The forests have been altered by logging and clearance for agriculture, urban and industrial development (including mining) with only small patches of original forest remaining, the largest of which is in the Great Smoky Mountains; nearly all of Shenandoah National Park, for example, is regrown forest but still vital habitat for wildlife. The spruce and fir forests of the highlands have been logged particularly intensively and in many cases have not regenerated leaving areas of Appalachian balds heath. Also, as large predators such as wolves and cougars have been removed, the forests are now being overgrazed by deer. Plants and animals are also threatened by introduced species including the gypsy moth (Lymantria dispar), spruce budworm (Choristoneura fumiferana), hemlock woolly adelgid (Adelges tsugae), balsam woolly adelgid (A. piceae) and the Discula destructiva that affects dogwoods and is similar to chestnut blight.