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Ecoregions Map of North America: Explanatory Note

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United States Department of Agriculture Ecoregions Map of North America Forest Service Explanatory Note Miscellaneous Publication Number 1548

1 « % K m S' Historic, archived document

Do not assume content reflects current scientific knowledge, policies, or practices. » Wisdom. Inc.: reproduced with permission. image from Mountain High Maps ». Copyright 1995 by Digital Ecoregions Map of North America Explanatory Note

May 1 998

Prepared in cooperation with The Nature Conservancy and the U.S. Geological Survey by

Robert G. Bailey, 1 Geographer Ecosystem Management Coordination Staff USDA Forest Service, Washington, DC

' Address: Ecosystem Management Analysis Center, USDA Forest Service, 3825 East Mulberry Street, Fort Collins, CO 80524 USA. Bailey, Robert G. 1998. Ecoregions map of North America: Acknowledgements Explanatory note. Misc. Publ. 1548. Washington, DC:

USDA Forest Service. 10 p. I am indebted to John M. Crowley, who began the task of classifying the natural ecosystems of the continent and their This publication explains the basis of map units shown distribution. Recognition should also go to Denny Gross- on the second (revised) edition of the map, Ecoregions man. Chief Ecologist of The Nature Conservancy, for his of North America (Bailey 1997). Climate diagrams are support. The first draft of the map was made by Jon Havens included to help explain the conditions that create a of LCT Graphics. I am most grateful to the U.S. Geological particular ecoregion. The revised map at a scale of Survey, which helped fund the preparation of the base map.

1:15.000.000 accompanies this explanatory note. As always, it has been a pleasure to work with Loreen Utz and Dave Dee of the National Mapping Division of the Sur- Keywords: ecosystem geography, ecoregions, North America vey, who did the final map compilation and cartography. Ecoregions Map of North America: Explanatory Note

Land management is undergoing enormous change: away from managing single resources to managing ecosystems. An ecosystem is an area, of any size, in which there is a distinctive association of causally interconnected features. A change in one feature causes a change within another with corresponding geographic distribution, as when certain vegetation and soil types occur together with certain types of climate. To manage ecosystems we must understand where they are located and why. We need to do this at multiple scales because ecosystems occur in a hierarchy of varying sizes.

Ecosystems of regional extent, those at the macro scale, are called ecosystem regions, or ecoregions. Ecoregions are useful in addressing environmental issues over large areas, i.e., issues that transcend agency, watershed, and political boundaries and borders, such as air pollution, declining anadromous fisheries, forest disease, or threats to biodiversity.

The second (revised) edition of the map, Ecoregions of North America (Bailey 1997), is the result of cooperation among the USDA Forest Service, The Nature Conservan- cy, and the U.S. Geological Survey. The first edition of the map was published in 1981 by the U.S. Fish and Wildlife Service (Bailey and Cushwa 1981).

Since that time, more ecological mapping has been earned out in some parts of the continent (e.g., Dinerstein and others 1995) and new or updated national maps have been compiled (e.g., Ecoregions Working Group 1989: Bailey 1994, 1995); it was therefore decided that a second revised edition of the map should be published. It has been compiled from a number of sources, both new since 1981 and older; the most important of which are listed in the Sources.

The map uses a worldwide classification developed by Bailey (1983, 1989. 1998) and Bailey and Hogg (1986) from concepts advanced by Crowley (1967). The general principle followed has been to identify ecosystem regions of continental scale based on macroclimate (i.e., the climate that lies just beyond the local modifying irregulari- ties of landform and vegetation). Macroclimates are among the most significant factors affecting the distribution of life on earth. As the macroclimate changes, the other components of the ecosystem change in response. Macroclimates influence soil formation and help shape surface topography, as well as affecting the suitability of a given system for human habitation. As a result, ecosystems of different macroclimates differ significantly.

