Ecoregions of the Southwest
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8d 81g 9g 14b 14b 23c 6d 81o 20 5a 79b 13q 6h 6k 78n 13n 78 24 4e 6ac 20 13b 81i 13s 81b 79b 23 22y 14c 14a 80j 14b 8f 81g 79b 14b 81k 23j 78h 81i 79b 7a 1l 79b 81d 23 4 20h 13q 20h 81i 85k 7h 81i 13b 79e 13q 14b 14i 13k 79 13t 81k 6ao 13b 14b 14b 13h 6ah 5i 79b 7d 81i 14b 81k 14k 13t 80j 80d 13c 13s 13s 23 14b 5c 14b 78i 79b 7b 81k 13p 14j 81l 14b 79b 81i 81a 14k 79b 6k 14a 14b 13b 7a 23c 19 14b 14c 22r 23d 13k 13q 5a 79e 81a 6q 14j 6p 23d 13h 79c 81i 80e 13e 81k 1o 13s 4g 13a 23l 13q 85a 80j 78d 23b 81l 6ad 81a 81l 81h 7v 8f 6aa 14k 4e 13v 13q 13ab 23l 13q 8f 13h 7h 13e 81i 81i 80b 79b 13l 6ab 13q 22y 13q 13z 13t 85c 13x 13q 81k 13w 14f 13q 81i 81k 7a 13k 78a 14k 1a 81k 80a 81d 13a 14 79e 23l 13q 80a 13a 1 13q 13h 13z 13l 13l 13v 13k 81k 81k 13w 24c 14b 79c 85j 13a 81i 79c 81l 13aa 81i 14j 1k 13k 80d 79b 14f 79e 13e 20h 81k 14d 5c 13t 13x 13q 8f 13h 80k 13q 13t 80j 8f 79b 4e 13k 80j 80j 81k 14f 13v 80 81l 79d 13y 13b 13a 13l 7s 23d 23c 13q 14f 14l 81l 14b 13s 14b 79b 80j 4d 81i 13b 13ad 80b 14o 14l 13h 13q 13a 14l 4f 14f 14n 8b 8b 8f 14k 85c 14f 14h 14c 14n 14n 14c 14b 14c 14c 81i 8d 8f 8f 85j 85j 78m 78o 78o 78o 78l 78l 78l 78l 78l 78l 78l 78l 80a 9n 80j 80j 4f 4f 4d 6ar 6g 1m 6p 5a 5a 13aa 13y 13y 13y 5a 5k 5i 5i 6ab 6ab 5m 5m 5n 5l 14l 14c 14l 14h 14l 14m 14f 13y 14a 14n 14b 14c 14b 81i 81g 13o 13a 13g 13e 13e 13b 13a 13b 13z 13h 13t 13z 13s 13t 13l 13h 13l 13h 13h 13l 13t 13t 14b 14b 14f 14f 20c 20c 20e 20e 20h 20c 20c 22i 23i 23l 23d 23l 23l 23l 23l 23h 23l 23b 23b 23i 79c 79c 81k 81m 81d 81i 81i 81k 81k 81i 81i 81k 81k 81k 79a 79c 79c Goose Lake 22r 79e 81k 81k 81k 81i 81i 81g 81d 14b 14b 14b 14b 14f 14f 13h 13h 13h 13v 13v 78j 78d 78l 78k 78k 78k 78o 78o 78e 78d 78d 4e 4e 9i 4e 4f 4f 4f 4e 5c 5c 5c 5c 5c 5b 5b 5b 13y 13y 13y 13y 13y 5k 8f 8f 8f 85c 85c 85l 85l 85l 8f 81h 81h 81d 81i 81d 14f 14f 14l 14b 14b 14f 14f 14n 14n 14f 14a 14a 14f 14o 14b 14f 14o 14f 14o 14o 14b 14b 14b 14b 14b 14b 14k 14k 14k 14f 14k 14k 14k 14k 14k 14k 14k 14o 14o 14o 14f 14f 14o 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C O C E A N San Pablo Bay San Francisco Bay S a n Joaquin River Mono Lake Walker Lake MONTEREY BAY Owens Lake L os A n g e l e s A q u educt California Aqued u ct K e r n R i v e r Salinas River SANTA MONICA BAY Salton Sea C o l o r a d o R i v e r Lake Mead Lake Powell Gila River S a n P e d ro R i v e r Gila R i v e r V erde River Little C olo ra do Riv e r V i r gi n R i v er H u m b oldt R i v e r 108° 109° 109° 110° 110° 111° 111° 112° 112° 113° 113° 114° 114° 115° 115° 116° 116° 117° 117° 118° 118° 119° 119° 120° 120° 121° 121° 122° 122° 123° 123° 124° 124° 125° 125° 126° 126° 127° 127° 128° 42° 41° 41° 40° 40° 39° 39° 38° 38° 37° 37° 36 36° 35° 35° 34° 34° 33° 33° 32° 32° 0 50 100 150 Miles 0 75 150 225 Kilometers SCALE 1:2,000,000 NAD 1983 California Teale Albers Projection Standard parallels 34ºN and 40.5ºN Ecoregions of the Southwest (Arizona, California, Nevada) Ecoregions are areas where ecosystems (and the type, quality, and quantity of environmental resources) are generally similar. They are designed to serve as a spatial framework for the research, assessment, management, and monitoring of ecosystems and ecosystem components. These Level III and IV ecoregions, compiled at a scale of 1:250,000, revise and subdivide an earlier, smaller-scale national ecoregion map (Omernik, 1987). The ecoregions were identified by analyzing the spatial patterns and the composition of biotic and abiotic phenomena that affect or reflect differences in ecosystem quality and integrity (Omernik, 1987, 1995). These phenomena include geology, landforms, soils, vegetation, climate, land use, wildlife, and hydrology. The relative importance of each characteristic varies from one ecological region to another regardless of the hierarchical level. An ecoregion framework is critical for structuring and implementing ecosystem management strategies across federal agencies, state agencies, and nongovernment organizations that are responsible for different types of resources within the same geographic areas (McMahon and others, 2001; Omernik and Griffith, 2014). A Roman numeral hierarchical scheme has been adopted