Philippe Clement / Hiking boots drying out in tundra, Denali NP, Alaska, USA.

Staffan Widstrand / Reindeer trekking with Saami, Lapland, Sweden, Model released

Staffan Widstrand / Silhouette of ecotourist Reindeer trek camp site with Saami, Lapland, Sweden.

Claudio Contreras / Tourists trekking on domestic Arabian / Dromedary Camel (Camelus dromedarius) with shadows cast on sand, Erg Chebbi dunes near Merzouga, Sahara Desert, Morocco, October

Claudio Contreras / Tourists trekking on domestic Arabian / Dromedary Camel (Camelus dromedarius) with shadows cast on sand, Erg Chebbi dunes near Merzouga, Sahara Desert, Morocco, October

Claudio Contreras / Guide and Arabian / Dromedary Camel (Camelus dromedarius) trekking, Erg Chebbi dunes near Merzouga, Sahara Desert, Morocco, October

Staffan Widstrand / Wild Wonders of China / Wildlife photographer Jed Weingarten trekking over a logbridge , Tangjiahe National Nature Reserve,Qingchuan County, Sichuan province, China

Ashley Cooper / Trekkers at Annapurna base camp at 4130 metres looking towards Machapuchare, Annapurna Sanctuary, Himalayas, Nepal. December 2012.

Ashley Cooper / Trekking group at Annapurna base camp at 4130 metres in front of Annapurna South summit, Annapurna Sanctuary, Himalayas, Nepal. December 2012.

Ashley Cooper / Climber with spindrift during high winds moving snow above Grasmere, Lake District, England, UK. December 2010

Ashley Cooper / A climber being blasted by spindrift during high winds moving snow above Grasmere, Lake District, UK. December 2010

Ashley Cooper / Climberwith spindrift during high winds moving snow above Grasmere, Lake District, UK. December 2010