Based on macroclimatic conditions and on the prevailing plant formations determined by those conditions, I subdivided the continent into ecoregions with three levels of detail. Of these the broadest, domains, and within them divisions, are based largely on the broad ecological climate zones of W. Koppen (as modified by Trewartha 1968,

: Appendix 1). Thermal and moisture limits for plant growth determine their

2 Other methods for mapping zones at the global scale are those of Thornthwaite (1931, 1933). Holdridge (1947). and Walter and Box (1976). All methods appear to work better in some areas than in others, and to have gained their own adherents. I chose the Koppen system as the basis for ecoregion delineation because it has become the international standard for geographical purposes. boundaries. Domains are groups of related climates. There are four groups. Three are humid, thermally differentiated: polar, with no warm season; humid temperate, rainy with mild to severe winters; humid tropical, rainy with no winters. The fourth, dry, is defined on the basis of moisture alone, and transects the otherwise humid domains. Within these groups are 15 types of climate based on seasonality of precipitation or on degree of dryness or cold, e.g., within the humid tropical domain, rainforests with year-round precipitation can be distinguished from savannas with winter drought.

Divisions correspond to these types. Each division is clearly defined by a particular type of climate diagram that helps explain the conditions that create them (see Appen- dix 2 for stations thought to be representative of each division). For more informa- tion, including illustrated, detailed descriptions of the divisions, see my related book, Ecoregions (Bailey 1998).

The climate is not completely uniform within divisions, so that a further subdivision can be undertaken. Within the dry climates, for example, there is a wide range of degree of aridity, ranging from very dry deserts through transitional levels of aridity in the direction of adjacent moist climates. We refer to these as climate subtypes. The subtypes largely correspond to major plant formations (for example, broadleaved forest), which are delimited on the basis of macro features of the vegetation by concentrating on the life-form of the plants. They form the basis for subdividing ecoregion divisions into provinces, and are based on a number of sources, including a world map of landscape types (Milanova and Kushlin 1993).

The arrangement of the ecological climate zones depends largely on latitude and continental position. This pattern, however, is overlain by mountain ranges, which cut across latitudinally oriented climatic zones to create their own ecosystems. Altitude creates characteristic ecological zones that are variations of the lowland climate.

Mountains show typical climatic characteristics, depending on their location in the overall pattern of global climatic zones. The mountain ranges of Central America, for example, experience the same year-round, high-energy input, and seasonal moisture regime consisting of a relatively dry winter and rainy summer typical of their neigh- boring lowlands (see the diagrams for Mexico City and San Salvador in Appendix 2).

Every mountain within a climatic zone has a typical sequence of altitudinal belts, with different ecosystems at successive levels: generally montane, alpine, and nival, but exhibiting considerable differences according to the zone where they occur. When a mountain extends over two or more climatic zones it produces different vertical zonation patterns. Mountains exhibiting altitudinal zonation and the climatic regime of the adjacent lowlands are distinguished according to the character of the zonation by listing the altitudinal zones present. Such mountainous environments are termed mountain provinces.

Thirty-four provinces and 29 mountain provinces are differentiated and represented on the present map (within 15 divisions and four domains). Note that these ecoclimatic zones are greatly simplified and do not show soil-related or human influences. The only major exception is where intrazonal contrasts (related to groundwater) form riverine forests along the lower Mississippi River valley. Also, the boundaries shown are only approximate and give a broad-brush picture. The actual boundaries may be very irregular and much modified by human interference.

The similar colors on the map show the major climatic zones: the mountains in each zone are shown by pattern. The names of the provinces retain the names of the most obvious vegetation indicator: tundra, broadleafed forest, etc. The terms used in describing the provinces may not be familiar and so need explanation. They are listed in the Glossary. In mountain areas, the altitudinal zonality-types are named from the lower- and upper-elevation (subnival) belts: (e.g., forest - alpine meadow), which vary considerably according to the zones in which they occur. Each type corresponds to a typical sequence of altitudinal belts.

When it is necessary to emphasize the existence of intermediate belts in the structure of similar spectra, the name of the most characteristic intermediate belt is added to the designation; for example, mixed forest - coniferous forest - tundra. In low- and medium-relief mountains, the zonal spectra are incomplete. In such cases, the type is designated by the character of the lower belt. More details are presented elsewhere (Bailey 1983, 1996).

