THE PANTANAL WETLANDS - FORM, FUNCTION AND HISTORY

The Pantanal is the world’s largest tropical wetland and a biodiversity hotspot located in central South America (Brazil, Bolivia and Paraguay). Long in the scientific shadow of the neighboring Amazon, recent geological research has achieved a deeper level of comprehension about the form, function and history of this ecologically-sensitive wetland system. The Pantanal (Portuguese for “swamp”) takes its form principally from backbulge basin development associated with Andean orogenesis. Several fluvial megafans debouch into basin from highlands to the east, creating a low-elevation mosaic of floodplains juxtaposed with the axial Paraguay River, which flows along the basin’s western margin and controls local base level. The Pantanal wetlands function largely because of the seasonal flooding of the Paraguay River, which initiates with summer monsoon rainfall. The Paraguay River flood pulse controls the community structure of plants and animals, productivity and nutrient cycling within the wetlands. An understanding of the Late Quaternary environmental history of the Pantanal is emerging from a growing database of lake and floodplain sediment core records that have been dated using radiocarbon or optically stimulated luminescence. Strong variability in sediment fabric, biogeochemistry and sponge spicule content in these records appears to reflect the influence of climate change on lake levels, floodplain geomorphology and fluvial processes. Holocene rainfall dynamics impacting the Pantanal are most likely linked to fluctuations in Southern Hemisphere summer insolation and sea surface temperature gradients. These new insights are critical for managing and mitigating potential threats to the Pantanal posed by global change and human development.