<P> The landscape of the plateau is mostly savanna scattered with trees . It mostly lacks deep soil suitable for farming, though the soil is fertile mollisols and some cotton, grain sorghum and oats are grown . For the most part, though, the thin soil and rough terrain areas are primarily grazing regions, with cattle, sheep and Angora goats predominant . Several rivers cross the region, which generally flow to the south and east through the Texas Hill Country toward the Gulf of Mexico; springs occur (in wet years), but permanent surface water supplies are sparse throughout the area, except for man - made reservoirs . The area is well drained; rainwater flows into the Edwards Aquifer recharge zone at the south of the plateau to feed rivers to the south . Rainfall varies from 15 to 33 inches per year, on average, from northwest to southeast, and the area has a moderate temperature and a reasonably long growing season . </P> <Dl> <Dt> Flora </Dt> </Dl> <P> Trees of the savanna include a juniper - oak mix and a mesquite - acacia mix scattered over fairly short grasses, which traditionally were affected by droughts and regular fires . Some pecan trees are found near the springs and rivers . The Balcones Fault is associated with the Edwards Plateau formation . This fault line is an ecological demarcation for the range definition of a number of species . For example, the California fan palm, Washingtonia filifera, is known to occur only west of the Edwards Plateau or Balcones Fault, and Buddleja racemosa is known only from the southern edge of the plateau . </P> <Dl> <Dt> Fauna </Dt> </Dl>

How have the physical features of the edwards plateau limited human activities in the region