Chapter 18 - Neotropical Savanna Environments in Space and Time: Late Quaternary Interhemispheric Comparisons

Abstract

To obtain a better insight into past vegetational, and climatic changes along the Pole-Equator- Pole: Americas transect, 32 late Quaternary pollen records from savanna, forest-savanna transition regions of the South American neotropics, and north and south of the equator, have been compared in this chapter. During pre-full glacial times, environmental changes in savannas were spatially complex. Some records show either stable grassland, where forest exists today, or a repeated alternation between forest, and savanna. During the full glacial period, neotropical savannas, both north and south of the equator, expanded because of markedly drier conditions. In the southern neotropical regions, savanna area was reduced, and replaced by subtropical grassland by cold climatic conditions during glacial periods. During the late glacial period, climate changed to wetter conditions north of equator earlier at 16,000-14,000 14C B.P., in montane regions. Wetter conditions were not recorded in the high plains or lowlands. During the early Holocene, the climate was drier in most of the South American savannas. Early Holocene distribution of savanna was much larger than during the late Holocene. The general synchrony of paleoenvironmental changes since the full glacial period, from neotropical savanna sites north and south of the equator, suggests changes in the latitudinal migration of the Intertropical Convergence Zone (ITCZ) may have played an important role. The movement of the high pressure cell over the South Atlantic, and changes in frequency of the tracks of the Antarctic cold fronts were also important.