for different levels of ecological regions. Level I is the most general level, dividing North America into 15 ecological regions. Level II divides the continent into 50 regions (Commission for Environmental Cooperation, 1997, 2006). At level III, the continent contains 183 ecological regions of which 105 occur in the continental United States (United States Environmental Protection Agency [U.S. EPA], 2013; Wiken and others, 2011). The Level III and IV ecoregions of the Southwest were mapped in state-level projects in Arizona (Griffith and others, 2014), California (Griffith and others, 2016) and Nevada (Bryce and others, 2003). These projects were conducted primarily by the U.S. EPA National Health and Environmental Effects Research Laboratory (Corvallis, Oregon) in collaboration with U.S. EPA Region 9, state resource management agencies, and other federal agencies, such as the U.S. Geological Survey, U.S. Department of Agriculture (USDA)–Natural Resources Conservation Service, USDA–Forest Service, and the Bureau of Land Management. The mapping was associated with an interagency effort to develop a common framework of ecological regions (McMahon and others, 2001). Although there are differences in the conceptual approaches and mapping methodologies used by the different federal agencies for developing their own regional frameworks, these collaborative ecoregion projects were a step toward attaining consensus and consistency in ecoregion frameworks for the entire nation. Explanations of the methods used to define these ecoregions are given in Omernik (1995, 2004) and Omernik and Griffith (2014). Additional maps, publications, and GIS data for U.S. and North American ecoregions can be obtained at www.epa.gov/eco-research/ecoregions. REFERENCES Bryce, S.A., Woods, A.J., Morefield, J.D., Omernik, J.M., McKay, T.R., Brackley, G.K., Hall, R.K., Higgins, D.K., McMorran, D.C., Vargas, K.E., Petersen, E.B., Zamudio, D.C., and Comstock, J.A., 2003, Ecoregions of Nevada: Reston, Virginia, U.S. Geological Survey (map scale 1:1,350,000). Commission for Environmental Cooperation, 1997, Ecological regions of North America – toward a common perspective: Montreal, Quebec, Canada, Commission for Environmental Cooperation, 71 p. (map revised 2006), www.epa.gov/eco-research/ecoregions-north-america. Griffith, G.E., Omernik, J.M., Johnson, C.B., and Turner, D.S., 2014, Ecoregions of Arizona: U.S. Geological Survey Open-File Report 2014-1141, with map, scale 1:1,325,000, http://dx.doi.org/10.3133/ofr20141141 Griffith, G.E., Omernik, J.M., Smith, D.W., Cook, T.D., Tallyn, E., Moseley, K., and Johnson, C.B., 2016, Ecoregions of California (poster): U.S. Geological Survey Open-File Report 2016–1021, with map, scale 1:1,100,000, http://dx.doi.org/10.3133/ofr20161021. McMahon, G., Gregonis, S.M., Waltman, S.W., Omernik, J.M., Thorson, T.D., Freeouf, J.A., Rorick, A.H., and Keys, J.E., 2001, Developing a spatial framework of common ecological regions for the conterminous United States: Environmental Management, v. 28, no. 3, p. 293-316. Omernik, J.M., 1987, Ecoregions of the conterminous United States (map supplement): Annals of the Association of American Geographers, v. 77, no. 1, p. 118-125, scale 1:7,500,000. Omernik, J.M., 1995, Ecoregions – a framework for environmental management, in Davis, W.S. and Simon, T.P., eds., Biological assessment and criteria-tools for water resource planning and decision making: Boca Raton, Florida, Lewis Publishers, p. 49-62. Omernik, J.M., 2004, Perspectives on the nature and definition of ecological regions: Environmental Management, v. 34, Supplement 1, p. s27-s38. Omernik, J.M., and Griffith, G.E., 2014, Ecoregions of the conterminous United States ‒ evolution of a hierarchical spatial framework: Environmental Management, v. 54, no. 6, p. 1249-1266, http://dx.doi.org/10.1007/s00267-014-0364-1 U.S. Environmental Protection Agency, 2013, Level III ecoregions of the continental United States: Corvallis, Oregon, USEPA – National Health and Environmental Effects Research Laboratory, www.epa.gov/eco-research/level-iii-and-iv-ecoregions-continental-united-states. Wiken, E., Jiménez Nava, F., and Griffith, G., 2011, North American Terrestrial Ecoregions - Level III. Commission for Environmental Cooperation, Montreal, Canada. 