Direct clearing of vegetation.
Changes in fire frequency.
Soil changes -- plowing, deep chiseling, salinization.
Hydrological changes -- dams, diversions, levees, watertable changes, flood frequency changes.
Atmospheric deposition of nitrogen from pollution.
Displacement of traditional peoples & loss of their land management practices.
Extinction of "keystone" predators, herbivores, etc., leading to community restructuring.
Artificially maintained high herbivore stocking.
Atmospheric deposition of pesticides & industrial pollutants.
Cryptic disturbance often overlooked.