Parson's chameleon (Calumma parsonii) in Ranomafana National Park, Madagascar

Tourists view Dettifoss waterfall in Northern Iceland.

Children photographing wildlife from the open roof of a safari vehicle in the Masai Mara National Reserve, Kenya.

Southeast Madagascar near Kianjavato village, showing a lone figure in terraced rice paddies surrounded by rainforest and traveller's palms.

Close-up of the head of a male Parson's chameleon (Calumma parsonii) in Ranomafana National Park, Madagascar

Young ring-tailed lemur looking down from a tree at Anja Community Reserve in the Central Highlands of Madagascar, near Ambalavao

Ring-tailed lemur in Namaza Gorge, Isalo National Park, Madagascar

Scale-like leaves of the octopus tree (Didierea madagascariensis), Ifaty Spiny Forest in Southwest Madagascar

Emerald green giant pill millipede (zoosphaerium neptunus) swarm on the rainforest floor of Andasibe-Mantadia National Park, Madagascar

Parson's chameleon (Calumma parsonii) in Andasibe-Mantadia National Park, Madagascar

Interior of Loggers Lodge, a luxury retreat near Lulea in Swedish Lapland, showing the large central wood-burning stove

The Cabin (designed by architects Cyren & Cyren) suspended in pine trees at the Treehotel near Lulea, Lapland, Sweden.

The Mirrorcube or 'Cube' (designed by architects Tham & Videgard) suspended in pine trees at the Treehotel near Lulea, Lapland, Sweden.

Aurora borealis, the northern lights photographed during the polar night above the mountains near Longyearbyen, Spitsbergen, Svalbard

Sami storyteller at Malangen Resort near Tromso in northern Norway, walking through winter woodland with an oil lamp

River flowing through autumn woodland, Kennall Vale Nature Reserve, Cornwall, England

Tunnel of trees leading to Halnakar Windmill, West Sussex, England

Rainbow over the Great Langdale Valley viewed from Blea Tarn, with the Pike of Stickle mountain in the background, Lake District, Cumbria, England

Broadway Tower, an 18th-century folly in the Cotswolds designed by Capability Brown, Worcestershire, England

The water mill in the Cotswold village of Lower Slaughter, photographed during spring when marsh marigolds are in flower along the River Eye, Gloucestershire, England

Mist rising above the River Windrush at sunrise, with the church at Burford in the background, Oxfordshire Cotswolds, England

Wave breaking off Cape Cornwall, with the Brisons islands offshore, Cornwall, England

Female white-tailed ptarmigan in summer plumage at Lake Louise, Banff National Park, Alberta, Canada

Bald eagle soaring with wings outstretched against a clear blue sky, Vancouver Island, British Columbia, Canada

A herd of Burchell's (or plains) zebra kicking up dust during the late afternoon in Limpopo-Lipadi Wilderness Reserve, Botswana

Baobab trees, Kubu Island, Makgadikgadi Pans, Botswana

Oak Beach near Port Douglas on the tropical North Queensland Coast, Australia, photographed at sunrise from the small headland at the northern end of the beach

Lion at a waterhole, Madikwe Game Reserve, South Africa, illuminated by spotlight shortly after dusk

Oil lamps lighting the path to a tent at Namaqua Flower Beach Camp, Namaqua National Park, Northern Cape, South Africa

Sunset at Slangkop Lighthouse, near Kommetjie and Cape Town, South Africa

African penguins, Boulders Beach, near Simon's Town, Cape Peninsula, South Africa

Detail of the Aboriginal rock art at the Art Gallery in Carnarvon Gorge (Carnarvon National Park, Queensland, Australia) showing a close-up of hand prints produced using the stencil art technique

Eastern grey kangaroo with joey in pouch at Carnarvon National Park, central highlands of Queensland, Australia

A lower set of falls called Litlanesfoss at Hengifoss in the East Fjords region of Iceland cascades through dramatic formations of columnar basalt

Mountains of Iceland's East Fjords reflected in calm water near Djupivogur

Alaska, USA. The Matanuska Glacier viewed from the Glenn Highway to the north of Anchorage, with fireweed (Chamerion angustifolium) growing in the foreground

Alaska, USA, Denali National Park. The 6,194m (20,320ft) peak of Mt McKinley (Denali) rising above the tundra of Denali National Park.

Alaska, USA, Denali National Park. Mt McKinley (Denali) and part of the Alaska Range reflected in Wonder Lake at sunrise, Denali National Park

Simple Italian salad of tomatoes, fresh basil leaves and mozzarella cheese, Umbria, Italy.

