Environmental Engineering Reference
In-Depth Information
enter a country. Political interference can over-ride justifi ed safety measures. Thus,
the risks of the introduction of invasive species are often substantially increased
during such a process. It is predicted that the need for food aid is likely to increase
with the effects of global warming with a resulting increase in risk of invasions. The
application of controls in source countries probably has the greatest potential to
lower the likelihood of entry of invasive species into recipient countries.
1.4.3 Deliberate introductions
Deliberate introductions of alien species for any purpose, including pasture and
genotype improvement, new crops, biological control, land rehabilitation (e.g. for
erosion control or post-mining activities), leisure activities (e.g. gardening), the
pet trade, hunting, research, agricultural or horticultural purposes can have wide
reaching, and often unexpected, consequences. Hence, there should be careful
consideration of impacts beyond those of the immediate focus of the introduction
programme when undertaking a risk analysis before importation.
A large number of invasive species have been human assisted at least in the fi rst
instance, a process that has been going on for thousands of years. During the coloniza-
tion of the New World, especially in the 1800s, there were proactive moves to intro-
duce a greater range of species into new areas for food or utility, for ornament, as pets,
or for hunting (acclimatization societies) to make the new lands 'feel like home'. Birds
were often introduced to control insect outbreaks and later on, mammalian preda-
tors were introduced to control outbreaks of the previous 'useful' introductions. A few
of those introduced to Africa, Australia, and New Zealand include common mynahs
(Aves: Sturnidae: Acridotheres tristis ), rabbits (Mammalia: Oryctolagus cuniculus ), foxes
(Mammalia: Canidae: Vulpes vulpes ), stoats (Mammalia: Mustelidae: Mustela erminea ),
weasels (Mammalia: Mustelidae: Mustela nivalis ), European starlings (Aves: Sturnidae:
Sturnus vulgaris ), sparrows (Aves: Passeridae: Passer domesticus ), deer (Mammalia:
Cervidae: Cervus spp.), lantana (Magnoliopsida: Verbenaceae: Lantana camara ),
prickly pear (Magnoliopsida: Cactaceae: Opuntia spp.), pasture grasses (Liliopsida:
Poaceae), goats (Mammalia: Bovidae: Capra hircus ), and pigs (Mammalia: Suidae: Sus
spp.). Many of these introductions, especially food plants, have been critical to the new
colonies. Some introductions, when undertaken with appropriate consideration of the
potential off -target impacts, can be highly benefi cial, such as biological control agents.
A major trap for those proposing to import new organisms is that most spe-
cies are normally not considered invasive in their home range. When introduced
to a new range, these same species, by adaptation to new hosts or niches, have
resulted in drastically altered habits and ecosystems, including the extinction of
some native species. h e consequences of many of the above introductions still
have major impacts today.
1.4.3.1 Biological control
Biological control usually involves the deliberate introduction and release of new
organisms into areas, often in a repetitive manner. The objective of quarantine
 
 
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