Transcript 6 Human Impacts on Ecosystems

Humans & Ecosystems
Humans depend on ecosystems for:
-Food
-Habitat
-Oxygen and clean air
-Energy…
There are lots of ways humans have
changed the Earth’s ecosystems. We will
focus on the following
• Habitat change
• Overexploitation
• Pollution
• Invasive species
For each impact you should be
able to answer:
1. How are humans impacting the ecosystem?
2. Is this linked to the cycling of nutrients (carbon or
nitrogen) impacted?
3. How does this impact aquatic and terrestrial
ecosystems?
4. How does this impact the lithosphere, hydrosphere
and/or atmosphere?
5. How is the human impact changing the health of
the ecosystem?
6. Is the human interaction sustainable?
Invasive Species
(in Canada) p59
• Species that are introduced to an
ecosystem that were not originally present
are considered EXOTIC species
• Often these species can thrive and their
population increases greatly. They may
even out-compete native species. These
are then considered invasive. They can
decrease biodiversity if they decrease the
numbers of native species.
Check out www.invasive.org
Exotic Species
Dandelion – introduced
1800’s. Settlers brought
them from Europe
because they thought
they were a pretty
plant.
Also arrived at the
same time: Norway
maples, smallpox &
measles among other
things!
Invasive Species in Ontario
Purple loostrife was a plant that people thought was pretty and
started planting in small backyard ponds without considering the
impact of the exotic species. It spread through waterways and has
clogged up many wetlands and waterways due to its prolific
production – 2-3million seeds a year and no native (in Ontario)
animals to eat it. This plant was out-competing native plants for
space and nutrients. To try to alleviate the problem scientists
introduced another non-native species the seed weevil in 1994. This
was an insect that would eat the purple loostrife and it was hoped
would fit into the Southern Ontario food web.
Purple loostrife (Lythrum salicaria L.)
Invasive Species
• Asian carps (Silver carp, Bighead carp,
Grass carp, Black carp):
http://www.youtube.com/watch?v=rPeg1tbBt0A
These are found in large numbers in the US
(Illinois) but could follow waterways into the
Great Lakes and they have the potential to
outcompete native species like salmon, lake
trout and walleye.
Invasive Species
Emerald Ash Borer Beetle introduced in
2007. Currently is attacking Ash trees in southern
Ontario. In Kitchener conservationist are removing
the trees in the hopes to starve the beetle and
prevent it from spreading further north. The ash
trees will ideally be replanted once the beetle is no
longer such a problem. In the Windsor area
woodpeckers have started to eat the ash borer and
it is hoped that these birds will keep the ash borer
beetle in check!
CTV news clip
http://kitchener.ctvnews.ca/kitchener-to-cut-down-hundreds-of-trees-as-emerald-ash-borer-battle-heats-up-1.1139834
More examples of Invasive
Species – Zebra Mussels
Brought to Great Lakes
on ships in their ballast
water!
Invasive Species
Both round goby
(Neogobius
melanostomus) and zebra
mussel (Dreissena
polymorpha)
Exotic species are almost always introduced intentionally
or unintentionally by human travel.
Upcoming extensions…Preventing Invasive species – see p 100-101 in text
Endangered Species pp94- in
text
• A species that faces extinction or
extirpation (extinct in some areas).
Spotted Owl
Grizzly Bear
Endangered Species
Species become endangered for a variety of
reasons:
•Hunting/ poaching
•Habitat loss or fragmentation
•Overexploitation of a resource like water
•Disease
•Exotic species
• the vast majority of southern Ontario used to be one giant
forest. Now much of it is farms and cities with small islands
of forest scattered throughout.
• This is known as habitat fragmentation, where only small
chunks of the original habitat are left interspersed between
developed land.
• Overexploitation
• This is when a resource is used up faster
than it can be replaced.
• A common example of this is overfishing.
• The cod fishery in Atlantic Canada collapsed
in the 1990’s. The fishing industry got more
efficient at gathering fish and gathered them
all up. They took the young and the old and
then there were none left. The cod
population still has not recovered.
