Download Why Are Invasive Alien Species a Problem?

Activity 3.3 – Invasive Species
Use the information from environment Canada below to answer the following
questions (type directly into the word document below each question). Use full
sentences and put answers in your own words.
1) What is the difference between a native and alien (or introduced) species?
2) What is the difference between an alien species and an alien invasive
species?
3) Invasive species are a huge threat to biodiversity. What is the only threat to
biodiversity that is bigger than invasive species?
4) Why do most introduced species not become invasive?.
5) What are the three factors that enable invasive species to thrive?
6) What are the three categories of impacts invasive species can have? Give an
example of each.
7) Find the list of invasive species specific to BC in the information below. Pick
ONE plant or animal and research the following information on the internet:
a) Where in BC is this invasive species found?
b) How is it thought to have been introduced?
c) What sorts of damage has it caused (list several).
****INCLUDE THE ADDRESSES FOR THE WEBSITES FROM WHICH YOU
OBTAINED YOUR INFORMATION ****
8) What are the two main categories of “pathways” to introduce species?
9) Read about the many different pathways that are responsible for moving
invasive species. How can individual’s actions help with some of these)
Alien Species
Courtesy: Environment Canada
http://www.ec.gc.ca/eee-ias/Default.asp?lang=En&n=C4637128-1
What Are Alien and Invasive Alien Species?
Across the world, many species of plants, animals and even micro-organisms have moved
beyond their native range and habitat only to become established in a completely new
location. Sometimes species commonly found in one part of Canada become established
outside their natural range in another region of the country where they have not
historically been found. Most however, come from outside Canada and were relocated as
a result of human activity.
Species that have become established in areas outside their natural range are known as
"alien species". Generally, alien species do not pose a significant risk and many are even
beneficial. However; when alien species are capable of causing significant harm to our
environment, the economy or to society, they are referred to as "invasive alien species".
Canada has many examples of both alien species and invasive alien species. A few
examples are shown below.
Alien Species
Invasive Alien Species
Black-footed
spider
Emerald Ash
Borer
Common
plantain
Green crab
Canada has many examples of both alien species and invasive alien species. A few
examples are shown below.
Alien Species
Invasive Alien Species
European hare
Butternut Canker
Red-eared slider
Giant Hogweed
Native Species
Native species are those species that are indigenous to a particular area or region.
Typically, these species have evolved over thousands of years, adapting to their
surroundings, and have become an important part of the local ecosystem.
Like most species, native species are constantly competing for resources. Changes to the
climate, weather disturbances, fires, floods, the introduction of invasive alien species and
human influences can have a significant impact on the growth or decline of a native
population. Over time, some species may even be pushed out of a region or area
altogether.
© Kenneth E. Gibson, USDA Forest Service, Bugwood.org
Growing or shrinking native species populations can have a big impact on local
ecosystems. In some cases, these shifts can be very harmful. For example, the forest tent
caterpillar (Malacosoma disstria) is a native species whose populations can sometimes
grow so quickly that it will strip the leaves from large areas of hardwood forest. Even
though this species often lives in balance with other species, its varying population size
can cause considerable economic, environmental and social harm.
© Erich G. Vallery, USDA Forest Service - SRS-4552, Bugwood.org
The Mountain Pine Beetle (Dendroctonus ponderosae) is another native species that can
cause devastation to its environment. Adult mountain pine beetles lay their eggs on the
bark of a variety of different pine trees. After the eggs hatch, the larva feed on the phloem
(inside bark area) which can ultimately kill the tree. Like the tent caterpillar, major
increases in the beetle larvae population can seriously harm the local tree population.
The mountain pine beetle has coexisted with the pine forests of British Columbia for
centuries, and although outbreaks have occurred, they have been short-lived and regional
in area. Recently however, the Mountain Pine Beetle population has exploded causing
unprecedented tree mortality and problems for forest industry.
Although the scale of this epidemic has never been experienced before, the mountain pine
beetle is currently only impacting forests within its historic or native range. This situation
is being closely monitored however and its status will be re-evaluated should the
conditions change and it moves into areas where it is considered to be invasive.
