Two men standing on a high catwalk, surveying the construction of the Brooklyn Bridge, with Manhattan in the background, New York City, 1877. (Photo by Museum of the City of New York/Archive Photos/Getty Images)

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)

The 3D street painting “Crevasse” by artist Edgar Mueller is seen in this undated picture during the “Festival of culture”, 2008 in Dun Laoghaire, Irland. Edgar Mueller put a part of the eastern Pier into the ice age. This project has been supported by the Goethe Institution Germany. (Photo by Edgar Mueller/Getty Images)

Carlos Melendez prepares to feed his pet squirrel “Colita” in downtown San Salvador January 29, 2015. (Photo by Jose Cabezas/Reuters)

Steam emerges from a cooling tower of the nuclear power plant Leibstadt near Leibstadt, Switzerland, November 18, 2014. (Photo by Arnd Wiegmann/Reuters)

A picture taken on October 17, 2014 in Vevey shows a giant fork designed by Switzerland's artist Jean-Pierre Zaugg to commemorate Nestle's Alimentarium Food Museum 10th anniversary. World's biggest food company, Swiss Nestle Group announced results sales down by 3.1% for the first nine months of 2014 to 66.2 billion Swiss francs (55.1 billion euros). (Photo by Fabrice Coffrini/AFP Photo)

A stewardess holding a lightsabre poses for photos with visitors during a tour of the Star Wars themed All Nippon Airways ANA R2D2 Boeing 787 Dreamliner aircraft at Singapore's Changi Airport November 12, 2015. The aircraft was opened to the media on Thursday as it makes its first Asian stop outside Japan. (Photo by Edgar Su/Reuters)

The Mayon volcano continues to erupt as the sun sets behind Legazpi city, Thursday, January 25, 2018 in Albay province, roughly 340 kilometers, (200 miles) southeast of Manila, Philippines. (Photo by Bullit Marquez/AP Photo)