Fire history of Patagonia: clima te versus human cause

Abstract

Vera MARKGRAF Lysanna ANDERSON Human society' s concern about future environmental changes in response to both natural forcings, such as climate, and ever increasing human impact can only be addressed if the interaction between the natural and man-made forcings are fully understood. One parameter that lends itself for such analysis is fire. The historical record is toa short and ambiguous to provide data adequate to discriminate between natural and man-induced changes in fire frequencies. Paleoenvironmental records, inclusive of both the historic and the prehistoric past, can provide an appropriate data set with which to address this questionoThese data include paleoclimate reconstructions, pollen, and charcoal records from dated sediment sections, and information on past human impact derived from historical and archaeological evidence. The Patagonian region is well suited for such a study because of its climatic diversity, its wide range of ecosystems, and the adaptation of its ecosystems to fire. Records from latitudes 36°t o 55°S suggest that a1thoughprehistoric human activities may have amplified extent of fires, climate played the central role. Changes in patterns of climate variability were particularly important. Whenever variability was high, during the late glacial and the late Holocene, fires were abundant. Late glacial variability is probably related to fluctuations in the extent of Antarctic sea-ice which in turn influences the latitudinal position of the westerly stormtracks; late Holocene variability, on the other hand, is related to the influence of EI Nifío/Southern Oscillation.

Fire History and Vegetation Changes in Northern Patagonia, Argentina

“…Pre-1880: Native American Influences Paleoenvironmental records document fire at least as early as 12,600 BP in the southern Andean region (Heusser 1987(Heusser , 1994Markgraf and Anderson 1994). During the prehistoric period in northern Patagonia, fires were ignited both by humans and lightning.…”

Western Patagonia: A Key Area for Understanding Quaternary Paleoclimate at Southern Mid-Latitudes

“…The co-occurrence of charcoal particles pollen assemblages of Younger Dryas-age in a few sites has been explained as direct evidence of paleoindian burning (Heusser, 1994), or decreased precipitation and high climate variability extrapolated to both sides of the Andes between 40° Sand 54° SLat. (Markgraf and Anderson, 1994).…”

Soil seed bank of Austrocedrus chilensis (D. Don) Pic. Serm. et Bizarri related to different degrees of fire disturbance in two sites of southern Patagonia, Argentina

“…Ancient chronicles (Fonk, 1900;Willis, 1914;Rothkugel, 1916;Musters, 1979) and recent studies about pollen and charcoal records from dated sediments (Veblen and Markgraf, 1988;Markgraf and Anderson, 1994;Schäbitz, 1994;Goldammer et al, 1996), as well as tree ring analyses and vegetation structure (Veblen and Fig. 1.…”