Oriol Alamany / Hikers crossing scree along the 'Carros de foc' trail, Boi valley, Aiguestortes i Estany de Sant Maurici National Park, Pyrenees, Catalonia, Spain. No release available.

Paul D Stewart / Aerial view of Grand Prismatic thermal spring in Yellowstone National Park, USA. The bright colours are natural, coming from thermophile bacteria in the water. People can be seen walking on the raised...

Charlie Summers / Stars draw traces above Naabi Hill acacia trees, Serengeti National Park, Tanzania

Nick Turner / Family walking up steps from Durdle Door Beach onto the South West Coast Path National Trail, Dorset, UK, May 2009.

Nick Turner / Walkers on the South West Coast Path National Trail near Durdle Door, Dorset, UK, May 2009.

Martin Gabriel / Hiking trail along ancient aqueduct in Los Tilos National Park. World Biosphere Reserve, La Palma Island, Canary Islands, February.

Matthew Maran / Waterfall on the the Darling River with a fallen tree as a bridge over the waters. West Coast Trail, Pacific Rim National Park Reserve, west coast of Vancouver Island, Canada, September 2010.

Matthew Maran / Hikers crossing a thin footbridge over a river. The West Coast Trail, Pacific Rim National Park, Vancouver Island, Canada, September 2010, model released

Matthew Maran / Hikers building up a fire in their cliff-overhang cave. The West Coast Trail, Pacific Rim National Park, Vancouver Island, Canada, September, Model released

Matthew Maran / A man sitting in the cable car of a chair bridge as it crosses a river. The West Coast Trail, Pacific Rim National Park, Vancouver Island, Canada, September 2010. Model released

Matthew Maran / A man looking out to sea by coastal rock stacks. The West Coast Trail, Pacific Rim National Park, Vancouver Island, Canada, September 2010. Model released.

Matthew Maran / Hikers talking as they warm themselves by a campfire on a beach. The West Coast Trail, Pacific Rim National Park, Vancouver Island, Canada, September 2010. Models released.

Matthew Maran / A hiker building a fire at his campsite. The West Coast Trail, Pacific Rim National Park, Vancouver Island, Canada, September 2010. Model released.

Matthew Maran / Two people pausing on a woodland path. The West Coast Trail, Pacific Rim National Park, Vancouver Island, Canada, September 2010. Model released.

Anup Shah / Bornean Orangutan (Pongo pygmaeus wurmbii) female 'Gara' carrying her baby 'Gita' aged 2 years walking down a trail. Camp Leakey, Tanjung Puting National Park, Central Kalimantan, Borneo, Indonesia. J...

Inaki Relanzon / Star trails above Baobab trees (Adansonia za) at night, Zombitse National Park, Madagascar, June 2010

Graham Eaton / An underwater view of a mountain stream showing internal reflections on the water surface, Snowdonia NP, Gwynedd, Wales, UK, December 2009.

Alan Watson / Alpine paintbrush (Castilleja rhexifolia) in an alpine meadow along the Rockwall trail, Kootenay National Park, British Columbia, Canada. (World Heritage Site)July 2009

Jerry Monkman / Lone hiker at sunrise on the Bold Coast trail in Cutler, Maine, USA, June 2009. Model released

Jack Dykinga / Pinyon pine (Pinus edulis) and Utah juniper (Juniperus osteosperma) on kaibab limestone spires in morning fog, North Rim, North Kalbab Trail, Grand Canyon National Park, Arizona, USA

Jerry Monkman / Woman and child (aged 6) walking through woodlands in autumn, Lincoln's Woods Trail, White Mountains National Forest, New Hampshire, USA. Model Released. October 2007

Jerry Monkman / Two children (ages 4 and 6) walking across a wooden suspension bridge, Lincoln's Woods Trail, White Mountains National Forest, New Hampshire, USA. Model Released. October 2007

