Geoscience Reference
In-Depth Information
C
OMMENTARY ON
F
IGURE
1.6.- Oxygen has only played an important
biogeochemical role since its first global accumulation at the beginning
of the Proterozoic Period (2.5 billion years ago). However, it is
possible that it had a role previously (in the Archaean Period), by
promoting the Darwinian selection of the first manifestations of
aerobic respiratory metabolism in a few local environments where
oxygen had already accumulated.
1.6.2.
The anthropogenic disturbance of the Earth system
For two centuries, the demographic, technological and industrial
development of human society has been such that it now has a global
impact on the functioning of the Earth system. This is what is known
as the 'anthropogenic disturbance'.
Certainly, this does not date from the industrial revolution since,
from the Neolithic Period, man has modified his environment by
deforestation and the mobilization of surfaces dedicated to agriculture
and rearing livestock. Nevertheless, it is only from the end of the 19th
Century that the global impact has started to be felt with the large-
scale use of coal and then of petroleum and natural gas. This evolution
very quickly accelerated in the course of the 20th Century with
technological developments and the demographic explosion of the
human population and its needs.
Technological progress is made available to a large proportion of
people (electricity, automobiles, the personal computer, the mobile
telephone, etc.), thus multiplying the industrial need for energy to
make industrial products and meet individual energy needs for their
use. In parallel, technological progress has enabled the mobilization of
natural resources of solar fossil energy, through the combustion of
coal and petroleum and natural gas, using oxygen from the
atmosphere. The most recent technologies for exploration and
exploitation now permit us to look for resources which, until recently,
would have been impossible to access (e.g. deep oceanic environments,
polar regions and shale gas), whereas the economic conditions of today
render possible exploitation of reserves that were not, or were less,
profitable a short time ago (e.g. bituminous shale and certain types of