149 p., http://ecologicalregions.info/htm/pubs/NA_TerrestrialEcoregionsLevel3_Final- 2june11_CEC.pdf CITING THIS MAP: U.S. Environmental Protection Agency. 2016. Ecoregions of the Southwest (Arizona, California, Nevada). U.S. EPA, National Health and Ecological Effects Research Laboratory, Western Ecology Division, Corvallis, Oregon. Map scale 1:2,000,000. https://www.epa.gov/eco-research/ecoregion-download-files-region#pane-09. Support for the production of this map provided by: U.S. Geological Survey, Western Geographic Science Center, Menlo Park, California, and U.S. Environmental Protection Agency, National Health and Ecological Effects Research Laboratory, Western Ecology Division, Corvallis, Oregon. Level III boundary Level IV boundary International boundary State boundary County boundary 85 Southern California/Northern Baja Coast 85a Santa Barbara Coastal Plain and Terraces 85b Oxnard Plain and Valleys 85c Venturan-Angeleno Coastal Hills 85d Los Angeles Plain 85e Diegan Coastal Terraces 85f Diegan Coastal Hills and Valleys 85g Diegan Western Granitic Foothills 85h Morena/Boundary Mountain Chaparral 85i Northern Channel Islands 85j Southern Channel Islands 85k Inland Valleys 85l Inland Hills 85m Santa Ana Mountains 81a Western Sonoran Mountains 81b Western Sonoran Mountain Woodland and Shrubland 81c Western Sonoran Basins 81d Sand Hills/Sand Dunes 81e Upper Coachella Valley and Hills 81f Imperial/Lower Coachella Valleys 81g Lower Colorado/Lower Gila River Valleys 81h Sonoran Playas 81i Central Sonoran/Colorado Desert Mountains 81j Central Sonoran/Colorado Desert Basins 81k Arizona Upland/Eastern Sonoran Mountains 81 Sonoran Basin and Range 81l Arizona Upland/Eastern Sonoran Basins 81m Sonoran Lava Fields 81n Gila/Salt Intermediate Basins 81o Middle Gila/Salt River Floodplains 80a Dissected High Lava Plateau 80b Semiarid Hills and Low Mountains 80d Pluvial Lake Basins 80e High Desert Wetlands 80g High Lava Plains 80j Semiarid Uplands 80k Partly Forested Mountains 80l Salt Shrub Valleys 80 Northern Basin and Range 79a Apachian Valleys and Low Hills 79b Lower Madrean Woodlands 79c Madrean Pine-Oak and Mixed Conifer Forests 79 Madrean Archipelago 79e Madrean Basin Grasslands 79d Willcox Playa 78a Rogue/Illinois/Scott Valleys 78d Serpentine Siskiyous 78e Inland Siskiyous 78g Klamath River Ridges 78h Border High-Siskiyous 78i Western Klamath Low Elevation Forests 78j Western Klamath Montane Forests 78k Eastern Klamath Low Elevation Forests 78l Eastern Klamath Montane Forests 78m Marble/Salmon Mountains-Trinity Alps 78n Scott Mountains 78o Klamath Subalpine 78p Duzel Rock 78q Outer North Coast Ranges 78r High North Coast Ranges 78 Klamath Mountains/ California High North Coast Range 14a Eastern Mojave Basins 14b Eastern Mojave Low Ranges and Arid Footslopes 14c Eastern Mojave Mountain Woodland and Shrubland 14d Eastern Mojave High Elevation Mountains 14e Arid Valleys and Canyonlands 14f Mojave Playas 14g Amargosa Desert 14h Death Valley/Mojave Central Trough 14i Mesquite Flat/Badwater Basin 14j Western Mojave Basins 14k Western Mojave Low Ranges and Arid Footslopes 14l Western Mojave Mountain Woodland and Shrubland 14m Western Mojave High Elevation Mountains 14n Mojave Lava Fields 14o Mojave Sand Dunes 14 Mojave Basin and Range 14p Lower Grand Canyon 13a Salt Deserts 13aa Sierra Nevada-Influenced Semiarid Hills and Basins 13ab Sierra Valley 13ac Upper Owens Valley 13ad Mono-Adobe Valleys 13ae Bishop Volcanic Tableland 13b Shadscale-Dominated Saline Basins 13c Sagebrush Basins and Slopes 13d Woodland- and Shrub-Covered Low Mountains 13e High Elevation Carbonate Mountains 13g Wetlands 13h Lahontan and Tonopah Playas 13j Lahontan Salt Shrub Basin 13k Lahontan Sagebrush Slopes 13l Lahontan Uplands 13m Upper Humboldt Plains 13n Mid-Elevation Ruby Mountains 13o High Elevation Ruby Mountains 13p Carbonate Sagebrush Valleys 13q Carbonate Woodland Zone 13r Central Nevada High Valleys 13s Central Nevada Mid-Slope Woodland and Brushland 13t Central Nevada Bald Mountains 13u Tonopah Basin 13v Tonopah Sagebrush Foothills 13w Tonopah Uplands 13x Sierra Nevada-Influenced Ranges 13y Sierra Nevada-Influenced High Elevation Mountains 13z Upper Lahontan