A digital version of the map is available in ARC/INFO format from the USDA-Forest Service, Ecosystem Management Analysis Center, on a cost-of-production basis. Glossary

Broadleafed—with leaves other than linear in outline: as Nival—of or relating to a region of perennial snow. opposed to needleleafed or grass-like (graminoid). Open woodland (also called steppe forest and woodland- Coniferous—trees bearing cones and commonly having savanna)—open forest with lower layers also open, needleshaped leaves usually retained during the year; having the trees or tufts of vegetation discrete but

adapted to moisture deficiency due to frozen ground or averaging less than their diameter apart. soils that are not moisture-retentive. Paramo—the alpine belt in the wet tropics.

Deciduous—woody plants, or pertaining to woody plants, that Prairie—consist of tall grasses, mostly exceeding 1 m in

seasonally lose all their leaves and become temporarily height, comprising the dominant herbs, with subdomi- bare-stemmed. nant forbs (broadleafed herbs). Desert—supporting vegetation of plants so widely spaced. Riverine forest (also called galeria and floodplain forest)— or sparse, that enough of the substratum shows through to dense tropical, subtropical, or prairie, forest living along

give the dominant tone to the landscape. the banks of a river. Dry steppe—with 6-7 arid months in each year. Savanna—closed grass or other predominantly herbaceous Evergreen—plants, or pertaining to plants, which remain vegetation with scattered or widely-spaced woody plants green in parts of the year around, either by retaining at least usually including some low trees.

some of their leaves at all times, or by having green stems Semidesert (also called half-desert)—is an area of which carry on the principal photosynthetic functions. xerophytic shrubby vegetation with a poorly-developed Forest—open or closed vegetation with the principal layer herbaceous lower layer, e.g., sagebrush. consisting of trees averaging more than 5 m in height. Semi-evergreen forest (also called a monsoon forest)—

Forest-steppe—intermingling of steppe and groves or strips where many, although not all, of the trees lose their of trees. leaves; adaptation to a dry season in the tropics. Forest-tundra—intermingling of tundra and groves or strips Shrub—a woody plant less than 5 m high. of trees. Steppe (also called shortgrass prairie)—open herbaceous

Heath—an area of largely treeless country, dominated by vegetation, less than 1 m high, with the tufts or plants various grasses able to thrive on poor acidic soils, often discrete, yet sufficiently close together to dominate the accompanied by dwarf shrubs. landscape. Meadow—closed herbaceous vegetation, commonly in Tayga (also spelled taiga)—a parkland or savanna with stands of rather limited extent, or at least not usually needleleafed (usually evergreen) low trees and shrubs. applied to extensive grasslands. Tundra—slow-growing, low-formation, mainly closed Mixed forest—forest with both needleleafed and vegetation of dwarf-shrubs, graminoids. and cryp- broadleafed trees. tograms, beyond the subpolar or alpine tree-line. Sources

The sources listed below have been consulted during the Ecoregions Working Group. 1989. Ecoclimatic regions of process of creating and updating the second edition. Canada, first approximation. Ecological Land Classif.

Series No. 23. Ottawa: Environment Canada. 119 p. with

Bailey, R.G. 1983. Delineation of ecosystem regions. Envi- separate map at 1:7,500,000.

ronmental Management 7: 365-373. Ewel, J.J.; Whitmore, J.L. 1973. The ecological life zones of Bailey, R.G. 1989. Explanatory supplement to ecoregions Puerto Rico and the U.S. Virgin Islands. Forest Service

map of the continents. Environmental Conservation Research Paper ITF-18. Rio Piedras, PR: Institute of

16:307-309 with separate map at 1:30,000,000. Tropical Forestry. 72 p. with separate map at 1 :250,000.

Bailey, R.G. 1994. Map: Ecoregions of the United States Eyre, S.R. 1963. Vegetation and soils: a world picture.

(rev.). Washington, DC: USDA Forest Service. Chicago: Aldine. 324 p. 1:7,500,000. Fosberg. F.R.; Gamier, B.J.: Kuchler, AW. 1961. Delimita- Bailey, R.G. 1995. Description of the ecoregions of the Unit- tion of the humid tropics. Geographical Review 51:333-

ed States. 2d ed. rev. and expanded (1st ed. 1980). Misc. 347 with separate maps at 1:60.000,000.

Publ. 1391 (rev.). Washington, DC: USDA Forest Ser- Government of Canada. 1974. National atlas of Canada,

vice. 108 p. with separate map at 1:7.500.000. vegetation regions. 4th ed. (rev.). Toronto: Macmillan: Bailey, R.G. 1996. Ecosystem geography. New York: 45-46. In association with the Department of Energy,

Springer-Verlag. 216 p. Mines and Resources, and Information Canada, Ottawa. Bailey, R.G. 1997. Map: Ecoregions of North America 1:15,000.000.

