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1.3 Ecology and ecosystems
Ecology and 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.

This page most readers might find very elementary and skip. However, if you are uncertain about basic ecological concepts, please browse through!

  1. Ecology is the study of environmental systems and how they intra- and interact.
    This includes the abiotic (non-living) environment or the litosphere, the hydrosphere (water), the atmosphere (air),
    the cryosphere (the frozen areas) and the biosphere (the living).

    Photo: Å. Bjørke. Cape Town.
    An ecosystem:
    • Litosphere: the ground; earth, rocks, dust, gravel.
    • Hydrosphere: the river. (any body of water)
    • Atmosphere: the air.
    • Biosphere: the vegetation and animals

  1. In principle we start out with a big piece of rock and dust: The Litosphere.
    To the litosphere we add water: The hydrosphere.
    On top of this we add air - The atmosphere.
    Close to the litosphere is The troposphere - about 10 km up in the air is The stratosphere.

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

    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 have to struggle to maintain homeostasis.

    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 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.

    Photo: P. Prokosch. Waterbuck (1st consumer), Masai Mara
  1. Ecosystems are composed of a part of the litosphere, water, air, living organisms.
    These components interact with each other and with their environment within the ecosystem.
    In this interaction, energy is exchanged and cycles of elements emerge.
    In a sustainable ecosystem everything moves in cycles.
    Nothing can accumulate at points within the system for longer periods.
    There is no waste or garbage.

    Photo: Å. Bjørke: Leopard (second consumer). Masai Mara
  1. Energy flow and pollution

    Energy flows from:
    • producers - the plants - to
    • 1st consumers - plant-eaters to
    • 2nd and 3rd etc consumers - the meat-eaters and parasites- to
    • Decomposers: worms, snails, bacteria, fungi

    When certain chemicals enters the food chains, they may accumulate in the fatty tissues or bones and increase in amount for every step in the food chain. Persistent Organic Pollutants (POPs) are regarded as particularly dangerous accumulating chemicals.



    Photo: Å. Bjørke: Coral reef. A complex ecosystem. Cape Town aquarium
  1. Ecosystems can be disrupted
    Eosystems may change suddenly or over time. If the change happens over a long period of time, most species can adapt to the new conditions.

    Ecosystems may be disrupted through natural causes, such as a natural change in climate, or natural disasters like earthquakes, volcanic eruptions and tsunamies. Human activities may also disrupt ecosystems, locally as well as globally. Human activities may enhance existing natural processes or cycles, such as the greenhouse effect, or create completely new conditions, such as depleting the ozone layer with ozone depleting chemicals, or add POPs to the energy flow in the food chains.

    Pollution through high concentrations of waste and secreta may affect water bodies and cause eutrophication.

    Ecosystem services
    Ecosystem services are the benefits people obtain from ecosystems. These include provisioning services such as food, water, timber, and fiber; regulating services that affect climate, floods, disease, wastes, and water quality; cultural services that provide recreational, aesthetic, and spiritual benefits; and supporting services such as soil formation, photosynthesis, and nutrient cycling
    Millennium Ecosystem Assessment - Synthesis

    More comprehensive information


    Photo: Jens Timenes. Water hyacinth - eutrophication, Sri Lanka
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The Greenhouse effect, Climate Change and the road to sustainability
1. 1 Greenhouse effect
2. 2 Science
3. 3 Mitigation
4. 4 Impacts
5. 5 Solutions?