Basin 13 Central Basin and Range 20c Semiarid Benchlands and Canyonlands 20d Arid Canyonlands 20e Escarpments 20h Sand Deserts 20 Colorado Plateaus 20i Cold Desert Sagebrush-Grasslands 22d Virgin/Shivwits Woodland 22i San Juan/Chaco Tablelands and Mesas 22j Semiarid Tablelands 22o Northeast Arizona Shrub-Grasslands 22p Little Colorado Valley/Painted Desert 22q Dinetah Tablelands 22r Mesa Highlands 22s Hopi Buttes 22t Chinle Valley and Mesas 22u Kaibito/Moenkopi Sandy Plateaus 22v Marble Platform 22 Arizona/New Mexico Plateau 24a Chihuahuan Basins and Playas 24c Low Mountains and Bajadas 24 Chihuahuan Deserts 23b Madrean Lower Montane Woodlands 23c Montane Conifer Forests 23d Arizona/New Mexico Subalpine Forests 23e Conifer Woodlands and Savannas 23h Lower Mogollon Transition 23i Montane and Subalpine Grasslands 23j Northern Woodlands and Sagebrush 23k Sunset Crater Volcanics 23l Mogollon Transition Conifer Forests 23 Arizona/New Mexico Mountains 22w Grand Canyon 22x Arizona Strip Plateaus 22y Uinkaret/Aubrey Montane Conifer Forest 22z Chino/Coconino Grasslands and Shrubsteppe 22aa Hualapai/Coconino Woodlands 9 Eastern Cascades Slopes and Foothills 8a Western Transverse Range Lower Montane Shrub and Woodland 8b Western Transverse Range Montane Forest 8c Arid Montane Slopes 8d Southern California Subalpine/Alpine 8e Southern California Lower Montane Shrub and Woodland 8f Southern California Montane Conifer Forest 8g Northern Transverse Range 8 Southern California Mountains 7a Northern Terraces 7b North Valley Alluvium 7c Butte Sink/Sutter and Colusa Basins 7d Southern Hardpan Terraces 7e Sacramento/Feather Riverine Alluvium 7f Sutter Buttes 7g Yolo Alluvial Fans 7h Yolo/American Basin 7j Delta 7k Lodi Alluvium 7l Stockton Basin 7m San Joaquin Basin 7n Manteca/Merced Alluvium 7o Westside Alluvial Fans and Terraces 7p Granitic Alluvial Fans and Terraces 7q Panoche and Cantua Fans and Basins 7r Tulare Basin/Fresno Slough 7s Kern Terraces 7t South Valley Alluvium 7u Antelope Plain 7v Southern Clayey Basins 7 Central California Valley 6a Tuscan Flows 6aa Eastern Hills 6ab Pleasant Valley/Kettleman Plain 6ac Temblor Range/Elk Hills 6ad Grapevine Transition 6ae Tehachapi Foothills 6af Salinas Valley 6ag Northern Santa Lucia Range 6ah Santa Lucia Coastal Forest and Woodland 6ai Interior Santa Lucia Range 6aj Southern Santa Lucia Range 6ak Paso Robles Hills and Valleys 6al Salinas-Cholame Hills 6am Cuyama Valley 6an Carrizo Plain 6ao Caliente Range 6ap Solomon-Purisima-Santa Ynez Hills 6aq Santa Maria/Santa Ynez Valleys 6ar Upper Sacramento River Alluvium 6b Northern Sierran Foothills 6c Southern Sierran Foothills 6d Camanche Terraces 6e Tehama Terraces 6f Foothill Ridges and Valleys 6g North Coast Range Eastern Slopes 6h Western Valley Foothills/Dunnigan Hills 6i Clear Lake Hills and Valleys 6j Mayacmas Mountains 6k Napa-Sonoma-Lake Volcanic Highlands 6l Napa-Sonoma-Russian River Valleys 6m Sonoma-Mendocino Mixed Forest 6n Bodega Coastal Hills 6o Marin Hills 6p Bay Flats 6q Suisun Terraces and Low Hills 6r East Bay Hills/Western Diablo Range 6s San Francisco Peninsula 6t Bay Terraces/Lower Santa Clara Valley 6u Livermore Hills and Valleys 6v Upper Santa Clara Valley 6w Monterey Bay Plains and Terraces 6x Leeward Hills 6y Gabilan Range 6z Diablo Range 6 Central California Foothills and Coastal Mountains 5a Sierran Alpine 5b Northern Sierra Subalpine Forests 5c Northern Sierra Upper Montane Forests 5d Northern Sierra Mid-Montane Forests 5e Northern Sierra Lower Montane Forests 5f Northeastern Sierra Mixed Conifer-Pine Forests 5g Central Sierra Mid-Montane Forests 5h Central Sierra Lower Montane Forests 5i Eastern Sierra Great Basin Slopes 5j Eastern Sierra Mojavean Slopes 5k Southern Sierra Subalpine Forests 5l Southern Sierra Upper Montane Forests 5m Southern Sierra Mid-Montane Forests 5n Southern Sierra Lower Montane Forest and Woodland 5o Tehachapi Mountains 5 Sierra Nevada 4d Cascade Subalpine/Alpine 4e High Southern Cascades Montane Forest 4f Low Southern Cascades Mixed Conifer Forest 4g California Cascades Eastside Conifer Forest 4h Southern Cascades Foothills 4 Cascades 1a Coastal Lowlands 1i Northern Franciscan Redwood Forest 1j King Range/Mattole Basin 1k Coastal Franciscan Redwood Forest 1l Fort Bragg/Fort Ross Terraces 1m Point Reyes/Farallon Islands 1n Santa Cruz Mountains 1o San Mateo Coastal Hills 1 Coast Range 9g Klamath/Goose Lake Basins 9h Fremont Pine/Fir Forest 9i Southern Cascades Slope 9j Klamath Juniper Woodland/Devils Garden 9k Shasta Valley 9l Pit River Valleys 9m Warner Mountains 9n High Elevation Warner Mountains 9o Likely Tableland 9p Modoc/Lassen Juniper-Shrub Hills and Mountains 9q Adin/Horsehead Mountains Forest and Woodland 9r Adin/Dixie Low Hills 9s Modoc Lava Flows and Buttes 9t Old Cascades
