Introduced Species: Impacts on Biodiversity
PowerPoint script
Prepared by Woodland Park Zoo Education Department
2001
This presentation, designed for students of grades 5-12, can be used as an introduction to
a unit on introduced species or as a supplement to a unit on biodiversity or endangered
species. Although the presentation as designed is most appropriate for grades 5-12, you
may adapt text or format, or hide slides as necessary to adapt the presentation to a wider
range of grade levels.
Using this script, you can present this PowerPoint for your students, or have students
work together to present the PowerPoint to the rest of the class. The presentation will take
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the images. See Slide 20 of the PowerPoint for image credits.
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Slide 1
Woodland Park Zoo logo
Slide 2
Introduced Species: Impacts on Biodiversity
Slide 3
Threats to biodiversity
Scientists agree that the following five factors are the major problems contributing
to the current loss of biodiversity:
1. habitat destruction
2. introduced species
3. pollution
4. overexploitation
5. population growth
Slide 4
Terms
 Alien = (see introduced and exotic)
 Exotic = a species not native to an area; a species that has been introduced to an area
(see introduced)
 Introduced = a species that has been brought into an area (accidentally or
intentionally) where it did not naturally or historically occur
 Invasive = an introduced species that rapidly populates and expands its range in an
area and causes or is likely to cause economic or environmental harm or harm to
human health
 Nonnative = a species not indigenous to a specific area (see introduced)
 Noxious = an introduced, non-native species that may be aggressive, competitive,
highly destructive or difficult to control; most often refers to plants
 Nuisance = introduces species that threaten the diversity or abundance of native
species or the integrity of a natural ecosystem; most often refers to aquatic species
 Indigenous = a species originating from or occurring naturally in a specific region
 Native = a species indigenous to a specific region
What do these terms mean to you?
Native - how far back in time do you go? 300 - 500 years ago = prior to major European
settlement and ecological influence in the New World? 10,000 years ago (prior to
movement of humans from Asia)?
Connotations of words - negative, neutral, confusing, realistic?
Slide 5
Introduced Species
 Introduced species have been moved from their native habitats to new habitats usually by humans, accidentally or intentionally.
 Some introduced species become invasive in their new habitats = successfully
reproduce, spread and cause economic or environmental harm or harm to human
health
Example: Herb robert (Geranium robertianum) is an invasive species of Pacific
Northwest forests. This geranium, an escaped ornamental plant, is native to forests of
Europe, Asia and North Africa. Herb robert is very shade tolerant and invades forests
understories and can outcompete native understory species. Herb robert has a distinctive,
“foxy” odor when the leaves are crushed.
Slide 6
Pathways: How are species introduced?
 Intentional introductions for agriculture, horticulture, research, biological
control
 Unintentional introductions through contaminated agricultural products, timber,
etc.
 Attached to or carried in freight, packing materials, shipping containers, ships,
boats, cars, planes and other modes of transport
These pathways are factors of modern technology and systems of transportation and
global trade. The history of species introductions parallels the history of trade and
transportation in human societies.
Examples: An intentional introduction was the introduction of cane toads (Bufo marinus)
to northeastern Australia in the 1930s to control a sugar cane insect pest. Unfortunately,
the toads were ineffective against the insects, but became invasive and have had negative
impacts on native Australian wildlife. Accidental introductions occurred when rats
stowed away on European ships in the 16th to 19th centuries and were transported to many
places. Rats have particularly impacting ground-nesting birds and lizards on islands by
feeding on their eggs and young.
Slide 7
Biological attributes of invasive species
 This is an area of current research
 Difficult to generalize
 Usually a lag phase before a species becomes invasive - difficult to tell which
introduced species will die out and which will become invasive
= difficult to decide whether to make the effort to control the species at this point
or not
 Pinpointing these attributes would provide a valuable tool for preventing
invasions
Slide 8
Theories about why some introduced species succeed:
These theories take into account attributes both of the species and the communities
being invaded:
 Introduced species have escaped from natural constraints (predators, parasites,
etc.)
 Introduced species may occupy a niche that was vacant
 The invasion of species is most often aided by humans, usually through the
disturbance of the native community
Only a small percentage of introduced species establishes themselves in the new
ecosystem and become invasive. The number of individuals released and the number of
times and places a species is released can affect the establishment and invasion of a
species.
