Lindsay Heimbach goes airborne while sledding down a hill on Mt. Lemmon December 27, 2008. (Photo by James Gregg/Arizona Daily Star)

Cara Delevingne and Kate Moss attend the Burberry Prorsum show during London Fashion Week Spring Summer 2015 on September 15, 2014 in London, England. (Photo by Anthony Harvey/Getty Images)

Two young boys kneel on stools on either side of a round table as one uses a match to this the other's cigarette, November 12, 1928. (Photo by FPG/Getty Images)

A boy looks at a six-metre tall luminescent puppet, operated by ten performers, during a preview of Vivid Sydney, promoted as the world's largest festival of light, music and ideas, in Sydney, Australia on May 23, 2018. “Vivid” is a major outdoor cultural event featuring light installations and projections with the annual event this year running from May 25 to June 16, 2018. (Photo by David Gray/Reuters)

“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)

A one and a half months old baby elephant stands close to its mother at Chitwan National Park in Chitwan, south of Kathmandu December 30, 2014. (Photo by Navesh Chitrakar/Reuters)

Local villagers ride a local coal powered steam train on March 27, 2015 at a station in the town of Shixi , Sichuan Province, in Southern China. While China boasts the world's most extensive high-speed rail infrastructure with over 16,000 kilometers of track, the Shixi-Bagou railway is still a primary connection for local villagers between towns and is kept alive by tourist cars carrying passengers for ten times the price. The rail line came into service in the late 1950s and the train was initially used to transport coal from a now-shuttered mine before passenger carriages were added. (Photo by Kevin Frayer/Getty Images)

Locals sort through garbage at a roadside dump in New Delhi on January 10, 2017 The national capital has been reeling under tonnes of garbage after sanitation workers went on a strike demanding payment of pending salaries. (Photo by Chandan Khanna/AFP Photo)