We show with a series of climate model simulations of the last glacial maximum that the extent of humid regions in Amazonia depends considerably on the ability of vegetation to recycle soil moisture. When deep roots and the associated large soil water storages are included in the simulations, enhanced transpiration leads to enhanced continental moisture recycling and a cooler surface climate. These differences are similar in magnitude to those introduced by the glacial conditions. As a result, the extent of humid regions is considerably enlarged, in particular for the Amazon basin. A series of indications support the consequences of this effect, suggesting that the Amazonian biogeography during glacial periods may not have been drastically different from today. ¿ 2001 American Geophysical Union