The invasions of species, like the introduction of species, is also tied to patterns of human
settlement, transport and trade. Some ecological communities were disturbed by human
activities prior to widespread introductions of native species. These disturbances possibly
set the stage for the introduced species to invade. Characteristics of the introduced
species and the habitat interact to facilitate (or deter) invasions.
For example, Scotch broom (Cytisus scoparius), originally introduced to the US as a
garden ornamental, was also introduced along roadways in the Pacific northwest to
control erosion. Scotch broom has many characteristics that contribute to its invasiveness
such as profuse seed production, seeds that are projected far from the parent plant and
germinate in exposed soil, deep roots, ability to sprout from stumps, rapid vertical growth
and intense spatial competition. These and other characteristics allow Scotch broom to
outcompete other plants in disturbed habitats such as roadways, forming dense stands.
Some invasive species facilitate others; e.g. feral pigs in Hawaii disperse seeds of
invasive strawberry guava.
Slide 9
Impacts on Biodiversity
 Invasive species can have a multitude of impacts:
 prey on or cause disease of native species
 outcompete native species for resources or breeding sites
 hybridization with native species
 habitat modification (change hydrology, encourage fire, alter nutrient cycles)
 agricultural/natural resource losses (pests, diseases)
Can also harm human health.
Slide 10
Impacts on Biodiversity
Examples: Herb robert (Geranium robertianum) can outcompete native understory
species in Pacific northwest forests. Cichlid fish in Lake Victoria in Africa have been
impacted by the introduction of Nile perch for the fishing industry. A large number
(approximately 400) of diverse cichlid species once inhabited Lake Victoria. It is now
believed that half of these species have gone extinct due to impacts from the introduction
of Nile perch in combination with other factors. English ivy (Hedera helix) is a plant
native to Europe, western Asia and north Africa that has been introduced across much of
the United States. English ivy is very invasive and can cover the ground as well as engulf
other plants and trees, preventing sunlight from reaching other plants and thus
outcompeting the native species.
Slide 11
Western pond turtle
Populations have declined, in large part due to predation by introduced bullfrogs
Slide 12
Economic Impacts of Invasive Species
 Loss of potential economic gain:
 crop production
 domestic animal and fisheries industries
 forest products
 Expense of fighting invasions
 preventing invasions (quarantine)
 controlling populations of invasive species
 eradication
A recent study estimated the economic cost of invasive species in the US to amount to
$137 billion annually. (Pimentel, D., L. Lach, R. Zuniga, and D. Morrison. 2000.
“Environmental and economic costs of nonindigenous species in the United States.”
BioScience 50:53-65.) It was calculated that in 1998 five Texan cities (Austin, Dallas,
Fort Worth, Houston and San Antonio) together spent $580 million on controlling fire
ants, repairing damage they had done and providing medical treatment for people stung
by them. Fire ants, accidentally introduced into the US from Brazil in the 1930s, invade
buildings in search of food and moisture, often gathering around electrical wiring. The
ants can cause power outages and fires, as well as injuring people with their bites and
stings. Fire ants have impacted native insect species by preying heavily on them.
Slide 13
What is being done?
 In February of 1999, President Clinton signed an executive order which expands
and coordinates federal efforts to address the threat of invasive introduced
species and to prevent the future introduction of nonnative species.
 The Invasive Species Council, created by the order, has developed a National
Management Plan for invasive species.
The final version of the National Management Plan was completed in January 2001. The
plan includes recommendations for actions that will be undertaken by the Council in
coordination and partnership with other stakeholders as appropriate. These actions fall
into nine categories: Leadership and Coordination, Prevention, Early Detection and Rapid
Response, Control and Management, Restoration, International Cooperation, Research,
Information Management, and Education and Public Awareness.
www.invasivespecies.gov
Slide 14
What is being done? Regulating Introductions
 Invasive species, once established, are very difficult to eradicate
 prevention of invasions is key
 International treaty:
Agreement on the Application of Sanitary and Phytosanitary Measures (SPS)
 WTO members can restrict movement of species that may pose a threat to
human, animal or plant life
In some cases, if a nation attempts to ban importation of a species, WTO can rule that the
ban is an unlawful or a protectionist trade barrier rather than a legitimate attempt to
exclude pests.
