. The Conservation Atlas of Tropical Forests: the Americas. The History of the Forests and Climate of Tropical South America 9 10 20 30 40 50 60 70 80 90 1007, 100 90 80 70 60 50 40 30 20 10 0% 18500 ± 150 BP approximately 42500 ± 2500 BP. yellow-grey nT\l sandy clay I- â 'â I yellow brown and _â. red clay with t^i soil fragments '^^ black and dark p==j grey clay ^3 grey clay [ Elements of the wcl trupical tt»rcst 1^1'- Savanna elements (principally Gramineae) Figure Pollen records from Capoeira (top) and Katira (bottom) (Rondonia. Brazil, latitude 4'=S; longitude 6°W) in the Amazon Ba
. The Conservation Atlas of Tropical Forests: the Americas. The History of the Forests and Climate of Tropical South America 9 10 20 30 40 50 60 70 80 90 1007, 100 90 80 70 60 50 40 30 20 10 0% 18500 ± 150 BP approximately 42500 ± 2500 BP. yellow-grey nT\l sandy clay I- â 'â I yellow brown and _â. red clay with t^i soil fragments '^^ black and dark p==j grey clay ^3 grey clay [ Elements of the wcl trupical tt»rcst 1^1'- Savanna elements (principally Gramineae) Figure Pollen records from Capoeira (top) and Katira (bottom) (Rondonia. Brazil, latitude 4'=S; longitude 6°W) in the Amazon Basin. The diagram reflects a dramatic change from dense tropical forest towards grass-savanna and vice versa. Source: After Absy and Van der Hammen (1976) type of change registered at the end of the dry periods would mean a lowering of at least 500 mm in the annual precipitation (from 2000-1500 mm to 1500-1000 mm) in the drier Amazonian corridor and eventually the fragmentation of the Amazon rain forest area into two large parts. Van der Hammen and Absy (1994) have mapped the poten- tial distribution of rain forest in the Amazon Basin at an annual precipitation of 500 mm (Figure ) and 1000 mm (Figure ) lower than at present (Figure ). As illustrated in Figure , the sites of Katira and Carajas. which experienced savanna conditions some 20,000 years BP, would have been located in savanna vegetation. Interestingly, the same figure suggests that Georgetown would also have experienced savanna conditions with precipitation reduced by 1000 mm. This conclu- sion is supported by pollen records (Van der Hammen, 1963). These data show that considerable areas of tropical forest were once replaced by savanna and savanna woodland or cerrado types of vegetation. It is highly probable, therefore, that the Amazonian forest was, at times, reduced to a number of larger and smaller fragments that could be called forest refuges. Prehistoric .Man and Forests People may ha'e
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