Throughout history, if generally more conspicuously in the Old World than the New, military activities have locally and sometimes regionally shaped the face of the Earth by construction of defense works in earth or stone. Military enhancement of terrain features by fortification, scarping, or flooding to form obstacles that counter or deflect attack may thus complement the effects of natural geomorphologic agents. Military operations and exercises have polluted parts of the Earth's surface through use of explosive ordnance and by fuel leakage, and disfigured it by redundant construction works. German military geologists in particular have necessarily developed peacetime roles to protect the environment rather than the state. Yet because agricultural use and urban sprawl are restricted within the large tracts of countryside designated as military training areas, these may preserve a heritage of habitats in a fairly natural state—as valuable in terms of conservation as the many sites worldwide now preserved for their military historical record.