Academic journal article Current Politics and Economics of Africa

Late Quaternary Enironmental Change in the Namibia of Southern Africa *

Academic journal article Current Politics and Economics of Africa

Late Quaternary Enironmental Change in the Namibia of Southern Africa *

Article excerpt

1.INTRODUCTION: THE IMPORTANCE OF THE NAMIBIA QUATERNARY

One of the reasons for the Quaternary environment research is that it is an imperative to understand environmental changes of the past as a key to more appropriate management of changes evidently occurring at present and in the future (Meadows, 2011). The historical (documentary) record of climate change is impossibly short and a full comprehension of the dynamics of contemporary environmental systems, i.e., distinguishing 'noise' from 'oscillations' and 'trends' requires a much longer-time perspective. Study of the Quaternary not only confirms the ubiquity of change but also the detailed responses of the flora and fauna (including our own species) to such change. In short, the Quaternary is the archive against which is measured the nature, causal factors, frequency and magnitude of contemporary environmental dynamics.

But what of the Namibia Quaternary in particular is? The territory of Namibia is located in Southern Africa of the southern hemisphere, an area of the African continent south of approximately 19°S (19-29°S, 12-21°E) (Figure 1) and a subcontinent with a varied but coherent set of physical geographical characteristics.

In a global scale, the southern hemisphere occupies a key position in the global climate system because, in comparison to the northern hemisphere, it is much more oceanic in character and therefore plays the dominant global role in redistributing solar radiation energy. Climate is closely linked to oceanic circulation, a linkage that is manifested in the salinity and temperature gradients producing the thermohaline circulation, or conveyor, which ultimately transfers North Atlantic Deep Water to the southern oceans and in the process impacts on global energy distribution (Broecker et al., 1985). An understanding of Quaternary environmental changes within and offshore southern Africa becomes a significant element in the reconstruction of the dynamics of this thermohaline conveyor (the return limb of which passes offshore of the subcontinent from east to west), which has been held responsible for sub-Milankovitch scale global climate changes, such as the Younger Dryas at the end of the last glacial (Broecker and Denton, 1990). Changes in the southern African environment arguably are also of significance to the understanding of environmental perturbations at lower latitudes in intertropical Africa.

Tropical to sub-tropical southwestern Africa (between about 17°S and 30°S) experiences semi-arid to hyper-arid conditions (Tyson, 1986) due its position in-between the influence of precipitation from low-latitude tropical climate systems in the north and mid-latitude climate systems in the south. The climate of southern Africa is inherently variable on a wide range of time scales (Tyson, 1986), through seasonal, annual, decadal up to millennial and beyond. This manifests itself particularly in terms of fluctuations in the amount and seasonality of rainfall. For example, Tyson et al. (1975) have described the importance of a spatially coherent 18-year oscillation in rainfall values over the summer rainfall region for the meteorological record (1910 to 1972). The existence of such fluctuations over longer time periods is also apparent and it becomes clear that significant variations in the patterns of precipitation and temperature, some of which are in phase with global climate-forcing factors, such as the perceived solar radiation changes due to orbital eccentricities (Partridge, 1997), are a key component of southern Africa's environmental situation and one that needs to be elucidated as far as possible. Unfortunately, due to this aridity, long terrestrial palaeoclimate records are rare and thus our understanding of past changes in precipitation remains incomplete.

Integral to the variability of rainfall and other climate elements is the issue of natural resource management. The economy of southern African nations (Namibia) is based primarily on resource extraction, the agricultural and pastoral component of which is strongly responsive to climate variability. …

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