A propaganda troupe perform a flag- waving routine outside the central railway station in Pyongyang, North Korea on September 27, 2017. (Photo by Ed Jones/AFP Photo)

People feed the birds in Battery Park in the Manhattan borough of New York, December 18, 2014. Hart has been feeding the birds three times a week for the last three years. (Photo by Carlo Allegri/Reuters)

Walkers cross the river Waalbrug during the first day of the 98th annual four-days walking event, the “Vierdaagse” in Nijmegen, Netherlands, July 15, 2014. The “Nijmeegse Vierdaagse” is an annual public four-day field march which is held since 1909 in the third week of July. (Photo by Erik van 't Wout/EPA)

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)

Members of a cheerleading team warm- up during the Russian Cheerleading Championship of students in Moscow on November 20, 2016. (Photo by Natalia Kolesnikova/AFP Photo)

A reveller poses for a photo during the LGBT Pride Parade in Copacabana beach in Rio de Janeiro, Brazil, November 15, 2015. (Photo by Pilar Olivares/Reuters)

A Sri Lankan activist, who wrapped himself with fire crackers, walks in Colombo on July 23, 2014 to symbolically demonstrate against people burned during Anti-Tamil riots on the island thirty-one years ago. Official accounts placed the death toll at 400 while human rights activists put the toll at thousands. (Photo by Ishara S.Kodikara/AFP Photo)

Growing cities, overuse of fertilizers and factory wastewater have degraded China's water supplies to the extent that half the nation's rivers and lakes are severely polluted. China aims to spend $850 billion to improve filthy water supplies over the next decade, but even such huge outlays may do little to reverse damage caused by decades of pollution and overuse in Beijing's push for rapid economic growth. Photo: Fishermen row a boat in the algae-filled Chaohu Lake in Hefei, Anhui province, June 19, 2009. (Photo by Jianan Yu/Reuters)