Environmental change and fire history of southern Patagonia (Argentina) during the last five centuries

Geochemical, geophysical, charcoal and pollen analyses from the very poorly investigated southern Patagonian steppe area show that in the vicinity of Laguna Potrok Aike (Santa Cruz Province, Argentina) and north of the Strait of Magellan the detectable impact of Europeans as explorers, settlers and farmers on fire intensity, vegetation and lake ecosystems started with first regional signs during the 1840s. A massive anthropogenic impact on a supra-regional scale followed as the result of the introduction of sheep farming at the end of the 19th century. Furthermore, since the first European explorations, fires in the steppe areas of southernmost Patagonia as recorded at Laguna Potrok Aike occurred contemporaneously in the steppe-forest ecotone further west and probably also in the Andean forest itself. Environmental changes which are not caused by anthropogenic influence are also revealed and were most likely the result of temperature variations and enhanced and reduced wind speeds, respectively. A fire event around AD 1600, before the arrival of European settlers, occurred during a dry period in the forest and steppe-forest ecotone and followed a wet phase in the steppe that caused favorable ignition conditions in all environments.