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J. Touza, K. Dehnen-Schmutz, and G. Jones
and of disturbed land. A more recent paper by the same authors examines
import tariffs in combination with regulatory measures, such as import
inspections (McAusland and Costello 2004). They show that the interaction
between inspections and tariffs is determined by the level of infection/infestation
of the traded goods. Both policies (inspections and tariffs) increase
with the proportion of traded goods which may become invasive but this proportion
may reach a point after which inspections are decreasing. This means
that, when the level of infection/infestation of the imported material reaches
a given level, it is optimal to inspect less and to have tariffs as the dominant
prevention policy. McAusland and Costello (2004) also conclude that
importers should apply a tariff which covers the inspection costs, and the
expected damage from infested goods received which were undetected during
inspections. Furthermore, the optimal level of these tariffs should depend on
the characteristics of the trade partners in terms of the risk and potential
damage of accidentally introduced IAS. This view, requiring an analysis of the
risk characteristics of the trading partners, surfaces again in research on IAS
and tradable permits discussed below.
Such tariffs are not possible under the non-discriminatory policies (i.e.
discriminating against foreign goods are prohibited) which characterise
international trade agreements. Margolis et al. (2005) argue that, if national
governments could select tariffs freely, import tariffs should include the
potential invasive species damages. However, tariffs may be used as instruments
of disguised protectionism if pressure from lobby groups lead to tariffs
that exceed the optimum level. Such pressure for protectionism could be
avoided if there were an international agreement on how to measure damage
from invasive species. However, the lack of such agreement makes it difficult
to recognise when disguised protectionism may be occurring. It should also
be noted that regulatory measures (inspections, quarantine, black and white
lists, etc.) are not free from the potential influence of interest groups. For
example, the appropriateness of quarantine regulations depends on the complex
economic interests of stakeholders, different attitudes to risks, the uncertainties
associated with these risks, and the considerable costs for the trading
partners of over-controlled national borders (Mumford 2002). Even the efficiency
of risk assessments is compromised because of political influence and
regulators’ competing requirements to, for example, facilitate exports and
control invasion risk (Simberloff et al. 2005).
20.2.3 Tradable Permits
This section deals with an increasingly popular economic instrument to control
environmental “bads”: systems of tradable permits. Such systems are
based on the principle that any increase in “emissions” must be offset by an
equivalent decrease elsewhere (Perman et al. 2003). There is usually a limit set