Why Are Invasive Alien Species a Problem?
Introduction
According to the World Conservation Union, invasive alien species are the second most
significant threat to biodiversity, after habitat loss. In their new ecosystems, invasive
alien species become predators, competitors, parasites, hybridizers, and diseases of our
native and domesticated plants and animals.
It takes the right conditions for an alien species to become established and grow. In fact,
most introduced species do not become permanently established in their newly found
environment. They either find the wrong type of conditions for survival, or there they are
unable to produce enough offspring to maintain a viable population. For those species
that are able to reproduce and survive, most never cause significant problems. They
survive, spread and reproduce but generally do not pose a risk to Canada’s economy,
environment or society.
Some introduced species however, are able to thrive and even flourish at their new
location. They have the right biological properties that allow then to grow in numbers
quickly. In addition, they are usually able to reproduce and spread quickly, often outcompeting native plant and animal species for food water and space.
Invasive alien species generally share common characteristics which can make them
difficult to control and contain, including:
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Higher rates of reproduction – it has been estimated that one Purple Loosestrife
plant can produce 3 million seeds.
Fewer natural predators – newly introduced species are often free of predation and
disease, two major factors that keep native plant and animal populations in
balance.
Ability to thrive in different environments – most invasive alien species are
generalists, meaning they can survive in a variety of different habitat types and
climate regions.
The impact of invasive alien species on native ecosystems, habitats and species is severe
and often irreversible, and can cost billions of dollars each year.
Invasive Alien Species Impacts
Environmental Impacts
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Can negatively impact biodiversity
Can cause species extirpation and even extinction
Can cause soil degradation, and erosion
Can alter fire cycles
Societal Impacts
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Can cause disease
Can cause human or animal suffering
Can reduce land and water recreational opportunities
Economic Impacts
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Control and management costs can be significant
Can reduce productivity in forestry, agricultural, and fishing sectors
Can cause export and import trade restrictions
Can reduce property values
The following are just some examples of invasive alien species impacts in Canada and
abroad. Check regularly as this list will be continuously updated.
Species
Zebra Mussel
Dreissena
polymorpha
Table 1: Types of Species and their Impacts to Canada
Type of impact
(economic,
Description of impact
environmental,
societal)
Zebra muscles will infest almost every hard
surface including rocks, boat hulls, and water
Environmental
intake pipes. They can even grow on the shells of
our native clam species, reducing their ability to
feed and as such increase mortality.
Japanese
Knotweeds
Fallopia
japonica &
Polygonum
cuspidatum
Environmental
West Nile Virus
Social
Family:
Flaviviridae
Emerald Ash
Borer
Economic
Agrilus
planipennis
Japanese Knotweed is a perennial shrub from
Asia, often considered one of the most persistent
of all weeds. Once established in disturbed areas
or along stream banks, this highly invasive species
can displace virtually all other types of
vegetation.
The West Nile Virus originated in Africa and
Europe. Since its discovery in North America,
public health agencies have been waging an
aggressive campaign to inform the public about
the risks associated with contracting this disease.
The cost of eradication and control efforts
associated with this invasive insect have totalled
in the millions per year.
Global Impacts
Table 2: Types of Species and their Impacts Globally
Species
Type of impact
(economic,
environmental,
societal)
Economic
This small jellyfish, native to estuaries of eastern North
and South America, was almost certainly exported to
the Black Sea in ship ballast water. Since it was first
discovered in 1992, it has single-handedly caused the
collapse of the entire anchovy fishery, an industry once
worth millions of dollars per year.
Environmental
This invasive alien species first introduced to Guam
shortly after World War II, has caused immeasurable
damage to the Island's ecosystem. The Brown Tree
Snake has been directly linked to the extirpation of
several native species of birds (8), lizards (3), and
mammals (2 bats).
Social
Originally from the Amazon basin, this water plant has
spread to many aquatic ecosystems around the world.
Whole communities around Lake Victoria, Africa’s
largest lake, have had to move to gain better access to
open water and fish stocks.