(rev.). Washington, DC: USDA Forest Service in coopera- Hammond, E.H. 1954. Small-scale continental landform tion with The Nature Conservancy and the U.S. Geologi- maps. Annals Association of American Geographers.

cal Survey. 1:15,000,000. 44:33-42.

Bailey. R.G. 1998. Ecoregions: the ecosystem geography of the Holdridge, L.R. 1947. Determination of world plant forma-

oceans and continents. New York: Springer-Verlag. 192 p. tions from simple climatic data. Science 105:367-368. Bailey, R.G.; Cushwa, C.T 1981. Map: Ecoregions of North Koppen, W. 1931. Grundriss der klimakunde. Berlin: Walter

America. FWS/OBS-81/29. Washington, DC: U.S. Fish de Gruyter. 388 p. and Wildlife Service. 1:12,000,000. Kuchler, A.W. 1964. Potential natural vegetation of the con- Bailey, R.G.; Hogg, H.C. 1986. A world ecoregions map terminous United States (map and manual). American

for resource reporting. Environmental Conservation Geographical Society Special Publication 36. 116 p. with

13:195-202. separate map at 1:3,168,000.

Borchert, J.F. 1950. The climate of the central North Ameri- Lobeck, A.K. 1948. Map: Physiographic provinces of North can grassland. Annals Association of American Geogra- America. Maplewood NJ: Hammond. 1:12.000,000. phers. 40:1-39. Milanova, E.V.; Kushlin, A.V.. eds. 1993. World map of pre-

Cleland. D.T.; Avers, P.E.; McNab, W.H.; Jensen, M.E.: Bai- sent-day landscapes: an explanatory note. Moscow:

ley, R.G.; King, T.; Russell, W.E. 1997. National Moscow State University. 33 p. with separate map at

hierarchical framework of ecological units. In: Boyce, 1:15,000,000.

M.S.; Haney, A., eds. Ecosystem management. New Rowe, J.S. 1972. Forest regions of Canada. Canadian

Haven. CT: Yale University Press: 181-200. Forestry Service Publ. No. 1300. 172 pp. with separate

Crowley, J.M. 1967. Biogeography [in Canada]. Canadian map at 1:6,336.000.

Geographer 11: 312-326. Schmithtisen, J. 1976. Atlas zur biogeographie. Mannheim-

Dinerstein, E.; Olson, D.M.; Graham, D.J.; Webster, A.L; Wien-Zurich: Bibliographisches Institut. 33 p. Primm, S.A.; Bookbinder. M.P; Ledec, G. 1995. A Shelford, V.E. 1963. The ecology of North America. Urbana:

conservation assessment of the terrestrial ecoregions of University of Illinois Press. 610 p. Latin America and the Caribbean. Washington, DC: The Thornthwaite, C.W. 1931. The climates of North America

World Bank in association with The World Wildlife Fund. according to a new classification. Geographical Review

129 p. with separate map at 1:15,000.000. 21:633-655 with separate map at 1:20.000.000. Thornthwaite. C.W. 1933. The climates of the Earth. Geo- Walter. H.: Box. E. 1976. Global classification of natural

graphical Review 23:433-440 with separate map at terrestrial ecosystems. Vegetatio 32:75-81.

1:77,000.000. Walter. H.: Harnickell. E.; Mueller-Dombois. D. 1975. Cli- Trewartha, G.T. 1968. An introduction to climate. 4th ed. mate-diagram maps of the individual continents and the

New York: McGraw-Hill. 408 p. ecological climate regions of the Earth. Berlin: Springer-

Udvardy, M.D.F. 1975. A classification of the biogeographi- Verlag. 36 pp. with 9 maps.

cal provinces of the world. Occasional Paper No. 18. Walter. H.: Lieth. H. 1960-1967. Klimadiagramm Weltatlas. Morges, Switzerland: International Union for Conserva- Jena. East Germany: G. Fischer Verlag. maps, diagrams,

tion of Nature and Natural Resources. 48 p. profiles. Irregular pagination. Appendix 1: Ecological climate zones"

