摘要：The Okavango Delta is the largest inland
delta on Earth, spreading over 15,000 km2
of the Kalahari sands of Botswana. Though
commonly referred to as a delta, it is actually
a landlocked wet-fan comprising three
active subsystems: permanent, seasonal
and intermittent fl oodplains bounded by
fossil fl oodplains that mark the coterminous
extent of a more extensive wetland
during the historical past (Fig. 1). Contemporary
perspectives on climate change
in this sub-region are dominated by two
competing discourses. The fi rst maintains
that the current trend in increasing aridity
is part of periodic variation within a stable
equilibrium and need not be interpreted
as sustained deterioration of climatic conditions.
The second argues that though periodic
variation is evident, close examination
of this periodicity reveals a persistent
downward trend; a trend that may imply
only limited prospects for recovery to the
wetter climatic conditions of the historical
past. Recent long-term evidence compiled
from disparate sources about this sub-region’s
climate since the beginning of the
19th century suggests that there is need
to question the validity of the stable-equilibrium
hypothesis.
