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invasive alien species has been introduced, then early detection and rapid
eradication are crucial to prevent its establishment. Only when prevention has
failed and an unwanted alien species has established into the wild is eradication
the preferred response, when this option is feasible. If eradication does
not appear to be feasible, then containment and long-term control measures
should be implemented, if appropriate.
22.1.2 History and Recent Developments
With his arrival on earth, Homo sapiens has directly caused the extinction of
many species, either from localised geographic areas or from the entire biosphere.
The history of human-mediated extirpations ranges from mass extinctions
of megafauna through overharvesting in the Pleistocene (Lyons et al.
2004) to more recent cases, such as the passenger pigeon Ectopistes migratorius
which became extinct at the beginning of the last century (Blockstein and
Tordoff 1985). Extermination of species has been in some cases the result of a
clear commitment and policy by man, as in the case of all large carnivore
species eradicated from western Europe in the 19th century because of predation
on livestock, or of eradications carried out for health purposes. For example,
smallpox has been successfully extirpated from earth, and mosquito
species have been eradicated from many areas of the world to combat malaria
(e.g. Anopholes labranchiae eradicated from Sardinia between 1946 and 1951;
Hall 2004).
We humans have indeed a unique ability to exterminate organisms from all
taxonomic groups, even if long-established or inhabiting very large areas. In
most cases, this is simply a matter of time and perseverance. The fast-growing
number of biological invasions calls upon us now to use this ability to preserve
biological diversity, rather than reducing it.
The first eradications of alien species have been carried out for sanitary
purposes; for example, Anopheles gambiae from over 30,000 km 2 of Brazil in
the 1950s, to combat a yellow fever outbreak and prevent a spread of the disease
to North America (Davis and Garcia 1989). Eradications carried out for
conservation purposes started in the 1930s, and have become a routine management
action only in the 1980s. Over 156 eradications have been successfully
carried out so far in New Zealand to protect native species, 23 on islands
of NW Mexico and 48 on islands of NW Australia. Most eradications have
involved terrestrial vertebrates but there have also been many successful campaigns
in other taxonomic groups, including freshwater fishes (e.g. Copp et al.
2005) and several terrestrial invertebrates, such as the fruit fly, successfully
eradicated from Nauru (Allwood et al. 2002) or the screw-worm (Cochiomyia
hominivorax) extirpated from the south-eastern United States, Central America
and North Africa (Myers et al. 2002). Even some marine organisms have
been eradicated (when invasion was still localised), such as a mussel (Mytilop-