Jami Tarris / Caribou (Rangifer tarandus) entering teepee for food, Khovsgol, Mongolia

Mark Raycroft / Woodland Caribou (Rangifer tarandus caribou) mother nursing calf, Newfoundland, Canada

Mark Raycroft / Woodland Caribou (Rangifer tarandus caribou) male, Newfoundland, Canada

Donald M. Jones / Caribou (Rangifer tarandus) bull in tundra, Denali National Park, Alaska

Nick Garbutt / Urial sheep (Ovis vignei) herd running across steep barren slopes. Himalayas near Ulley, Ladakh, India.

Floris van Breugel / Driving the remote dirt roads, 11000ft altitude, White Mountains, California, USA, June

Floris van Breugel / Beavertail cactus (Opuntia basilaris) in otherwise stark desert, Alabama Hills, Owen's Valley, California, USA May

Sergey Gorshkov / Siberian Tundra Reindeer (Rangifer tarandus sibiricus) herd migrating through snow, Putoransky State Nature Reserve, Putorana Plateau, Siberia, Russia

Donald M. Jones / Barren-ground Caribou (Rangifer tarandus groenlandicus) bull in tundra, central Alaska

Donald M. Jones / Barren-ground Caribou (Rangifer tarandus groenlandicus) bull in tundra, central Alaska

Donald M. Jones / Barren-ground Caribou (Rangifer tarandus groenlandicus) bulls in rainfall, central Alaska

Donald M. Jones / Barren-ground Caribou (Rangifer tarandus groenlandicus) bulls in rainfall, central Alaska

Roland Seitre / Svalbard Reindeer (Rangifer tarandus platyrhynchus) male and females running, Spitsbergen, Svalbard, Norway

Roland Seitre / Svalbard Reindeer (Rangifer tarandus platyrhynchus) pair, Spitsbergen, Svalbard, Norway

Roland Seitre / Svalbard Reindeer (Rangifer tarandus platyrhynchus) male, Spitsbergen, Svalbard, Norway

Colin Monteath / Caribou (Rangifer tarandus) and Tsataan reindeer herders in winter camp, Hunkher Mountains, northern Mongolia

Mark Raycroft / Caribou (Rangifer tarandus) bull on autumn tundra

Steve O. Taylor (GHF) / Rocky landscape of northern Niger, 2005.

Laurent Geslin / Indian gazelle (Gazella bennetti) Thar desert, Rajasthan, India

Eric Dragesco / Wild male Snow Leopard (Panthera uncia) running down barren mountainside with snow covered patches, Altai mountains, Mongolia. February

Eric Dragesco / Wild male Snow Leopard (Panthera uncia) running down barren mountainside with snow covered patches, Altai mountains, Mongolia. February

Michael Quinton / Caribou (Rangifer tarandus) pair running in snow, Alaska

David Noton / Person walking along sand dunes, Namib Desert, Namibia, Southern Africa. Model released.

Eric Baccega / Aerial view of Devon Island, Nunavut, Canada, June 2012.

Eric Baccega / Scientist taking a photograph of Lichen in Dundas Harbour. Devon Island, Nunavut, Canada, August 2010

Ingo Arndt / Caribou (Rangifer tarandus) herd crossing a Kongakut River during summer migration, Arctic National Wildlife Refuge, Alaska

Ingo Arndt / Caribou (Rangifer tarandus) pair crossing a river during summer migration, Arctic National Wildlife Refuge, Alaska

Ingo Arndt / Caribou (Rangifer tarandus) bull crossing a river during summer migration, Arctic National Wildlife Refuge, Alaska

Ingo Arndt / Caribou (Rangifer tarandus) mother and calf crossing a river during summer migration, Arctic National Wildlife Refuge, Alaska

Donald M. Jones / Caribou (Rangifer tarandus) bull on tundra, central Alaska

Donald M. Jones / Caribou (Rangifer tarandus) bull on tundra, central Alaska

Donald M. Jones / Caribou (Rangifer tarandus) bull on tundra, central Alaska

Donald M. Jones / Caribou (Rangifer tarandus) bull in velvet, central Alaska

Donald M. Jones / Caribou (Rangifer tarandus) bull in velvet, central Alaska

Donald M. Jones / Caribou (Rangifer tarandus) bull in velvet, central Alaska

Jasper Doest / Caribou (Rangifer tarandus), Abisko, Sweden

Yva Momatiuk & John Eastcott / Volcanic Ubehebe Crater, Death Valley National Park, California

Jasper Doest / Caribou (Rangifer tarandus) herd in snowy landscape, Abisko, Sweden

Jasper Doest / Caribou (Rangifer tarandus) in the snow, Abisko, Sweden

Jasper Doest / Caribou (Rangifer tarandus) in snowy landscape, Abisko, Sweden

Jasper Doest / Caribou (Rangifer tarandus) in snowy landscape, Abisko, Sweden

Mark Raycroft / Caribou (Rangifer tarandus) male standing on autumn tundra, Canada

Sergey Gorshkov / Caribou (Rangifer tarandus) mother and calf nuzzling, Kamchatka, Russia

Tim Fitzharris / 750 foot tall sand dunes, tallest in North America, Great Sand Dunes National Monument, Colorado

Mitsuaki Iwago / Cape Barren Goose (Cereopsis novaehollandiae) mother foraging with gosling, Kangaroo Island, Australia

Gerry Ellis / Caribou (Rangifer tarandus) silhouetted against sky, Alaska

Yva Momatiuk & John Eastcott / Caribou (Rangifer tarandus) portrait of bull in summer tundra, Denali National Park and Preserve, Alaska

Yva Momatiuk & John Eastcott / Caribou (Rangifer tarandus) young bull in summer tundra, Denali National Park and Preserve, Alaska