Transcript of Ecoregions of the Southwest
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Mesa
Reno
Tucson
Fresno
Phoenix
Anaheim
ModestoFremont
Oakland
Chandler
Glendale
Pasadena
Flagstaff
San Jose
Stockton
San Diego
Santa Ana
Henderson
Las Vegas
RiversideScottsdale
Long Beach
Sacramento
Chula Vista
Los Angeles
Carson City
Bakersfield
San Francisco
Yuma
Prescott
Sierra Vista
Nogales
Sedona
WinslowKingman
Blythe
BullheadCity
El Centro
Oxnard
Santa Barbara
Lancaster
Salinas
SantaCruz
Redding
Eureka
UTAH
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NEW
MEX
ICO
SONORA
BAJA CALIFORNIA
Santa Cruz Island
San Clemente Island
Santa Miguel Island
San Nicolas IslandSanta Catalina Island
Santa Rosa Island
Santa Barbara Island
Anacapa Island
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Klamath River
Klamath River
ShastaLake
Clear Lake Reservoir
LowerKlamath
Lake
Honey Lake
Pyramid Lake
LakeTahoe
Sacr
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iver
Clear Lake
PAC
I FI C
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Mono Lake
WalkerLake
MONTEREY BAY
OwensLake
Los Ang
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qued
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California Aqueduct
Kern River
Salinas River
SANTAMONICA
BAY
SaltonSea
Col
orad
o R
iver
LakeMead
LakePowell
Gila River
San Pedro River
Gila River
Verde River
Little Colorado River
Virg
in River
Humboldt River
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0 50 100 150Miles
0 75 150 225Kilometers
SCALE 1:2,000,000
NAD 1983 California Teale Albers ProjectionStandard parallels 34ºN and 40.5ºN
E c o r e g i o n s o f t h e S o u t h w e s t ( A r i z o n a , C a l i f o r n i a , N e v a d a )
Ecoregions are areas where ecosystems (and the type, quality, and quantity of environmental resources) are generally similar. They are designed to serve as a spatial framework for the research, assessment, management, and monitoring of ecosystems and ecosystem components. These Level III and IV ecoregions, compiled at a scale of 1:250,000, revise and subdivide an earlier, smaller-scale national ecoregion map (Omernik, 1987). The ecoregions were identified by analyzing the spatial patterns and the composition of biotic and abiotic phenomena that affect or reflect differences in ecosystem quality and integrity (Omernik, 1987, 1995). These phenomena include geology, landforms, soils, vegetation, climate, land use, wildlife, and hydrology. The relative importance of each characteristic varies from one ecological region to another regardless of the hierarchical level. An ecoregion framework is critical for structuring and implementing ecosystem management strategies across federal agencies, state agencies, and nongovernment organizations that are responsible for different types of resources within the same geographic areas (McMahon and others, 2001; Omernik and Griffith, 2014).A Roman numeral hierarchical scheme has been adopted for different levels of ecological regions. Level I is the most general level, dividing North America into 15 ecological regions. Level II divides the continent into 50 regions (Commission for Environmental Cooperation, 1997, 2006). At level III, the continent contains 183 ecological regions of which 105 occur in the continental United States (United States Environmental Protection Agency [U.S. EPA], 2013; Wiken and others, 2011). The Level III and IV ecoregions of the Southwest were mapped in state-level projects in Arizona (Griffith and others, 2014), California (Griffith and others, 2016) and Nevada (Bryce and others, 2003). These projects were conducted primarily by the U.S. EPA National Health and Environmental Effects Research Laboratory (Corvallis, Oregon) in collaboration with U.S. EPA Region 9, state resource management agencies, and other federal agencies, such as the U.S. Geological Survey, U.S. Department of Agriculture (USDA)–Natural Resources Conservation Service, USDA–Forest Service, and the Bureau of Land Management. The mapping was associated with an interagency effort to develop a common framework of ecological regions (McMahon and others, 2001). Although there are differences in the conceptual approaches and mapping methodologies used by the different federal agencies for developing their own regional frameworks, these collaborative ecoregion projects were a step toward attaining consensus and consistency in ecoregion frameworks for the entire nation.Explanations of the methods used to define these ecoregions are given in Omernik (1995, 2004) and Omernik and Griffith (2014). Additional
maps, publications, and GIS data for U.S. and North American ecoregions can be obtained at www.epa.gov/eco-research/ecoregions.REFERENCES
Bryce, S.A., Woods, A.J., Morefield, J.D., Omernik, J.M., McKay, T.R., Brackley, G.K., Hall, R.K., Higgins, D.K., McMorran, D.C., Vargas, K.E., Petersen, E.B., Zamudio, D.C., and Comstock, J.A., 2003, Ecoregions of Nevada: Reston, Virginia, U.S. Geological Survey (map scale 1:1,350,000).
Commission for Environmental Cooperation, 1997, Ecological regions of North America – toward a common perspective: Montreal, Quebec, Canada, Commission for Environmental Cooperation, 71 p. (map revised 2006), www.epa.gov/eco-research/ecoregions-north-america.
Griffith, G.E., Omernik, J.M., Johnson, C.B., and Turner, D.S., 2014, Ecoregions of Arizona: U.S. Geological Survey Open-File Report 2014-1141, with map, scale 1:1,325,000, http://dx.doi.org/10.3133/ofr20141141
Griffith, G.E., Omernik, J.M., Smith, D.W., Cook, T.D., Tallyn, E., Moseley, K., and Johnson, C.B., 2016, Ecoregions of California (poster): U.S. Geological Survey Open-File Report 2016–1021, with map, scale 1:1,100,000, http://dx.doi.org/10.3133/ofr20161021.
McMahon, G., Gregonis, S.M., Waltman, S.W., Omernik, J.M., Thorson, T.D., Freeouf, J.A., Rorick, A.H., and Keys, J.E., 2001, Developing a spatial framework of common ecological regions for the conterminous United States: Environmental Management, v. 28, no. 3, p. 293-316.
Omernik, J.M., 1987, Ecoregions of the conterminous United States (map supplement): Annals of the Association of American Geographers, v. 77, no. 1, p. 118-125, scale 1:7,500,000.
Omernik, J.M., 1995, Ecoregions – a framework for environmental management, in Davis, W.S. and Simon, T.P., eds., Biological assessment and criteria-tools for water resource planning and decision making: Boca Raton, Florida, Lewis Publishers, p. 49-62.
Omernik, J.M., 2004, Perspectives on the nature and definition of ecological regions: Environmental Management, v. 34, Supplement 1, p. s27-s38.
Omernik, J.M., and Griffith, G.E., 2014, Ecoregions of the conterminous United States ‒ evolution of a hierarchical spatial framework: Environmental Management, v. 54, no. 6, p. 1249-1266, http://dx.doi.org/10.1007/s00267-014-0364-1
U.S. Environmental Protection Agency, 2013, Level III ecoregions of the continental United States: Corvallis, Oregon, USEPA – National Health and Environmental Effects Research Laboratory, www.epa.gov/eco-research/level-iii-and-iv-ecoregions-continental-united-states.
Wiken, E., Jiménez Nava, F., and Griffith, G., 2011, North American Terrestrial Ecoregions - Level III. Commission for Environmental Cooperation, Montreal, Canada. 149 p., http://ecologicalregions.info/htm/pubs/NA_TerrestrialEcoregionsLevel3_Final-2june11_CEC.pdf
CITING THIS MAP: U.S. Environmental Protection Agency. 2016. Ecoregions of the Southwest (Arizona, California, Nevada). U.S. EPA, National Health and Ecological Effects Research Laboratory, Western Ecology Division, Corvallis, Oregon. Map scale 1:2,000,000. https://www.epa.gov/eco-research/ecoregion-download-files-region#pane-09.
Support for the production of this map provided by: U.S. Geological Survey, Western Geographic Science Center, Menlo Park, California, and U.S. Environmental Protection Agency, National Health and Ecological Effects Research Laboratory, Western Ecology Division, Corvallis, Oregon.