Koppen group and types Ecoregion equivalents

A Tropical and humid climates Humid tropical domain (400) Tropical wet (Ar) Rainforest division (420) Tropical wet-dry (Aw) Savanna division (410)

B Dry climates Dry domain (300) Tropical/subtropical semi-arid (BSh) Tropical/subtropical steppe division (310) Tropical/subtropical arid (BWh) Tropical/subtropical desert division (320) Temperate semi-arid (BSk) Temperate steppe division (330) Temperate arid (BWk) Temperate desert division (340)

C Subtropical climates Humid temperate domain (200) Subtropical dry summer (Cs) Mediterranean division (260) Humid subtropical (Cf) Subtropical division (230) Prairie division (250) b D Temperate climates Temperate oceanic (Do) Marine division (240) Temperate continental, warm summer (Dca) Hot continental division (220) Prairie division (250) b Temperate continental, cool summer (Deb) Warm continental division (210) Prairie division (250) b

E Boreal climates Polar domain (100) Subarctic (E) Subarctic division (130)

F Polar climates

Tundra (Ft) Tundra division (120)

Ice Cap (Fi) Icecap division (110) Definitions and Boundaries of the Kbppen-Trewartha System Ar All months above 18°C and no dry season. Aw Same as Ar, but with 2 months dry in winter.

BSh Potential evaporation exceeds precipitation, and all months above 0°C.

BWh One-half the precipitation of BSh, and all months above 0°C.

BSk Same as BSh, but with at least 1 month below 0°C.

BWk Same as BWh, but with at least 1 month below 0°C. Cs 8 months 10°C, coldest month below 18°C, and summer dry. Cf Same as Cs, but no dry season. Do 4 to 7 months above 10°C, coldest month above 0°C. Dca 4 to 7 months above 10°C, coldest month below 0°C, and warmest month above 22°C. Deb Same as Dca, but warmest month below 22°C. E Up to 3 months above 10°C. Ft All months below 10°C.

Fi All months below 0°C.

A/C boundary = Equatorial limits of frost; in marine locations, the isotherm of 18°C for coolest month. C/D boundary = 8 months 10°C. D/E boundary = 4 months 10°C. E/F boundary = 10°C for warmest month.

B/A, B/C, B/D. B/E boundary = Potential evaporation equals precipitation.

Based on the Koppen system of classification (1931). as modified by G.T. Trewartha ( 19681. Koppen did not recognize the Prairie as a distinct climatic type. The ecoregion classification

system represents it at the arid sides of the Cf. Dca, and Deb types, following Borchert ( 1950).

8 Appendix 2: Climate diagrams of representative climate stations (based on Walter and Lieth 1960-67, Walter and others 197

Polar Domain

120 110 Icecap mm Tundra nun 130 Subarctic mm Barrow, Alaska (4 m) Ft Vermilion, Alberta m) Eismitte, Greenland (3030 m) 20 B0 (290 60 C -30.0°C mm -12.2 C 104 mm -1.8°C 323 mm iiii o JFMAMJJASOND -10-

°C M130 Subarctic mm Humid Temperate Domain r Aishihik (966 m) 30 H 60 300 300 -3.6°C 248 mm 210 Warm Continental -200 220 Hot Continental 200 Duluth, Minnesota (354 m) Ft. Wayne, Indiana (244 m) 100 100 3.4°C /\ 755 mm 9.9°C 869 mm

JFMAMJJASOND

-10 -10-

-20' -20- mm mm 300 300 230 Subtropical 240 Marine M220 Hot Continental 200 200 BoonejM. Carolina. ^(1016m) Atlanta^Georgia (297 m) ^Vancouver, British Columbia (8 rcj^" 100 100 16.8°C "~~\10.0°C 1050 mmf~

°c 30- \ / 20- \_/

10-

i i i i i i i i i i

JFMAMJJASOND J r MAMJJASOND J MAMJJASOND

-10' -10- 10

-20 -20 -20' mm mm mm 300 300 300 250 Prairie 260 Mediterranean M260 Mediterranean 200 200 200 Fargo, N. Dakota (273 m) Pasadena, California (263 m) Jahoe, California (1900 m) 100 100 100 4.9°C 476 mm