Matthias Breiter / Caribou (Rangifer tarandus) calf running on the tundra, Arctic National Wildlife Refuge, Alaska

Matthias Breiter / Caribou (Rangifer tarandus) two males sparring, Denali National Park and Preserve, Alaska

Matthias Breiter / Caribou (Rangifer tarandus) two males sparring, Denali National Park and Preserve, Alaska

Michio Hoshino / Caribou (Rangifer tarandus) pair of bulls, Alaska

Michio Hoshino / Caribou (Rangifer tarandus) bull calling on autumn tundra, Alaska

Michio Hoshino / Caribou (Rangifer tarandus) bull, Alaska

Michio Hoshino / Caribou (Rangifer tarandus) bull, Alaska

Michio Hoshino / Caribou (Rangifer tarandus) herd crossing misty tundra during migration, Alaska

Michio Hoshino / Caribou (Rangifer tarandus) herd, Arctic National Wildlife Refuge, Alaska

Michio Hoshino / Caribou (Rangifer tarandus) herd migrating across tundra, Arctic National Wildlife Refuge, Alaska

Michio Hoshino / Caribou (Rangifer tarandus) group swimming during migration, Kobuk River, Alaska

Jim Brandenburg / Peary Caribou (Rangifer tarandus pearyi) pair running, Ellesmere Island, Nunavut, Canada

Michio Hoshino / Caribou (Rangifer tarandus) herd migrating in summer, Arctic National Wildlife Refuge, Alaska

Michio Hoshino / Caribou (Rangifer tarandus) herd migrating across tundra, Arctic National Wildlife Refuge, Alaska

Michio Hoshino / Caribou (Rangifer tarandus) herd stampeding, Arctic National Wildlife Refuge, Alaska

Michio Hoshino / Caribou (Rangifer tarandus) of the western Arctic Herd swimming across the Kobuk River during migration to their winter range, Alaska

Michio Hoshino / Caribou (Rangifer tarandus) male with full rack, Alaska

Michio Hoshino / Caribou (Rangifer tarandus) stampeding herd crossing river, Arctic National Wildlife Refuge, Alaska

Michio Hoshino / Caribou (Rangifer tarandus) group swimming during migration, Kobuk River, Alaska

Jim Brandenburg / Peary Caribou (Rangifer tarandus pearyi) running, Ellesmere Island, Nunavut, Canada

Michio Hoshino / Caribou (Rangifer tarandus) of the Porcupine Herd climb Brooks Range foothills at midnight during migration, Alaska

Michio Hoshino / Caribou (Rangifer tarandus) pair grazing on autumn tundra near Mt Denali, Denali National Park and Preserve, Alaska

Michio Hoshino / Caribou (Rangifer tarandus) grazing on autumn tundra, Denali National Park and Preserve, Alaska

Michio Hoshino / Caribou (Rangifer tarandus) bull grazing beneath Mt Denali, Denali National Park and Preserve, Alaska

Michio Hoshino / Caribou (Rangifer tarandus) bull at waters edge, Denali National Park and Preserve, Alaska

Michio Hoshino / Caribou (Rangifer tarandus) bull on autumn tundra, Denali National Park and Preserve, Alaska

Michael Quinton / Caribou (Rangifer tarandus) mother and calf crossing snow field, Alaska

Shin Yoshino / Caribou (Rangifer tarandus) bull grazing, Denali National Park and Preserve, Alaska

Mitsuaki Iwago / Cape Barren Goose (Cereopsis novaehollandiae) parent and goslings, Kangaroo Island, Australia

Michio Hoshino / Caribou (Rangifer tarandus) group crossing through river during migration, Alaska

Robert Fulton / Aerial view of mountains near Salar de Uyuni, Bolivia

Robert Fulton / Aerial view of mountains near Salar de Uyuni, Bolivia

Jami Tarris / Caribou (Rangifer tarandus) herders leading herd in winter, Khovsgol, Mongolia

Jami Tarris / Caribou (Rangifer tarandus) slept on by Tsaatan child, Khovsgol, Mongolia

Nigel Cattlin / Barren brome (Bromus sterilis) panicle.

Nigel Cattlin / Barren brome (Bromus sterilis) unripe nodding panicle.

Mark Raycroft / Woodland Caribou (Rangifer tarandus caribou) male, Newfoundland, Canada

Mark Raycroft / Woodland Caribou (Rangifer tarandus caribou) male, Newfoundland, Canada

Mark Raycroft / Woodland Caribou (Rangifer tarandus caribou) male, Newfoundland, Canada

Mark Raycroft / Woodland Caribou (Rangifer tarandus caribou) male and females, Newfoundland, Canada

Mark Raycroft / Woodland Caribou (Rangifer tarandus caribou) male scenting females, Newfoundland, Canada

Mark Raycroft / Woodland Caribou (Rangifer tarandus caribou) male drinking, Newfoundland, Canada

Mark Raycroft / Woodland Caribou (Rangifer tarandus caribou) male, Newfoundland, Canada

Mark Raycroft / Woodland Caribou (Rangifer tarandus caribou) male displaying, Newfoundland, Canada

Mark Raycroft / Woodland Caribou (Rangifer tarandus caribou) male, Newfoundland, Canada

Mark Raycroft / Woodland Caribou (Rangifer tarandus caribou) male and female, Newfoundland, Canada

Mark Raycroft / Woodland Caribou (Rangifer tarandus caribou) male, Newfoundland, Canada

Marie Lochman / Biodiversity of flora in heath / Kwongan habitat dominated by Scarlet Banksia (Banksia coccinea) and Smokebush (Conospermum teretifolium) with West Mt. Barren in the background, Western Australia, Sou...