Vulnerability, Impacts and Adaptation of Coastal Zones to Global Change - Vulnerability of Coastal Ecosystems and Adaptation - page 155

practically doubled each decade since 1960 [DIA 08]. Ocean
deoxygenation is mainly caused by the massive influx into the ocean
of nitrate fertilizers, used in intensive agriculture, of untreated
wastewater and indirectly by the use of fossil fuels. These processes
enrich the coastal waters with nitrogen and phosphorus, nutrients that
lead to the overproduction of algae and cyanobacteria the
decomposition of which favors the growth of bacteria that consume
the dissolved oxygen.
Anthropogenic climate change also contributes to ocean
deoxygenation for two main reasons: first, because warmer water can
hold less dissolved oxygen than colder water and second, because
global warming, by contributing to the stratification of the upper
layers of the ocean, makes it more difficult for oxygen to reach the
deeper ocean. The deoxygenation of the ocean, which is stronger in
the coastal waters than in the open sea, reduces the production of
phytoplankton, at the base of the food chain, whereby it leads to
negative impacts on fishing stocks.
In certain marine regions, the combination of ocean warming,
ocean acidification, ocean deoxygenation, ocean pollution resulting
from certain human activities and overfishing constitutes a very
serious menace for the ocean and for the sustainability of the services
rendered by the marine ecosystems.
4.3.4.6. Impacts of precipitation regime changes
Climate change scenarios project an increase in average
precipitation over high latitudes, especially in the northern
hemisphere, and over some of the regions of intertropical
convergence, but predict a decrease over several regions in the middle
latitudes, such as the Mediterranean Basin, the south of Europe, the
south-east of the United States, the north of Mexico and the south of
Africa. There is also a tendency toward an increase in the frequency of
extreme precipitation, in particular droughts and heavy precipitation
events followed by flooding. In mountains, the current tendency
toward a decrease in the time period of snow coverage, a reduction in
the volume of snow and in the volume of glaciers will be aggravated.
The combination of these climate change impacts with the