| During the last ice age, the South American tropics were much drier than they are now. There was probably much less forest coverage in general in South America during that time. For example, grassland and savanna existed north of the Amazonian region, in an area where open deciduous forest grew in recent times. | The Amazon rainforest is now one of the major expanses of forest on earth. But how long has this forest been around? Not much is known about the Amazonian region during the last ice age. There is almost no question that dense tropical rainforest existed in the central Amazon basin even during the height of the ice age, but no one is sure how far that forest extended into surrounding lands. |
| Even the present rainfall patterns in the Amazon Basin are not understood completely because of large yearly fluctuation, local variations, and the lack of weather stations to record information. |
| The most popular theory is that the Amazonian forest was greatly reduced in size because of cool, dry conditions which favored the growth of savanna and grasslands. However, the Amazonian region wasn't necessarily arid simply because conditions in other parts of the continent were very dry. |
| Pollen samples have shown that it's possible the Amazon Basin may even have had a cool, moist climate at that time. Evidence of many grassland and savanna plants have been found in the Amazonian region, but there was also a high density of plants that need more water. It's possible that the forest wasn't substantially smaller than the present forest, and the grassland only moved into marginal areas around the drier south-east edge of the forest. |
| Other evidence shows a different situation. Widespread "downcutting" or lowering of riverbeds at this time has been discovered, and this would happen under dry conditions when there was less water. The "downcutting" created canyons, effectively moving the water even farther away from the forest, and contributing to the growth of savanna in the place of trees. | The effects of the last major ice age in tropical Africa are difficult to measure and because the continental shelf is so steep, there wasn't much additional land exposed from the lower sea levels. | Because of the cooler climate, more temperate forests were found in the tropics at relatively low elevations. During the ice age, tropical forest may have been confined to areas under 500 meters in elevation. Forests growing above this elevation would have been "semi-temperate". There is no present-day equivalent to these forests. |
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[tropical forests] [water] [climate] [pollen]
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