A handout photograph provided by Brian Kubicki of Costa Rican Amphibian Research Center on 26 April 2016 shows a “Crystal frog”, Hyalinobatrachium dianae (H. diane). This frog was discovered by US biologist Brian Kubicki and Costa Ricans Stanley Salazar and Robert Puschendorf in a rainy forest of Costa Rican caribbean after 40 years without notice of any new example of this kind. (Photo by Brian Kubicki/EPA/Costa Rican Amphibian Research Center)

These adrenaline-junkie climbers go to extraordinary lengths, and heights, to take a selfie. Hundreds of metres above the ground, the climbers risk their life and liberty as they scale huge structures and photograph the results. Known as urban exploration, the aim is to find extremely high and almost inaccessible city buildings and reach their dizzying summits. (Photo by Yaroslav Segeda/Solent News)

“Environmental Migrants: The Last Illusion” by photographer Alessandro Grassani, documents the life of people in Kenya, Mongolia and Bangladesh who migrate to escape environmental stresses to the city of their own countries in hopes for a better life. Here: Asia, Mongolia, March 27, 2011. A view of Ulaan Baator over the shoulder of a slumbering drunk. Alcoholism is a huge problem in the city, home to almost half of Mongolia's people. The capital's population has doubled in the past two years. High levels of unemployment and poverty await herders who abandon rural areas and arrive in the city, illiterate and untrained in any skills necessary for urban jobs. (Photo by Alessandro Grassani)

in Qayyarah, about 31 miles (50 km) south of Mosul, Iraq, Sunday, October 23, 2016.in Qayyarah, some 50 kilometers south of Mosul, Iraq, Sunday, Oct. 23, 2016. Islamic State fighters torched a sulfur plant south of Mosul, sending a cloud of toxic fumes into the air that mingled with oil wells the militants had lit on fire to create a smoke screen. (Photo by Marko Drobnjakovic/AP Photo)

Iraqi army soldiers warm themselves next to a fire near the Qayara air base, south of Mosul, Iraq, Tuesday, November 1, 2016. The U.N. human rights office is lauding efforts by the U.S.-led coalition in the battle against the Islamic State group in Mosul. The office in Geneva says coalition flights over Iraq have largely succeeded in preventing IS from bringing in 25,000 more civilians to the city center, where the militant group has been using people as human shields as Iraqi forces advance on Mosul. (Photo by Felipe Dana/AP Photo)

German police officers take pictures as fireworks explode next to the Quadriga sculpture atop the Brandenburg gate during New Year celebrations in Berlin, Germany, January 1, 2017. (Photo by Fabrizio Bensch/Reuters)

A horse- drawn carriage rides along the race course through the Thuringian Forest in Oberhof, Germany, 05 January 2017. Winter found its way to Saxony, Saxony- Anhalt, and Thuringia. In some regions it can get as low as negative 20 degrees overnight. (Photo by Martin Schutt/Zentralbild/DPA)

Indian tourists walks during heavy snowfall by Dal Lake in Srinagar on January 6, 2017. The sub-zero temperatures has frozen many water bodies in Kashmir and even drinking water taps have frozen at some places. (Photo by Tauseef Mustafa/AFP Photo)