Native grasslands are among the rarest and most endangered habitats in the region. Agriculture and urban development destroy grasslands, and natural processes also change them. Left alone, grasslands are naturally replaced by brush and small trees in a process called succession. Here, that did not happen because for 40 years the U.S. Army, former managers of the area, regularly mowed these grasslands for security purposes. Now the Refuge staff periodically mows or burns them to maintain the native grassland community.