Transcript Chapter4

• International trade and travel are believed to be the leading
cause of harmful intentional introductions.
• Most plant and vertebrate species introductions have been
intentional for e.g. plants as ornamentals, mammals and birds
as game, and fish for sport fishing.
• Most invertebrates and microbe introductions have been
accidental, often attached to other species introduced
intentionally.
• Agricultural weeds have often been introduced as contaminants
or crop seeds.
DELIBERATE OR INTENTIONAL INTRODUCTIONS
• Agriculture and forestry species
• Plants for soil improvement and
stabilisation
• Ornamental plants
• Hunting and sport (e.g. red deer in New
Zealand, rainbow trout in Chile and New
Zealand)
• Food resources (birds, fish, mammals,
crop plants – e.g. rabbit in Australia,
pig in Hawaii)
Gulley erosion caused by
rabbits in Australia
DELIBERATE OR INTENTIONAL INTRODUCTIONS
• Biological control (e.g. fox to control rabbits; giant toad to
control cane beetles in Australia; mongoose to control rats in
Hawaii)
• Fishery releases
• Pet trade
• Fashion and aesthetics (e.g. songbirds in Hawaii, house
sparrow and starling in North America and SA, and grey
squirrel in Europe; possums for fur trade in New Zealand)
WHY INTRODUCE THESE SPECIES? – a closer look
Comfort and familiarity (recreate “home”)
Ignorance re use of native species
Cultural and religious reasons
Biological control and restoration
Pets, sport, fashion, aesthetics
Economic benefit
Community upliftment (aid agencies)
Most intentional introductions economic purposes (McNeely,
1999).
http://www.midatlantic.net/8x10/
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The general result of deliberate introductions has been termed
the ‘Frankenstein Effect’ because so many well-intentioned
introductions have had unexpected consequences, usually
negative (Moyle and Light, 1996).
HORTICULTURE
• Major pathway of invasive alien species introductions.
• Horticulture includes not only species introduced for ornamental
purposes, but also for agricultural, medicinal or aesthetic
purposes, to botanical gardens, nurseries, culinary stores
(herbs for cooking), pharmaceuticals (human and veterinarian
medicines) and engineering companies (for land restoration,
reclamation and stabilisation) (Reichard and White, 2001).
http://www.daylilyladies.com/
http://www.garringer.net/foam/archives/images/NURSERY.gif
HORTICULTURE cont.
• The Spanish were the first to introduce the peach to America.
Later, apple, pear and cherry trees were introduced.
• Other US examples include the Norway maple, Japanese
barberry, English Ivy and Oriental bittersweet all of which have
escaped from cultivation (Baskin, 2002; Harrington et al, 2003).
http://www.unc.edu/~pyzuo/teaching.html
• Education is essential to controlling random import of species
for cultivation (Harrington et al, 2003).
The advantage of recognising this is that it is a
potentially easy pathway to manage.
DELIBERATE FISH INTRODUCTIONS
http://www.pasarmalam.com.sg/~dragongate/images/photos/big-fish/nileperch02-l.jpg
• In the 1950’s, colonial authorities began stocking Lake Victoria
with the Nile perch. This has led to the disappearance of ± 200
native cichlid fish species (Lodge 2001).
• Mosquito fish are still being released in some countries as
biocontrol, even though it is an invasive alien and causes harm
by predating on many indigenous species. It was initially
introduced to reduce mosquito populations, and thought to
consume large amounts of mosquito larvae, but discovered to be
no more effective than native fish species.
POSSUMS
http://www.richard-seaman.com/Mammals/Australia/
Brush-tailed possums from Australia were introduced into New
Zealand between 1858 and 1900 to establish a fur trade, but in
New Zealand there were fewer competitors, predators and
parasites than in Australia, so they have successfully spread and
sometimes reached densities ten times that in Australia. These
possums have caused considerable damage to native forests,
through defoliation and elimination of preferred food plants
(McNeely, 1996).
PET TRADE
The pet trade often introduces exotic species into novel areas. Many
of these species can be selected and bought from catalogues over
the internet. Many of these species are difficult to care for or simply
can’t exist in these new areas, and are set free into the wild (some
may escape) when people no longer can or want to care for them.
ROSE-RINGED PARAKEET
The rose-ringed parakeet was introduced into Cape Town in the
1850s as a caged bird. The feral population started after accidental
escape or possibly liberated aviary birds. There are feral
populations in many parts of the world and in SA they currently
exist in KwaZulu-Natal and Johannesburg. With increased
introductions and increasing numbers, it can become a serious
threat to crops and indigenous hole-nesting birds (Dean, 2000).
ACCIDENTAL INTRODUCTIONS FROM INITIALLY
INTENTIONAL INTRODUCTIONS INTO CAPTIVITY
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Escaped species from zoos and botanical gardens
Farmed animals and pet trade
Aquaculture and mariculture
Research
ACCIDENTAL INTRODUCTIONS
• Contaminants of agricultural produce (seeds, plants, fruit
and vegetables, wood, soil)
• Soil-inhabitants
• Species hidden on machinery, equipment, vehicles
• Hitch-hikers in package material, cargo, mail, planes http://www.soultravel.nu/2003/
031010-celebs-NDU/index.asp
• Ballast soil and sediments
• Ballast water and hull fouling
• Debris
• Tourists and their luggage or equipment
• Diseases in animals traded for other purposes
• Parasites, pathogens and hitch-hikers of agriculture &
mariculture
• Whereas purposeful introductions might be controlled
by legislation or regulation, accidents may be far more
important in the spread of introduced species and
much more difficult to control (McNeely, 1999).
VECTORS OF SPREAD AFTER INTRODUCTION
• Spread from neighbouring countries
• Human-made structures which enhance
the spread of alien species (inter-basin
transfers, canals)
• Human alteration of habitats and
changed in agricultural practices
• Some species introductions have been
facilitated by human activities, but have
traveled under their own power to new
areas.
http://www.photoatlas.com/pics02/pictures_of_panama_74.html
VECTORS OF SPREAD AFTER INTRODUCTION cont.
• Some have taken advantage of man-made corridors to cross
previously impenetrable barriers. E.g. Sea lamprey was able to
invade the upper Great Lakes where it decimated native
populations of lake trout and white fish, after construction of the
Welland Canal enabled it to bypass the Niagara Falls.
• Similarly the Suez Canal has enabled
the introduction of at least 30 fish
species into the Mediterranean Sea
from the Red Sea.
• Clearing of forest and introduction of
domestic livestock has enabled the
cattle egret to colonize South America
from Africa.
Chapter 1 Definitions
Chapter 2 History, globalisation and GMOs
Chapter 3 The human dimension
Chapter 4 Pathways of introduction
Next
Chapter 5 Characteristics of invasive alien species
Chapter 6 The ecology of biological invasions
Chapter 7 Impacts of invasive alien species
Chapter 8
Chapter 9
Chapter 10
Chapter 11
Chapter 12
I hope that you found chapter 4 informative and that
you will enjoy chapter five!