Biology Reference
In-Depth Information
Fig. 1.1
Illustration of the multiplicative protection provided by erecting programmatic barriers
to the spread of invasive alien species at the three stages of pre-entry (preventing transportation),
port-of-entry (preventing introduction), and immediately post-entry (rapidly eradicating new
incursions). The cost of control is less to intercept aliens early in the invasion process, and the ease
of control and effectiveness are also higher. Costs increase and probability of successful preven-
tion decrease as a species wends its way through the invasion process
approaches. I will briefly consider topics relevant to each stage of response activity,
including certain limitations of each, because these highlight the need for compre-
hensive response programs that do not overly rely on one method alone.
Strategic Considerations
Before considering different response screens, a few cross-cutting strategic con-
siderations merit consideration first. Although the probability that a particular
species becomes an invasive pest is low, the costs if it does so can be very high.
This combination of low risk of invasion with high potential hazard can easily
skew human perception of risk (Perrings et al., 2005), making sensible assessment
of management options problematic. The history of alien-species invasions serves
as testimony to the ease with which this skewed judgment operates. The need for
the future is to minimize the risk of additional introductions and effectively man-
age the numerous pests that have already invaded. For reasons given above, risk of
