Jerry Monkman / A man hiking at Arethusa Falls, Crawford Notch State Park, White Mountains, New Hampshire, USA. August 2009

Jerry Monkman / Two people hiking at Arethusa Falls, Crawford Notch State Park, White Mountains, New Hampshire, USA. August 2009

Wild Wonders of Europe / Munier / .Rear view of person walking with backpack in Forollhogna National Park, Norway, September 2008

David Tipling / Mother carrying toddler in backpack while bird watching along coastal path, North Norfolk, UK, January 2008, model released

Tim Laman / Bees (Apis sp) gather on a sweaty backpack, Bioko Island, Equatorial Guinea, Rapid Assessment Visual Expedition, International League of Conservation Photographers, January 2008

Oriol Alamany / Mountain rescue dog (Canis familiaris) female carrying a backpack, near Nuria in Ribes valley, Pyrenees mountains, Catalonia, Spain

Oriol Alamany / Mountain rescue dog (Canis familiaris) female carrying a backpack, near Nuria in Ribes valley, Pyrenees mountains, Catalonia, Spain

Colin Monteath / Trekker under Mera Peak, Hinku Valley, Makalu-Barun National Park, Nepal

Roy Mangersnes / Silhouette of hiker with backpack against snow, Norway. April

Nick Turner / Adult walker carrying child in backpack with another child walking, in waterfall country along the Nedd Fechan, Brecon Beacons National Park, Powys, Wales

Yva Momatiuk & John Eastcott / Man hiker, 52, in shorts, boots and hat, carrying backpack and water bottle, standing and looking ahead at the difficult and rocky broken terrain he wants to hike in, autumn noon, Badlands National Pa...

Yva Momatiuk & John Eastcott / Man hiker wearing shorts, a hat and a backpack, 52, walking alone in a big sprawling landscape of sand and distant mountains, across white sand dunes, evening, autumn, White Sands National Park, New M...