Reappraisal of contemporary perspectives on climate change in southern Africa's Okavango Delta sub-region

This paper provides a reappraisal of contemporary perspectives on climate change in southern Africa's Okavango Delta sub-region by drawing on time-line evidence from historical/archival records, field-compiled information and multi-date remotely sensed imagery. By using temporal variations in stream discharge and surface and groundwater distribution as proxies of declining rainfall from the beginning of the 19th century, trends emerging from this reconstruction suggest that progressive contraction of the Delta's permanent floodplains, the desiccation of Lake Ngami in its distal reaches, fossilization of receiver channels, sustained dewatering of aquifers, and changes in vegetation from grassland to drought-tolerant woody species are non-transient precursors of increasing aridity and deteriorating climatic conditions. With evidence pointing to persistent drying sequences and system failures to revert to moister climate conditions of the recent historical past, hypotheses that characterize deteriorating rainfall and recurring flood failures in this environment as isolated singularities in a punctuated equilibrium need to be reconsidered in order to provide empirically grounded planetary change perspectives that are consistent with evidence over long-term temporal horizons. (C) 2008 Elsevier Ltd. All rights reserved.