Exergy consumption

teleonomic adjustment

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The background to ecosystem development can be found in basic thermodynamics.

Ecosystems are self-organising systems. Their development can be understood in the light of how such systems behave in the vicinty of an exergy gradient.


Let's make an experiment of thought: The sun shines equally on spaces with different properties. Since they have different biological qualities, they consume exergy at different efficiencies. Hence, the reflected radiation get different temperatures.

That is, the Outgoing longwave Radiation= OLR will have different wavelenghts.

Consider a 'perfect' mirror where all the sunlight is reflected without exergy losses. A measurement of the temperature of the reflected radiation a special day gives a certain value, e.g. 80 degrees centigrade. Say, that the surface is asphalt instead of a perfect mirror. Then, some quantum chemical processes will occur in the asphalt. All processes consume exergy (degrade energy quality). Hence, the reflected radiation will contain less exergy, i.e. the outgoing radiation will be cooler even if the incoming radiation has the same intensity as above. If the surface is a lawn, in addition to the quantum chemical processes, some metabolic processes of the grass will occur. Hence, the reflected radiation will contain even less exergy, i.e. will be even cooler with the same incoming radiation. If the lawn is not mowed and it undergoes ecological succession, bushes and shrubs will invade the area, and even more biological activities will occur. Hence, the outgoing radiation during the same circumstances will be cooler. At the climax development stage, a lot of animals and plants will have settled in the area, maximizing the consumption of available exergy. Therefore, the outgoing radiation will be rather cool compared to that of the perfect mirror.

In a varied landscape, therefore, the outgoing radiation will have a varying temperature, depending on the amount of exergy consuming processes that occur.
If you measure a diversified landscape, you would therfore be able to measure a range of differents temperatures (OLR)


This is also true on a larger scale. Here is a NOAA image of the OLR (Outgoing Longwave Radiation) from the Earth. It shows a considerably lower temperature from the rainforest areas (for example in the amazon basin near the center of the image) than the nearby desert zonessuch as the Chilean coast zone just below it. The rainforest OLR is as low some of the winter areas in the Northern hemishere.

This is an effect worth noting; and one that is not commonly being discussed in the public discussions about the deforestation of rainforests!

(NOOA dec-jan 1991)

The conclusion is that the more mature an ecosystem is, the better it consumes exergy.

A small article (1977d, in Swedish) on the Gaia system, which is what this page is about

Thus, the prescence of living activities, especially those of complex, mature ecosystems, will make the entire planet cooler compared to what it would have been without those activities.



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