Tourists pose with pigeons in the flooded St. Mark's Square in Venice, on November 7, 2014. The high water, a combination of high tides and a strong Scirocco wind in the Adriatic Sea, stood at 110 centimeters early on November 7. The city has for years been wrestling with the problems posed by the threat of rising sea levels. (Photo by Olivier Morin/AFP Photo)

“The Net thrower”. The fisherman are conducting activities on Situgunung Lake. Photo location: Situgunung lake, Sukabumi, West Java, Indonesia. (Photo and caption by Dody Kusuma/National Geographic Photo Contest)

In this March 13, 2015 photo, Yohan, 4, from left, Cristian, 7, and Angelo, 6, playfully toss coca leaves into the air, singing: “I have a lot of money, look at all the money I have”, in La Mar, province of Ayacucho, Peru. Hauling cocaine out of the remote valley is about the only way to earn decent cash in this region where a farmhand earns less than $10 a day. Beyond extinguishing young lives, the practice has packed Peru's highland prisons with cocaine backpackers while their bosses evade incarceration. (Photo by Rodrigo Abd/AP Photo)

A young girls holds a ballot during the Greek referendum in Athens on July 5, 2015. Greek voters headed to the polls today to vote in a historic, tightly fought referendum on whether to accept worsening austerity in exchange for more bailout funds, in a gamble that could see it crash out of the euro. (Photo by Aris Messinis/AFP Photo)

Britain's Chris Froome, wearing the overall leader's yellow jersey, is followed by Spain's Alberto Losada, Italy's Vincenzo Nibali and Spain's Alejandro Valverde as they speed downhill during the seventeenth stage of the Tour de France cycling race over 161 kilometers (100 miles) with start in Digne-les-Bains and finish in Pra Loup, France, Wednesday, July 22, 2015. (Photo by Christophe Ena/AP Photo)

A woman mourns the loss of her husband, next to a placard which reads “I'm a pusher”, who was shot dead by an unidentified gunman in Manila on July 23, 2016. Philippine President Rodrigo Duterte swept to power in May on a promise to clampdown on drugs, and police have since confirmed killing nearly 200 people in a two-month crime blitz. There has also been a surge in killings by anti-drug vigilantes who leave victims' corpses on city streets wrapped in packaging tape with signs accusing them of being drug dealers. (Photo by Noel Celis/AFP Photo)

Germany's Angelique Kerber reacts after popping a bottle of champagne, a day following her win in the final match at the Australian Open tennis tournament, at the Government House in Melbourne, Australia, January 31, 2016. (Photo by Issei Kato/Reuters)

An undated handout picture made available on 29 April 2016 by the Toronga Zoo shows a baby echidna making a remarkable recovery after being attacked by chickens in a family's backyard at the Taronga Zoo in Sydney, Australia. (Photo by EPA/Taronga Zoo)