Twin cubs asleep in a snow den in Wapusk National Park, Manitoba, Canada (© AF archive/Alamy)

Lightning strikes near Church Rock, New Mexico, USA (© Tim Fitzharris/Minden Pictures)

Marmot with the peak of Grossglockner in the background, Austria (© SeppFriedhuber/Getty Images)

Colossal limestone statues on Mount Nemrut, Adiyaman, Turkey (© Peerakit JIrachetthakun/Getty Images)

Great spotted woodpecker on Scots pine tree, Glenfeshie, Cairngorms National Park. (© Nature Picture Library/Alamy Stock Photo)

Sandstone formation and pools of water in The Wave, Paria Canyon-Vermillion Cliffs National Monument, Arizona, USA (© Dennis Frates/Alamy)

Mount Sefton in Aoraki/Mount Cook National Park, South Island, New Zealand (© AWL Images/Danita Delimont)

Great grey owls in Montreal, Canada (© rollandgelly/Getty Images)

Northern Vosges Regional Nature Park, France (© Michel Rauch/Minden Pictures)

Moon dog photographed at Hug Point Falls on the Oregon coast, USA (© Ben Coffman/Tandem Stills + Motion)

Nieve penitente ice formations seen on Agua Negra Pass in the Coquimbo region of the Andes, Chile (© Art Wolfe/Danita Delimont)

The Langdale Pikes in winter under fresh snow, Lake District, Cumbria (© Nigel Wilkins/Alamy Stock Photo)

Muskox with newborn in the central Arctic coastal plain in Alaska, USA (© Steven Kazlowski/Danita Delimont)

Eastern bluebirds in Charlotte, North Carolina, USA (© Elizabeth W. Kearley/Getty Images)

Ocean waves crashing over a heart-shaped rock island off the coast of Sydney, Australia (© Kristian Bell/Getty Images)

Panoramic view of the city of Toledo after sunset, Spain (© Frank Fischbach/Alamy)

View of Wotton-Under-Edge, Cotswolds, in winter with snow (© Peter Adams Photography/Alamy Stock Photo)

Perito Moreno Glacier in Patagonia's Los Glaciares National Park, Argentina (© Juergen Schonnop/Getty Images)

Stones in a river near the hamlet of Lavertezzo, in the Valle Verzasca of Switzerland (© Robert Seitz/Offset by Shutterstock)

Parrotfish off the coast of the Philippines (© Tim Fitzharris/Minden Pictures)

Hikers on alpine glacier, Mont Blanc, Chamonix, France (© agustavop/Getty Images)

Porto, Portugal (© Kanuman/Shutterstock)

The Cobb breakwater, Lyme Regis, Dorset (© Ross Hoddinott/Offset by Shutterstock)

Dalmatian pelicans on ice, Lake Kerkini, Greece (© Guy Edwardes/Minden Pictures)

Le Morne Brabant, Mauritius (© Hemis/Alamy)

Almond blossoms overlooking Trevi, Perugia district, Umbria, Italy (© Maurizio Rellini/eStock Photo)

Red lanterns hanging in Jinli Street, Chengdu, China (© Philippe LEJEANVRE/Getty Images)

Traditional farmhouses at Skaftafell, Vatnajökull National Park, Iceland (© Jarcosa/Getty Images)