Environmental problems – An overview - Environmental Deterioration and Contamination: Problems and their Management - page 7

Figure 1.4 Simplified food chain with four typical trophic levels and the organic matter depleting and
mineralizing community.
and the carrying capacity of a certain area. When the intake (input) and output turn
imbalanced, one of them will increase, until the system is able to rebalance the sit-
uation. For example, continuous material loss from an average terrestrial ecosystem
may lead to desertification. The new equilibrium state is a desert ecosystem. When
intake increases, the produced biomass will increase, and consequently, more efficient
substrate utilization and faster element cycles will develop as observed in connection
with global warming.
The elements' cycling through the physical phases (gas, liquid, solid), atmosphere,
lithosphere, hydrosphere, and biosphere is fluctuating between living and nonliving.
The cycling of elements and the ecosystem can be characterized by clear trends which
occur in time and space from the poles to the equator.
It is an interesting mental experiment to imagine where all the elements and
molecules that constitute our body come from; some of them may come newly from
the lithosphere, some others are derived from the space, Egyptian mummies, or from
even older ages (e.g., from the “primeval soup''). Will the former fate of molecules
play a role in the new combination of a human being? By following more realistic
elements' cycles and substance pathways it is evident that the transport velocity of
most elements and compounds is different—some are taken up, transformed or elimi-
nated without transformation at high speed, some at low speed or not taken up at all.
The latter ones are accumulated in the organisms and magnified along the food chain
(Figure 1.4) or within the complex food webs. The high-positioned organisms in the