Advances in Geosciences www.adv-geosci.net 1680-7340 1680-7359 6 1st Alexander von Humboldt International Conference 2006 10.5194/adgeo-6-69-2006 http://www.adv-geosci.net/6/69/2006/ http://www.adv-geosci.net/6/69/2006/adgeo-6-69-2006.html http://www.adv-geosci.net/6/69/2006/adgeo-6-69-2006.pdf 69 72 2006-01-09 A synthesis of ENSO effects on drylands in Australia, North America and South America M. Holmgren P. Stapp C. R. Dickman C. Gracia S. Graham J. R. Gutiérrez C. Hice F. Jaksic D. A. Kelt M. Letnic M. Lima B. C. López P. L. Meserve W. B. Milstead G. A. Polis M. A. Previtali M. Richter S. Sabaté F. A. Squeo Resource Ecology Group, Wageningen University, Bornsesteeg 69, Building 119, 6708 PD Wageningen, The Netherlands Department of Biological Science, California State University, PO Box 6850, Fullerton, CA 92834-6850, USA Institute of Wildlife Research, University of Sydney, NSW 2006, Australia Dept. d’Ecologia, Fac. de Biologia, Univ. de Barcelona; Av Diagonal, 645; 08028 Barcelona, Catalunya, Spain CSIRO Sustainable Ecosystems, GPO Box 284, Canberra ACT 2601, Australia Departamento de Biología, Universidad de La Serena, Casilla 599 and Centro de Estudios Avanzados en Zonas Áridas (CEAZA), La Serena, Chile Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA Center for Advanced Studies in Ecology and Biodiversity (CASEB), Santiago, Chile Dept. of Wildlife, Fish and Conservation Biology, University of California, Davis, CA 95616, USA Parks and Wildlife Service of Northern Territory, P.O. Box 30, Palmerston NT, 0831 Australia Northern Illinois University, DeKalb, IL 60115, USA National Park Service, University of Rhode Island, Kingston, RI 02881, USA Department of Environmental Science and Policy, University of California, Davis, CA 95616, USA Institute of Geography, FAU, Kochstr. 4/4, D 91054 Erlangen, Germany Fundamentally, El Niño Southern Oscillation (ENSO) is a climatic and oceanographic phenomenon, but it has profound effects on terrestrial ecosystems. Although the ecological effects of ENSO are becoming increasingly known from a wide range of terrestrial ecosystems (Holmgren et al., 2001), their impacts have been more intensively studied in arid and semiarid systems. In this brief communication, we summarize the main conclusions of a recent symposium on the effects of ENSO in these ecosystems, which was convened as part of the First Alexander von Humboldt International Conference on the El Niño Phenomenon and its Global Impact, in Guayaquil, Ecuador, from 16–20 May 2005. Participants in the symposium shared results and perspectives from research conducted in North and South America and Australia, regions where the ecological effects of ENSO have been studied in depth. Although the reports covered a wide array of organisms and ecological systems (Fig. 1), a recurring theme was the strong increase in rainfall associated with ENSO events in dry ecosystems (during the El Niño phase of the oscillation in the Americas and the La Niña phase in Australia). Because inter-annual variability in precipitation is such a strong determinant of productivity in arid and semiarid ecosystems, increased ENSO rainfall is crucial for plant recruitment, productivity and diversity in these ecosystems. Several long-term studies show that this pulse in primary productivity causes a subsequent increase in herbivores, followed by an increase in carnivores, with consequences for changes in ecosystem structure and functioning that can be quite complex.