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Southern California Project Abstract Image of Southern California Study Area

Western United States Landscape Characterization
Southern California Study Area

The United States Environmental Protection Agency's Environmental Monitoring and Assessment Program (EMAP) is conducting a pilot study in the western United States. This study will advance the science of ecological monitoring and demonstrate techniques for regional-scale assessment of the condition of aquatic resources in the 14 western states in EPA Regions 8, 9, and 10 (shown below). This browser is a demonstration of a versatile communication device for our landscape ecological assessment products, reports, assessments, data studies, and analysis tools.

image of study areas

Human stresses on the natural resources of the United States are intense. These pressures have resulted in many unintended changes in our ecosystems -- loss of biodiversity, increases in the number of endangered species (e.g. salmon), habitat degradation, and increases in contamination and pollution. Major public and private efforts have gone into controlling pollution, and protecting and restoring natural resources and the ecosystems they depend on. Corrective actions have, and will continue to have, an impact upon how we all lead our lives. We react to the problems that are most visible and thus receive the greatest amount of publicity. To make the most of our environmental efforts, we need to understand and assess the status and trends in the condition of our ecological resources and the stressors affecting these systems. It is not at all clear that we are currently targeting financial resources and/or lifestyle changes on problems or at locations where they will have the most effect.

The landscape component of the Western Pilot Study provides information that has multiple management implications. Regional Landscape products will be provided to assess the spatial distribution of landscape stressors on aquatic ecosystems across each region. This will assist regional managers in understanding how landscape conditions contribute to varying aquatic resource conditions. As such, the products also will contribute to formulation of specific management actions for different geographic locations within each region. The first step in providing regional products will be to test and demonstrate landscape assessment methodologies on sub-regional areas of high importance to each Region. This browser concentrates on the Region 9 Southern California pilot area.

Southern California Pilot Study Area

The Western EMAP Southern California Pilot Study Area (SCPSA) is a contiguous tract of land located along the coastal areas and mountainous terrain of the southwestern corner of the State of California and extends southward into the northwestern most portion of the State of Baja California Norte, Mexico. The SCPSA occupies approximately 37,371 km2 (14,429 mi2 ) in land area and is somewhat oblong in shape. The study area boundary follows the Pacific Ocean coastline from Point Arguello in California, south to Tijuana, Mexico, then southeast into a sparsely populated region of northernmost Baja California Norte. The northeastern and eastern boundary travels south from the Sierra Madre Mountains near Santa Barbara, bending around the eastern foothills of the Coast Ranges and tracing the ecotone where the mountains meet the lower elevations of first the Mojave and then the Colorado desert bioregions through south-cental California and across the international border into Mexico.

Many major transportation corridors converge in and pass through the SCPSA including interstates 5, 10, 15, and 18 and their auxiliary routes; US Route 101; Mexico Route 1D; and numerous state and county roads. The Pacific Crest National Trail hugs the northeastern study area boundary in the higher elevations, extending from the international border north to the confluence of the California and Los Angeles aqueducts, where it then leaves the study area, trending toward the southern foothills of the Sierra Nevada. Much of the coastal portion of the SCPSA is occupied by either high-density urban centers, including the greater metropolitan areas of Los Angeles, San Diego, and San Bernadino/Riverside, or by US military facilities and installations. Many state beaches are also located mainly in the non-urban sections of the coastal areas. Throughout a great deal of the coastal and mountain-foothill regions of the study area, the land is also privately owned, including significant tracts of forest lands, hardwood rangelands, and agricultural lands. In addition, the southern portion of the study area east and northeast of San Diego is dotted with Indian reservations. Approximately one quarter of the SCPSA is administered by the USDA Forest Service, most of which is located in the Coast Ranges situated along the northern and eastern sides of the study area and which includes several small wilderness areas as well as a condor sanctuary and refuge.

Elevations within the SCPSA range from sea level to approximately 300 m (1,000 ft) in the coastal foothills to as high as 3505 m (11,499 ft) at Mt. San Gorgonio the San Bernardino Mountains northwest of Palm Springs. Characteristic topographic features include steep slopes in the mountainous regions, gently rolling hills in the mountain foothills, and flat, rocky terrain in the desert areas. The average annual precipitation can range from less than 250 mm (10 in.) in the lower desert regions to as much as 1000 mm (40 in.) the higher mountains in the central portions of the study area. Although several small rivers and creeks and their tributaries flow down from the higher elevations within the study area toward the Pacific Ocean, many of the water courses, including the Tijuana River which flows north from Mexico into California, are either ephemeral or are dammed, channelized, or have otherwise been significantly affected by anthropomorphic modifications. The SCPSA contains many different vegetation types including various pine species, Douglas fir and other fir species, and piņon pine-juniper in the coastal mountains; montane hardwoods, oak woodlands, and grasslands in the lower-elevation foothills; and chaparral, sagebrush, and desert scrub in the low desert regions.


California Department of Forestry. California Land Cover Mapping and Monitoring Program. Exit EPA Disclaimer

California Coastal Commission's California Coastal Resource Guide Exit EPA Disclaimer

Tijuana River Watershed Atlas. San Diego State University. Exit EPA Disclaimer

Oregon State University. Oregon Climate Service. Average Annual Precipitation - California. Spatial Climate Analysis Service, 2000.

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EPA - EMAP Western Pilot Study


Region 8

Region 9

Region 10

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