Includes our current knowledge of the invasion or encroachment and cause
of population growth and spread of some dry land, arid zone woody
legumes. Community structure, population growth, and competition of
these woody legumes will also be examined. These species and ecosystems
are both extensive and dynamic. They occur worldwide, but mainly in the
arid zones of the tropics and sub-tropics. The cause of the growth and
spread of these species and communities has long been claimed to be
caused by distal factors rather than proximal ones. However, these
species appear to be influenced and perhaps controlled by anthropogenic
factors, specifically grazing and fire or lack of fire. Their overall
worldwide distribution has probably changed little in the recent past,
but their populations have expanded into grasslands and their density
has increased in many places. Some associated communities have shown
dramatic changes in response to recent large-scale droughts and the loss
of most of the dominant overstory species. However, changes in the woody
legume communities and their species are generally unknown.