Issues in Ecology Number 5 Spring 2000 Biotic Invasions:Causes,Epidemiology Global Consequences and Control by Richard N.Mack,Chair,Daniel Simberloff.W.Mark Lonsdale Harry Evans,Michael Clout,and Fakhri Bazzaz INTRODUCTION effects of human-caused invasions threaten efforts to conserve biodiversity.maintain productive agricultural Biotic invasions can occur when organisms are sys tems,sustain fun tioning na al o and als transported to new,often distant,ranges where their protect human health.We outline below the epidemiol descendants proliferate.spread,and persist.In a strict ogy of invasions,hypotheses on the causes of invasions sense,invasions are neither novel nor exclusively human- the environmental and economic toll they take,and tools and strategies for reducing this toll. and the number of have grown end THE EPIDEMIOLOGY OF INVASIONS the past 200 vears.Few habitats on earth remain free o Biotic invasions constitute only one outcome species introduced by humans:far fewer can be consid- indeed,the least likely outcome-of a multi-stage pro ered immune from this dispersal.The species involved cess that begins when organisms are transported from represent an array of taxonomic categories and geo their native ranges to new reaions first many if not graphic origins that defy any ready classification most.perish en route to a new locale.if they succeed in The erse con ces of biotic i sions are reaching a new site,immigrants are likely to be destroyed Invaders can alter funda iot agents. mental ecological properties such as the dominant spe cies in a community and an ecosystem's physical features, of species that are actually dispersed from their native nutrient cycling,and plant productivity.The aggregate ranges,the number that subsequently perish,and the num Flgure 1-Some invaders,such as the shrub Lantana camara,have been introduced repeatedly in new ranges,the results of global human colonization and commerce.As the array of estimated years of introduction indicates,lantana was introduced throughout the 19th and early 20 century in new sub-tropical and tropical ra es.In each new range it has become highly destructive,both in agricultural and natural communities(Cronk and Fuller 1995). Issues in Ecology Number 5 Spring 2000 2 by Richard N. Mack, Chair, Daniel Simberloff, W. Mark Lonsdale, Harry Evans, Michael Clout, and Fakhri Bazzaz Biotic Invasions: Causes, Epidemiology Biotic Invasions: Causes, Epidemiology, Global Consequences and Control Global Consequences and Control Global Consequences and Control INTRODUCTION Biotic invasions can occur when organisms are transported to new, often distant, ranges where their descendants proliferate, spread, and persist. In a strict sense, invasions are neither novel nor exclusively human￾driven phenomena. But the geographic scope, frequency, and the number of species involved have grown enor￾mously as a direct consequence of expanding transport and commerce in the past 500 years, and especially in the past 200 years. Few habitats on earth remain free of species introduced by humans; far fewer can be consid￾ered immune from this dispersal. The species involved represent an array of taxonomic categories and geo￾graphic origins that defy any ready classification. The adverse consequences of biotic invasions are diverse and inter-connected. Invaders can alter funda￾mental ecological properties such as the dominant spe￾cies in a community and an ecosystem’s physical features, nutrient cycling, and plant productivity. The aggregate effects of human-caused invasions threaten efforts to conserve biodiversity, maintain productive agricultural systems, sustain functioning natural ecosystems, and also protect human health. We outline below the epidemiol￾ogy of invasions, hypotheses on the causes of invasions, the environmental and economic toll they take, and tools and strategies for reducing this toll. THE EPIDEMIOLOGY OF INVASIONS Biotic invasions constitute only one outcome - indeed, the least likely outcome - of a multi-stage pro￾cess that begins when organisms are transported from their native ranges to new regions. First, many, if not most, perish en route to a new locale. If they succeed in reaching a new site, immigrants are likely to be destroyed quickly by a multitude of physical or biotic agents. It is almost impossible to obtain data quantifying the number of species that are actually dispersed from their native ranges, the number that subsequently perish, and the num￾Figure 1 - Some invaders, such as the shrub Lantana camara, have been introduced repeatedly in new ranges, the results of global human colonization and commerce. As the array of estimated years of introduction indicates, lantana was introduced throughout the 19th and early 20th century in many new sub-tropical and tropical ranges. In each new range it has become highly destructive, both in agricultural and natural communities (Cronk and Fuller 1995)