Download File

3.3 Human Impacts On Biodiversity
Big ideas to keep in mind:
• Major threats to biodiversity caused by human
activity include habitat loss, invasive species,
pollution, overexploitation and climate change
• Conservation biology focuses on protecting
ecosystems and species
On The Waterfront
• More than half of the population of North America
lives on the continent’s coasts
– Including the shores of the Great Lakes
• Coastal areas and shorelines are also major areas of
biodiversity
• As human populations grow in these areas, more
land is needed for agriculture, roads, buildings and
other human activities that reduce biodiversity
• Establishing more agricultural lands may lead to
more fertilizer runoff that flows into the water,
creating dead zones, which are areas with low
levels of oxygen that cannot support life
• The Great Lakes Water Quality Agreement pledges
to reduce fertilizer runoff, improve sewage
treatment and help protect ecosystems
Threats To Biodiversity
• Throughout Earth’s history species have become
extinct
• Periods of mass extinction most likely occurred as a
result of drastic climate change caused by volcanic
eruptions or asteroid collisions
• It is believed that an asteroid impacted the Yucatan
peninsula during the Cretaceous period causing a
mass extinction, causing extinction of most the
dinosaurs
• There is currently another period of mass extinction
taking place on Earth
• Its scale is uncertain since the known number of
living species (about 1.5 million) is probably only a
fraction of the total number of species around
• But there are signs that species are disappearing at
a dramatic rate:
– about 12% of the 9900 bird species in the world are
endangered
– about 300 of the 20 000 known plant species in North
America are at risk
– About 37% of the known fish species have become
extinct or are at risk
What is causing these threats to biodiversity?
4. Overexploitation
1. Habitat Loss
2. Invasive Species
5. Climate Change
3. Pollution
Habitat Loss
• Greatest threat to the biodiversity
• This is the factor that endangers 50% of all
threatened species
• As human populations grow and develop land for
communities, they destroy natural ecosystems
• If the species that inhabit those ecosystems cannot
relocate or adapt to the changing conditions, they
will die
• Some developments split habitats into fragments
• Habitat fragmentation alters small areas within a
large region creating a patchwork of altered and
original habitats
• Ex: building a road through a forest creates a barrier
that may prevent species from using resources in all
parts of the forest
• The smaller the fragments, the less species they can
support
• Deep sea trawling is similar to deforestation,
destroys coral reefs which are rich in biodiversity
Invasive Species
• The next greatest threat to biodiversity
• Invasive species are non-native species that harm
ecosystems where they are introduced
• They often prey on native species or outcompete
them for resources
– Population size
meaning resource consumption
• Humans can introduce them to new areas
intentionally or accidentally as people travel
• More than 160 invasive species have entered
southern Ontario and the Great Lakes region
Examples:
• Accidental: seeds/spores
from plants stuck in shoes,
clothes, tires;
pet releases;
ship ballasts;
cargo containers/dunnage
• Intentional: In 1930s, kudzu plant in the southern
US to help control erosion along irrigation canals…
grew out of control, now as far north as Ontario
Pollution
• Burning coal to produce electricity is one of the
greatest contributors to impacting biodiversity
• Coal-fired power plants emit more CO2 than vehicles
• SO2 is also produced which results in acid rain when
it combines with water vapour
– Acid rain damages organisms, as well as lowers the pH of
soil and water
• Also, cleaning coal results in toxins such as mercury,
lead, arsenic which could enter ecosystems
Overexploitation
• The unsustainable use of resources
• Humans harvest many natural resources and
organisms faster than the resources can be
replenished and the organisms can reproduce
• Ex: The North Atlantic cod fisheries
annual catch dropped from
479 141 tons in 1988 to
12 490 tons in 1995
Climate Change
• Many human activities contribute to climate change
by emitting CO2 into the atmosphere which is
believed to increase global warming
• Human activities such as burning fossil fuels,
clearing land by slash and burn methods, raising
livestock, draining wetlands all have harmful effects
on the environment
• The impacts of several human activities can
combine to produce synergistic effects resulting in
greater damage than the individual activities
Ex: Climate change modifies
the pattern of water runoff
and precipitation in NW
Ontario, increasing the
number of droughts. Organic
matter that is normally
deposited into the lakes with
runoff is reduced greatly
Pollution from coal mining
releases S and NO’s into the
surrounding air causing acid
rain. The acidification of the
water decreases the amount
of algae in the lake
Without algae and organic material in the lake, lake water
becomes much clearer and harmful UV radiation penetrates
deeply into the water and further harms protists, plants,
animals, all of which are integral parts of the food web in an
ecosystem
Conserving Biodiversity
• Objective: protect ecosystems (abiotic + biotic)
• Plants and animals do not follow political
boundaries, therefore it needs to be an
international effort
• Convention on Biological Diversity (161 countries)
employs two strategies:
– ex-situ conservation: protecting species by removing
them from their natural habitats
– in-situ conservation: protecting species in their natural
habitats
Protecting Species Beyond Their
Habitats
• Ex-situ conservation is used when a species’ habitat is
threatened or no longer exists, or the existing
population of the species is very small
• The at-risk species live in zoos, gardens, reserves
• Plants: storage of seeds, cuttings of plants, living plants
• Ex: the Metro Toronto Zoo breeds
and maintains a population of
black-footed ferrets which no
longer exist in the wild in Ontario;
some have been reintroduced
Protecting Species In Their Habitats
• Ex-situ conservation is considered a last resort
• In-situ conservation involves establishing protected
areas, restoring habitats and adopting laws to
protected threatened species
• Ex: The Lake Ontario Atlantic Salmon Restoration
Program has stocked a million young salmon in
three Lake Ontario streams
in an effort to bring back
salmon to Lake Ontario
Take Action To Conserve Biodiversity
• Ecological Footprint: an estimate of all the land and
water needed to produce the resources you
consume and to absorb the wastes you produce
• The average Canadian requires ____ ha or ____
football field to maintain their lifestyle!
– this is not sustainable, because if everyone on Earth had
the same ecological footprint, we would need____Earths
• You can conserve biodiversity by reducing your
ecological footprint in the biosphere
• The goal of sustainable development is to develop
natural resources so that they can renew
themselves and be available for the future
• Sustainable development depends on the continued
research and applications of ecology and
conservation biology
• The challenge is to meet the
needs of Earth’s population
while conserving ecosystems
and resources to meet the needs
of the planet’s other populations as well