Study co-author Ivan Rudik said air quality warnings issued by parks and other government agencies may be causing the visitation drop.
There are between 200,000 and 500,000 sage grouse in the West, down from a peak population of about 16 million.
People have not been coming to Colorado, "spending their last dime on cannabis and then lining up at soup kitchen queues" one of the study's authors says.
E.R. Dr. Emmy Betz and Dr. Larry Wolk, the head of the state's public health department, talk about a lack of funding for gun research, and a few bright spots.
Keep your eyes out for a Dodge Sprinter van around Boulder. What looks like a nondescript cargo van is actually a cutting-edge marijuana research lab.
The National Ice Core Laboratory in Denver needs major renovations to keep its cool, for the sake of a treasure trove of research.
Just as the ranks of Alzheimer's patients is growing, so is the political will to find a cure.
Colorado researchers are studying a disease that's led some parts of Central America to be called "Land of the Widows."
Nighttime storms have baffled scientists for years. Now, a very large group of scientists is pulling all-nighters to solve the mystery.
Hampton Sides profiles several scientists who are taking a serious look at marijuana through advanced research.