Gallery forests are able to exist where the surrounding landscape will not support forests for a number of reasons. The riparian zones in which they grow offer greater protection from fire which would kill tree seedlings In addition the alluvial soils of the gallery habitat are often of higher fertility and better drainage than the soils of the surrounding landscape and have a more reliable water supply at depth. As a result the boundary between gallery forest and the surrounding woodland or grassland is usually very abrupt, with the ecotone being only a few metres
Gallery forests have shrunk in extent worldwide as a result of human activities, including domestic livestock preventing tree seedling establishment and the construction of dams and wiers causing flooding or interfering with natural stream flow. In addition to these distrubances gallery forests are also threatened by many of the same processes that threaten savannas.