Transcript How Introduced Species Affect Ecosystems

How Introduced Species
Affect Ecosystems
Chapter 3.3
Some Terms
• Native species: plants and animals that
naturally inhabit an area.
• Introduced (foreign) species: a species
that is not native to the area and has
been introduced (usually) by humans,
accidently or intentionally.
Invasive Species
• Many introduced species help or at least
do not harm the ecosystem they come
to.
• However, some take over the habitat of
the native species. These are called
invasive species.
• Invasive species often have high
reproduction rates, are aggressive
competitors, and lack natural predators.
Invasive Species
Purple Loosestrife
Invasive Species
Eurasian Milfoil
Invasive Species
The aquatic weevil (native in
BC) is a natural control for
milfoil (it eats it). The challenge
is getting it in our lakes.
Invasive Species
American Bullfrog
Invasive Species
European Starling
The Starling Outcompetes the
Western Bluebird for Nesting Sites
4 Ways Invasive Species Can Be
Harmful
• 1) Competition
- compete against native species for
resources (food, habitat)
Ex: Florida wasp became extinct a
few years after the southeast Asian
wasp became established.
4 Ways Invasive Species Can Be
Harmful
• 2) Predation
- introduced predators can have a
BIGGER impact on prey than native
predators.
In New Zealand,
European rats have
caused the extinction
of 9 species of birds.
Why are Introduced Predators
Different?
• Predator-prey relationships develop
over thousands of years
• Native species have no defenses and
may be consumed to the point of
extinction is a short time
• The loss of the native species can throw
the whole ecosystem (food chain) out of
balance
4 Ways Invasive Species Can Be
Harmful
• 3) Disease/ Parasites
- invasion of parasites and disease
can weaken immune response of
native species.
Parasitic lamprey sucks
the fluids from other
fish.
Disease/ Parasites
• Many Hawaiian birds became
extinct after falling victim to
malaria, brought by the
introduced Asian songbird.
I’iwi bird, endemic to the
Hawaiian Islands is
endangered.
4 Ways Invasive Species Can Be
Harmful
• 4) Habitat Alteration
- when an invasive species makes a
habitat unsuitable for native species.
On Haida Gwaii (Queen
Charlotte Islands),
introduced deer have
changed the ecosystem
Habitat Alteration
Island with deer
Island without deer
Habitat Alteration
• What are some other ways that invasive
species can alter habitats?
– Change in light levels
– Change in dissolved oxygen (water)
– Change in soil chemistry
– Upset the nutrient cycle balance