Oriol Alamany / Two hikers with backpacks walking through the old-growth forest of Carmanah-Walbran Provincial Park, Vancouver Island, British Columbia, Canada

Oriol Alamany / Hiking boots and backpacks at the entrance of Grey mountain hut, trekking in National Park Torres del Paine, Patagonia, Chile

Nick Turner / Walkers carrying backpacks on the Cotswold Way National Trail at Painswick, Gloucestershire, UK, May 2008.

Bryan and Cherry Alexander / Park warden on patrol at Tanquary Fiord. Ellesmere Island, National Park Reserve, Canada, 1994.

Jerry Monkman / Mothers taking their babies for a hike through the forest near Meadow Pond, Stephenson's Way, Groveland, Massachusetts, USA

Nick Turner / Walkers carrying backpacks hiking above Llyn y Fan Fach, a glacial cirque, beneath Black Mountain in the Brecon Beacons National Park, Powys, Wales

Nick Turner / Walkers carrying backpacks above Llyn y Fan Fach, a glacial cirque, beneath Black Mountain in the Brecon Beacons National Park, Powys, Wales

Fabio Liverani / Hikers with backpacks walking through rocky landscape, Sardinia, Italy