I heard it on CNN this morning and noticed that two of the top three endangered are home to the trails, Shenandoah and Great Smoky Mountains.
'NPCA blames air pollution from vehicles and coal-burning power plants for harming the vistas at Shenandoah and Great Smoky Mountains national parks. ' CNN
So tread carefully this year and keep in mind that little thing called low impact camping. Its only a drop in the bucket but it is your bucket.