J FMAMJJASOND J — MAMJJASOND

-10- -10-

-20- -20-'- Dry Domain mm 300 300 300 r 330 Temperate Steppe 310 Tropical/Subtropical 200 320 Tropical/Subtropical 200 200 Steppe Desert Colorado Springs, Colorado (1855 m) 100 100 100 Abilene, ATexas (534 m] Brawley, California (-36 m) 8.7°C 363 mm 18.1°C /\ 622 mm 22.0°C 58 mm 30

60

40

20

JFMAMJJASOND_! I 1 1 I I L_ JFMAMJJASOND JFMAMJJASOND

-10 -10- -10

-20 -20' -20 mm 300 300 M330 Temperate Steppe 200 340 Temperate Desert 200 Pikes Peak, Colorado (4301 m) Salt Lake City, Utah (1300 m) 1 00 100 -7.0°C y\ P\ 752 mm 10.6°C 414 mm

Humid Tropical Domain

410 Savanna M410 Savanna 420 Rainforest San Salvador, El Salvador Mexico City, Mexico m) Belize, Belize (698 m) mm (2280 mm (5 m) mm 23.2°C _ 1770 mm 15.6°C 588 mm 29.5°C 1810 mm 300 300 I- 300 200 200 200 100 100 100

°c 30

20-

10

1_ J_ I I I I I J FMAMJJASOND J FMAMJJASOND J FMAMJJASOND

Exp anation

Division 2 30- Location (Altitude) -60 I CO Mean annual temp. Mean annual pptn. Q_ "o E CD ^20- -40 o. Relative period __ _cz of drought -y£ ^s< ^ §10- -20 "1 E E cz

3 S 5 l F M A M J J A S N Months

10 Revised

North America Ecoregions Map The USDA Forest Service recently published a revised version of the ecoregions map of North America by Robert G. Bailey in cooperation with The Nature Conservancy and the U.S. Geological Survey. This 29" x 32" full-color map shows, at a scale of 1:15,000,000, the division of the continent into a hierarchy of ecosystem regions. The map replaces the now outdated map of North America ecoregions which was issued in 1981 by the U.S. Fish and Wildlife Service. The revised map can be used to address environmental issues that transcend agency, watershed, and political boundaries and borders.

Part of Ecoregions Map of North America, 1997 edition. Source scale 1:15,000,000

-v (r Mil

For a/ree copy, write the author at: USDA Forest Service Ecosystem Management 3825 East Mulberry Street Fort Collins, Colorado 80524 USA 10/97

The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, gender, religion, age, disability, political beliefs, sexual orientation, and marital or family status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDAs TARGET Center at 202-720-2600 (voice and TDD).

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DC 20250-9410 or call 202-720-5964 (voice or TDD). USDA is an equal opportunity provider and employer.

2

PROVINCES OF AGRICULTURE ECOREGION U.S. DEPARTMENT 70° 60° 100 POLAR DOMAIN FOREST SERVICE eo° 110 ICECAP DIVISION

in Glacial ice 120 TUNDRA DIVISION

i2i deserts | Ice and stoney 160° I

122 | Arctic tundras I

123 | Tundras | Ml TUNDRA MOUNTAINS

KM12M Polar desert

X44\ Tundra - polar desert

j/M 123/1 Tundra - meadow

170° ['Ml 2jt| Oceanic meadow - heath

130 SUBARCTIC DIVISION

i3i open woodlands j Forest-tundras and |

132 forests) | (boreal | Tayga 50° Ml 30 SUBARCTIC MOUNTAINS

^mbi^J Open woodland - tundra

[Mi32a^| Tayga - tundra, medium

1 I'M 132b Tayga - tundra, high 180° ] 200 HUMID TEMPERATE DOMAIN

210 WARM CONTINENTAL DIVISION

2ii forests | Mixed deciduous-coniferous I M210 WARM CONTINENTAL MOUNTAINS

[M2iia] Mixed forest - coniferous forest - tundra, medium

^M2iibj Mixed forest - coniferous forest - tundra, high 220 HOT CONTINENTAL DIVISION

221a Broadleaved forests, oceanic 170° 221b Broadleaved forests, continental M220 HOT CONTINENTAL MOUNTAINS

