As a result of inventory and condition and trend studies, park staff members frequently identify problems with park resources. The presence of exotic plants, elevated levels of ozone in the air, and trampling of rare plants are three examples of resource problems at Shenandoah. many of these problems are described in the Environmental Factors pages. Park personnel engage in "Stewardship Activities" in an effort to correct these problems. These activities are wide ranging and include things like restoration of species that are rare or non-existent in the park like Peregrine Falcons, removal of exotic plants like Tree of Heaven and Japanese Stiltgrass, and reviews of applications for air pollution emission permits.