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Limits and Potentialities of Eradication as a Tool for Addressing Biological Invasions 393
fully eradicate the alien mollusc species. In all, 187 t liquid sodium hypochlorite
and 7.5 t copper sulphate were pumped into the area. The decision to proceed
with the treatment of the bay was taken considering that, once the eradication
was completed, all native species could re-colonize the area from
nearby coastal environments (Bax et al. 2002). It is interesting to note that
even when using toxicants in marine environments, it may be possible to
avoid the large-scale diffusion of chemicals. In the eradication of C. taxifolia
from California (cf. above), chlorine was applied by using underwater tarps,
anchored and sealed to the bottom, thereby much reducing the diffusion of
the chemical into these waters.
Aside from environmental risks, it should be noted that the use of toxicants
can also affect human wellbeing and health, in some cases causing serious
concern to local residents. For the eradication of malaria from Sardinia, some
10,000 t of DDT mixture were doused on the island in 5 years, associated with
risks to the local population and livestock. Still, the campaign eradicated this
pathology from the island where, in the 1930s, over 70,000 Sardinians suffered
from malaria (Hall 2004).
Not only toxicants can cause undesired effects. If not properly planned,
also biological control agents or genetically engineered viruses can severely
impact non-target species (Chaps. 17 and 23), and require careful risk evaluation
before being released in the wild (Cory and Myers 2000).
Considering the risks of undesired effects of removal methods, an adequate
monitoring program should always be carried out during and after the
eradication, in order to facilitate the prompt detection of any impacts on nontarget
species, to assess the achievement of objectives, and to enable rapid
response in case of reinvasion. This latter aspect is a particularly challenging
element of eradications, as removing single reinvading individuals can be disproportionately
difficult (Russell et al. 2005).
22.2.4 Costs
The economics of eradications has scarcely been investigated so far, although
the cost/benefit ratio of removal campaigns is indeed a critical element for
defining future policies on invasive alien species. In fact, in order for eradications
to progress from an anecdotic to a routine management tool, it would be
necessary to identify those resources required to ensure the ability of competent
authorities to rapidly remove new, unwanted introduced species and to
implement large-scale eradication campaigns.
Eradications are often viewed as extremely costly programs and, indeed,
many campaigns (albeit not necessarily the most successful ones) have
required huge monetary resources. In only 2 years, an attempt to eradicate
the medfly from California required (converted into €) over € 80 million
(Myers et al. 2000). Coypu eradication in East Anglia cost € 5 million in