[M22i/| Deciduous or mixed forest - coniferous forest - meadow

|^M222J Broadleaf forest - meadow 230 SUBTROPICAL DIVISION

231 Broadleaved-coniferous evergreen forests

232 Coniferous-broadleaved semi-evergreen forests

I M230 SUBTROPICAL MOUNTAINS

LM23n Mixed forest - meadow i / / /I 40° 240 MARINE DIVISION

241 Mixed forests 160° M240 MARINE MOUNTAINS

iMMi'j Deciduous or mixed forest - coniferous forest - meadow

[M242a] Forest - meadow, medium

^M242bi Forest - meadow, high 250 PRAIRIE DIVISION

251 Forest-steppes and prairies | \

252 savannas | Prairies and I 260 MEDITERRANEAN DIVISION

261 j steppe | Dry

262 evergreen forests, open woodlands and shrub | Mediterranean hardleaved |

263 Redwood forests I \ M260 MEDITERRANEAN MOUNTAINS

[M26i^ Mixed forest - coniferous forest - alpine meadow

yM262y\ Mediterranean woodland or shrub - mixed or coniferous forest - steppe or meadow

Shrub or woodland - steppe - meadow

300 DRY DOMAIN

310 TROPICAL/SUBTROPICAL STEPPE DIVISION

3ii and semideserts j open woodland | Coniferous

312 j Steppes I

313 shrubs j and | Steppes

314 Shortgrass steppes | M310 TROPICAL/SUBTROPICAL STEPPE MOUNTAINS

[-mmi^ Steppe or semidesert - mixed forest - alpine meadow or steppe 320 TROPICAL/SUBTROPICAL DESERT DIVISION

321 | Semideserts

322 | semideserts j Oceanic 20° 323 sand j Deserts on I M320 TROPICAL/SUBTROPICAL DESERT MOUNTAINS

Semidesert - shrub - open woodland - steppe or alpine meadow

yyup^ Desert or semidesert - open woodland or shrub - desert or steppe 330 TEMPERATE STEPPE DIVISION

331 | Steppes I

332 steppes | Dry I M330 TEMPERATE STEPPE MOUNTAINS

Forest-steppe - coniferous forest - meadow - tundra

Steppe - coniferous forest - tundra

£m333^J Steppe - coniferous forest no | Icecap |

- - alpine • M33J Steppe - open woodland coniferous forest meadow 120 1 Tundra | DESERT DIVISION 130 Subarctic 340 TEMPERATE [ / |

341 j Semideserts 210 | 1 Warm Continental |

220 Hot Continental 342 deserts I | | Semideserts and I

230 Subtropical I | M340 TEMPERATE DESERT MOUNTAINS

240 Marine - I | pM341/ Semidesert - open woodland - coniferous forest alpine meadow

250 Prairie I | 400 HUMID TROPICAL DOMAIN 260 1 Mediterranean 1 410 SAVANNA DIVISION 310 Tropical/Subtropical Steppe 1 | 411 woodlands, shrubs, and savannas [ Open 320 Tropical/Subtropical Desert | | forests 412 j Semi-evergreen 330 Steppe | j Temperate 1

Temperate Desert |^| Deciduous forests

410 j Savanna M410 SAVANNA MOUNTAINS

420 - - forest - steppe or meadow | Rainforest forest coniferous | fwu^ Open woodland deciduous

Mountains with altitudinal zonation Forest steppe 100° 90° 420 RAINFOREST DIVISION INTERIOR - GEOLOGICAL SURVEY. RESTON. VA • 1998 421 and evergreen forests II Semi-evergreen Base from World Databank I | Prepared by the U.S. Geological Survey ECOREGIONS OF NORTH AMERICA Everareen forests Representative climate station M420 RAINFOREST MOUNTAINS

By Robert G. Bailey - meadow or paramos Boundary of domain Evergreen forest U.S. Department of Agriculture, Forest Service Boundary of division INTRAZONAL REGIONS Washington, DC Boundary of province L Riverine forest Jointly supported by the U.S. Forest Service and Mountains with altitudinal zonation. These provinces are named 101 the spectrum The Nature Conservancy, Conservation Science Division of /ones from lower to upper (subnival); e.g.. semidesert coniferous forest alpine meadow REVISED-1997 View publication stats