干旱区生态环境知识资源中心

Climatic interpretations are derived indirectly from evidence for vegetation changes based on the remains of micromammals (small rodents and shrews) from archaeological sites. Thus far, only Border Cave has provided evidence apparently referable to the earlier altithermal in oxygen-isotope substage 5e. Vegetation zones, and by implication climatic zones, apparently extended 3-degrees and more south of their present southern limits. Rainfall may have been up to 100% more than it is today and much more seasonal, with drier winters. Mean annual temperatures were perhaps about 1-degrees-C higher on other evidence.

Eight other sites provide evidence concerning conditions during the Holocene altithermal (7000-6000 yr B.P.). The evidence seems to indicate relatively low annual precipitation in the main, summer-rainfall, region and an extended rainfall season in the southwestern, winter-rainfall, region. It is less clear whether or not annual rainfall was relatively high at this time in the latter region although in the Namib Desert conditions were apparently wetter. This tends to agree with the dry-period analogue of Cockcroft et al. (1987) and would imply reduced seasonality of precipitation throughout the region in contrast to the situation during the earlier altithermal. Apparent conflict with palynological evidence may be explainable but requires further examination.