Comb
Jellyfish
Mnemiopsis
leidyi
Brown Tree
Snake
Boiga
irregularis
Water
Hyacinth
Agrilus
planipennis
Description of impact
Where Are Invasive Alien Species Found in Canada?
Introduction
According to the World Conservation Union, invasive alien species are the second most
significant threat to biodiversity, after habitat destruction. No single region of Canada is
immune from the potential for invasive alien species and many, if not all ecosystems are
already experiencing some impact.
In their new ecosystems, invasive alien species become predators, competitors, parasites,
hybridizers, and diseases of our native and domesticated plants and animals. The impact
of invasive alien species on native ecosystems, habitats and species is severe and often
irreversible.
In 2002, it was estimated that 24 percent of the species listed as “at risk” by the
Committee on the Status of Endangered Wildlife could be threatened with extinction by
invasive alien species. Some of the 90 native species on this list that are considered
threatened by invasive alien species include ancient murrelets, island blue butterfly,
golden paintbrush, tiger salamander, northern prairie skink, American chestnut, eastern
flying squirrel and ginseng.
Similarly, in the Great Lakes, now home to more than 160 alien species, sea lamprey
have been implicated in the extinction of the deepwater cisco, and zebra mussels have
extirpated native mussels from some areas.
Clearly, invasive alien species are an increasingly important factor in the decline of
native species in both aquatic and terrestrial ecosystems.
Invasive Alien Species in Terrestrial Environments
Many of Canada’s diverse terrestrial environments have been impacted by invasive alien
species of plants, animals, insects and disease. Invasive alien species are most often
found in or near urban areas, as well as throughout the settled landscape. Invasive alien
species can also be found in many of Canada’s more remote regions including the arctic.
Here are just a few invasive alien species found in Canada’s terrestrial environments.
Table 1: Invasive Alien Species in Terrestrial Environments
Name of
Species:
Japanese
Knotweed
(plant)
Description:
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Norway Rat
(mammal)
European
Earwig
(insect)
Butternut
Canker
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Large perennial plant native to China, Japan and Korea
Fast growing - can grow 2 or more meters in one growing season
This plant spreads primarily from discarded plant material or soil
containing plant material
Found in many urban centres across Canada, and along some
roadsides in Nova Scotia
Dense thickets will exclude other vegetation
A mammal species originally native to central Asia
A species that has followed human settlement patterns across all
continents of the world
Prolific breeders
Can cause significant damage to crops, buildings, food stores
Poses a significant human health risk
Norway rats are found in every province except Alberta which has
been waging an active campaign to keep them out for over 50
years
First noted in Newfoundland 1827 to 1835
Have since spread to all urban centres across Canada
Not directly harmful to humans
Nocturnal scavengers of decaying plant material, as well as leaves,
flowers and fruit
Can become a significant pest of urban properties and may enter
dwellings if populations are high enough
This disease is a serious threat to Butternut trees across its native
range
Table 1: Invasive Alien Species in Terrestrial Environments
Name of
Species:
(disease)
Description:
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Scientists are currently unsure of the origins of this fungus but
hypothesize it was originally introduced from outside North
America
Butternut is now a species at risk in Ontario
Cankers formed on stems and branches can cut off the movement
of water and nutrients within the tree
Cankers on the main stem will most often kill the tree
Invasive Alien Species in Aquatic Environments
Many aquatic environments like rivers, lakes and oceans have been seriously impacted by
invasive species. Whether these invaders were first released in ballast water discharged
from a ship, or from fisherman emptying bait buckets containing non-native species, or
even from people discarding unwanted aquarium plants and animals, the end result is the
same: a new aquatic alien species that can upset the natural balance of the ecosystem in
which they were released.