Slide 15
What is being done? Regulating Introductions
 Animal and Plant Health Inspection Service (APHIS) of the Department of
Agriculture
 attempts to prevent the introduction of nonnative agricultural pests and
diseases
 focused mainly on protecting agriculture, but also serves to prevent ecosystem
damage caused by nonnative species and diseases
The present US approach is "innocent until proven guilty" = not very effective in
preventing new invasions
Slide 16
What is being done? Eradication and Control
 Methods of eradication:
 chemical
 mechanical (including manual)
 biological
 Often, eradication efforts are too little, too late
 If eradication fails, then maintenance control is the goal
 same methods as for eradication
The goal is to maintain or increase native species diversity and to maintain a
functional ecosystem that leads to that level of diversity (may have to accept
invasives in the mix)
Chemical - insecticides, herbicides; when invasives have taken over a large area,
chemical control can have health impacts and other negative impacts on the ecosystem
Mechanical – for plants: cutting, burning, pulling; for animals: hunting, trapping, fencing
Biological control – pests such as insects or diseases that are specific to the invasive
species you are trying to eradicate or control. Has been the most successful of the three
methods in eradication and control; however, has also lead to some of the worst
invasions. Biological control agents are rigorously tested for host-specificity (whether
they will attack only the target species), but some have attacked non-target species.
These methods of control may work most effectively in combination for some situations.
There is a need for long-term, large-scale view on these issues. Eradication and control
must be coupled with monitoring.
Ecosystem restoration/habitat management - in some cases, restoring ecosystem
functions can favor native species over introduced species (e.g. restoring shallows and
flood regimes in Ohio River could reduce zebra mussels and encourage reestablishment
of native mussels)
Slide 17
What is being done? Eradication and Control
Example: In Australia, European red foxes were released in the mid-1880s for
recreational hunting purposes. Foxes have subsequently reproduced and spread across
the country, threatening both livestock and native wildlife. Poisoning with the compound
1080 has been very successful in Western Australia because this compound is naturally
found in native pea bushes in the region, so many native species show high tolerance to
the poison while foxes succumb to it. Rebounds in populations of native species have
already been documented in natural areas of Western Australia.
Slide 18
What can you do?
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In the garden - choose native plants and pull exotic weeds
Do not release exotic pets or dump aquariums containing exotic pets or plants
Avoid transporting fresh fruits, vegetables, grains or meats across state or
country lines
Volunteer to control invasive species or plant native species in a local natural
area
Be aware of the issues and help to educate others
Slide 19
The next invaders?
Not if you can help it! Walkingsticks are popular classroom animals, however, they have
the potential to become invasive and could damage local plant populations. Being a
responsible walkingstick owner is one way that you can help to prevent future invasions.
Walkingsticks pose a particular risk due to the females’ ability to lay hundreds of viable
eggs without ever mating (parthenogenesis). There is no way to tell what effects
walkingsticks could have on our local habitats if they were to establish themselves in the
wild. Proper management of your walkingstick colony will prevent this from happening.
Tips for managing your walkingstick colony:
 Keep track of your walkingsticks – be certain that they remain in the tank, or if you
do remove them for observations, make sure they are returned to the tank.
 Know what walkingstick eggs look like. The eggs generally look like small,
uniformly-shaped, oval seeds (somewhat similar to mouse droppings). Some species
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drop the eggs randomly throughout the bottom of the tank. Other species attach their
eggs to objects in the tank, such as pieces of bark, or on the lid of the tank.
When cleaning out your walkingstick tank, look for eggs. If you want to hatch one
more walkingstick, keep a few eggs in a small, plastic container (with a mesh cover)
with a small capful of cotton balls (keep moist). Put all the rest of the eggs into a
small, plastic container and keep in a freezer for at least two weeks before disposing.
When cleaning out the tank, place any dried leaves and dirt inside two plastic bags
and store in a freezer for two weeks before disposing. (There may be eggs you have
missed on the leaves or in the dirt.) If you cannot keep the leaves and dirt in a
freezer, wrap the refuse tightly inside two plastic bags and dispose of in the garbage.
It is best to manage your colony well and not have to give away any surplus
walkingsticks. However, if you must give away walkingsticks, be sure that anyone
who gets a walkingstick from you is responsible, understands the threats these
animals pose to our native ecosystems, knows the importance of managing their
colony, and has this care information. It is unadvisable for teachers to give
walkingsticks to their students.
Slide 20
Produced by Woodland Park Zoo, Education Department, 2001
Photo credits:
All photos by K. Remine/M. White except:
Slide 11 - Western pond turtle by Kate Slavens.
Used with permission.