SYMPOSIUM: ECOSYSTEM DISRUPTIONS IN THE AMERICAS

Understanding the effects of human–inducedperturbations, “disruptions”, on ecosystemfunctions is essential to be able to designsustainable environmental practices for theprotection of biodiversity. It has been well-documented on all continents that Euro-American cultures have had severe anddeleterious effects upon biodiversity during thelast three centuries (Deloria 1996). Humanimpacts since New World colonisation haveaccelerated species extinctions and thedisruption and degradation of ecosystemsprocesses and services, many of which havealready been reduced to isolated fragments, andnumerous species and genetically distinctpopulations have been lost in the process. Infact, between one-third to one half of the landsurface have been transformed by human action(Vitousek et al. 1997) and is currently composedof what Brown et al. (2003) call “semi-naturalmatrix” or “...land neither intensively used forcities or agriculture nor set aside as naturalreserves.” Perhaps more disturbing are the lesswell-known and more subtle disruptions tofundamental ecosystem processes: theconsequences of which are yet to be seen.During this new millennium, the tragedy ofthe commons is likely to become morecommon, particularly in developing countrieswhere the pressures are both global and local.Under these circumstances, environmentalscientists face the challenge of providing theinformation upon which future social andenvironmental policy needs to be based. Thischallenge requires a careful scrutiny andexamination of scientific data, models andother available empirical evidence within aninterdisciplinary setting. Other critical tasksinclude: (1) the explicit consideration of theinteraction between science and society indeveloping sustainable initiatives (Bradshaw B namely the comparison ofNorth and South Americas.North and South American ecosystemsshare a long history of cultural and ecologicalinteractions and have sustained similartransformations and disruptions through humanimpacts. Both continents are subject to large-scale climatic drivers such as the ENSOphenomenon. To a certain extent, North andSouth America exist as mirror images of eachother in climatic and biological patterns. This isparticularly true for the western regions ofNorth and South America where similarprogressions of major ecosystems types exist,along and in similar geographic and geologicalsettings, respectively. Temperate areas in Northand South America share striking climaticsimilarities, notwithstanding theirbiogeographic, cultural and socioeconomicdifferences. For example, the analysis of globalcirculation models (Lauenroth et al. 2004)predict that under a scenario of an effectingdoubling of CO