Here are just a few species currently found within Canadian waters:
Table 1: Aquatic Invasive Species in Saltwater Environments
Name of
species:
Description:
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Green Crab
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Tunicates
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Also known as the "cockroach of the sea"
Was first introduced to the waters off Cape Cod over 100 years ago
It had spread to the waters of New Brunswick by the 1950’s and
British Columbia in 1998
Occupies the same habitat as native crabs, clams, oysters, and
mussels
Invasive tunicates or ‘sea squirts’ are a type of filter-feeding animal
Table 1: Aquatic Invasive Species in Saltwater Environments
Name of
species:
Description:
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that grow on submerged stationary objects
There are five know invasive tunicate species affecting the
aquaculture and fisheries of Canada’s east and west coasts
Table 2: Aquatic Invasive Species in Freshwater Environments
Name of
species:
Description:
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Chinese
mitten crab
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Zebra
Mussel
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Round
goby
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(fish)
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This crab spends much of its lifecycle in fresh water environments
Canada has no native freshwater crab species
Although first discovered in Lake Erie in 1965, it has not been able to
become established in the Great Lakes, probably due to its need for
both fresh and saltwater environments when completing its lifecycle
This species does represent a significant threat to St. Lawrence River
and its many tributaries
First discovered in the Great Lakes around 1986
Have significantly change the nature of the lake bottom, affecting fish
habitat and spawning
Mussel populations often dominate near shore zones changing natural
process such as nutrient flow into deeper waters
Mussels also excrete nutrients creating an environment that may be
linked to water quality problems, such as algal fouling on rocky
shorelines, off-tastes in drinking water and lethal outbreaks of
botulism in wildlife, especially during warm water periods
Introduced to the St. Clair River in 1990 probably through ballast
water from ships originating from southern Europe
Have since colonized all five Great Lakes
Have impacted native fish populations
In Ontario, it is illegal to possess living round goby or to use them as
bait
Can spawn more then once per year
Invasive Plants and Animals in BC
Courtesy: Invasive Species Council of BC
http://www.bcinvasives.ca/invasive-species
-Blueweed
Canada Thistle
Giant hogweed
Gorse
Himalayan Blackberry
Hoary Alyssum
Leafy spurge
Common tansy
Hawkweeds
Knotweeds
Hound’s-tongue
Marsh Plume Thistle
Rush skeletonweed
Oxeye daisy
Scentless chamomile
Spotted & Diffuse Knapweed Sulphur Cinquefoil
Yellow Flag Iris
Purple Loosestrife
Scotch broom
Tansy ragwort
Common Carp
Didymo or “Rock Snot”
European Cottontail Rabbit Largemouth Bass
Rusty Crayfish
Zebra and Quagga Mussels
yellow perch
Eastern grey squirrel
New Zealand mudsnail
European fire ant
How Do Alien Species Get in Canada?
Introduction
Every species has a natural geographic area in which it is considered part of the native
flora and fauna that make up the biodiversity of the region. Some species have a very
small geographic range, while others may be found over multiple provinces or even one
or more continents.
“Alien” species are those species that have moved outside their natural range into an area
where they would not normally be found. One of the best opportunities we have to reduce
the impact of invasive alien species is to prevent them from becoming established in the
first place. To do this, we need to understand how they manage to move, or be moved,
outside of their native range.
Natural Movement
Between approximately 12 and 80 thousand years ago, there were periods of time when
much of North America was covered by ice. During these periods, plants and animals
were pushed well beyond their natural range by the advancing ice and the changing
climate.
When the climate warmed, and the glaciers began to recede, these same species slowly
followed the glaciers north, and established new habitat. At the same time, the sheer
volume of ice at the north and south poles caused a significant decrease in sea level
exposing a land bridge between Alaska and Russia. It is thought that many mammal
species moved from Asia to North America at this time.
While the native range of any species may change naturally with changes in climate and
landform, they do so very slowly, often taking many hundreds if not thousands of years.
Unnatural or Human-assisted Movement
The problems we are experiencing today with invasive alien species are for the most part
caused by unnatural species movement where a plant, animal insect or disease organism
is moved outside its natural range into an area or ecosystem that they wouldn’t normally
be able to get to on their own.
Human activity has been, and remains today, the primary means by which new species
enter Canada. Throughout time, humans have both intentionally and unintentionally
introduced species into new environments.
Figure 1. The cumulative number of species introductions into Canada since early
1600's.
The graph above demonstrates how over time the cumulative number of new species
entering Canada has increased at what appears to be an exponential rate.
