Transcript snc1d u1 lesson 11 assessing the impact of human activities on ecosystems 1

ASSESSING THE IMPACT OF
HUMAN ACTIVITIES ON
ECOSYSTEMS 1
Lesson 11
September 9th. 2010
The Impact of Human Pollution

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The United Nations Environment Programme
(UNEP) estimates that plastic debris kills more than
a million sea birds every year.
Sea birds, sea turtles, and other animals mistake
bits of plastic for food items.
Plastic pieces can last for over 50 years in the
ocean
Acid Rain and Ontario’s Ecosystems
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Emissions from a variety of human activities contain
pollutants that enter the atmosphere and can have
wide-ranging effects on the environment.
Acid Rain and Ontario’s Ecosystems
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Nitrogen- and sulphur-containing substances
are two of the most common pollutants in
emissions
 They
combine with water vapour in the air and
form acids.

The acids formed in the air by emissions fall as
acid rain.
 Acid
rain affects soils, vegetation, lakes, rivers, and
terrestrial and aquatic animals.
Effects of Acid Rain
Destroys coatings on leaves  Infection
 Burns some organisms skin
 Increases soil acidity - plants cannot absorb
nutrients as well.
 Increases acidity of bodies of water.
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 Can
dissolve Shellfish shells
 Acid lakes contain no life
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Government Response
companies installed scrubbers  Reduced
emissions
 Mining
Effects of Acid Rain
Assessing Impacts on Ecosystems
Assessing Soils
 Soil - is a loose covering on the ground containing a
mixture of organic matter, minerals, and moisture.
Soil quality has 3 parts.
1. Soil Profile
 Topsoil is the uppermost layer in soil.
 Contains
 Humus
– decaying organic matter
 Rock particles
 Bacteria, fungi, insects and worms.
Assessing Soils

Subsoil is the layer below topsoil.
 Little
or no organic matter except roots of very
large trees and bacteria.

Bedrock forms the bottom of the soil profile.
 solid
rock
 Water sits above it

The top surface of ground water is called the
water table.
Assessing Soils
2. Soil Types
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Loam soil
 Most
fertile
 Loose, Contains air and water
 Contains lots of humus
 Good for growing plants Agriculture
2. Soil Types

Clay Soil
 Packed
tightly
 Few air pockets
 Traps water
 Little growth

Sandy Soil
 contains
sand particles
 Contains air pockets
 Drains easily, looses nutrients easily

Not as fertile as loam, better than clay.
Soil Types
3. Acidity Levels
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Acidity is an abiotic factor that is connected to the
chemical environment of soil. Soils vary in their
acidity
To precisely assess acidity levels in soil, a special
scale is used. The pH scale
3. Acidity Levels
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The pH of a soil can be measured by testing the
moisture in the soil with specially treated strips of
paper that change colour depending on the pH.
High pH = Alkaline
Most organisms prefer neutral soil.
3. Acidity Levels
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pH Scale
Human Impacts on Soils
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Soil erosion is the loss of soil when water or wind
washes or blows it away.
The roots of plants normally hold the topsoil in
place. When soil is ploughed, or tilled, the topsoil is
exposed to wind and water, which can erode it.
Overgrazing by livestock animals, such as cows and
sheep, can also erode the soil.
Human Impacts on Soils

If the same type of crop is grown in the same
soil year after year, the nutrients in the soil get
used up, and the crops no longer grow well in
the soil.
 Crop
rotation is the practice of planting a different
type of crop in a particular field each year.
Human Impacts on Soils
Human Impacts on Soils
 Plants
of the legume family, such as soybeans,
peas, lentils, and alfalfa, have a symbiotic
relationship with nitrogen-fixing bacteria. By
planting nitrogen-fixing plants, the nitrogen in the
soil gets replenished.
 If farmers do not rotate their crops, they have to
supply nutrients to the soil by adding fertilizers.