Holocene environmental catastrophes in South America: From the Lowlands to the Andes

PIOVANO, VILLALBA, LEROY

QUATERNARY INTERNATIONAL

Año: 2006 vol. 158 p. 1 - 3

1040-6182

Concern over future recurrences of recent environmental catastrophes, such as the Indian Ocean tsunami or the devastating hurricane season of 2005, are everyday discussions not only for scientists but also for people overall the globe. In addition, global-warming induced changes in mean climate states and in the frequency and magnitude of extreme climatic events, increasing human vulnerability to environmental catastrophes. For geoscientists, environmental catastrophes include short-time (tsunami, volcanic eruption, earthquake) or long and slowevolving events lasting years or even decades (persistent floods or droughts) that produce considerable and extended effects on civilizations and natural systems. A major hindrance in appreciating the full range of environmental changes—especially extreme events—is the general paucity of long-term instrumental records, particularly in southern latitudes. Consequently, high-resolution climate reconstructions beyond these records become critical to understand natural climate variability and, therefore, to unveil the mechanisms behind abrupt and unpredicted reactions of the Earth system. The Argentinean Pampas, a broad region in southeastern South America, is a key area to identify the nature and causes behind the observed 20th century climatic variability. Instrumental and historical records show that long dry intervals characterized the first 75 yr of the 20th century, whereas positive hydrological balances—without precedents from periods previous the Little Ice Age—have occurred after the 1970s . The most recent wet trend, affecting a large, highly productive region of southeastern South America, is profoundly disrupting the traditional socio-economic activities related to agriculture and hydroelectric production. Palaeohydrological reconstructions based on limnogeological data reveal the recurrence of dry (cold) and wet (warm) periods since the Late-Glacial Holocene transition. Past positive hydrological balances, equivalent to the present-day conditions, took place during the Early Holocene, at times of reduced human influences in the region.