Gas-masked men of the British Machine Gun Corps with a Vickers machine gun during the first battle of the Somme, 1916. (Photo by General Photographic Agency/Getty Images)

Commuters hang off a local passenger train in the morning in Colombo, Sri Lanka September 8, 2016. (Photo by Dinuka Liyanawatte/Reuters)

A protester is taken to hospital after he was wounded by birdshot during a street protest after it was announced that the runoff Jan. 24, presidential election had been postponed, in Port-au-Prince, Haiti, Friday, January 22, 2016. The Provisional Electoral Council in Haiti has postponed the election amid escalating protests by the opposition, which claims the first round was marred by fraud in favor of a government-backed candidate. (Photo by Dieu Nalio Chery/AP Photo)

This file photo provided on Sunday February 15, 2015 by the Syrian anti-government activist group Aleppo Media Center (AMC), which has been authenticated based on its contents and other AP reporting, shows Syrian rebels firing locally made shells against the Syrian government forces, in Aleppo, Syria. (Photo by AP Photo/Aleppo Media Center)

Zulmira Jesus poses for a portrait at a street in Povoa de Agracoes, near Chaves, Portugal April 19, 2016. In the villages of Agracoes and Povoa de Agracoe, the steady drip-drip of emigration has brought down population numbers from more than 50 residents to fewer than a dozen each. These remaining villagers share the same glum acceptance that, after they have gone, their villages will die out too. It is the same desolate picture in scores of other backwater settlements in Portugal's interior, north to south. (Photo by Rafael Marchante/Reuters)

The sun rises beside St Mary's Lighthouse in Whitley Bay, Tyne and Wear, as the unseasonably cool weather continues on Thursday, April 28, 2016. (Photo by Owen Humphreys/PA Wire)

An internally displaced Afghan girl holds a child at a refugee camp in Kabul, Afghanistan May 31, 2016. (Photo by Mohammad Ismail/Reuters)

Shortlisted: Pooyan Shadpoor, Houcheraghi. While walking along the shore of Larak, Iran – an island in the Persian Gulf – Shadpoor came across this luminous scene. The “magical lights of (the) plankton ... enchanted me so that I snapped the shot”, he writes. (Photo by Pooyan Shadpoor/2016 EPOTY)