Abstract

The central Andes span the tropical and subtropical latitudes in South America and play a key role in the altitudinal and latitudinal extent of summer and winter rainfall belts. There are now over 70+ paleorecords available from this region that include ice, lake and salt cores, U-Th series dating on elevated shorelines, timing of alluvial and paleowetland sequences, and rodent middens. Combined, these records reveal millennial-scale “pluvials” or periods of much greater rainfall than today during the late Quaternary. One of these, the Central Andean Pluvial Event (CAPE) lasted from 17-10 ka (or thousands of years BP) and occurred after the Last Global Glacial Maxima (LGM, 21-19 ka). New paleoecologial and glacial records from the western slope of the Andes indicate that the CAPE extended throughout the central Andes and may have reached as far south as 30 °S latitude. Paleoecological evidence shows that as recurring pluvials waxed on the hyperarid western slopes of the Andes, vegetation migrated downslope with increasing precipitation, only to migrate upslope during drier intervals. These pluvials thus have a key role in explaining historical distributions of the Atacama flora and the presence of past and present refugia as well as how they bear on current distributions that should be considered relicts of these past events. In particular, we point out the possible role of the Altiplano as a refuge for many plants during extensive glacial periods when colder temperatures may force many of these species downslope into the adjacent Atacama and Monte Deserts.