On public land south of Mountainaire, Arizona, nature lovers can enjoy a vista of thousands of lush ponderosa pines blanketing the base of the San Francisco Peaks. The dense forest is beautiful — and unnatural. It was sparse until humans changed the landscape in the late 19th century. And now, humans are trying to change it again. One way is through the Four Forest Restoration Initiative (4FRI), a partnership that includes the U.S. Forest Service, Arizona Game and Fish Department and the Grand Canyon Trust. The goal is to restore 2.4 million acres of pine stretching across northern Arizona from the Grand Canyon to the New Mexico line, but progress has been slow and costly. The program, which is being managed by a wealth of agencies, involves the Coconino, Tonto, Apache-Sitgreaves and Kaibab national forests.