4. Ecosystems

Basic knowledge in natural sciences like physics, biology, chemistry and ecology is necessary to understand what happens to Earth, the planet on which we all live.

Ecology is the study of environmental systems and how they intra- and interact.

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The litosphere, the hydrosphere, the atmosphere and the biosphere interact. Changes in one place can have impacts elsewhere in the complex ecological cycles. (Lake Chilwa, Photo: Å. Bjørke)

The building blocks of an ecosystem

In principle we start out with a big piece of rock and dust, The Litosphere, circling around the sun in our solar system. The outer part of the litosphere is the earth’s crust, less than 1% of the litospheric mass. The litosphere in itself does not sustain life. The “magic”, lifegiving factor is water, The Hydrosphere. In order for more complex organisms to survive, air is needed as well. This factor is called the area of breathing, The Atmosphere.
The lower part of the atmosphere, where living organisms can exist, is a 10 km thick layer of air called The Troposphere. If we compare the Earth to an egg, the troposphere would have a thickness of the thin film under the eggshell. Basically life can exist only in this thin film between the litosphere and the upper limit of the troposphere called the tropopause.

As a protective layer of thin air outside the tropopause comes The Stratosphere. No ordinary life can survive there.

With energy from the sun, the system is ready for the next step:
The Biosphere. The biosphere includes all living organisms: plants, animals, bacteria and fungi.

Temperature variations  and homeostasis

In order for complex ecosystems to thrive, it is necessary to have a fairly stable temperature.
When day and night temperatures vary by more than 30 centigrades, more complex living organisms will struggle to maintain Homeostasis.


River near Termessos-Gulluk Dağ National Park, Lycia, Turkey. Photo: P.Prokosch

Greenhouse gases in the atmosphere prevent drastic temperature falls at nighttime or in dark periods by slowing down the outward going energy that is leaving the planet in the form of infrared light.

On our planet such greenhouse gases comprise roughly 1% of the atmosphere, water vapour included.
In other words, we do not need very much greenhouse gas to obtain the desired effect.

With a fairly stable average global temperature of around 14 centigrades, rather than 30 centigrades colder,  as it would have been without greenhouse gases, the basis for higher forms of life is present. Without greenhouse gases, freshwater would freeze every night.
Frozen water, The Cryosphere, is difficult to access for living organisms.

In other words; the biosphere will not thrive if the hydrosphere is only available in the form of a cryosphere. On the other hand, mountain glaciers provide important freswater storages, feeding meltwater into rivers during the warm seasons. Without mountain glaciers, several rivers would dry up during summer seasons, in other words periodically removing the hydrosphere from the ecosystem.

A “correct” chemical composition of gases in the atmosphere is thus crucial for the development of higher forms of life.

The biosphere is divided in producers or plants, consumers or animals and parasites at various levels and decomposers: worms, bacteria and fungi.

Online lecture: The Basics of Ecology and the important Greenhouse Effect

Produced by Yannick Schillinger



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Chapter 3 3. Impacts
Chapter 4 4. Ecosystems
4.1 Ecosystems and energy flow
4.2 Forests
4.3 Agricultural land
 4.4 Oceans
Chapter 5 5. Green economy