Papua New Guinea - Vegetation and Farming The drier highlands along the centre of the island support one of the oldest farming communities in the world, surviving on a limited diet of domesticated wild root crops such as yams and taro. Almost the entire coastline is lined by mangrove swamp and tropical palms. Further inland, river valleys host plentiful sago palm, which affords a limited degree of nutrition. Other potential domesticates include sugar cane and bananas .But their geographic isolation from each other, meant farmers were unable to build powerful, native agricultural economies. Back