Transcript UNIT 6 PART 2 Human ecology

UNIT 6 PART 2: HUMAN
ECOLOGY
• Human activities have damaged the
environment, and the damage may be
dangerous and permanent.
• There are also many
things we can do to
minimize or prevent
the damage.
• Human ecology deals
with the relationship
between humans and
their environment.
1
Most of the things we have done that have
harmed the environment are due to an
increasing human population:
• Development and industrialization – turns
natural ecosystems into concrete and
black top
• Farming, overgrazing, and over hunting –
reduces biodiversity and can leave land
barren causing soil erosion
• Pollution – can cause contamination
making land and water unusable
2
• Introducing foreign (invasive) species – may
compete with native species and force them
out
• Clear cutting, mining,
and mountain-top
removal – destroys
habitat and
causes pollution
All of these destroy habitats and ecosystems
for other living things.
3
Poor farming practices have led to
soil erosion
• When crops are grown most of the plant
parts are removed- nutrients are not returned
to the soil.
• The fields become less fertile and are
abandoned.
• Without vegetation topsoil is eroded by wind
and rain and land becomes unusable.
• Overgrazing by animals also leaves land
bare which leads to erosion.
4
Ways to Prevent Soil Erosion
• Cover crops - plant crops that cover a
whole field such as clover, alfalfa, oats and
wheat.
• Strip cropping – row plants and cover plants
• Terracing or contour farming
• Windbreaks – rows of trees
• Crop rotation
• Fertilizers
• Dams
5
Fertilizers and dams may be ways to
prevent soil erosion, but they can also be
harmful to the environment.
• Fertilizers add nutrients to the soil in large
quantities. If the crops don’t use it all,
where do the leftovers end up?
• Dams hold back water which can prevent
soil erosion. What are some other
consequences of building a dam?
• Making environmental impact decisions
often involves tradeoffs – some harm is
done in one area to gain something good
in another.
6
Pollution
• Adding anything to the environment or
affecting the environment in any way that
makes it less fit for living things is called
pollution.
Noise pollution can
come from
construction sites,
airplanes, cars, loud
music, or leaf blowers.
7
Water Pollution
• Much of the available
water is polluted from:
– Organic wastes
– Inorganic chemicals
– Disease-causing
microorganisms
– Changes in water
temperature
– Oil spills
– Radioactive wastes
8
Water Pollution by Organic Wastes
• Organic wastes are from plants and animals.
• They are biodegradable, which means they
can be broken down by bacteria.
• This process requires oxygen. When there is
too much waste the bacteria use up all the
oxygen and aquatic life dies.
9
Eutrophication
• Some organic wastes are plant nutrients which
encourage excess plant growth.
• Algae grow on top of the lake and other plants at
the edges.
• As these die the lake fills in faster speeding
succession. This is called eutrophication.
• More dead plants = more oxygen used up so no
aquatic life.
10
Biological Magnification
• Heavy metals, such as mercury (Hg) and lead
(Pb), pesticides, and other toxic chemicals
like PCBs are inorganic pollutants.
• These accumulate in larger quantities as you
move up the food chain.
Swan eats 3 fish
Fish eats 5 flies
Fly eats 12
phytoplankton
11
Bioremediation
• Some bacteria are essential for life. They
help in digestion, converting N in soil,
decomposition, and genetic engineering.
• They can also be used to help clean up
pollution.
• In a process known as bioremediation,
bacteria are added to water or soil to
convert toxic pollutants, such as pesticides
and oil, into harmless substances.
12
Thermal
Pollution
• Water is often used to
cool industrial
equipment in factories
and power plants.
• Warm water is then
returned to the river.
• Changes in water
temperature can kill
aquatic organisms.
• Warm water carries
less oxygen than cold
water.
13
Air Pollution
• Over 200 million metric tons of pollutants
are put into the U.S. air each year.
• Some are aerosols, which are small
particles or droplets that remain suspended
in the air.
– These scatter light
and lower the
amount reaching
the Earth.
• Some are gases that mix with the air.
14
Global
Warming
• An increase in the
average
temperature of the
Earth’s surface.
• The Earth has
natural cycles of cooling and warming, but scientists
believe that the Earth is warming now faster than it
should be.
• This increase in warming is thought to be caused by
the greenhouse effect which is caused by a build
up of certain gases in the atmosphere that trap heat
in, such as CO2, CH4 (methane), and NO2.
15
• Burning fossil fuels
such as oil, coal, and
gas produce sulfur
dioxide (SO2) and
nitrogen oxides (NO
and NO2)
• They combine with
water in the
atmosphere to produce
sulfuric and nitric acid
which can kill plants
and animals.
• Acid rain has a pH of
5.0 or less.
Acid Rain
16
The Ozone Layer
• Ozone filters out the
sun’s UV rays and
protects life from
mutations and cancer.
• CFCs, such as Freon,
in aerosols and
refrigerants break
down ozone making
“holes” in the
atmosphere.
• Mutations & cancer
increase under these
holes.
17
Land Pollution
• More people means more waste and garbage.
• Two good ways of disposing of garbage are
– Sanitary landfills
– Incinerating
18
Tokyo, Japan
Reduce, Reuse, and Recycle
• Reducing the amount of waste and
garbage each of us produces will lessen
the amount in landfills.
• Find another use for items such as boxes,
milk jugs, and bottles.
• Recycle plastics, papers,
cans, and glass.
• This will help to conserve
our natural resources.
19
Natural Resources Must Be
Conserved
• Materials in the environment that are used
by people are natural resources.
• Renewable resources can be replaced.
These include wind, water, soil, sunlight,
and living things such as trees.
• Nonrenewable resources can be taken
from the earth only once. These include
oil, coal, natural gas, metals, and minerals.
20
RENEWABLES VS. RECYCLING
• Resources are raw materials used to
make something: trees are the resources
used to make paper.
• When the paper is made the tree is used
up. If a new tree is planted and grows,
then the tree has been replaced. This is
what makes trees renewable.
• Paper does not come from nature so it is
NOT a resource, but it can be used to
make more paper. This is recycling.
21
Conserving Wildlife
Many habitats have been lost to urbanization,
farming, mining, and deforestation.
Protecting existing undisturbed areas from
destruction will save species.
Hunting has caused extinction of some
species and near-extinction of many others.
Hunting and fishing laws now restrict how many
can be hunted, size, sex, and season.
Many preserves outlaw hunting.
Pesticides and herbicides have killed many.
Their use is now restricted.
22
Controlling Pests Biologically
Introduction of a natural enemy of the pest
Ladybugs to control aphids
Loosestrife eating beetles for purple loosestrife
Bacteria and viruses that attack insect pests
Crop rotation removes a favored food source
of a pest thus reducing their numbers
Pheromones are insect sex attractants and
can be used to lure insects into traps
Introduction of sterile males into the population
23
Invasive Species
• When using biological controls, one must
be certain of the effects before introduction.
• Species in their natural habitats have
enemies that prey upon them. A species
introduced into a different habitat may have
no natural predators and breed out of
control. These are invasive species.
– Purple loosestrife, Zebra mussels, Japanese
beetles in USA
– Cane toads and rabbits in Australia
24
Controlling Pollution: What We Can Do
• Emission controls on automobiles and the
use of unleaded gasoline – helps fight global
warming
• Install filters and scrubbers on industrial
smokestacks – reduces acid rain
• Ban the use of aerosols and CFCs – protects
the ozone layer
• Sewage treatment plants – returns water
• Control and contain runoff from parking lots
• Stop the dumping of wastes into waterways
25
• Reclaim land that has been strip-mined