Farming of crops like cocoa, cassava and oil palm has resulted in widespread deforestation and degradation of West Africa's tropical forest area, a study says. Cocoa production in West Africa is an important economic activity and a source of income for about 2 million households in the region, and the Ivory Coast, Ghana, Nigeria and Cameroon account for 70 percent of global cocoa supply. Researchers at the International Institute for Tropical Agriculture and the Center for International Forestry Research report cocoa production in West Africa's Guinean Rainforest region doubled between 1987 and 2007, but most of the increase came at the cost of clearing forest areas. resulting in large losses of biodiversity and high carbon emissions, an IITA release said Thursday. The principal cause of this environmental change has been the expansion of smallholder agriculture that depends on environmentally destructive practices like slash-and-burn and land clearing, the report said. Strategies to reduce deforestation and conserve biodiversity in West Africa must focus on transforming agricultural practices from those traditional practices to modern science-based methods, researchers said. "There are no longer any frontier forests in West Africa for future generations to exploit," IITA agricultural economist Jim Gockowski said.