Environmental Engineering Reference
In-Depth Information
a baseline state for marine ecosystems upon which to evidence changes
by comparison. This chapter will narrow down to the discussion on some
of the anthropogenic disturbances that impact coastal marine ecosystems.
The coastal zone is the region that runs from the inner shelf to the
coastline, usually defi ned as an interface where the land meets the ocean,
encompassing shoreline environments as well as adjacent coastal waters
(Post and Lundin 1996). It is a geologically-young and dynamic area with
changing biological, chemical and geological attributes. Coastal ecosystems
are highly productive and biologically diverse and can act to moderate the
impacts of pollution originating from land (Post and Lundin 1996).
Coastal areas provide critical ecological services such as nutrient cycling,
fl ood control, shoreline stability, beach replenishment and genetic resources
(Post and Lundin 1996, Scavia et al. 2002). Some estimates by Boesch (1999),
mention that the ocean and coastal systems contribute 63% of the total
value of Earth's ecosystem services (worth $21 trillion year
-1
). Population
growth is a major concern for coastal areas with more than 50% of the world
population concentrated within 60 km of the coast (Post and Lundin 1996);
in the United States the expected tendency for the next decades is that the
coastal population will increase by ~ 25% (Scavia et al. 2002). The continued
growth of human population and of
per capita
consumption have resulted
in unsustainable exploitation of Earth's biological diversity, exacerbated by
climate change, ocean acidifi cation, and other anthropogenic environmental
impacts. The effective conservation of biodiversity is essential for human
survival and the maintenance of ecosystem processes.
Our discussion of coastal zone impacts will necessarily be diverse (e.g.,
coastal zones vary from place to place), fragmentary (e.g., not all coastal
regions have been studied) and incomplete (e.g., not all coastal regions have
been studied with the same scope and extent). Also important to bear in
mind is that even though we will try to focalize on the impacts to coastal
locations, the distinction is not real or absolute, since coastal ecosystems are
not separate compartments of the world's oceans and no boundaries exist.
In fact they are better defi ned by their interconnections with other regions of
the ocean, and are better interpreted as
open-sided
systems (Steele 1998).
Climate change
per se
is not the foremost pervasive human disturbance
to coastal ecosystems, nor is it usually the original cause of major impacts,
but its effects constitute a major concern for coastal ecosystems in the long
run (Jackson et al. 2001). In that sense, it is important to remember that
more direct human disturbances do not have isolated or punctual impacts,
but they rather combine in a synergistic fashion to amplify their pervasive
effects to coastal ecosystems. Jackson et al. (2001) proposed a sequence of
historical events of disturbances for coastal ecosystems, in which overfi shing
precedes other phenomena like pollution, eutrophication, outbreak of
disease or climate change. In their scheme, climate change constitutes a
