TheImprovement ofTropical and Subtropical Rangelands

IMPROVEMENT OF TROPIOAL AND SUBTROPIOAL RANGELANDS
FIGURE 2-1
O'Rourke)
Camel'raupon 1D 'he HiP A'lu Dear M'del', Morocco. (J.
planta that 8l'e 1_ sUlIICeptible to annual val'iations in weather than
are annual food crops.
Livestock herds in semial'id and marginal regions are rarely confined
to the same pastures year-round. Seasonal movement is a common
feature of livestock production even among sedentary groups
(figure 2-1). A noteworthy difFerence between agro-pastoralists and
pastoralists is that the former do not often move u complete families
with their herds, whereas family members often accompany herds
among pastoralista. The movement of animals may be as little as
a few kilometers or as much as hundreds of kilometers. Movement,
however, permits herds to take advantage ofseasonally rich putures,
helps to adjust to spatial variances in precipitation, and reduces the
strea that is placed on vegetation through constant grazing and
trampling (Wagner, 1983).
Mobility is probably the key production strategy for pastoral nomads.
Strategies of mobility, BUch u nomadism and transhumance,
are particul8l'ly prevalent in areas where the pattem of rainstorms
is such that there can be wide difFerences between the amount of
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