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sustainable management of complex land/seascapes, where lagoons are major
components.
• On average, only 0.25% of the solar energy reaching the land and ocean
surface and 0.5% of the solar energy absorbed by the primary producers
• The greatest part of the planet, about 75% of the surface, including
oceans and land, has the lowest efficiency in absorption and concentra-
tion of solar energy. The density of the energy flow concentrated in these
types of ecological systems does not exceed 1000 kcal
yr
−1
, and
this provides only 35% of the ecosphere's gross primary production
(35% of the energy is concentrated by the primary producers of the
ecosphere).
• The density of the energy flow is concentrated at the level of the primary
producers from the following natural and semi-natural ecological systems:
estuaries and lagoons, coral reefs, wet forests, floodplains, and agriculture.
These ecological systems represent only 10% of the total of the ecosphere,
but nonetheless the density of energy flow is of the greatest values
(10,000-40,000 kcal
⋅
m
−2
⋅
yr
−1
). The primary producers of these categories
of ecological systems provide almost 38% of the ecosphere's gross pri-
mary production.
• Agriculture covers about 0.8-1% of the total surface of the planet and
provides 5% of the gross primary production of the ecosphere. In order
to maintain a concentrated solar energy flow, equal to that of the estuaries,
lagoons, wet tropical, and subtropical forests, etc., agriculture requires a
large amount of fossil fuel (up to 1000-2000 kcal
⋅
m
−2
⋅
yr
−1
).
• The quantity of energy absorbed and concentrated by the dominant pop-
ulations or cohorts in the tropho-dynamic modules, represented by the
first-order (herbivorous) and by the second- and third-order consumers,
decreases from one tropho-dynamic module to another. In general, the
energy assimilated (absorbed and concentrated) by a tropho-dynamic
module made up of heterotrophic
species represents only 5-20% of the
energy concentrated by the tropho-dynamic module, which is the energy
source
(
Figures 2.7b and c)
.
This rule explains why the sequence of tropho-dynamic modules directly
or indirectly using the energy concentrated by the primary producers
(Figure 2.7a) includes, in any ecological system, only three to four modules.
Note also that organic matter (and the potential energy it stores) that is not
consumed or digested by the components of a trophic module, or that is
represented by intermediary metabolites (containing considerable quantities
of concentrated energy) is transferred into two main reservoirs. These are
dissolved organic carbon (DOC) and particulate organic carbon (POC).
They become, in turn, sources of concentrated energy that support the other
two series of tropho-dynamic modules which are complementary to the first
one. Note that natural and seminatural ecological systems have and develop
structures which use “waste” having a concentrated energy content. They
⋅
m
−2
⋅
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