Sunflowers in full bloom during August in a field near Perugia, Umbria, Italy

Northern fulmar (Fulmarus glacialis) perched on basalt sea cliffs along the stretch of coast near Hellnar on the Snaefellsnes Peninsula, Iceland

Orcas off the coast of the Snaefellsnes Peninsula, Iceland, with the mountain of Kirkjufell (near Grundarfjordur) in the background, photographed in March

Red fox (Vulpes vulpes) viewed from a hide in the Alutaguse forest, Eastern Estonia

Yellow-billed stork feeding in a backwater of the Rufiji River, Selous Game Reserve, Tanzania

Nile crocodile hiding in vegetation on the banks of the Rufiji River, Selous Game Reserve, Tanzania

Black-bellied bustard, Ruaha National Park, Tanzania. The male of this ground-dwelling species is distinguished from the female by its black throat and belly.

Close up of moss and berries in coastal tundra, Vesteralen Islands, Norway

Bull African elephants in Tsavo East National Park, Kenya.

Boy on safari with buffalo skull at one of the entrances to Tsavo National Park, Kenya.

White-backed vulture, Masai Mara National Reserve, Kenya.

White-backed vulture, Masai Mara National Reserve, Kenya.

Girl learning to scuba dive in a swimming pool, Leopard Beach Resort, Diani Beach, Kenya.

Girl next to safari campfire in Elerai Conservancy, near Amboseli National Park, Kenya.

Andriamamovoka Waterfall (Chute Andriamamovoka) on the Namorona River in Madagascar's Ranomafana National Park â€" showing the cascade in full flow after heavy rainfall in December.

Hands cupping bright red seeds of a rainforest tree which will be used to grow seedlings at Kianjavato Ahmanson Field Station, Madagascar, for reforestation work in areas of slash and burn.

Greater bamboo lemur chewing bamboo stem in Ranomafana National Park, Madagascar

Madagascar golden orb weaver spider (Nephila inaurata madagascariensis) â€" also known as red-legged orb weaver, golden silk spider or palm spider â€" on its web in Ranomafana National Park.

Madagascar yellow-spotted tree frog (Heterixalus alboguttatus) resting during the day on a leaf in Ranomafana National Park.

Madagascar yellow-spotted tree frog (Heterixalus alboguttatus) resting during the day on a leaf in Ranomafana National Park.

Young woman weaving silk (from wild-harvested silk worm cocoons) on a wooden loom in the village of Soatanana, Madagascar

Strands of naturally-dyed silk (from wild-harvested silk worm cocoons) hanging up to dry at a silk-weaving co-operative in the village of Soatanana, Madagascar

Soatanana, Madagascar â€" wild-harvested silk worm cocoons are boiled in an iron pot before being dried and hand-spun into threads of silk at a women's silk-weaving co-operative

Glowing at sunset, thunderclouds build over Madagascar's Ranomafana National Park

The Three Sisters â€" Granite monliths at Anja Community Reserve in the Central Highlands of Madagascar, near Ambalavao

Young ring-tailed lemur riding on its parent's back at Anja Community Reserve in the Central Highlands of Madagascar, near Ambalavao

Forest growing beneath the Three Sisters â€" Granite monliths at Anja Community Reserve in the Central Highlands of Madagascar, near Ambalavao

A lone cyclist (carrying bags of charcoal) in front of the Bishop's Hat â€" a conspicuous granite mountain visible from the road between Isalo and Fianarantsoa, Madagascar

Zebu cart in the Central Highlands of Madagascar

Isalo National Park, Madagascar â€" early evening sunlight lights up the arid sandstone massif, viewed from Isalo Rock Lodge

Ring-tailed lemur in Namaza Gorge, Isalo National Park, Madagascar

Family of ring-tailed lemurs in Namaza Gorge, Isalo National Park, Madagascar

View from the Namaza Trail, desending into the gorge of Isalo National Park, Madagascar

View from the Namaza Trail, desending into the gorge of Isalo National Park, Madagascar

Landscape of the of Isalo National Park, Madagascar

View from the Namaza Trail, desending into the gorge of Isalo National Park, Madagascar

Hubbard’s sportive lemur â€" a nocturnal species â€" resting in a tree hole, Zombitse-Vohibasia National Park, Madagascar

Lone woman carrying a child along the RN7 highway next to a lone baobab, near Zombitse National Park, Madagascar

Baobab (Adansonia za) in the Ifaty Spiny Forest of Southwest Madagascar, near Toliara

Radiated tortoise (Astrochelys radiata), Ifaty Spiny Forest, Southwest Madagascar

Village and farmland bordering the Spiny Forest of Southwest Madagascar, with baobabs in the background