Environmental Engineering Reference
In-Depth Information
Traceability
An alternative to punitive taxes and seizures is to impose liability rules on importers and
consumers of imported goods. When an outbreak or release can be traced back to the
party responsible for the original release, this policy channel has potential. This may be a
likely candidate in the case of nursery stock, where the NIS risk is clear and present to all
parties, and genetic forensics can in theory identify the source of an invasion with preci-
sion. However, as is well known from the literature on liability as a tool for regulating pol-
lution from nonpoint sources, when the source of an accident is di
cult to identify,
liability rules become a blunt tool for preventing release. With respect to NIS, in many
cases we do not observe an infestation until long after its introduction, rendering the
causal link di
cult to establish (see Costello and Solow, 2003).
Thomas and Randall (2000) examine liability and assurance bonds to reduce inten-
tional introductions of (what turn out to be) harmful species. They propose a mixed policy
under both imperfect
ex ante
knowledge about damage and imperfect
ex post
revocabil-
ity. In the general context of uncertain environmental damages, Shogren et al. (1993)
examine bonds as a mechanism for compliance. They provide a useful taxonomy of
cases in which bonds cannot be e
ff
ectively implemented (e.g. due to liquidity or legal
constraints).
Predictability
Probably the key dimension along which NIS di
er from other trade and environment
problems is predictability. Unlike most other defects in traded goods - e.g. lead in paint -
NIS reproduce. Thus an importer's ultimate damages from NIS introductions may be only
weakly related to the size of its initial exposure. To the extent that native, but harmful,
bacteria can reproduce and contaminate a considerable fraction of a nation's food supply
depending on its distribution system, NIS reproduction has many parallels with food
safety research.
ff
Growth
A small literature on regulation under uncertainty regarding growth dynamics
focuses on NIS (e.g. see Olson and Roy, 2002). The substantially larger non-NIS litera-
ture on resource extraction under uncertainty focuses primarily on bene
cial resources,
where the 'take' is economically valuable and the goal is to maintain the reproducing pop-
ulation (see, e.g., Reed, 1979). In the NIS context, however, the emphasis is reversed: the
goal is usually to eradicate, if possible, the invasive population and the 'take' usually has
no economic value. While the insights from this literature are instructive for designing
post-introduction policy, it sheds little light on pre-emptive policy design.
Before import, the growth function for an NIS (and the associated damage) is
unknown. While recent modeling e
fi
ff
orts enhance predictive power, our ability to forecast
damage, before
fi
rst introduction, is weak (Simberlo
ff
, 2006). Further, because host and
native regions di
ff
er climactically and geographically, exhibit di
ff
erent populations of
competing and complementary species, and experience di
erent levels of disturbance,
observing growth dynamics in the NIS' native region gives an imperfect indicator of
dynamics in the host region. Accordingly, there may be some scope for learning about NIS
susceptibility. Intentional releases of NIS for biological control programs are used to
assess the performance of both the introduced NIS and the native ecosystem (NRC, 2002;
Grevstad, 1999). Many Agricultural Extension programs currently engage in cooperative
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