Geoscience Reference
In-Depth Information
Highest
2.0 m
200
in Figure 19.41a transpire.
As potentially bad as the impact of
rising sea levels may be on coastal communities in the United
States and other developed countries, at least the very security
of the nation will not be threatened as it is in some places. An
area that is particularly threatened by rising sea levels is the
Pacific Island region, which contains hundreds of low-lying
atolls and volcanic islands. Countries such as the Marshall Is-
lands, which consists of an archipelago of 34 atolls and coral
reefs with a maximum elevation of less than 3 m (10 ft) above
sea level, are already being affected by rising sea level. Several
islands have been lost to erosion throughout the Pacific Island
region, and plans are being developed in many places to re-
locate coastal inhabitants to more interior locations within the
islands. In response to this regional crisis, people of the various
island nations have formed the
Alliance of Small Island States
to lobby the United Nations about their particular plight, which,
they argue, is impacting them disproportionately given that they
produce only 0.06% of all carbon emissions.
Observed
Scenarios
160
120
Intermediate-High
1.2 m
80
Intermediate-Low
0.5 m
Lowest
0.2 m
40
0
-40
1900
1950
2000
Year
2050
2100
(a)
Coral-Reef Bleaching
Another by-product of global cli-
mate change is the impact that warmer ocean waters are having
on coral-reef systems around the world. These systems are being
affected by a process called
coral bleaching
, which occurs when
coral reefs are stressed by warmer-than-normal waters. Coral
bleaching can occur naturally as a result of short-term tempera-
ture changes, such as those that occurred in association with the
El Niño in the early 1980s. Coral bleaching also occurs due to
overexploitation of coral resources by people and other forms
of local environmental degradation. Since the 1980s, however,
growing stress caused by warmer oceans has been increasingly
linked to coral bleaching. This stress loosens the algae that help
feed the coral-building organisms from the reef. Because the
algae give the corals their color, the starved corals look pale or
bleached. Ultimately, continued bleaching kills corals.
In the past decade, significant amounts of bleaching associ-
ated with above-normal ocean temperatures have been reported
in a variety of Pacific islands, the Caribbean Sea, Indian Ocean,
and along the coast of Australia. In August 2010, for example,
a major bleaching event occurred in the corals of Sumatra in
Indonesia. Over 60% of corals in the area were bleached, with
over 80% of some species lost. This event occurred because
ocean temperatures were over 32ºC (90ºF).
North
Carolina
below 1.5 meters
1.5-3.5 meters
above 3.5 meters
0
30 km
KEY CONCEPTS TO REMEMBER ABOUT
HUMAN IMPACTS ON COASTLINES
0
30 mi
1.
Coastlines are favored places for people to work, live,
and play. Given the inherent sensitivity of the coastal
landscape, human impacts are significant and growing.
Most human impacts along coastlines are associated
with beach stabilization, protection, and access (to port)
maintenance.
(b)
Figure 19.41
(a) Potential sea-level rise scenarios by 2100.
Present research suggests that sea level will rise somewhere be-
tween 20 cm (8 in.) and 2 m (6 ft) this century. (b) Predicted extent
of coastal flooding in North Carolina. Much of the coastline lies
less than 1.5 m (5 ft) above sea level and thus will likely be im-
pacted to some extent by coastal flooding associated with global
warming. (
Source
: a: NOAA.)
2.
Beaches are stabilized predominantly in two ways:
beach nourishment and groin construction. Beach
