Organisation at the Ecosystem Level 61
• Substances that harm due to their excessive quantity, even though
they are not foreign to natural ecosystems (e.g. dead organic matter
in the water). If pollution does not exceed certain limits, ecosystems
have significant assimilation ability, thus the presence of pollutants
will not act as a limiting factor.
• Substances that harm, due to their toxicity, even in small concentrations (e.g. some heavy metals or radioactive substances). In such
cases, pollution avoidance will abolish the limiting factor.
Generally, the most productive terrestrial ecosystems can be found in
the Equatorial regions, where increased sunlight and humidity are present.
On the contrary, the most productive marine ecosystems are often far from
the Equator, in points where sea currents convene and, in particular, when
there are upwellings (upward water movements) that bring nutrients from
the bottom to the surface. Many coastal ecosystems are productive for the
same reason.
Comparative examination of our planet’s natural ecosystem’s primary
production illustrates the superiority of tropical rainforests, coral reefs, and
some wetlands. Deciduous tropical forests, temperate coniferous or deciduous forests, cold northern forests and savannahs rank second; shrub, lakes,
rivers, marine upwelling regions and coastal zones rank third; tundra ,
deserts and the deep ocean rank last with some deserts and polar areas at
the extreme limit of low productivity. Agriculture is mostly placed approximately in the middle of this scale. Extremely productive cultivations, such
as that of sugarcane, can be compared with the most productive natural
ecosystems, although this only occurs due to great energy, fertilizers, pesticides, and water inflow from the outside.
Total solar energy converted into chemical energy through photosynthesis
is the gross primary production for the whole biosphere. Deducting respiration from this amount, net primary production results; about two-thirds
of this amount come from terrestrial ecosystems, whereas one-third come
from marine ecosystems. Net primary production represents available
energy for the biosphere’s food chains.
4.3 biogEochEMical cyclES
In each ecosystem an uninterrupted circulation of material substances is
tence of an organism’s groups with complementary needs within the ecosystem allows the recycling of the chemical elements. Various populations
constantly seek and utilize the substances necessary for their increase, conservation, and reproduction and discard inorganic and organic waste in the
• Substances that harm due to their excessive quantity, even though
they are not foreign to natural ecosystems (e.g. dead organic matter
in the water). If pollution does not exceed certain limits, ecosystems
have significant assimilation ability, thus the presence of pollutants
will not act as a limiting factor.
• Substances that harm, due to their toxicity, even in small concentrations (e.g. some heavy metals or radioactive substances). In such
cases, pollution avoidance will abolish the limiting factor.
Generally, the most productive terrestrial ecosystems can be found in
the Equatorial regions, where increased sunlight and humidity are present.
On the contrary, the most productive marine ecosystems are often far from
the Equator, in points where sea currents convene and, in particular, when
there are upwellings (upward water movements) that bring nutrients from
the bottom to the surface. Many coastal ecosystems are productive for the
same reason.
Comparative examination of our planet’s natural ecosystem’s primary
production illustrates the superiority of tropical rainforests, coral reefs, and
some wetlands. Deciduous tropical forests, temperate coniferous or deciduous forests, cold northern forests and savannahs rank second; shrub, lakes,
rivers, marine upwelling regions and coastal zones rank third; tundra ,
deserts and the deep ocean rank last with some deserts and polar areas at
the extreme limit of low productivity. Agriculture is mostly placed approximately in the middle of this scale. Extremely productive cultivations, such
as that of sugarcane, can be compared with the most productive natural
ecosystems, although this only occurs due to great energy, fertilizers, pesticides, and water inflow from the outside.
Total solar energy converted into chemical energy through photosynthesis
is the gross primary production for the whole biosphere. Deducting respiration from this amount, net primary production results; about two-thirds
of this amount come from terrestrial ecosystems, whereas one-third come
from marine ecosystems. Net primary production represents available
energy for the biosphere’s food chains.
4.3 biogEochEMical cyclES
In each ecosystem an uninterrupted circulation of material substances is
tence of an organism’s groups with complementary needs within the ecosystem allows the recycling of the chemical elements. Various populations
constantly seek and utilize the substances necessary for their increase, conservation, and reproduction and discard inorganic and organic waste in the