Region
United States
10
Tropics
7
West (U.S.)
4
Africa, Sub-Saharan
2
Developing countries
2
Europe
2
Arizona
1
Australia
1
Balkan Peninsula
1
Canada
1
Colorado Plateau
1
Fort Valley Experimental Forest (Ariz.)
1
High Plains (U.S.)
1
Japan
1
Madrean Archipelago
1
Mediterranean Region
1
Middle East
1
Northeastern States
1
Pacific Ocean
1
Persian Gulf States
1
Rocky Mountains
1
Southern States
1