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)

Ukrainian President Petro Poroshenko gestures during a news conference in Kiev, Ukraine, June 5, 2015. REUTERS/Mykhailo Markiv/Ukrainian Presidential Press Service/Pool

Mayon Volcano spews ash and lava in the town of Daraga, Albay province, Philippines, 25 January 2018. Mayon volcano located in eastern Philippines and active over the last 10 days spewed fresh lava and ash while the number of evacuees exceeded 60 thousand in the face of the threat of an even more potent explosion. The Philippines, which currently has 23 active volcanoes, is situated on the so-called 'Pacific Ring of Fire', an area known for its intense seismic activity which extends from the west coast of the American continent to New Zealand, Japan, the Philippines and Indonesia. (Photo by Francis R. Malasig/EPA/EFE)

Labourers pour molten iron into a container at a foundry in Xiangfan, Hubei province in this July 2, 2010 file photo. Iron ore is enjoying its biggest rally in years, outpacing copper and oil so far in 2016, but still weak forward prices show it may be tough to stretch the bullish outlook. Improving steel prices in top market China are helping fuel iron ore's climb as producers gear up for a seasonal uptick in demand. Yet there is no shortage of doubters who see gains in the bulk commodity as fleeting given a large glut and challenges for China's economy. (Photo by Reuters/Stringer)

Inflatable dolls in the shape of ducks are seen in front of the National Congress during a protest against tax increases in Brasilia, Brazil, March 29, 2016. The campaign “I will not pay the Duck” is organized by the Federation of Industries of Sao Paulo (FIESP) and uses the duck symbol in reference to industries that pay high taxes. (Photo by Gregg Newton/Reuters)

Inmates are seen at the transgender gallery in La Joya prison on the outskirts of Panama City, Panama February 3, 2016. Inmates of La Joya prison on the outskirts of Panama City are housed in makeshift cells amid heavy overcrowding, living in grimy conditions and with limited medical attention. Many prisoners in the Central American nation languish for years without being sentenced. (Photo by Carlos Jasso/Reuters)

In this May 3, 2016 photo provided by the New York State Department of Environmental Conservation, a deer with its head caught in the globe from a lighting fixture over its head stands in the woods in Centereach, N.Y. The deer was able to extricate itself with the help of Environmental Conservation Officer, Jeff Hull. Hull wrestled with the deer for a while and the globe shook free in the process. (Photo by New York State Department of Environmental Conservation via AP Photo)

In this timed-exposure night photo taken early on February 12, 2017, Mount Sinabung volcano spews reddish smoke and ash, as seen from the Karo district in North Sumatra province. Activity levels have increased in the past week, with Sinabung shooting hot ash clouds into the sky dozens of times, according to the local volcano monitoring agency. (Photo by AFP Photo/Stringer)