Global Issues and
Human Impact
Notes
Overpopulation
The first homo sapiens walked the earth 200,000 years ago.
It took until 1804 for the global population to reach 1 billion.
123 years later in 1927, it reached 2 billion.
34 years later in 1961, it reached 3 billion.
13 years later in 1974 it reached 4 billion.
13 years later in 1987 it reached 5 billion.
12 years later in 1999 it reached 6 billion.
Today it reached 7,377,334,325
In 2025 it is projected to hit 8 billion!
Overpopulation
Earth’s Carrying Capacity
• In 1961 the earth had 3 billion people. They
were using ½ of the Earth’s resources.
• In 1987 the earth had 5 billion people. They
were using ALL of the resources.
Ever since then we have been
putting TOO MUCH stress on
the planet!!
►overexploiting fisheries.
►overgrazing to the point of desertification.
►destroying forests.
►polluting the waters and
atmosphere, including
greenhouse gasses.
At the rate we are going, we will need 2 WHOLE
planets to sustain our appetites by 2050.
Something has
obviously
got to
give!!
How it Hurts!!
Because of the stress we are putting on the planet
several global issues are now SERIOUS problems.
Deforestation
Acid Rain
Ozone Depletion
Biological Magnification
Global Warming
These are NOT the only problems caused by
overpopulation…but they are the ones we will focus
on.
Deforestation
The cutting down of trees
WHY?
Two MAIN reasons:
1. Raw materials (paper, housing, firewood, etc.)
2. Space (industrial use – homes, schools, factories, etc)
There are, of course, other reasons…but these are the main reasons
So What!?!
What are the consequences of deforestation?
NUMEROUS!!
Here are the main consequences:
1.More CO2 and Less O2 – due to a lack of photosynthesis
2.Increased soil erosion and lower soil quality
3.Loss of habitats for animals – this disrupts food webs & ecosystems
4. Messes up the water cycle - lessens the amount of transpiration &
lowers the water table
Loss of Biodiversity
In 1960 a person with leukemia had a 1 in 5 chance of survival
In 1980 the chance of survival was 4 in 5
This was due to the Rosy Periwinkle flower
Out of 32 common chemotherapy drugs…28 of them came from
plants!!
So far scientists have only explored 1% of plant and animal species for
medicinal use.
Scientists estimate that 100 species go extinct every day!!
What happens if you need a medicine
one day to survive…but we killed off
the plant species that it comes from?
Acid Rain
• Sulfur Dioxide (SO2) and Nitric
Oxides (NOx) are emitted as car
exhaust and factory emissions.
• They combine with water vapor in
the atmosphere forming acid
droplets.
• They become part of the
water cycle…and fall to
the Earth as acid
precipitation.
So What !?!
• Rivers, streams and lakes become acidic
– Fish and other aquatic species die
• Ground water can become acidic
– Vegetation and trees die
Acid rain affects trees by washing away the minerals
and nutrients in the soil that help trees to grow.
Acid Rain
Normal Rain
Concrete, marble and stone
are weakened
Over 40% of the nations
bridges and overpasses and
“structurally deficient”
That means they could
collapse!!
B
E
F
O
R
E
A
F
T
E
R
Ozone Depletion
• We have already explored the Ozone…what
does it do for us?
• Absorbs dangerous UV rays so it doesn’t reach
the Earth
CFC’s – Banned in 1978
Chlorofluorocarbons were found in:
styrofoam
air conditioners & refrigerators
aerosol cans
How Does CFC Destroy Ozone?
Ozone Depletion was recognized as a Global issue around
1975.
It took until September 24, 2010 for the ozone damage to
FINALLY stop!
Scientists think
that the Ozone
will regain its
healthy density
around 2050.
75 years later!!
Can we afford to
wait 75 years to
solve our other
Global Issues?
Biomagnification
When chemicals (like
pesticides) are added
to the ecosystem, they
get into the food web…
Pesticides are often
NONBIODEGRADABLE,
this means they DO
NOT BREAK DOWN!!
As animals eat other
animals, the chemicals
build up in their
body…causing serious
illness or death!!
DDT (a spray to kill
mosquitoes) caused the
death of most Bald Eagles
– putting them on the
Endangered Species List
for 40 years (1967-2007)
This
can
affect
ANY
food
chain!!
Even the ones HUMANS are a part of!
Biological Controls
Using a natural predator is an environmentally
friendly way to control pests!!
No chemicals added into the ecosystem!
BUT BEWARE!!
You need to be careful when adding a species
into an environment…they could TAKE
OVER!!
Cane Toad
SKIP TO GLOBAL WARMING
Greenhouse Effect vs. Global Warming
Greenhouse Effect
☼ NORMAL trapping of some of the
Sun’s heat
☼ Keeps our planet warm enough
to support life
Global Warming
☼The thickening of the atmosphere
with greenhouse gasses (CO2, CH4
and N2O)
☼More of the Sun’s heat gets
trapped…increasing the planet’s
temperature.
Causes of Global Warming
• Two main causes for higher levels of CO2
1. Increased burning of fossil fuels (cars, factories,
etc.)
2. Increased deforestation is limiting the
conversion of CO2 back into O2 for us to breathe
So What!?!
Some of the consequences of global warming:
Spread of disease
As northern countries warm,
disease carrying insects
migrate north, bringing plague
and disease with them.
Warmer Waters –
More Hurricanes
As the temperature of oceans
rises, so will the probability of
more frequent and stronger
Increased Probability and
Intensity of Droughts and Heat
Waves
Although some areas of Earth will
become wetter due to global
warming, other areas will suffer
serious droughts and heat waves.
Africa will receive the worst of it,
with more severe droughts also
expected in Europe. Water is
already a dangerously rare
commodity in Africa, and according
to the Intergovernmental Panel on
Climate Change, global warming will
worsen the conditions and could
lead to conflicts and war.
Polar Ice Caps Melting
The ice caps melting is a four-pronged danger.
First, it will raise sea levels. With all glaciers melted, the seas
would rise about 230 feet.
Second, melting ice caps will throw the global ecosystem out
of balance. The ice caps are fresh water, and when they melt
they will desalinate the ocean, or in plain English – make it
less salty.
The desalinization of
the Gulf current will
”mess up" ocean
currents, which
regulate
temperatures.
Third, temperature rises and
changing landscapes in the
Arctic Circle will endanger
several species of animals.
Only the most adaptable will
survive.
Fourth, global warming
could increase with the ice
caps gone. Ice caps are
white, and reflect sunlight,
much of which is reflected
back into space, further
cooling Earth. If the ice caps
melt, the only reflector is the
ocean. Darker ocean
absorbs sunlight, further
warming the Earth.
Other Consequences
Floods
Stronger Storms
Wildfires
Desertification of Soil
Loss of Biodiversity & Habitats
Species Extinction
Diminished Food & Water Supply
Death of Phytoplankton
Phytoplankton do MORE
THAN 50% of the planets
photosynthesis!!
Time to Change Your Thinking!?!