Scott Leslie / Boardwalk in old-growth forest, Kejimkujik National Park, Nova Scotia, Canada

Jack Dykinga / Ponderosa pines {Pinus ponderosa}, Promontory Butte on General George Crook Trail along the Mogollon Rim, Apache Sitgreaves National Forest, Arizona, USA

Jim Brandenburg / Giant Sequoia (Sequoiadendron giganteum) and star trails in King's Canyon National Park, California

Kirkendall-Spring / Spearhead Peak in the distance, viewed from Death Canyon Shelf, Teton Crest Trail, Grand Teton National Park. Wyoming, USA, July 2011

Kirkendall-Spring / Spearhead Peak in the distance, viewed from Death Canyon Shelf, Teton Crest Trail, Grand Teton National Park. Wyoming, USA, July 2011

Kirkendall-Spring / Man hiking along the Death Canyon Shelf on the Teton Crest Trail in Grand Teton National Park. Wyoming, USA, July 2011

Kirkendall-Spring / Campsite tent erected on the Death Canyon Shelf along the Teton Crest Trail in Grand Teton National Park. Wyoming, USA, July 2011 Model released

Kirkendall-Spring / Fox Creek Pass at the top of Death Canyon along The Teton Crest Trail. Wyoming, USA, July 2011

Kirkendall-Spring / Backpacker above frozen Marion Lake along the Teton Crest Trail in Grand Teton Natoinal Park. Wyoming, USA, July 2011 Model released

Kirkendall-Spring / Night time view of a campsite tent on the Death Canyon Shelf along the Teton Crest Trail in Grand Teton National Park. Wyoming, USA, July 2011

Kirkendall-Spring / Night time view of a campsite tent on the Death Canyon Shelf along the Teton Crest Trail in Grand Teton National Park. Wyoming, USA, July 2011

Kirkendall-Spring / Man hiking along the Teton Crest Trail between Marion Lake and Fox Creek Pass, Grand Teton Natoinal Park. Wyoming, USA, July 2011. Model released

Kirkendall-Spring / Man hiking along the Teton Crest Trail between Marion Lake and Fox Creek Pass, Grand Teton Natoinal Park. Wyoming, USA, July 2011. Model released

Kirkendall-Spring / Marion Lake, frozen over, Teton Crest Trail in Grand Teton National Park. Wyoming, USA, July 2011

Kirkendall-Spring / Birch tree (Betula sp) along the Old Logging Trail in Lake Bemidji State Park. Minnesota, USA, August

Kirkendall-Spring / Bridge crossing Daley Bay along the Kab-Ash Trail in Voyageurs National Park. Minnesota, USA, August 2011

Kirkendall-Spring / Hiker on the Kab-Ash Trail in Voyageurs National Park. Minnesota, USA, August 2011 Model released

Kirkendall-Spring / View of Kabetogama Lake along the Blind Ash Bay Trail in Voyageurs National Park. Minnesota, USA, August 2011

Kirkendall-Spring / View of Blind Ash Bay along the Blind Ash Bay Trail in Voyageurs National Park. Minnesota, USA, August 2011

Mark Hamblin / 2020VISION / Close up of Water Birds Trail sign post, Woodwalton Fen National Nature Reserve, Cambridgeshire, England, UK, July 2012.

Wild Wonders of Europe / Widstrand / Park ranger with pack mules on the main trail, Paklenica National Park, Velebit Nature Park, Rewilding Europe area, Velebit mountains, Croatia June 2012

Staffan Widstrand / Wilderness trail guide Artist Ngwetha, iMfolozi National Park, South Africa 2011

Staffan Widstrand / Rifle of Wilderness trail guide Wayne Saunders, iMfolozi National Park, South Africa 2011

Staffan Widstrand / Ranveig Eckhoff, a journalist, on a wilderness trail hike in iMfolozi National Park, South Africa

Rob Brown / Highlands near Mount Hrafntinnusker, Laugavegur Trail, Fjallabak Nature Reserve, South Iceland, Iceland

Floris van Breugel / Red Fox (Vulpes vulpes) follows its winter hunting trail through the Lamar Valley in Yellowstone National Park, Wyoming, USA. December.