Level III boundaryLevel IV boundaryInternational boundaryState boundaryCounty boundary
85 Southern California/Northern Baja Coast85a Santa Barbara Coastal Plain and Terraces85b Oxnard Plain and Valleys85c Venturan-Angeleno Coastal Hills85d Los Angeles Plain85e Diegan Coastal Terraces85f Diegan Coastal Hills and Valleys85g Diegan Western Granitic Foothills85h Morena/Boundary Mountain Chaparral85i Northern Channel Islands85j Southern Channel Islands85k Inland Valleys85l Inland Hills85m Santa Ana Mountains
81a Western Sonoran Mountains81b Western Sonoran Mountain Woodland and Shrubland81c Western Sonoran Basins81d Sand Hills/Sand Dunes81e Upper Coachella Valley and Hills81f Imperial/Lower Coachella Valleys81g Lower Colorado/Lower Gila River Valleys81h Sonoran Playas81i Central Sonoran/Colorado Desert Mountains81j Central Sonoran/Colorado Desert Basins81k Arizona Upland/Eastern Sonoran Mountains
81 Sonoran Basin and Range
81l Arizona Upland/Eastern Sonoran Basins81m Sonoran Lava Fields81n Gila/Salt Intermediate Basins81o Middle Gila/Salt River Floodplains
80a Dissected High Lava Plateau80b Semiarid Hills and Low Mountains80d Pluvial Lake Basins80e High Desert Wetlands80g High Lava Plains80j Semiarid Uplands80k Partly Forested Mountains80l Salt Shrub Valleys
80 Northern Basin and Range
79a Apachian Valleys and Low Hills79b Lower Madrean Woodlands79c Madrean Pine-Oak and Mixed Conifer Forests
79 Madrean Archipelago
79e Madrean Basin Grasslands79d Willcox Playa
78a Rogue/Illinois/Scott Valleys78d Serpentine Siskiyous78e Inland Siskiyous78g Klamath River Ridges78h Border High-Siskiyous78i Western Klamath Low Elevation Forests78j Western Klamath Montane Forests78k Eastern Klamath Low Elevation Forests78l Eastern Klamath Montane Forests78m Marble/Salmon Mountains-Trinity Alps78n Scott Mountains78o Klamath Subalpine78p Duzel Rock78q Outer North Coast Ranges78r High North Coast Ranges
78 Klamath Mountains/ California High North Coast Range
14a Eastern Mojave Basins14b Eastern Mojave Low Ranges and Arid Footslopes14c Eastern Mojave Mountain Woodland and Shrubland14d Eastern Mojave High Elevation Mountains14e Arid Valleys and Canyonlands14f Mojave Playas14g Amargosa Desert14h Death Valley/Mojave Central Trough14i Mesquite Flat/Badwater Basin14j Western Mojave Basins14k Western Mojave Low Ranges and Arid Footslopes14l Western Mojave Mountain Woodland and Shrubland14m Western Mojave High Elevation Mountains14n Mojave Lava Fields14o Mojave Sand Dunes
14 Mojave Basin and Range
14p Lower Grand Canyon
13a Salt Deserts
13aa Sierra Nevada-Influenced Semiarid Hills and Basins13ab Sierra Valley13ac Upper Owens Valley13ad Mono-Adobe Valleys13ae Bishop Volcanic Tableland
13b Shadscale-Dominated Saline Basins13c Sagebrush Basins and Slopes13d Woodland- and Shrub-Covered Low Mountains13e High Elevation Carbonate Mountains13g Wetlands13h Lahontan and Tonopah Playas13j Lahontan Salt Shrub Basin13k Lahontan Sagebrush Slopes13l Lahontan Uplands13m Upper Humboldt Plains13n Mid-Elevation Ruby Mountains13o High Elevation Ruby Mountains13p Carbonate Sagebrush Valleys13q Carbonate Woodland Zone13r Central Nevada High Valleys13s Central Nevada Mid-Slope Woodland and Brushland13t Central Nevada Bald Mountains13u Tonopah Basin13v Tonopah Sagebrush Foothills13w Tonopah Uplands13x Sierra Nevada-Influenced Ranges13y Sierra Nevada-Influenced High Elevation Mountains13z Upper Lahontan Basin
13 Central Basin and Range
20c Semiarid Benchlands and Canyonlands20d Arid Canyonlands20e Escarpments20h Sand Deserts
20 Colorado Plateaus
20i Cold Desert Sagebrush-Grasslands
22d Virgin/Shivwits Woodland22i San Juan/Chaco Tablelands and Mesas22j Semiarid Tablelands22o Northeast Arizona Shrub-Grasslands22p Little Colorado Valley/Painted Desert22q Dinetah Tablelands22r Mesa Highlands22s Hopi Buttes22t Chinle Valley and Mesas22u Kaibito/Moenkopi Sandy Plateaus22v Marble Platform
22 Arizona/New Mexico Plateau
24a Chihuahuan Basins and Playas24c Low Mountains and Bajadas
24 Chihuahuan Deserts
