Transcript Threats to Biodiversity

Threats to Biodiversity
Threats to Biodiversity
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If human actions lead to the destruction of
ecosystems, such as wetlands or rainforests,
biodiversity on Earth could decrease.
This would be bad.
Environmental awareness is good!
Threats to Biodiversity
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As scientists learn more about the effects of
human actions on ecosystems, we are
paying more attention to decreasing human
impact on ecosystems and restoring
ecosystems that have been altered.
Overview
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Threats to biodiversity include:
1. Habitat loss
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Natural disasters
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Volcanic eruptions, wildfires, drought
Human activity
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deforestation
– draining wetlands
2. Alien species
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Harmless
Invasive
3. Overexploitation (Eg: over-hunting)
Extinction
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Extinction occurs when all the individuals of a
species have died
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How does is occur?
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When the death rate of a species exceeds the
birth rate
Individuals removed > individuals added
Extinction
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Even in ecosystems un-affected by humans, things never
remain the same forever.
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Biotic and abiotic features change
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Biotic factor: arrival of new leaf-eating insect species
Abiotic factor: decline in rainfall  dry soil
These changes might not result in direct extinction, but if
the change results in death rate > birth rate for a long
time…extinction eventually occurs. 
Patterns of Natural Extinction
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Background extinction:
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As ecosystems change over looooong
periods of time, some existing species
become extinct while new species appear
via evolution
Patterns of Natural Extinction
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Mass extinction: sudden change in
ecosystems, making them unsustainable
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This is believed to have happened 5 times in
Earth’s history
Natural Extinction
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The most famous of these
events, the CretaceousTertiary (K-T) extinction 65
million years ago, is thought
to have been caused at
least in part by a giant
asteroid that struck Earth off
the coast of Mexico,
causing tidal waves and
climate-altering dust clouds.
Dinosaurs, along with twothirds of the other species
on Earth, were killed off by
the K-T extinction.
Causes of Natural Extinction
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Global cooling due to glaciation
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Earth’s elliptical orbit around Sun
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Increased volcanic activity  global warming
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Increased CO2 production  global anoxia
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Changing sea levels
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Extra-terrestrial impact
Earth’s 6th Mass Extinction…
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…is (theorized) to be happening right now.
Uh-oh.
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Ecologists estimate that the current rate of
extinction is 100-1000X higher than normal
background rate
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In one study, 40 000 species were assessed.
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39% at risk of extinction
The 6th Extinction
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This is being called the
“biodiversity crisis”
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Def: the current
accelerated rate of
extinctions
Why does losing another obscure
species matter??
Gastric brooding frogs, discovered in Australia in the 1980s, raise their young
in their stomachs and secrete a substance that protects them from being
digested. This promised to provide a new treatment for human peptic ulcers,
which afflict 25 million Americans. But when the species went extinct,
scientists abandoned the research.
So What Can We Do?
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Stewardship: All humans are responsible for
taking care of our biosphere
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For ourselves
For other human beings
For other organisms
For future generations
Restoration Ecology
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Def: The renewal of destroyed or degraded
ecosystems through human intervention
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Goal is to simulate natural processes of
regeneration
Don Valley Brick Works:
1891
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Present day
Ecological Restoration converted Toronto’s Don Valley Brick
Works into a natural heritage park
Methods:
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Reforestation – the regrowth of a forest
through natural processes or planting
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Wetlands restoration – water levels are
returned to normal
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Controlling Alien Species – Biocontrol is the
use of one species to control the pop. or
growth of an undesirable species