An aerial view of Karkar Island. A study of tropical mountain birds found that they were shifting their ranges upslope to escape warming temperatures. According to the report by Cornell Lab of Ornithology of the U.S. National Academy of Sciences, the activities of industrialised nations that cause climate change are causing birds in remote New Guinea, deep in tropical mountain forests, to move up the slopes to find their preferred habitat. On Karkar Island, 77 percent of all species in the survey moved upslope by an average of 500 feet. Because Karkar and other areas that were studied by the researches are so remote, there has been minimal human development. Researchers believe that climate change is the only major environmental change in those areas. The scientists say that climate change predictions suggest global warming will push at least four of these species into localised extinction by the end of the 21st century.