Ingots of 99.99 percent pure silver are cast at the Krastsvetmet Krasnoyarsk non-ferrous metals plant in the Siberian city of Krasnoyarsk, Russia, June 5, 2015. Krastsvetmet is one of the world's largest players in the precious metals industry. REUTERS/Ilya Naymushin

A tea garden worker plucks tea leaves inside Aideobarie Tea Estate in Jorhat in Assam, India, April 21, 2015. Unrest is brewing among Assam's so-called Tea Tribes as changing weather patterns upset the economics of the industry. Scientists say climate change is to blame for uneven rainfall that is cutting yields and lifting costs for tea firms. (Photo by Ahmad Masood/Reuters)

James Spears takes his 1964 German built Amphicar for a drive on Lake Mead in Nevada May 6, 2015. Its a journey many drivers dream of, rather than travelling round a lake simply driving through it. But for James Spears it may be time to make the most of the waters in Lake Mead in Nevada, as water levels are plunging as California struggles to cope with a fourthsuccessive year of droughts. (Photo by Mike Blake/Reuters)

Burundian refugees gather on the shores of Lake Tanganyika in Kagunga village in Kigoma region in western Tanzania with their belongings, as they wait for MV Liemba to transport them to Kigoma township, May 17, 2015. Burundi's embattled President Pierre Nkurunziza sacked his defense and foreign ministers on Monday, five days after surviving an attempted coup by generals opposed to his bid for a third term in office. (Photo by Thomas Mukoya/Reuters)

A farmer uses a GoPro as he takes a picture of his carabao kneeling during the annual Carabao Festival in Pulilan, Bulacan in northern Philippines May 14, 2015. Water buffalos, locally known as carabaos, are led during a parade in the streets of the town to honour its patron saint San isidro Labrador, and carabaos will kneel in front of the church to give thanks for a year-long bountiful harvest. (Photo by Lorgina Minguito/Reuters)

A florist waits for customers at the Piedra Liza flower market in Lima April 29, 2015. The market sells flowers that come from all over Peru. Peru is home to more than 25,000 varieties of flowering plants like geraniums, carnations, roses, hydrangeas and jasmine, according to local media. (Photo by Mariana Bazo/Reuters)

In this photo taken on Saturday, May 16, 2015, Snoek fish with salt on them after they were cleaned in Lambert's Bay, South Africa. The boats line up along the jetty, bobbing in the cold south Atlantic waters, bringing in the day's catch in the early afternoon. The long silver snoek fish is one of South Africa's traditional foods, and a main source of income for the town of Lambert's Bay. (Photo by Schalk van Zuydam/AP Photo)

Men wearing costume of traditional firefighters perform acrobatic stunts atop a bamboo ladder following a memorial service for firefighters at Sensoji temple in Tokyo's downtown of Asakusa May 25, 2015. Hundreds of firefighters in traditional costume gathered on Monday for the memorial service for firefighters who were killed performing their duties during the past 300 years. (Photo by Issei Kato/Reuters)