Geoscience Reference
In-Depth Information
carbonate cycle (section 4.3.2, equations [4.1]-[4.5], which may
contribute to regulating the concentration of atmospheric CO
2
and
hence the climate on Earth over hundreds or thousands of years.
However, its net effect is null over millions of years.
Over a few decades to centuries, human societies can themselves
be affected by changes that they have caused and are increasingly
causing to biogeochemical cycles. Examples of such feedback include
conflicts between countries for access to nitrogen (guano, 19th
Century; section 4.5.2), carbon (hydrocarbons, 20th and 21st Century;
section 4.3.2) and perhaps phosphorus in the 21st or 22nd Century
(apatite; section 4.6.2). In addition to these conflicts, the functioning
of human societies will be perturbed in the short- or medium term by
the depletion of deposits of many essential chemical elements or
compounds that had accumulated in the lithosphere over millions of
years (phosphorus, hydrocarbons, etc.) Finally, the huge injection of
chemical elements or compounds into the hydrosphere, atmosphere and
biosphere has already had and will continue to have global
consequences. These include, amongst others, the warming
of atmosphere and ocean, which leads to ocean deoxygenation
(section 4.4.2), sea level increase, ocean acidification (section 4.3.2)
and eutrophication of aquatic environments (sections 4.5.2 and 4.6.2).
This chapter has shown that biogeochemical cycles are not only
interesting to researchers, but are also extremely important to human
societies, because it is humans who modify the large natural cycles
and are negatively affected by the resulting feedbacks. This stresses
the need for better understanding the functioning of these cycles in
order to prevent their disruptions as much as possible.
4.8. Bibliography
[AUT 09] M
ULTIPLE AUTHORS
, “Special issue on the future of ocean
biogeochemistry in a high-CO
2
world”,
Oceanography
, vol. 22, no. 4,
December 2009.
[FAL 00] F
ALKOWSKI
P.,
S
CHOLES
R.J.,
B
OYLE
E.,
et al.
, “The global carbon
cycle: a test of our knowledge of Earth as a system”,
Science
, vol. 290,
no. 5490, pp. 291-296, 2000.
