"U.S. Curtails Snowmobiles in Yellowstone"
"The National Park Service has approved a plan to restrict the number of snowmobiles in Yellowstone National Park to fewer than half last winter’s limit."
Source: AP, 10/19/2009
"The National Park Service has approved a plan to restrict the number of snowmobiles in Yellowstone National Park to fewer than half last winter’s limit."

A new report identifies 25 park units considered to be most threatened, but the vulnerability principles spill over to hundreds of additional national park units and other types of natural areas that may be of interest to your audience.