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 motorcyclist performs the superman stunt on a highway in Kuala Lumpur, Malaysia, September 14, 2014. Crowds of small motorbikes ridden by racers – or “Mat Rempit”, as they are known in Malaysian slang – face off in impromptu races in the Malaysian capital after dark. The decades-old culture is widely frowned upon by largely conservative Malaysians, who fear its potential to encourage gambling, drug abuse, snatch thefts and sexual promiscuity. (Photo by Olivia Harris/Reuters)

A freighter trapped in ice is shown in this aerial photo near Whitefish Bay on Lake Superior northwest of Sault Ste. Marie, Ontario April 7, 2015. The biggest ice cover on the Great Lakes in decades is backing up shipments of everything from Canadian grain to U.S. iron and steel in one of North America's most important economic regions. (Photo by Kenneth Armstrong/Reuters)

A man holds a metal bar as a weapon during a training day for former soldiers and volunteers train in a makeshift camp in the outskirts of Port-au-Prince, Haiti, October 28, 2015. Haiti disbanded its abusive armed forces two decades ago but uniformed veterans and young recruits are resurfacing to add another destabilising factor to the volatile Caribbean nation already dealing with a political vacuum. (Photo by Andres Martinez Casares/Reuters)

Elephants are paraded in front of the Grand Palace to pay respects to the late Thai King Bhumibol Adulyadej in Bangkok on October 8, 2016. Thailand' s King Bhumibol Adulyadej died at the age of 88 on October 13 after years of ill health, ending a seven- decade reign and leaving the politically divided nation without its key pillar of unity. (Photo by Lillian Suwanrumpha/AFP Photo)

South Korean college students wearing masks hold up candles as they march after a rally calling for South Korean President Park Geun-hye to step down in Seoul, South Korea, Saturday, November 12, 2016. Hundreds of thousands of people flooded Seoul's streets on Saturday demanding the resignation of Park amid an explosive political scandal, in what may be South Korea's largest protest since it shook off dictatorship three decades ago. (Photo by Lee Jin-man/AP Photo)

Thai Princess Bajrakitiyabha (R) and Princess Sirivannavari Nariratana take part in the funeral procession for the late Thai king Bhumibol Adulyadej in Bangkok on October 26, 2017 A sea of black- clad mourners massed across Bangkok' s historic heart early on October 26 as funeral rituals began for King Bhumibol Adulyadej, a revered monarch whose passing after a seven- decade reign has left Thailand bereft of its only unifying figure. (Photo by Damir Sagolj/Reuters)

In this photograph taken on October 27, 2017 an Afghan woman collects saffron flowers after picking them in a field on the outskirt of Herat For years, Afghanistan has tried to give farmers alternatives such as fruit crops and saffron to wean them away from poppy farming – the lifeblood of the Taliban insurgency. International donors have splurged billions of dollars on counter- narcotics efforts in Afghanistan over the past decade, including efforts to encourage farmers to switch to other cash crops such as saffron. But those efforts have shown little results. (Photo by Hoshang Hashimi/AFP Photo)