In the United States, about 30%, of National Forest lands in 38 states and Puerto Rico are roadless areas, making up 58.5 million acres (237,000 km²). These areas provide critical habitat for more than 1,600 threatened, endangered, or sensitive plant and animal species. Roadless rules are also seen as a way to save taxpayers money. America’s National Forests are currently covered with of roads, enough to encircle the earth 15 times. A $4.5-billion maintenance backlog exists on National Forest roads, according to the agency's own estimates.