Doug Perrine / Silhouette of Blacktip shark patrolling {Carcharhinus limbatus} Walkers Cay, Bahamas, (Non-ex).

Doug Perrine / Caribbean reef sharks {Carcharhinus perezi} Walkers Cay, Bahamas, Caribbean Sea (Non-ex).

Daniel Heuclin / Walkers on the Salar of Atacama, Chile. September 2018.

Chris Gomersall / Walkers on coral sand beach on the isle of Eriskay in the Western Isles, Scotland. July 2017.

Chris Gomersall / Walkers on the isle of Eigg, in the Small Isles, Scotland. July 2017.

Chris Gomersall / Walkers climbing to the Gap among stone cleits on the island of Hirta in the Saint Kilda archipelago, Scotland. June.

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

Ashley Cooper / Walkers silhouhetted on a country lane near Troutbeck, Lake District, England, UK. November 2005

Ashley Cooper / Lateral Moraine with walkers doing the Tour du Mont Blanc. on the side of the rapidly retreating Glacier de Miage below Mont Blanc, Italy, August 2014

Ashley Cooper / Walkers on the Tour Du Mont Blanc share shelter from heavy rain with a goat on the Col Du Bonhomme near Les Contamines, French Alps. France. August 2014

Ashley Cooper / Walkers on the Tour Du Mont Blanc cross a suspension bridge across the meltwater river from the Bionnassay glacier; France. August 2014

Ashley Cooper / Quiet lane in the Hodder Valley in Lancashire, England, UK. This initiative encourages motorists to drive slowly as the road is used by walkers and cyclists.