Caribou swimming across Alaska's Kobuk River during fall migration (© Michio Hoshino/Minden Pictures)

Maple leaf under water; Grenville-sur-la-Rouge, Quebec (© Steeve Marcoux/Plainpicture/Design Pics)

Polar bears in Torngat Mountains National Park, Canada (© Cavan Images/Offset by Shutterstock)

Loch Leum na Luirginn and Loch Cleat seen from the Quiraing, Isle of Skye, Scotland, U.K. (© Sebastian Wasek/Sime/eStock Photo)

Albarracín, Spain (© Domingo Leiva/Getty Images)

West Indian manatees in Three Sisters Springs, Crystal River National Wildlife Refuge, Florida (© Norbert Probst/Getty Images)

Bison in Grand Teton National Park, Wyoming (© Brian Evans/Getty Images)

Derwent Island on Derwentwater in the Lake District National Park, Cumbria, England (© Chris Warren/eStock Photo)

The hills of Barolo vineyards in Piedmont, Italy (© Marco Arduino/eStock Photo)

Badlands National Park, South Dakota (© Dennis Frates/Alamy)

The tomb of the unknown soldier at the National War Memorial in Ottawa (© Norman Pogson/Alamy Stock Photo)

Connery Pond and Whiteface Mountain in New York state (© Henk Meijer/Alamy)

Ravens in a snowstorm near Kuhmo, Finland (© Frans Lemmens/Alamy)

Oil lamps being arranged on rangoli during Diwali (© Subir Basak/Getty Images)

Lupins on the shores of Lake Tekapo in New Zealand (© Stanislav Kachyna/Shutterstock)

The interior of the Abu Simbel Great Temple in Egypt (© George Steinmetz/Getty Images)

Andy Goldsworthy's 'Wood Line' installation along Lovers' Lane in the Presidio of San Francisco, California (© Chris LaBasco/Alamy)

Inukshuk silhouetted against the Northern Lights in Barren Lands, Northwest Territories (© Mark Duffy/Alamy Stock Photo)

Chestnut-mandibled toucan in nest cavity, Costa Rica (© Greg Basco/Minden Pictures)

Aerial view of the Aiguille du Midi in the Mont Blanc massif, France (© Amazing Aerial Agency/Offset by Shutterstock)

Wetlands in the Kitikmeot region of Nunavut (© Robert Simmon/NASA)

Common cranes in the Drömling wetland in Germany (© Mike Friedrichs/Getty Images)

Old Town of Bern, Switzerland (© Simon Zenger/Alamy)

Huge waves crashing on rocks along Asilomar State Beach, Pacific Grove, California (© Sheila Haddad/Danita Delimont)

A grove of American elm trees in Central Park's Mall, New York City (© AWL Images/Danita Delimont)

A Siberian chipmunk in Hokkaido, Japan (© plainpicture/Score. by Aflo/Takao Onozato/Aflo)

Kalbarri National Park, Australia (© AWL Images/Offset by Shutterstock)

Partly snow-covered slope in Val Cervara, an old-growth beech forest, in Abruzzo, Italy (© Bruno D'Amicis/Minden Pictures)

Mount Taranaki, Egmont National Park, North Island, New Zealand (© Francesco Vaninetti/plainpicture)

Eilean Donan Castle in Scotland (© CBW/Alamy)