Environmental Engineering Reference
In-Depth Information
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Pre-empting NIS introductions: targeting policy
Christopher Costello, Chad Lawley and
Carol McAusland
Introduction
Invasives are non-indigenous species (NIS) that out-compete native species for resources
and become pests in a host region. Because they are excellent competitors, invasives
impose costs on their hosts by displacing native species (facilitating species loss) and
heightening control costs. Costs from NIS can be considerable:
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the USA spends roughly
$1.5 billion to $2.3 billion annually on herbicides to combat non-native crop weeds (OTA,
1993) and su
ers $1 billion a year in fouling from zebra mussels alone (Pimentel et al.,
2005). Worldwide, competition from exotic species is the second leading cause of species
loss; invasives are implicated in the decline of 400 of the 958 species listed as endangered
in the USA (Wilcove et al., 1998). Pimentel et al. (2005) estimate that the annual cost of
dealing with harmful NIS is almost $120 billion.
Trade in goods and services plays a central role in many NIS Introductions. The
purpose of this chapter is to present a framework for tailoring trade (and other pre-
emptive policies) to NIS characteristics. We
ff
fi
nd that most NIS problems can be classi
fi
ed,
for policy response purposes, into a handful of categories, each with a speci
ed policy
response. For example, sometimes the traded product is the source of the introduction, as
with imports of horticultural stock.
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In other cases NIS introductions are purely acci-
dental, as when individuals hitchhike on imported goods, tourists, or packing materials.
Asian Tiger mosquitoes probably entered the USA in the wells of used tires (Hawley et
al., 1987), SARS (Severe acute respiratory syndrome) entered Canada via a returning
tourist (Varia et al., 2003), and Asian longhorned beetle entered the USA on wood
packing crates (Normile, 2004). Finally, NIS can also stow away in vessels transporting
traded goods, such as in airplane holds, or in ship ballast water, as was likely the case with
zebra mussels; since 1959, 24 animal NIS introduced via shipping became established in
the North American Great Lakes (Holeck et al., 2004). Our analysis extends to both
intentional and unintentional introductions.
Policies aimed at stemming damages from NIS take two broad forms: pre-emptive
policies - those designed to prevent NIS introductions in the
fi
fi
rst place - and reactive,
such as e
orts to control or eradicate NIS once they are established in the host region. We
focus primarily on the former. True, as we argue below, the bene
ff
ts from pre-emptive mea-
sures will depend on the types of control measures taken to combat NIS making it
through a country's borders. However, in many cases it is easy to incorporate damages
resulting from NIS introduction as a function of the process. As such, we can treat the
damages resulting from introductions as an exogenously determined function, one that
will be determined by the optimal control/eradication policy.
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In this chapter we develop a taxonomy of NIS characteristics that focuses on the
following four characteristics:
fi
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