Wildfire suppression in the United States has had a long and varied history. For most of the 20th century, any form of wildfire, whether it was naturally caused or otherwise, was quickly suppressed for fear of uncontrollable and destructive results. Over time, policies governing wildfire suppression changed due to scientific studies that recognized fire as a natural process necessary for new growth. Today, policies advocating complete fire suppression have been exchanged for those who allow fire to act as a tool in controlled burns.