© CHRISTOPHER BERKEY/epa/Corbiswhich is already suffering due to decades of overfishing
(see What a Scientist Sees). The environmental concerns
associated with extracting offshore energy resources are
discussed in Chapter 17.Climate Change, Sea-Level Rise,
and Warmer Ocean Temperatures
Scientists recognize that the ocean is warming and chang-
ing along with global climate, but the unprecedented
nature of these events hampers accurate predictions of
future consequences. Unanticipated effects from a glob-
ally warmed world will undoubtedly occur, however. For
example, there could be a disruption of the ocean con-
veyor belt, which transports heat around the globe (see
Figure 11.1b). Evidence from seafloor sediments and
Greenland ice indicates that the ocean conveyor belt
shifts from one equilibrium state to another in a relatively
short period (a few years to a few decades). Scientists are
concerned that human activities may affect this equilib-
rium and cause an abrupt climate shift. Models suggest
that climate warming, with its associated freshwater melt-
ing off the Greenland ice sheet, could weaken or even—
as a worst case—shut down the ocean conveyor belt in as
short a period as a decade. Such changes in the ocean
conveyor belt could cause major cooling in Europe, while
greater climate warming could occur elsewhere.
Sea-level rise, caused by melting ice sheets and gla-
ciers as well as seawater expanding as it warms, threatens
coastal areas and the large populations that live there.
Coastal erosion, wetlands loss, flooding risks, and saltwa-
ter intrusion are all likely to increase.
Until recently, climate scientists couldn’t predict
whether human-induced global climate change would
affect El Niño and La Niña events in the tropical Pacific
Ocean. Recent computer models indicate greater ex-
tremes of drying and heavy rainfall during El Niño events.
Scientists are still uncertain whether El Niño events will
occur more frequently with global climate change.- What are some of the harmful environmental
effects associated with the fishing industry?
with aquaculture? - How does the widespread use of plastics
contribute to ocean pollution? - How might the effect of global climate change
on the ocean alter the ocean conveyor belt?
most abundantly in the Pacific. Dredging manganese nod-
ules from the ocean floor would adversely affect sea life,
and the current market value for these minerals wouldn’t
cover the expense of obtaining them using existing tech-
nology. Furthermore, it isn’t clear which countries have
legal rights to minerals in international waters. Despite
these concerns, many experts think that deep-sea mining
will be technologically feasible in a few decades, and sev-
eral industrialized nations such as the United States have
staked claims in a region of the Pacific known for its large
number of nodules. To date, none have been mined.
Such potential exploitations of the ocean floor are
controversial. Many people think it is inevitable that min-
erals will be mined from the floor of the deep sea, but
others think the seabed should be declared off-limits be-
cause of the potential ecological havoc that mining could
cause on the diverse life forms inhabiting the ocean floor.
Offshore reserves of oil have long been tapped as a
major source of energy. However, obtaining oil and gas
resources from the seafloor generally poses a threat to
fishing (Figure 11.14). Fishermen and conservation-
ists worry that Congress may allow oil and gas wells to
threaten fisheries such as the Georges Bank fishery,Threats of energy exploration to marine life
UÊ}ÕÀiÊ££°£{Ê
A slick of crude oil and dispersants clotting the oil spreads
across a stretch of the Gulf of Mexico in May 2010, following the
Deepwater Horizon spill. Such disasters can potentially disrupt
or destroy affected fisheries.What natural resources are extracted in your
region? How are issues related to these
resources similar to or different from those
involved in offshore energy and mineral
extraction?GLOBALLOCAL