The Economics of Controlling a Stochastic Biological Invasion

The invasion of ecological systems by nonindigenous species is now recognized as a growing global problem that imposes significant economic and ecological damages. In the United States alone, the total costs of nonindigenous species have been estimated to be at least $137 billion per year (Pimentel et al.). Approximately one-fourth of the value of the country’s agricultural output is lost to nonindigenous plant pests or to the costs of controlling them (Simberloff). The economic damages from a single invasive species can be enormous. The costs of controlling the zebra mussel (Dreissena polymorpha) in the Great Lakes were estimated to reach $5 billion in 2001 (U.S. Geological Survey (USGS)) while the Russian wheat aphid (Diuraphis noxia) caused an estimated $600 million (1991$) in crop damages between 1987 and 1989 (Office of Technology Assessment (OTA)). Invasive species also cause significant ecological harm. They can alter ecosystem processes, act as vectors of disease, and reduce biodiversity (Vitousek et al.). Worldwide, out of 256 vertebrate extinctions with an identifiable cause, 109 are known to be due to biological invaders. In comparison, seventy such extinctions are known to be caused by human exploitation (Cox). The potential for a single invasive species to cause irreparable ecological damage is manifest in the extinction of twelve of Guam’s native bird species following the invasion of the island by the brown tree snake, Boiga irregularis, in the mid-twentieth century (Savidge). Environmental disturbances can either accelerate or slow the spread of invasive species. Weather events are an important factor in the