An anonymous reader writes: Wilderness areas around the world have experienced catastrophic declines over the last two decades, with one-tenth of global wilderness lost since the 1990s, according to a new study. Since 1993, researchers found that a cumulative wilderness area twice the size of Alaska and half the size of the Amazon has been stripped and destroyed. The shrinking wilderness is due, in part, to human activity such as mining, logging, agriculture, and oil and gas exploration. The researchers said theirfindings underscore the need for international policies to recognize the value of wilderness and to protect wilderness areas from the threats they face. Central Africa and the Amazon saw the most wilderness decline, the researchers found. Of the roughly 1.27 million square miles (3.3 million square kilometers) of global wilderness lost, the Amazon accounted for nearly one-third, and 14 percent of the world's wilderness was lost from Central Africa, according to the study. The researchers determined that only 11.6 million square miles (30.1 million square km) of wilderness is left, which equates to just 20 percent of the Earth's total land mass.