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)

HIV-positive 71-year-old Sylverio Hachiploa (R) talks with caregivers Glandwel Muleya (L) and Sister Abigail Mwaka Mazuba (C) in his thatched hut during a visit by a home-based care team in the village of Nedwmba, south of the Chikuni Mission in the south of Zambia February 23, 2015. The caregivers in the Jesuit-run home-based care project at the Chikuni Mission run a capacity-building and empowerment project at the household level, offering training and assistance in crop-growing and animal rearing, as well as offering companionship, pastoral care and monitoring of the antiretroviral treatment compliance of HIV-AIDS patients. (Photo by Darrin Zammit Lupi/Reuters)

A young man with an amputated leg poses for a photograph standing by his broken artificial limb in the rebel-controlled area of Maaret al-Numan town in Idlib province, Syria March 20, 2016. Two university students forced to interrupt their studies have learnt to make and fit hundreds of new limbs in the past four years in opposition-held areas of Syria. A mobile clinic operating from a truck has gone some way to improve access to treatment. While most patients are between 15 and 45, the clinic also helps children and the elderly with replacement limbs. (Photo by Khalil Ashawi/Reuters)

Hot air balloons take to the skies over Bristol city centre on August 6, 2012 in Bristol, England. The early morning flight of over twenty balloons over the city was organised as a curtain raiser for the four-day Bristol International Balloon Fiesta which starts on Thursday. Now in its 34th year, the Bristol International Balloon Fiesta is Europe's largest annual hot air balloon event in the city that is seen by many balloonists as the home of modern ballooning. (Photo by Matt Cardy)

Hot air balloons fly over Igualada during an early flight as part of the European Balloon Festival on July 10, 2014 in Igualada, Spain. The early morning flight of over 30 balloons was shorter than expected due to windy weather. This flight is organised as a curtain raiser for the four-day European Balloon Festival. Now is the 18th year of the most important hot air Balloon event in Spain and one of the biggest in Europe. (Photo by David Ramos/Getty Images)

Women stage a topless protest in Buenos Aires, Argentina on February 7, 2017. Activists take to streets of downtown after three women had been topless sunbathing on Necochea, near Buenos Aires, when they were approached by officers that told to cover their breasts. The sunbathers and officers argue, with the girls insisting going topless is not illegal, but the police insist they are offending the local culture. This protest is in support of the three women of Necochea. (Photo by Claudio Santisteban/ZUMA Wire/Rex Features/Shutterstock)

In this May 12, 2017 photo, Pupy, an African elephant, stands in the doorway of his enclosure at the former city zoo now known as Eco Parque in Buenos Aires, Argentina. A year ago the 140-year old Buenos Aires zoo closed its doors and was transformed into a park. The first director decided that the animals should be housed in buildings that reflected their countries of origin. A replica of a Hindu temple was built for the Asian elephants. (Photo by Natacha Pisarenko/AP Photo)

Visitors looks at the flying car Pegasus 1, built by French entrepreneur Jerome Dauffy at Paris Air Show, in Le Bourget, east of Paris, France, Tuesday, June 20, 2017. Aviation professionals and spectators are expected at this week's Paris Air Show, coming in, in a thousands from around the world to make business deals. (Photo by Michel Euler/AP Photo)