23b Madrean Lower Montane Woodlands23c Montane Conifer Forests23d Arizona/New Mexico Subalpine Forests23e Conifer Woodlands and Savannas23h Lower Mogollon Transition23i Montane and Subalpine Grasslands23j Northern Woodlands and Sagebrush23k Sunset Crater Volcanics23l Mogollon Transition Conifer Forests
23 Arizona/New Mexico Mountains
22w Grand Canyon22x Arizona Strip Plateaus22y Uinkaret/Aubrey Montane Conifer Forest22z Chino/Coconino Grasslands and Shrubsteppe22aa Hualapai/Coconino Woodlands9 Eastern Cascades Slopes and Foothills
8a Western Transverse Range Lower Montane Shrub and Woodland8b Western Transverse Range Montane Forest8c Arid Montane Slopes8d Southern California Subalpine/Alpine8e Southern California Lower Montane Shrub and Woodland8f Southern California Montane Conifer Forest8g Northern Transverse Range
8 Southern California Mountains
7a Northern Terraces7b North Valley Alluvium7c Butte Sink/Sutter and Colusa Basins7d Southern Hardpan Terraces7e Sacramento/Feather Riverine Alluvium7f Sutter Buttes7g Yolo Alluvial Fans7h Yolo/American Basin7j Delta7k Lodi Alluvium7l Stockton Basin7m San Joaquin Basin7n Manteca/Merced Alluvium7o Westside Alluvial Fans and Terraces7p Granitic Alluvial Fans and Terraces7q Panoche and Cantua Fans and Basins7r Tulare Basin/Fresno Slough7s Kern Terraces7t South Valley Alluvium7u Antelope Plain7v Southern Clayey Basins
7 Central California Valley
6a Tuscan Flows
6aa Eastern Hills6ab Pleasant Valley/Kettleman Plain6ac Temblor Range/Elk Hills6ad Grapevine Transition6ae Tehachapi Foothills6af Salinas Valley6ag Northern Santa Lucia Range6ah Santa Lucia Coastal Forest and Woodland6ai Interior Santa Lucia Range6aj Southern Santa Lucia Range6ak Paso Robles Hills and Valleys6al Salinas-Cholame Hills6am Cuyama Valley6an Carrizo Plain6ao Caliente Range6ap Solomon-Purisima-Santa Ynez Hills6aq Santa Maria/Santa Ynez Valleys6ar Upper Sacramento River Alluvium
6b Northern Sierran Foothills6c Southern Sierran Foothills6d Camanche Terraces6e Tehama Terraces6f Foothill Ridges and Valleys6g North Coast Range Eastern Slopes6h Western Valley Foothills/Dunnigan Hills6i Clear Lake Hills and Valleys6j Mayacmas Mountains6k Napa-Sonoma-Lake Volcanic Highlands6l Napa-Sonoma-Russian River Valleys6m Sonoma-Mendocino Mixed Forest6n Bodega Coastal Hills6o Marin Hills6p Bay Flats6q Suisun Terraces and Low Hills6r East Bay Hills/Western Diablo Range6s San Francisco Peninsula6t Bay Terraces/Lower Santa Clara Valley6u Livermore Hills and Valleys6v Upper Santa Clara Valley6w Monterey Bay Plains and Terraces6x Leeward Hills6y Gabilan Range6z Diablo Range
6 Central California Foothills and Coastal Mountains
5a Sierran Alpine5b Northern Sierra Subalpine Forests5c Northern Sierra Upper Montane Forests5d Northern Sierra Mid-Montane Forests5e Northern Sierra Lower Montane Forests5f Northeastern Sierra Mixed Conifer-Pine Forests5g Central Sierra Mid-Montane Forests5h Central Sierra Lower Montane Forests5i Eastern Sierra Great Basin Slopes5j Eastern Sierra Mojavean Slopes5k Southern Sierra Subalpine Forests5l Southern Sierra Upper Montane Forests5m Southern Sierra Mid-Montane Forests5n Southern Sierra Lower Montane Forest and Woodland5o Tehachapi Mountains
5 Sierra Nevada
4d Cascade Subalpine/Alpine4e High Southern Cascades Montane Forest4f Low Southern Cascades Mixed Conifer Forest4g California Cascades Eastside Conifer Forest4h Southern Cascades Foothills
4 Cascades
1a Coastal Lowlands1i Northern Franciscan Redwood Forest1j King Range/Mattole Basin1k Coastal Franciscan Redwood Forest1l Fort Bragg/Fort Ross Terraces1m Point Reyes/Farallon Islands1n Santa Cruz Mountains1o San Mateo Coastal Hills
1 Coast Range
9g Klamath/Goose Lake Basins9h Fremont Pine/Fir Forest9i Southern Cascades Slope9j Klamath Juniper Woodland/Devils Garden9k Shasta Valley9l Pit River Valleys9m Warner Mountains9n High Elevation Warner Mountains9o Likely Tableland9p Modoc/Lassen Juniper-Shrub Hills and Mountains9q Adin/Horsehead Mountains Forest and Woodland9r Adin/Dixie Low Hills9s Modoc Lava Flows and Buttes9t Old Cascades
