What's a park worth? Turns out, you can measure the value of outdoor recreation areas on social media. Researchers from the University of Vermont analyzed thousands of geotagged images posted on Flickr and other social media sites between 2007 and 2014, to determine what parks people visited in the northeast state. Is that a selfie taken in Lowell Lake State Park? A picture of a family of deer in the Jay State Forest? Laura Sonter, who led the study, explained that its purpose is to help states and cities "assess the value of protected lands for outdoor recreation." Since most park entrances are only staffed in the summer, it's hard to collect data about their use. Social media, she says, can help provide that data. Her study, published in PLOS ONE, estimated those parks, forests and recreation areas contributed $1.8 billion to Vermont's tourist industry over seven years. The pictures also revealed why some areas get more use than others. There were more images of forested land, trails, beaches and ski trails, which could help park managers determine where to invest to increase visitation to natural areas.