In the last couple of decades, visitation to national parks has increased significantly, but the number of law enforcement officers in the parks has fallen.
New findings by the nonprofit Public Employees for Environmental Responsibility show the National Park Service has reduced the number of special agents who handle complex criminal investigations by 45%.
The agency has also cut back on other law enforcement divisions, such as uniformed rangers and search and rescue.
PEER spokesman Jeff Ruch said the agency does not keep track of criminal activity in parks.