The Planetary Context

NORTH AMERICAN ECOREGIONS AND WATERSHEDS
Commission for Environmental Cooperation: Ecological Regions of North America (60 page pdf)
http://www.cec.org/files/pdf/BIODIVERSITY/eco-eng_EN.pdf

EPA Ecoregion maps and descriptions (maps and descriptions at different levels)
Ecoregions of Wisconsin
ftp://ftp.epa.gov/wed/ecoregions/wi/wi_eco_lg.pdf
Great Lakes Atlas and Resource Book
http://www.epa.gov/glnpo/atlas/

US Forest Service (Bailey) Ecoregions Center
Descriptions of Bailey’s ecoregions
http://www.fs.fed.us/land/ecosysmgmt/ecoreg1_home.html

Descriptions of the Sections as depicted on the map "Ecoregions and Subregions of the United States." National Hierarchical Framework of Ecological Units (ECOMAP 1993), devised by Bailey.
http://www.fs.fed.us/land/pubs/ecoregions/index.html

WATERSHEDS
Watersheds of North America (Bioregional Congress)
http://www.bioregional-congress.org/Maps/NAwatershed.html

Watersheds of the United States (USGS)
http://water.usgs.gov/wsc/map_index.html

WORLD ECOREGIONS

National Geographic / World Wildlife Fund Global 200
http://www.worldwildlife.org/science/ecoregions.cfm

Wikipedia listing
http://en.wikipedia.org/wiki/Global_200

Ecoregions in North America
http://www.worldwildlife.org/science/ecoregions/nearctic.cfm

Miklos Udvardy & World Wildlife Fund: ecozones (8):
http://en.wikipedia.org/wiki/Ecozones

Taktajan: Floristic Provinces
http://en.wikipedia.org/wiki/Floristic_province

World Watersheds
http://earthtrends.wri.org/maps_spatial/watersheds/index.php

WRI Earthtrends: Watersheds of the World
http://earthtrends.wri.org/maps_spatial/maps_detail_static.php?map_select=274&theme=2

BIOMES

Animal planet biomes
http://animal.discovery.com/guides/mammals/habitat/map.html

H. J. De Blij World Biomes
http://soils.usda.gov/use/worldsoils/mapindex/biomes.html

NASA Earth Observatory
coniferous forests: http://earthobservatory.nasa.gov/Laboratory/Biome/bioconiferous.html
temperate deciduous forests: http://earthobservatory.nasa.gov/Laboratory/Biome/biotemperate.html
deserts http://earthobservatory.nasa.gov/Laboratory/Biome/biodesert.html
grasslands http://earthobservatory.nasa.gov/Laboratory/Biome/biograssland.html
rainforests http://earthobservatory.nasa.gov/Laboratory/Biome/biorainforest.html
shrublands http://earthobservatory.nasa.gov/Laboratory/Biome/bioshrubland.html
tundras http://earthobservatory.nasa.gov/Laboratory/Biome/biotundra.html

NRCS Biome Map
http://soils.usda.gov/use/worldsoils/mapindex/biomes.html

U.C. Berkeley World’s Biomes Page
http://www.ucmp.berkeley.edu/glossary/gloss5/biome/

World Wildlife Fund Biomes by latitude and humidity (The 14 terrestrial biomes are further divided into 825 ecoregions)
http://en.wikipedia.org/wiki/Biome