almost exclusively a Sonoran Desert species. The same is true of the distribution of saguaros, foothill palo verdes, fishhook barrel cacti, and most of the hundreds of other plants growing here. These rugged ranges also provide natural refuges for a variety of wildlife, including desert bighorn and migratory pollinators. In addition to the biological resources, the area has abundant rock art sites and other archaeological sites.

Provides a detailed description of plants and animals that are being considered as potentially covered under the multi-species program, organized by taxonomic group. Two strong themes emerge when this compilation of species accounts is read together: one is the enormous importance of aquatic and riparian-based habitats to the majority of priority vulnerable species, and the other is the very bleak biological status of the riparian system.