U.S. DEPARTMENT OF THE INTERIORBUREAU OF LAND MANAGEMENT
Location and Setting
The ecoregion is divided into a lower, drier western section, that includes the Salton Sea basin and the lower Colorado Desert, and a somewhat higher eastern section that is also relatively more moist (by desert standards), as it experiences the summer monsoonal rains. In the winter, rainfall has the opposite pattern, decreasing from west to east. Annually across the region, precipitation ranges from 3 to 10 inches; in the desert a difference of one or two inches of precipitation can make a large difference in the vegetative cover.
The vegetation of the lower elevation western Sonoran is dominated by creosote bush and white bursage, but in the eastern upland, somewhat higher precipitation amounts support a more diverse vegetation community with palo verde, acacia, ocotillo, and a variety of cacti, such as saguaro.
The ecoregion has much of the same topography as the Mojave Basin and Range to the north. Both ecoregions have low mountains and large tracts of federally administered land, much of which is used for military training.
Conservation elements are resources of conservation concern within an ecoregion. This REA will assess the current status and forecast the future condition of these conservation elements:
A full list and description of conservation elements can be found in the Phase 1 Task 1 Memo.
In brief, the coarse-filter vegetation assemblages for the Sonoran Desert REA are Forest and Woodland; Shrub/Scrub; Grassland/Herbaceous; Woody Wetland/Riparian; Emergent Herbaceous Wetland; Sparsely Vegetated/Wetland; and Open Water.
Examples of fine-filter plant species include saguaro and creosote bush. For landscape-species conservation elements, the mountain lion, Lucy’s warbler, and the Gila topminnow are examples.
The REA will also address species that were not selected for inclusion in the suite of landscape species, known as “desired species,” such as the desert tortoise.
The assessment will also look at a suite of conservation elements representing sites and a suite of ecological functions and services of conservation concern as conservation elements. Sites include, as examples, NatureServe/Natural Heritage sites and national and state Parks. Surface and subsurface water availability — including for example, streams and groundwater protection zones — serve as ecological functions and services of conservation concern for the REA.
Change agents are disturbances on the landscape that can influence ecosystem health. They can have natural causes, such as wildfire; human causes, such as energy development; or result from the interaction of both, such as climate change. A key purpose of this REA is to understand the influences of significant, widespread change agents on the natural resources (represented by the conservation elements discussed above) of the Sonoran Desert Ecoregion.
This REA will examine the potential effects of the following change agents. A more complete discussion of change agents is presented in the Task 1 Final Memorandum.
Data, Maps, and Models
Memos and Reports