Oriol Alamany / Waves along the beach on South Beach Trail, Pacific Rim National Park. Vancouver Island, British Columbia, Canada

Oriol Alamany / Woman hiker walking the 'Carros de Foc' trail at Cirque de Travessani with Punta Alta peak (3013 m), Boi valley, Aiguestortes i Estany de Sant Maurici National Park, Pyrenees, Catalonia, Spain. Model...

Oriol Alamany / Hiker on a boggy trail in Valle del Frances, Torres del Paine National Park, Patagonia, Chile. Model released.

Oriol Alamany / Hiker on trail to Laguna Torre below Cerro Torre, with Mount Fitz-Roy in the background, Los Glaciares National Park, Patagonia, Argentina. January 2006. Model released.

Scott Leslie / Canadian Hemlock (Tsuga canadensis) old growth forest and trail, Kejimkujik National Park, Nova Scotia, Canada

Steven Kazlowski / Two men and a toddler take a break from mountain biking on the Russian River Falls trail. Kenai National Wildlife Refuge, Chugach National Forest, Alaska, May 2012.

Mark Hamblin / 2020VISION / Feature on woodland trail through Beinn Eighe National Nature Reserve, Scotland, UK, June

Mark Hamblin / 2020VISION / Walker on woodland trail through pinewoods, Beinn Eighe National Nature Reserve, Scotland, UK, model released, June 2011

Konstantin Mikhailov / View to Mt.Logan Ridge in low clouds from the Maple-Loop Trail in Rainy Pass area of North Cascades National Park, Cascade Range, Washington, USA, October 2009.

Konstantin Mikhailov / The spectacular Loop-Maple Trail heading up from Rainy Pass area of North Cascades Scenic Highway, above the tree line, with the islets of sub alpine fir and larch trees, North Cascades National Park...

Konstantin Mikhailov / The spectacular Loop-Maple Trail heading up from Rainy Pass area of North Cascades Scenic Highway, above the tree line, with the islets of sub alpine firs and larches, North Cascades National Park Cas...

Konstantin Mikhailov / The rocky highlands of North Cascades Range above the tree line in clouds on Maple-Loop Trail in Rainy Pass area, North Cascades National Park, Cascade Range, Washington, October 2009.

Konstantin Mikhailov / View to Mt.Logan Ridge in low clouds from the Maple-Loop Trail in Rainy Pass area of North Cascades National Park, Cascade Range, Washington, USA, October 2009.

Konstantin Mikhailov / View to Mt.Logan Ridge in low clouds from the Maple-Loop Trail in Rainy Pass area of North Cascades National Park, Cascade Range, Washington, USA, October 2009.

Konstantin Mikhailov / The Loop-Maple Trail heading up from Rainy Pass area of North Cascades Scenic Highway, above the tree line, with the islets of sub alpine firs and larches, North Cascades National Park Cascade Range,...

Konstantin Mikhailov / The rocky highlands of North Cascades Range above the tree line in clouds, on Maple-Loop Trail in Rainy Pass area, North Cascades National Park, Cascade Range, Washington, October 2009.

Mark Hamblin / 2020VISION / Trail through Abernethy Forest NNR. Cairngorms National Park, Scotland, UK, June 2011.

Kirkendall-Spring / Western gulls (Larus occidentalis) nesting along the trail across East Anacapa Island with with East Anacapa Island lighthouse in background, Channel Islands National Park, California, USA, April 2011...

Roland Seitre / Pepper Trail, ornithologist, examining dead bird at the National Fish and Wildlife Forensics Laboratory, Ashland, Oregon, USA

Gerrit Vyn / Women hiking in the North Cascades, Okanogan National Forest, Washington, USA, 2011

Nick Turner / Winter countryside scene after snowfall from the Cotswold Way National Trail, Coaley Peak, Gloucestershire, UK, January 2010.

