Environmental consequences and economic costs of alien species - Invasive Plants: Ecological and Agricultural Aspects - page 247

been responsible for the extinction of various animal species. Yet, for these
pest animals, only minimal cost data are known. Also, it is impossible to
assess the value of a species forced to extinction, although it is estimated that
40% of extinctions in the US are caused by alien species. If we had been able
to assign monetary values to species extinctions, losses in biodiversity,
ecosystem services, and aesthetics, the costs of destructive non-indigenous
species would undoubtedly be several times higher than the reported $120 bil-
lion per year. Yet even this understated economic loss indicates that alien spe-
cies are extracting a significant environmental and economic toll in the United
States and worldwide. The calculated dollar cost per capita for the losses
incurred due to biological invaders in the United States is approximately $420
per year.
Approximately 99% of all crop and livestock species are non-indigenous.
These alien crops (e.g., corn and wheat) and livestock (e.g., cattle and poultry)
are currently vital to maintaining world agriculture and the food system; yet
the lack of biodiversity in crops and livestock leaves them, in turn, highly sus-
ceptible to invasive plants, animals and microbes. The benefits of some non-
indigenous species do not diminish the enormous negative impacts of other
non-indigenous species on agricultural and on other managed and natural
ecosystems.
A real challenge lies in preventing further damage to natural and managed
ecosystems worldwide from invading alien species, especially with rapid
world population growth and increased human activities. The United States
has taken steps to protect the environment from biological invaders. For exam-
ple, President Clinton issued an Executive Order on 2 February 1999 allocat-
ing $28 million to develop the Interagency Invasive Species Council. The pur-
pose of this agency is the creation of a plan to mobilize the federal government
to defend the United States against non-indigenous species invasions. This
analysis suggests that a few million dollars spent on preventing future intro-
duction of potentially harmful alien species in the United States and other
nations will avoid billions of dollars in losses to agriculture, forestry, and other
aspects of our managed and natural environment worldwide.
References
1 Pimentel D, Lach L, Zuniga R, Morrison D (2000) Environmental and economic costs of non-
indigenous species in the United States. BioScience 50: 53-65
2 Pimentel D, McNair S, Janecka J, Wightman J, Simmonds C, O'Connell C, Wong E, Russel L,
Zern J, Aquino T et al. (2001) Economic and environmental threats of alien plant, animal, and
microbe invasions. Agric Ecosy Environ 84: 1-20
3 USBC (2003) Statistical abstract of the United States. US Bureau of the Census, US Government
Printing Office, Washington DC
4 PRB (2004) World Population Data Sheet. Population Reference Bureau, Washington DC
5 Bryan RT (1996) Alien species and emerging infectious diseases: past lessons and future applica-
tions. In: GT Sandlund, PJ Schel, A Viken (eds): Proceedings of the Norway/UN conference on
alien species, July 1-5. Norwegian Institute for Nature Research, Trondheim, Norway, 74-80