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Maintaining Sustainable
Environments Requires
Knowledge, Decisions, and
4.1 Intended and Unintended
Consequences of human Activities within
Human Impact on Ecosystems:
Chemical Use
 The use of pesticides by people, in addition to
the immediate solution they are intended to
produce, typically enter the food chain and
produce some very undesired results.
 The imbalance created by the impairment or
death of a species by these chemicals,
affects the entire ecosystem leading to
impairment or death of its predators and their
 Migratory species are very vulnerable to the
use of pesticides as they visit so many
 Example: The devastating affect the pesticide
DDT had on the people of Borneo. (pg 67).
Human Impact on Ecosystems: too
Little too Late?
 Human activity such as hunting, bioinvasion,
farming, urban development, and foresting
have affected species to varying degrees.
 __________
Threatened – when a species has
dramatically declined in numbers.
Ex. The wood bison and burrowing owl.
 Endangered
__________ – when a species is in danger of
Ex. The Beluga whale and Whooping crane.
Extinction – when a species has been
 ____________
entirely eliminated.
Ex. Dinosaurs
 Though extinction of a species is a natural
phenomenon, human activity has increased
the rate or altered the natural course of
succession entirely.
 Page 71 #’s 1-6
The birds
were affected
by DDT
because they
animals which
had absorbed
DDT into their
bodies, so up
the food chain
the DDT went.
Studies revealed the
peregrine was
originally threatened
by a pesticide the
bird carried in its
body that weakened
the shells not
permitting the
young inside to fully
Captive breeding programs were established to
assist with the bird’s reintroduction to its natural
A release and monitoring program have
observed the success of the program.
As a result of the scientific plan for the
peregrine’s return, the bird’s status has been
downgraded from endangered to threatened.
Peregrine Falcons have also been moved
to skyscrapers in major US cities where
their population have thrived due to the
abundance of pigeons.
4.3 There are Limitations to
Scientific and Technological
Where Did It Go?????
• In dealing with environmental issues,
science cannot always provide answers
due to a lack of evidence or studies.
– Example: The Golden Toad in Costa Rica has
vanished without a clue as to why.
• Frogs or amphibians are extremely sensitive
indicators of environmental changes, as the
uptake of oxygen and water through their skin
can increase concentrations of pollutants, and
the life cycle of frogs and toads exposes them to
water and airborne contaminants.
Amphibians are so sensitive to changes in the
environment that scientists have likened them to
a canary in a coalmine.
• In addition to the apparent die-offs,
deformities in other species of amphibians
have no clear explanation due to a lack of
evidence or obvious alteration to the
environment thought to be at fault.
• Scientists believe many amphibians are
at risk due to one of the following
Climate changes
ultraviolet radiation
4. 4 Using Evidence from
Many Sources can help
Analyze a Local
Environmental Problem.
Ecological Footprint
Ecological _______
footprint – is the
amount of land needed to sustain our
food, transportation, entertainment,
shelter, and sanitation needs.
 The average Canadian requires 7.7
hectares (77 000m²).
 1.7 ha actually available per person
on Earth.
Average ecological footprint
worldwide is 2.2 ha.
Humans use more of the Earth’s
resources than the environment can
safely support, but there are ways of
reducing our ecological footprint.
• Reduction in the amount of water used.
• Reduction in the use of energy.
• Reducing consumable materials.
• Reusing products where possible.
• Recycling waste materials.