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标题：The desiccation of southern Africa’s Okavango Delta: Periodic fl uctuation or long-term trend?
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作者：HAMISAI HAMANDAWANA
期刊名称：PAGES News
印刷版ISSN：1811-1602
电子版ISSN：1811-1610
出版年度：2007
卷号：15
期号：1
页码：12-12
出版社：PAGES International Project Office
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.