Name:
Period:
Date:
Human Impact on the Environment
One of the greatest threats to the health of the environment is the great number of humans that live
on the planet. It took thousands of years for the human population to reach 1 billion (reached in the year
1850). It took, however, just 80 years to reach 2 billion and only 45 years to reach 3 billion. The human
population explosion has led to numerous ecological tragedies. Some negative effects include: Greater
rates of deforestation and ecosystem destruction (as forests are converted to farmland and home sites), loss
of plant and animal species as their habitats diminish, higher levels of pollutants released into the air and
water (when human products are made and consumed). Greater use of natural resources (oil, natural gas,
minerals, metals, etc.), greater rates of infectious diseases and shortages in food and water supply.
The pollution generated by humans is classified as one of two types; point source pollution and
non-point source pollution. Point source pollution is pollution generated by specific sources (the source of
the pollution can be identified). Some examples include factory wastes, car exhaust, and releases from
sewage plants. Point source pollution has been linked to numerous environmental problems, including
photochemical smog, acid rain, ozone depletion, and the greenhouse effect.
Smog is caused when gases released in car exhaust react with sunlight to produce toxic ozone gas
(this ozone gas is the main component of smog). Smog not only produces short-term health effects such as
itchy, watery eyes and scratchy throat, it has also been linked to long-term health problems such as lowered
immune systems and lung problems such as asthma. The main cause of acid rain is emissions from
factories and power plants. Activities like the burning of coal or oil produces gases such as nitrogen oxides
and sulfur oxides. These emissions can react with water vapor in the atmosphere to form nitric acid and
sulfuric acid, which then falls back to earth as acidic precipitation. Acid rain is not only harmful to
organisms such as fish and plants; it can also damage stone buildings and cause the rusting of metals.
Excess carbon dioxide from factory and auto emissions allows sunlight to hit the Earth’s surface, but
believe prevents the heat from escaping into space. As the concentration of this gas increases, some
scientist believe that its heat-trapping effect (known as the Green House Effect) may change the climate of
Earth permanently in what is called Global Warming. Some believe that if the climate is permanently
changed, mass flooding (from the melting of polar ice caps) and crop deaths could occur from the increase
in temperature. The release of a different type of gas, chlorofluorocarbons (CFC’s), from appliances such
as refrigerators, air conditioners, fire extinguishers and aerosol cans is believed to be a leading cause of the
depletion of protective ozone from upper layers of the atmosphere. This “ozone layer” protects us from
ultra-violet (UV) radiation, which is the main cause of skin cancer. Despite these seemingly hopeless
forecasts, there is much that can be done to prevent these eco-catastrophes. First of all, emissions controls,
such as filters in factory numerous less toxic substitutes to CFC’s which are currently being used in things
like refrigerators and air conditioners, which do not have a harmful effect on the ozone layer. The search
for alternative energy sources holds much promise fro reducing the harmful emissions caused by the
burning of coal and oil. Some of these alternatives include electric cars, solar heating and wind power.
Similarly, using alternative modes of transportation, such as mass transit, bicycles and walking, can play a
role in reducing harmful emissions.
Non-point source pollution that comes from many different sources and is moved by runoff after it
rains or as snow melts. Non-point source pollution is harder to monitor and control since it comes from
many sources and is moved about randomly from its point of origin throughout an entire watershed.
Examples of non-point source pollution include excess fertilizers, herbicides and pesticides, car oil and
grease, road salt, sediment (soil that washes away from poorly managed farms or construction sites),
bacteria and nutrients from pet and livestock waste, garbage (cigarette butts, cans, etc.), thermal pollution
(heating of rain water from paved surfaces like parking lots), and household products (cleaners, detergents).
If these products are not used in a wise and safe manner, they can escape from their source and are then
washed away to pollute distant points, often accumulating at the end of a watershed.
Non-point source pollution causes many problems. Some of these problems include:
a) Excess nutrients from fertilizers promote the overgrowth of algae in water. This promotes the
growth of decomposing bacteria, which use up the oxygen in the water and leads to fish kills.
b) Excess herbicides and pesticides as well as chemicals like oil and grease are toxic to many plant
and animal species.
c) Salt washing into freshwater streams changes the salinity and leads to the death of plants and fish.
d) Excess sediment in the water can damage fish gills, interfere with the feeding and reproduction of
bottom dwelling fish and insects, and block sunlight (killing under water plants).
e) Disease causing microbes are carried in sewage (from animal wastes, leaky septic systems or boat
discharges)
f) Garbage eaten by animals can cause disease or death.
g) Increasing the temperature of streams even slightly can cause the death of many fish.
There is much that can be done to prevent the harmful effects of non-point source pollution. The
proper maintenance of cars and equipment prevents oil, grease and gas leaks. Recycling reduces the
amount of garbage generated and minimizes the pollution generated when making new products (such
as plastics). Levels of pollution can also be decreased by protecting large natural sites against human
development and creating and restoring natural sites, like wetlands, which help in wildlife conservation
and pollution control. The use of alternative cleaning products should be promoted over harsh
chemical cleaners that can damage the environment. For example, using non-toxic kitty litter or
sawdust to clean up spills, using phosphate-free detergents in designed spots that recycle water (like
car washes) to clean cars, and using fruit acids and beeswax instead of harsh cleansers and oils. Using
“Integrated Pest management (IPM)” procedures is a way to control pests and weeds without using
toxic chemicals. IPM strategies use mechanical methods (tilling, weeding, pruning, traps) for getting
rid of pests instead of chemical methods. IPM also focuses on using organic and non-toxic fertilizers
and pesticides. Some examples of biological alternatives to pest control include:
a) use ladybugs (which feed on aphids, mites and insects that eat plants) instead of chemicals
b) use natural hormones that prevent insects from molting (shedding “skin”) and growing
c) use bacteria that attack pests but do not harm other organisms
Questions
1) Determine or calculate the values that fit into the table below:
Year
1850
Years that Passed
Thousands of years
Population
80 years
3 billion
2000
6 billion
2050
2) List four negative consequences that have resulted from the drastic increase in human population.
1-
2-
3-
4-
3) What is the difference between point source pollution and non-point source pollution?
4) List some examples of point and non-point source pollution (lit at least three examples of each)
a) Point source pollution –
b) Non-point source pollution –
5) Fill out the chart below
Pollution Type
Photochemical Smog
Cause
Health/Environmental Effects
Factory emissions like nitrogen and sulfur
oxides combine with water vapor in the
atmosphere to form nitric and sulfuric
acid
Earth’s climate may be
permanently changed, resulting in
mass flooding (from melting of
polar ice caps) and crop deaths
(from temperature changes)
Ozone Depletion
6) List 4 ways that point source pollution can be reduced.
1–
2–
3–
4–
7) Why is non-pint source pollution harder to control and monitor than point source pollution?
8) In the chart below, list 4 problems that are caused by non-point source pollutants and ways that these
problems can be minimized.
Problem Caused by Non-Point Source Pollutants
Ways to Minimize Problems
9) “Integrated Pest Management” or “IPM” is a way to control pests and weeds without using what?
10) List some mechanical, chemical, and biological alternatives to chemicals that are used in IPM strageies.
a) mechanical –
b) chemical –
c)
biological –