Region
- Adirondack Mountains 2 results
- Afghanistan 2 results
- Africa 46 results
- Africa, Central 2 results
- Africa, East 8 results
- Africa, Eastern 2 results
- Africa, North 4 results
- Africa, Sub-Saharan 4 results
- Africa, West 8 results
- Alabama 14 results
- Alaska 40 results
- Alaska, Gulf of 2 results
- Alaska, Northwest 2 results
- Alaska, Southeast 2 results
- Aldo Leopold Memorial Reserve 2 results
- Alps 2 results
- Amazon River 2 results
- Amazon River Region 4 results
- Amazon River Valley 2 results
- Amazon River Watershed 2 results
- Ambon Island 2 results
- Amboseli National Park 1 results
- America 8 results
- Amérique du Nord 2 results
- Anderson Island 2 results
- Antarctic Ocean 2 results
- Antarctica 22 results
- Apostle Islands National Lakeshore 2 results
- Apostle Islands National Lakeshore (Wis.) 2 results
- Appalachian Mountains 4 results
- Appalachian Region 2 results
- Appalachian Region, Southern 2 results
- Appalachian Trail 4 results
- Appleton-Whittell Research Ranch Sanctuary 2 results
- Appleton-Whittell Research Ranch Sanctuary (Ariz.) 2 results
- Arab countries 2 results
- Aransas National Wildlife Refuge 2 results
- Aransas National Wildlife Refuge (Tex.) 2 results
- Arctic regions 16 results
- Argentina 10 results
- Arizona 4 results
- Arkansas 2 results
- Armenia (Republic) 4 results
- Asia 24 results
- Asia, Central 4 results
- Atlantic Coast 6 results
- Atlantic Coast (N.C.) 2 results
- Atlantic Coast (Nicaragua) 2 results
- Atlantic Coast (U.S.) 4 results
- Atlantic Coast (Va.) 2 results more…