TheImprovement ofTropical and Subtropical Rangelands

THE SOOIAL CONTEXT FOR RANGELAND IMPROVEMENT 45
major C8U8e of vegetative change and often inhibits the restoration
of plant cover.
Although these three actions of man are the main causes ofenvironmental
degradation, the reasons for increased degradation are still
debated. Four common reasons for environmental deterioration are
climatic change, population growth, economic change, and human
fallibility. Usually these factors interact. Over the past 30 years, the
human and animal populations using semiarid and marginal lands
have grown, thereby putting more preesure on the environment.
Given the cycles of wet and drought years common to semiarid regions,
such as the West African Sahel, this led to population growth
that could only support the population in wet periods. The shortsightedn8111
of governments and donor agencies also has contributed
to environmental deterioration. In Africa in particular, ill-conceived
water and livestock development projects contributed substantially
to overgrazing (Bemus, 1971; Haaland, 1977). These factors have all
contributed to the need for revesetation programs, but merely listing
the mechanisms and factors leading to environmental problems does
not explain the process by which this has occurred. Also, in many
cases, de8truction of plants in marginal areas has been occurring at a
faster pace than have climatic or population changes. This has been
due to factors that have reduced both the mobility and the diversity
of traditional economies. Theee factors also undermined traditional
mechanisms of environmental protection. The need for revegetation
and conservation has been accelerated by the growth in government
power, in modem economies, and in the use ofimproved technologies.
Changins political conditions have had severe impacts on many
pastoral eocieties ofMrica and Asia. In many cases, national boundaries
were created in such a way that gruing lands U8ed by one
people were split between two or more nations. Over time, nations
have increasinSly restricted the movement of people and animals
acroes frontiers. Such restrictions reduce the diversity of ecosystems
available to herders and lead to herds spending longer periods of
time in marginal areas than they had in the past. For example, it
has been argued that the imposition of the frontier between Uganda
and Kenya was the reason for overgrazing and the destruction of the
pastoral economy of the Karamajong of Uganda (Quam, 1978). The
imposition of national boundaries also had some impact on trading
activities.
The growth of state authority has impinged on pastoral production
systems in several other ways. To a large degree, governments