A bear that wandered into a University of Colorado Boulder dorm complex falls from a tree after being tranquilized by Colorado wildlife officials on April 26, 2012. Colorado wildlife official Jennifer Churchill said that the 200-pound male bear was tagged and relocated to a remote Rocky Mountain area. The bear was hit by two cars on May 3 and died. (Photo by Andy Duann)

An artist's impression of a growing supermassive black hole located in the early Universe is seen in this NASA handout illustration released on June 15, 2011. Using the deepest X-ray image ever taken, astronomers found the first direct evidence that massive black holes were common in the early universe. This discovery from NASA's Chandra X-Ray Observatory shows that very young black holes grew more aggressively than previously thought, in tandem with the growth of their host galaxies. (Photo by Reuters/NASA/Chandra X-Ray Observatory/A.Hobart)

Homeless man Alonzo Harrison, 47, takes a nap on a bench at Pershing Square decorated with Christmas lights in the background on Monday, December 4, 2017, in Los Angeles. A homeless crisis of unprecedented proportions is rocking the West Coast, and its victims are being left behind by the very things that mark the region's success: soaring housing costs, rock-bottom vacancy rates and a roaring economy that waits for no one. (Photo by Jae C. Hong/AP 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)

A woman carries a bag with a baby while being evacuated by local emergencies ministry members in Donetsk, Ukraine, February 2, 2017. (Photo by Alexander Ermochenko/Reuters)

A boy and a woman run across a railway track as a train approaches in Chengdu, Sichuan province, China, October 8, 2015. Many residents disregard sign prohibiting this kind of illegal crossing and choose to do so to save time, local media reported. (Photo by Hao Fei/Reuters/Western China Metropolis Daily)

Muslim girls are seen after prayers, in Lagos, Nigeria, Friday, July 31, 2020. Small groups of pilgrims performed one of the final rites of the Islamic hajj on Friday as Muslims worldwide marked the start of the Eid al-Adha holiday amid a global pandemic that has impacted nearly every aspect of this year's pilgrimage and celebrations. The last days of hajj coincide with the four-day Eid al-Adha, or “Feast of Sacrifice”, in which Muslims slaughter livestock and distribute the meat to the poor. (Photo by Sunday Alamba/AP Photo)

The provincial highest chimney collapses as it is demolished by explosives in Shenyang, Liaoning province, April 28, 2014. The 150-metre-high chimney used to be part of a local heating factory, according to local media. (Photo by Sheng Li/Reuters)