Alien Species.vp - IUCN

C.R. Veitch and M.N. Clout
Crop, livestock and pasture pests: These pests are usually recognized by only the farmer.
Crop weeds and insect pests are the most common, but birds and rodents can also have an effect
on crops and pastures, and some mammalian pests can carry livestock diseases.
Sporting species: Animal species which can be hunted or fished for sport, or because they are
edible, are fervently protected by those who do the hunting and fishing, or who sit in an
armchair dreaming about it. In New Zealand some of these animals are native (e.g. some
waterfowl), but many are introduced mammals (e.g. deer) or fish (e.g. salmonids).
“Benign” species: Many alien species are generally considered to be benign. They include
small, insignificant, plants, fish that are rarely seen, or insects that “are surely too small to be
damaging”.
Causes of perception
The first factor which causes people to consider a species to be an invasive pest is probably
damage to property. This may take the form of weeds in a crop, insects eating a crop, rodents
eating stored food, and many similar examples. People have been working to improve crops,
pasture and stored foods by controlling invasive species for many years. This, in turn, has led to
a dislike of some species regardless of where they are or what they are doing, notably most
rodent species. But the dislike of rodents, in this example, is tempered by the fact that some
children will keep rats or mice as pets and present-day houses are largely rodent-proof. This
means that mice may be quite acceptable occupants of a suburban garden shed.
Damage to natural ecosystems by invasive species have often been less visible to the public.
Often changes have been slow or inadequately recorded to show the change. However, the
more visible changes brought to natural ecosystems by invasive species, such as native trees
killed by browsing brushtail possums (Trichosurus vulpecula) or overtopped by old man’s
beard (Clematis vitalba), have dramatically demonstrated to the public that invasive species are
present and causing damage. With such knowledge in mind, the public are also able to perceive
damage by invasive species that occurs on a less visible scale.
The shape, size, colour and general “appeal” of a species, whether it is invasive or not, can
seriously influence public perception. For example spiders and wetas (large flightless crickets)
have no detrimental impacts, but are nevertheless generally disliked.
Some people will like or dislike a species simply because another person has told them it is
good or bad and they wish to accept the opinion of that person. In this way a person in a position
of power, or with a charismatic nature, can influence the public perception without giving them
facts.
Media portrayal can have a significant influence on public perception. If the media choose to
leave out one side of a discussion, or simply emphasize a point of view, then many people will
accept that as the correct situation.
The cost of managing a pest species will be a significant part of a decision-making process
about pest management. While this is usually not visible to the public, they can influence a
decision if they are made aware of a significant cost.
If the public sees detrimental impacts from a proposed pest management method, then they
may well demand that the management method be modified or the entire programme stopped.
Changes of public perception over time
Over the past half century the public perception of invasive species in New Zealand has
changed notably. The population structure of the country has changed significantly with the
emergence of an urban population, which has a limited relationship to the rural economy and to
historical rural attitudes to invasive species. The invasive species knowledge of the urban
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