Selfie picture shows Swiss pioneer Bertrand Piccard during the last leg of the round the world trip with Solar Impulse 2 over the Arab peninsula July 25, 2016. (Photo by Jean Revillard/Bertrand Piccard/Reuters/SI2)

Rays from the rising sun shine through the foliage of trees as fog covers the ground near the Guckler Karoly Observatory in Budapest, Hungary, 02 January 2017. (Photo by Balazs Mohai/EPA)

In this photograph taken on February 18, 2016, Pakistani children ride on swings in the predominantly Pashtun Korangi District of Karachi. In a rundown district of Karachi, Rabia balks at a neighbour's proposal to vaccinate her children, demonstrating one of the biggest hurdles to eradicating polio in Pakistan by the end of the year: confused and frightened parents. (Photo by Asif Hassan/AFP Photo)

A boy walks past boats docked at the entrance gate of the fishermen's village in the El Max area of the Mediterranean city of Alexandria September 12, 2014. El Max, where hundreds of boats dart through the canals, has been called the “Venice of Egypt” for its waterways and relaxed atmosphere. Its fishermen, however, worry about how they will make ends meet on meagre earnings they say are being reduced further by polluted waters that are making fishing more difficult. While the government has tried to fix the state's bloated finances by cutting subsidies and reining in spending, some argue the reforms hurt Egypt's most vulnerable who have long relied on a generous system of fuel and food subsidies to supplement low incomes. (Photo by Amr Abdallah Dalsh/Reuters)

The setting sun illuminates the sky behind wind turbines of a wind park near Neusiedl am See, December 22, 2014. (Photo by Heinz-Peter Bader/Reuters)

A reporter takes pictures of a soldier during the annual Han Kuang military exercise in Kinmen, Taiwan, September 7, 2015. Rustic Kinmen, with a population of less than 129,000, is a half-hour ferry ride to China, but it takes an hour to fly to major Taiwan cities. Just off its shores, glass-walled high-rises wink seductively from the booming mainland port of Xiamen in one of China's most prosperous provinces. (Photo by Pichi Chuang/Reuters)

The six-months-old female koala cub holds on to the back of zoo keeper Lena at the zoo in Duisburg, Germany, 23 October 2015. The yet unnamed baby weighs 580 grams. (Photo by Roland Weihrauch/EPA)

Members of the media film as a ranger performs a post mortem on the carcass of a rhino after it was killed for its horn by poachers at the Kruger national park in Mpumalanga province August 27, 2014. Rhino poachers in South Africa now risk giving themselves away when they shoot thanks to a high-tech, gunfire-detection system being piloted in the country's flagship Kruger National Park. The stakes are high, for rhinos are being slain in escalating numbers for their prized horns, alarming both conservationists and the government since wildlife in South Africa is an important tourist draw. (Photo by Siphiwe Sibeko/Reuters)