Environmental Engineering Reference
In-Depth Information
species risk assessment?
We need a formal approach to invasive species risk assessment because of the rap-
idly growing costs associated with harmful invasive plants, animals, and diseases
around the globe. Pimentel
et al
. (2005) estimate that in the United States alone,
the economic costs associated with invasive organisms exceeds $120 billion/year
in lost production, maintenance, eradication eff orts, and direct health costs. h ese
same authors suggest that up to 80% of endangered species worldwide could be
adversely aff ected by competition or predation by invasive species. For example,
the introduction of the brown tree snake in Guam led to the direct extinction of
a dozen species of birds (Jaff e 1994). Meanwhile, the costs to human health are
obvious from the notorious examples of plague, West Nile virus, and the potential
eff ects of Asian bird fl u.
h us, risk assessment for invasive species may expand the number of target spe-
cies being considered to any and all species in an ecosystem, including humans.
Typical target species, in addition to humans and charismatic animal species,
include threatened and endangered species, rare native species assemblages, and
selected ecosystem processes such as competition and predation (e.g. Connell
1983), ecosystem services (Gross 2006), and fi re frequency and intensity (Freeman
et al
. 2007), as seen by the increase in wildfi res aided by non-native annual grasses
in the western United States.
Formal approaches to ecological risk assessment are not new. In the 1990s, assess-
ments of 'ecological risks' expanded data requirements for complete and accurate
risk analyses by recognizing the inherent complexity of ecosystems. h e stressors
to ecosystems have grown to include climate change, genetically modifi ed organ-
isms, disturbance, and natural disasters such as earthquakes, fl oods, and wildfi res.
h is led Lipton
et al
. (1993) to suggest that information is needed on 'the biotic
components and organization of the system, as well as assessing the distribution
of the stressor within biotic components' including 'risk cascades' and 'biological,
ecological, and societal relevance'. Despite these general, well-recognized needs,
specifi c strategies, methods, and the costs and di culty of acquiring detailed
information on all relevant ecosystem components and processes relative to com-
plex stressors such as multiple air or water pollutants or climate change, remain
elusive (Stohlgren and Schnase 2006).
In this century, the challenges of risk assessment must take another astro-
nomical leap as consideration extends from abiotic, chemical, and climatic
threats to invasive non-native organisms. h ere are thousands of species of
plants, animals, and diseases that have invaded the United States from other
continents—species that can cause harm to the environment, our economy,
and to human health (Mack
et al
. 2000). Notorious examples in the United
States include zebra mussels, cheatgrass, West Nile virus, the brown treesnake,
plague, kudzu, salt cedar, the Argentine fi re ant, yellow star thistle, sudden oak
death, hydrilla, Burmese pythons, and Dutch elm disease, to name a few. It is