Nick Turner / Cotswold Way National Trail waymarker information sign and gate covered in snow, Coaly Peak, Gloucestershire, UK, January 2010.

Nick Turner / Cotswold Way National Trail information waymarker sign covered in snow, Coaly Peak, Gloucestershire, UK, January 2010.

Nick Turner / Waymarker information sign at Durdle Door on the South West Coast Path National Trail, Dorset, UK, May 2009.

Nick Turner / Family walking up steps from Durdle Door Beach onto the South West Coast Path National Trail, Dorset, UK, May 2009.

Nick Turner / Waymarker information sign at Durdle Door on the South West Coast Path National Trail, with coastline in the background, Dorset, UK, May 2009.

Nick Turner / Waymarker information sign at Durdle Door on the South West Coast Path National Trail, Dorset, UK, May 2009.

Nick Turner / Family walking on the South West Coast Path National Trail near Durdle Door, Dorset, UK, May 2009.

Nick Turner / Walkers on the South West Coast Path National Trail near Durdle Door, Dorset, UK, May 2009.

Nick Turner / Family walking on the South West Coast Path National Trail near Durdle Door, Dorset, UK, May 2009.

Nick Turner / Walkers on the South West Coast Path National Trail near Durdle Door, Dorset, UK, May 2009.

Nick Turner / Walkers on the South West Coast Path National Trail near Durdle Door, Dorset, UK, May 2009.

Nick Turner / South West Coast Path National Trail waymarker information sign, near Durdle Door, Dorset, UK, May 2009.

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

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

Konstantin Mikhailov / Mount McKinley from the Bar Trail, Wonder Lake camp area, Denali National Park, Alaska, USA, September 2009

Konstantin Mikhailov / Mount McKinley (Alaska Range) seen from the Bar Trail, Wonder Lake camp area, Denali National Park, Alaska, USA, September 2009

Konrad Wothe / Northern goldenrod (Solidago multiradiata) in flower on Burroughs Mountain Trail, Mount Rainier National park, Washington, USA, August

Inaki Relanzon / Remarkable Rocks, long exposure star trail shot at night, Flinders Chase National Park, Kangaroo Island, South Australia State, Australia, September 2011.

Kirkendall-Spring / Person hiking along the Burroughs Loop Trail near Sunrise in Mount Rainier National Park, Washington, USA, August 2009

Kirkendall-Spring / Hiker walking along trail on Mazama Ridge, passing through a field of flowers with the Tatoosh Range in the distance, Mount Rainier National Park, Washington, USA, August 2009

Kirkendall-Spring / Hiker on the Grey Butte Trail with Mount Shasta in the distance, Shasta-Trinity National Forest, California, USA, September 2010, Model released.

Kirkendall-Spring / Hiker on the Grey Butte Trail with Mount Shasta in the distance, Shasta-Trinity National Forest, California, USA, September 2010, Model released.

Kirkendall-Spring / Mount Rainier viewed from the Mazama Ridge Trail in Mount Rainier National Park, Washington, USA, August 2010

Kirkendall-Spring / Skyline Trail asending Mazama ridge through wildflower meadows, Mount Rainier National Park, Washington, USA, August 2010

Bryan and Cherry Alexander / Walkers descending along the trail between Antarctic Beech and Bahia Lapataia, Tierra del Fuego National Park, Argentina, October 2006.

Peter Cairns / 2020VISION / Signpost to Nature Trail through The National Forest, Moira, Derbyshire, UK, November 2011

Konstantin Mikhailov / Denali National Park, the Wonder Lake camp area. A view to Mt. McKinly (Alaska Range) across swampy landscape with White and Black spruces on the Bar Trail. Moose and Spruce Grouse habitat. North Ame...