Archaeologist Lewis Borck, PhD, would answer: quite a lot.
"Disturbance" describes an archaeological site that has been altered by either natural forces (erosion, animal activity, etc.), previous archaeological excavations, or - as is often the case these days - by vandalism or looting as shown in the photos. Dr. Borck explained in an article he wrote for the Fall 2019 issue of American Archaeology (Vol. 23 No. 3 at p. 44) that his research as a preservation archaeologist focuses upon disturbed sites rather than sites that may be more intact. He says, in part,