BELEM, BRAZIL - JUNE 07:  A worker offloads baskets of acai berry at the historic Ver-o-Peso market at dawn on June 7, 2012 in Belem, Brazil. Belem is considered the entrance gate to the Amazon and for more than 300 years, boats have unloaded their wares from deep in the Amazon at the market. Fishermen and others who make their livelihood on the waters of the Amazon basin face a variety of environmental hazards including pollution from mining, agricultural runoff and silting of the waters caused by deforestation. "Ver-o-Peso" means "see the weight" and was named after the colonial Portuguese mandatory weighing of merchandise to be taxed for the Portuguese crown.The Brazilian Amazon, home to 60 percent of the world’s largest forest and 20 percent of the Earth’s oxygen, remains threatened by the rapid development of the country. The area is currently populated by over 20 million people and is challenged by deforestation, agriculture, mining, a governmental dam building spree, illegal land speculation including the occupation of forest reserves and indigenous land and other issues. Over 100 heads of state and tens of thousands of participants and protesters will descend on Rio de Janeiro, Brazil, later this month for the Rio+20 United Nations Conference on Sustainable Development or "Earth Summit". Host Brazil is caught up in its own dilemma between accelerated growth and environmental preservation. The summit aims to overcome years of deadlock over environmental concerns and marks the 20th anniversary of the landmark Earth Summit in Rio in 1992, which delivered the Climate Convention and a host of other promises. Brazil is now the world’s sixth largest economy and is set to host the 2014 World Cup and 2016 Summer Olympics.  (Photo by Mario Tama/Getty Images)