TheImprovement ofTropical and Subtropical Rangelands

44 IMPROVEMENT OF TROPIOAL AND SUBTROPIOAL RANGELANDS
and market opportunities and political control reduce the effectiveness
of prior regulatory procedures. Studies of traditional management
systems indicate that in those areas where disease and warfare
do not prevent overgrazing, a variety of institutions regulate the use
of common resources. First, these lands are not open to all potential
users, but are either used exclusively by certain groups, or at the
very least, some groups are given priority over others. In the case
of cropland, people usually need permission from local leaders or
councils to use land. Even when access to pastures and woodland
was technically open to all, controls over access to water, shelter, and
minerals was controlled by localities or owned by individuals. For
example, wells and springs are often "owned" by individuals or by
small groups (Helland, 1982). Without access to water or to shelter,
no one can use pastures, even if they are technically common
resources.
Subsistence-oriented groups in semiarid lands do not necessarily
live in harmony with nature. Pastoralists and agro-pastoralists often
significantly alter the vegetation and fauna ofthe areas in which they
live. Sometimes they do destroy the resources upon which they depend.
If they do 10, they quickly destroy their ability to survive and
are either forced to move on or disappear. Direct dependency on the
immediate environment for most subsistence needs is a strong incentive
for the development of institutions to protect the environment.
While most groups living in marginal areas have only rudimentary
institutions, in some areas, such as southern Africa and the Atlas
Mountains of Morocco, elaborate institutions evolved to regulate
pasture use (Bourbouze, 1982; Gilles, 1982; and Odell, 1982). In
recent years, many of the mechanisms that have traditionally served
to protect vegetation have become less effective. The reasons for this
decline are discussed below.
CONTEXT OF ENVmONMENTAL DEGRADATION
Typically, lands requiring revegetation have had their plant cover
destroyed through improper farming methods, the extensive gathering
of wood for fuel or construction purposes, or through overgrazing.
In terms of destructive impact, cultivation and the gathering of
woody species probably have had more impact on the environment
than have grazing animals. Livestock are the primary cause of desertification
only in areas where large numbers of grazing animals are
concentrated, such as around boreholes. Overgrazing is, however, a