For Canada’s early settlers, bringing in new species was seen as a way to survive and
adapt to their new surroundings. They brought various plants and animals, including
some of the agricultural crops we depend on today like corn, wheat and potatoes. Some
species were also unintentionally introduced – brought in as stowaways on the ships that
brought people and supplies. The number of new species introductions started to grow
substantially around 1900. Since that time, increased global trade and travel has led to a
dramatic increase in the number of new introductions over the past several decades.
European Buckthorn (Rhamnus cathartica L) was brought to North America as an
ornamental shrub in the late 19th century. It is now a serious invader of many woodlands
in north eastern United States and south eastern Canada.
Early sailing vessels coming to North America used soil or rocks as ballast to stabilize
the ship as it crossed the open ocean. This ballast was often replaced with a cargo of
wood, fur or fish for the return journey to the home port. New species of insects and
plants were introduced in this way.
Pathways
For invasive species, the term “Pathway” is used to describe the means by which a
species travels from its natural habitat into a new one. A pathway can be either natural or
man-made. Natural pathways like wind and water currents account for very few of the
new species introductions. The vast majority of new species introductions are caused by
humans. There are also distinct pathways for aquatic and terrestrial species.
Aquatic Species Pathways
Seven major pathways for the transport of aquatic invasive species have been identified.
1. Shipping
Many species have been introduced to the Great Lakes and other water bodies through
shipping. Ballast water discharge and hull fouling have been responsible for such species
introductions as zebra mussel, spiny water flea, and the green crab.
Ballast water being discharged in port
2. Recreational and Commercial Boating
Pleasure craft and commercial boats and barges can inadvertently help spread invasive
species around Canadian waters. Many of these vessels sit idol in their home harbour for
long periods of time allowing species to grow and accumulate on their undersides; if
these boats are then moved to a new and uninfested port, invasive species can be
introduced into those water ways. Zebra mussels area a good example of this.
Eurasian Watermilfoil is a serious invader of fresh water ecosystems; even a small
segment of this species can infest new waterways.
3. Live Bait
Live bait used for fishing and released into Canada’s lakes and rivers has been
responsible for the movement of several species. The rusty crayfish is one example of a
species that was introduced to many water bodies through live bait release; this species,
native to Ohio, Kentucky and Tennessee has spread to many northern lakes and rivers.
4. Aquarium and Water Garden Trade
Aquariums and water gardens are popular hobbies for many Canadians. Unwanted fish
and plants however, can be a source of invasive species introductions.
Yellow Floating Heart is an invasive aquatic plant that was originally introduced as a
water garden species.
5. Live Foodfish
Many species of fish are imported live for food. If released into the wild, some of these
species could become invasive.
6. Unauthorized Introductions
Native fish species have been purposely released into water bodies where they don’t
belong. In some cases, these introductions have caused significant harm to the existing
ecosystem.
7. Canals and Water Diversions
The construction of canals and water diversions has allowed species to move into new
water bodies where they do not belong. Perhaps the best known case is the sea lamprey
that moved into the upper Great Lakes once the Welland Canal was opened.
Terrestrial Species Pathways
Terrestrial invasive species are introduced and move around in a number of ways.
1. Cargo Transport
The increase in global trade has led to an increase in cargo shipments from all over the
world – many thousands of cargo containers are brought into Canada each month. These
containers sometimes contain living plants and animals and insects that build new homes
here in Canada; these become invasive alien species.
2. Horticultural Planting
Many varieties of garden plants and herbs are imported into Canada. While the majority
of these species do not pose a significant risk, some do, and several well known invasive
species have escaped the confines of the garden to become a serious problem.
English ivy is one plant that has escaped to become a serious problem outside the
confines of the garden.
3. Accidental Release
A number of terrestrial species have escaped captivity to become invasive.
4. Fire Wood Movement
Although not responsible for new introductions, some invasive insect species can be
introduced to new (uninfested) areas through the transport of firewood, Christmas trees,
and other wood products.
The emerald ash borer is a destructive invasive pest of ash trees. Firewood movement has
contributed to its range expansion in Ontario.