Download Ecosystem Responses to Disturbance

PG diploma in Environment Education program
Unit 2.2 (3 Hrs.)
Ecosystem Sustainability: The human
factor, implications for human society,
ecosystem responses to disturbance.
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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PG diploma in Environment Education program
The Human Factor
Three Revolutions
1. Neolithic Revolution
2. Industrial Revolution
3. Environmental Revolution
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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PG diploma in Environment Education program
Implications for Human Societies
What sustains life on Earth? (Miller,
1996; page 91)
Life on Earth depends on three
interconnected factors:
1. The one-way flow of high–quality
(usable) energy from the sun.
2. The cycling of matter, or
nutrients, needed for survival by
living organisms through parts of
the ecosphere.
3. Gravity, caused mostly by the
attraction between the sun and
Earth.
Natural ecosystems are models of sustainability. Key to sustainability
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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- ecosystems use sunlight as their source of energy.
PG diploma in Environment Education program
Implications for Human Societies
How Does Sun Help Sustain Life On Earth?
•The sun is expected to provide
Earth with energy for at least
another 6.5 billion years.
•The sun is gigantic fireball of
hydrogen (72%) and helium
(28%) gases.
•About 34% of the solar energy
reaching the troposphere is
reflected back into space by
clouds, chemicals, dust, and
Earth’s surface (Figure).
•0.023% of solar energy is
captured by green plants and
bacteria.
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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PG diploma in Environment Education program
Implications for Human Societies
How do Nutrient Cycles Sustain Life?
Ecosystems dispose of wastes and replenish nutrients by recycling the
elements.
Human systems are based on a one-directional flow of elements.
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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PG diploma in Environment Education program
Ecosystem Responses to Disturbance
Community-Ecosystem Responses to Stress:
Succession (Miller, 1996, page 181; Wright, 2005, page 104)
The gradual process of change in the composition
and function of communities-especially their
vegetation-is called ecological succession, or
community development.
Ecologists recognize two types of ecological
succession;
primary and secondary.
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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PG diploma in Environment Education program
Ecosystem Responses to Disturbance
Community-Ecosystem Responses to Stress:
Succession (Miller, 1996, page 181; Wright, 2005, page 104)
Primary succession involves
the development of biotic
communities in a barren
habitat with very little or no
top soil (Fig.).
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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PG diploma in Environment Education program
Ecosystem Responses to Disturbance
Community-Ecosystem Responses to Stress:
Succession (Miller, 1996, page 183; Wright, 2005, page 104)
Secondary succession
begins in an area
where the natural
vegetation has been
disturbed, removed,
or destroyed but
where the soil or
bottom sediment
remains.
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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PG diploma in Environment Education program
Ecosystem Responses to Disturbance
A common process governing secondary succession is “inhibition”.
Inhibition is condition, where species present hinder establishment
and growth of other species.
In other cases, newly establishing species are largely unaffected by
already-established species, a phenomenon known as “tolerance”.
There is no consensus among ecologists over whether most of the
stages of secondary succession occurs because of inhibition,
tolerance, or some combination of these two processes.
Secondary succession also occurs in aquatic ecosystems.
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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PG diploma in Environment Education program
Ecosystem Responses to Disturbance
Aquatic Succession:
Natural succession also takes place
in lakes or ponds.
Succession occurs because soil
particles inevitably erode from the
land and settle out in ponds or
lakes, gradually filling them.
Aquatic vegetation produces detritus
that also contributes to the filling
process.
In time, the shoreline gradually
As the buildup occurs, terrestrial
advances toward the center of
species from the surrounding
the lake until, finally the lake
ecosystem can advance, and aquatic
disappears altogether. Here the
species must move farther out into
climax community may be a bog
the lake.
or a forest.
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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PG diploma in Environment Education program
Concluding remarks
From a human standpoint, Earth’s
ecosystems are classified into five main
types.
Natural ecosystems
Modified ecosystems
Cultivated ecosystems
Built ecosystems
Degraded ecosystems
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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PG diploma in Environment Education program
Concluding remarks
First, we have destroyed, degraded and simplified the
ecosystems.
Second, we have strengthened pest populations by speeding
up natural selection.
Third, we have eliminated predators.
Fourth, we have deliberately or accidentally introduced new
species.
Fifth, we have over harvested potentially renewable
resources.
Finally, we have interfered with the normal chemical cycling
and energy flows in ecosystem.
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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PG diploma in Environment Education program
Concluding remarks
Learning from Nature How to Live Sustainably:
Most ecosystems use sunlight as their primary source of
energy.
Ecosystems replenish nutrients and dispose of wastes by
recycling chemicals.
Soil, water, air, plants, and animals are renewed through
natural processes.
Energy is always required to produce or maintain an energy
flow or to recycle chemicals.
Biodiversity takes various forms in different parts of the
Earth because species diversity, genetic diversity, and
ecological diversity have evolved over billions of years.
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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PG diploma in Environment Education program
Concluding remarks
Complex networks of positive and negative feedback loops
give organisms and populations information and control
mechanisms for adopting-within limits-to changing
conditions.
The population size and growth rate of all species are
controlled by their interactions with other species and with
their non living environment.
Organisms- except perhaps humans- generally use only
what they need (not merely want) to survive, stay healthy,
and reproduce.
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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PG diploma in Environment Education program
Concluding remarks
Humans are violating various degrees of these principles of
sustainability.
No one knows how long we can stay on this ultimately
unsustainable and self –defeating path.
Remember:
We are part of- not part from-Earth’s dynamic web of life.
Our lives, lifestyles, and economies are totally dependent on
the sun and the Earth.
We can never do merely one thing.
Everything is connected to everything else; we are all in it
together.
Subodh Sharma Dr.nat.tech.; Aquatic Ecology Centre, P.O. Box: 6250, [email protected].
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