Endangered Species
• Once species populations become small it
becomes difficult to find mates and
inbreeding is an issue. This decreased
genetic diversity makes organisms
less adaptable to changes and diseases.
Endangered Species around the
world
Whale shark
Caught for it’s fins
White Rhino
Hunted for it’s horn
Natural Resources
Canada is so fortunate to have a large
variety of natural resources including:
-Metal deposits (gold, or mining copper…)
-Potash
-Oil sands
-Freshwater
-Forests
-Fisheries…
Human Impacts
Humans use these resources but we need
to get them from their natural environment.
This leads to our common practices of
mining, logging (clear-cutting), diverting
water for farming or dams, hunting, fishing.
All of these cause changes to populations
and habitats.
Habitat change
• This is the process by which humans alter
a habitat enough so that native species
can no longer live there.
• We alter habitats for a variety of reasons
including cities, agriculture, dammed rivers
etc.
Logging Forests
Clear-cutting: All trees are mechanically
removed.
Selective cutting: only valuable trees are
removed manually.
Clear Cutting
-
Less expensive to do
Safer for workers
Can choose what trees to re-plant
Causes soil erosion and runoff of nutrients
(soil quality decreases)
- Changes habitat
- Decreases biodiversity
Selective Cutting
Better ecological option but still:
•Destroys/changes habitat
•Decreases biodiversity
•Is more costly and more dangerous for
workers
Why do humans log forests?
•
•
•
•
•
Building materials
Paper products
Clear land for agriculture
Clear land for roads and human habitation
Get to materials under the land… mining,
oil sands…
The nature of things:
http://www.cbc.ca/natureofthings/episode/billion-dollar-caribou.html @ 28 min
Rick Mercer Potash mining
http://www.youtube.com/watch?v=
ZKQmsr5m_uY
Fort McMurray
http://www.youtube.com/watch?v=
HNSbiNxxlTQ
How does logging impact
species?
• Decreases habitat
• Decreases food
• Fragmenting of forests – changes
migration paths and breeding grounds
How do we decrease logging?
• Recycle & choose to buy recycled
materials
• Reduce use of …
• This does not just happen on land either. Some
fishing industries are clear cutting the ocean floor
with bottom trawling nets that scoop up everything
on the ocean floor and damage coral beds and
many other primary producers.
Farming
Current practices in farming include:
- clearing land and planting monocultures of
crops.
- clearing land and/or using grasslands to
feed animals for human consumption
Farming
Farming also uses pesticides to kill off
weeds that compete with crops (herbicides),
and decrease pests that eat the crops
(insecticides). These pesticides can affect
non-target organisms and will decrease the
biodiversity. Pesticides can also have
unintentional effects if they follow a food
chain – this is called bioaccumulation.
Farming and Fertilizers
Recall fertilizers are a way to add useful
nutrients like nitrogen to the soil. If not used
by the plants these nutrients can run-off the
soil into nearby aquatic ecosystems. This
increase in aquatic nutrients can lead to
huge changes in the water – algae blooms,
decreased oxygen, and increased organic
matter in the water.
Algae Blooms
Effects of Human Activities
on the Nitrogen Cycle
• Human activities
such as
production of
fertilizers now fix
more nitrogen
than all natural
sources
combined.
Figure 3-30
Recall: A way of fixing nitrogen without
fertilizers – crop rotation
Pollution (p58 in text)
• This is a substance added to the
environment that produces a condition that
is harmful to organisms.
http://www.cbc.ca/news/world/china-to-cough-up-283-billion-to-clean-up-airpollution-1.1324866
• One example of
pollution is CO2 gas
created by internal
combustion
engines.
• Burning fossil fuels
also releases
nitrous oxides and
sulphur oxides
which cause brown
smog and acid rain
• Point source pollution enters at a specific place from
a specific source. Eg. factories, sewage etc.
• Non-point source pollution enters indirectly when
snow or rain redistributes pollution into other areas.