Biology Reference
In-Depth Information
affected stakeholders. It has also been shown in Australia to be easily and cheaply
implemented. The advantages of such a system over the current, widespread use of
limited “black” lists prohibiting known pests is that a far larger pool of species can
be explicitly evaluated for invasiveness and that a “white” list of safe species is
simultaneously generated, providing a measure of regulatory stability and predicta-
bility useful when making economic decisions involving importation. The system
has also been shown to not only protect natural resources but also to generate net
economic benefits by exclusion of harmful pests (R.P. Keller et al., 2007).
Eradication/Control
When aliens slip through these prevention screens, the next-best means of avoiding
damage is to identify a new incursion as rapidly as possible and target it for eradica-
tion. For eradication to be successful requires that several conditions be met: proper
planning, socio-political commitment, a removal rate exceeding replacement rate,
that all individuals be placed at risk, and prevention of reinvasion (Bomford and
O'Brien, 1995; Clout and Russell, 2006). Systematic targeting of new incursions
requires having in place a systematic survey program and dedicated, permanently
funded staff to respond to new escapees. The former better guarantees identifying
new incursions before they have proliferated too far. Doing this successfully
requires sensitivity to the lag-phase phenomenon. Permanent staff are needed to
ensure that eradication measures continue for the length of time required to ensure
success, which can vary tremendously, depending on the species: large conspicuous
animals may often be eradicated in relatively short order; plants will produce a seed
bank that requires repeated control operations to remove all newly germinated
plants to prevent additional reproduction. Small and secretive animals, such as most
reptiles and amphibians, may be virtually impossible to eradicate once established
because they are difficult to detect and because feasible control methods are fre-
quently lacking.
Explicit use of eradication measures against incipiently established aliens is of
relatively recent occurrence and is currently limited, though expanding, in scope.
This method has proven successful against environmental pests in New Zealand,
Australia, and Hawaii and is becoming common procedure in those jurisdictions.
Invasions successfully prevented in this manner are varied, but I will give one
example to show what is achievable with rapid, competent response to new incur-
sions. Perhaps the most impressive instance is the eradication of the mussel
Mytilopsis sp. from Darwin Harbor, which was completed within one month of its
detection in three marinas, even though it occurred at densities as high as 23,650
individuals/m 2 . This carefully planned and orchestrated operation involved immediate
legislative action to authorize control activities, surveys of hundreds of ships and
man-made structures to delimit the range of the infestation, quarantine of three
infested marinas, laboratory trials of control methods, chemical treatment of the
infested areas totalling approximately 20ha of harbor, chemical treatment of
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