Vulnerability, Impacts and Adaptation of Coastal Zones to Global Change - Vulnerability of Coastal Ecosystems and Adaptation - page 156

overexploitation of water resources in some regions of the world will
change the flow regime of rivers and streams, in particular its seasonal
behavior, the frequency and intensity of floods and drought events.
There will be a progressive change in the quantity and quality of water
reaching the ocean, although very variable at a local and regional
level; these changes will have consequences on the transport of
sediments and contaminants to the sea, on the salinity of coastal
waters and on the estuarine and coastal ecosystems.
4.4. Impacts of cumulative global changes on coastal zones
In the preceding pages, several impacts of cumulative global
changes on coastal zones have been addressed. One of the most
important is the impact of the exploitation of surface and underground
water resources. On a global level, the water retention in dams and the
exploitation of aquifers contribute to changes in GMSL. It has also
been noted that the exploitation of water resources changes the river
regimes and influences the quantity and quality of the water that
reaches the estuaries and the seashore. In developing countries, more
than half of the used water flowing into the ocean is untreated; in
Latin America and in the Caribbean, the percentage is close to 85%;
in East Asia, it reaches 90%, and 80% in Central and Eastern Africa.
In the South-East Pacific, it exceeds 80% [GAP 06].
The anthropogenic perturbation of the nitrogen and phosphorus
cycles also has a strong impact on the coastal zones. It has been shown
that the intensive use of fertilizers in agriculture and the discharge of
urban waste in rivers, streams and lakes, leads to the eutrophization of
estuaries, gulfs and bays downstream from drainage basins and also
contributes, to the ocean deoxygenation. Aquaculture can also have
negative impacts on the coastal environment, in particular if it leads to
organic, chemical or genetic pollution.
In several regions of the world, the increasing organic and
inorganic pollution of water resources and soils, originating from
demographic growth and rapid industrial expansion without
environmental protection, seriously threatens the ecological
equilibrium of coastal zones. The presence of pollutants in coastal