People walk during a polluted day in Shenyang, Liaoning province, March 31, 2016. (Photo by Reuters/Stringer)

Police in riot gear hold back demonstrators against U.S. Republican presidential candidate Donald Trump outside the Hyatt hotel where Trump is set to speak at the California GOP convention in Burlingame, California, U.S., April 29, 2016. (Photo by Noah Berger/Reuters)

Chieftain Japarupi Waiapi shows a roasted monkey -part of Waiapi's diet, also based in Manioc and fruits- at the reserve in Amapa state in Brazil on October 13, 2017. When Waiapis walks into the Amazon forest surrounding their village, they do not see trees, but a kind of shopping mall providing medicine, food, shelter, tools and weapons all under the eye of multiple spirits. (Photo by Apu Gomes/AFP Photo)

A golden pheasant and squirrels are seen in Lushan County of Pingdingshan City, central China's Henan Province, November 14, 2017. (Photo by Liu Xianguo/Xinhua/Barcroft Images)

A bus goes through a flooded street in Wuhan, Hubei province, China July 6, 2016. (Photo by Reuters/China Daily)

Firefighters of the Texas Canyon Hotshot crew fight the Sand Fire on July 23 2016 near Santa Clarita, California. Fueled by temperatures reaching about 108 degrees fahrenheit, the wildfire began yesterday has grown to 11,000 acres. (Photo by David McNew/AFP Photo)

A Hindu holy man or Sadhu walks back to his ashram after taking a dip at Sangam, confluence of Ganges river, Yamuna river and mythical Saraswati river in Allahabad, India, Thursday, August 4, 2016. (Photo by Rajesh Kumar Singh/AP Photo)

A protester clashes with a police officer in Athens' central Syntagma (Constitution) Square in this June 15, 2011 file photo. Greece triggered the regional financial crisis in 2009 when a far higher budget deficit than previously calculated emerged. The collapse of talks with creditors in Paris last November set off a month-long sequence of events leading to elections this week and proving Greece is still the region's weak link. The vote is expected to be won by Syriza, a far-left party opposed to the bailout, worrying investors and creditors alike. (Photo by Yannis Behrakis/Reuters)