Page 455 - Environment: The Science Behind the Stories

FaQ Is the “Great Pacific Garbage Patch” Oil pollution comes from spills of all sizes
a huge mass of floating debris?
For many people, ocean pollution first brings to mind oil pol-
The vast majority of plastics that accumulate in the ocean are lution. About 30% of our crude oil and much of our natural
quite small and are dispersed over relatively large areas, so gas come from seafloor deposits. Most offshore oil and gas is
they are difficult to detect with the naked eye. Hence, a per- concentrated in petroleum-rich regions such as the North Sea
son expecting to see dense expanses of floating debris when and the Gulf of Mexico, but energy companies extract smaller
traveling through the Great Pacific Garbage Patch and other amounts from diverse locations, among them the Grand Banks
hotspots of oceanic pollution is likely to be disappointed. This and adjacent Canadian waters. Proposals to drill for oil and
can incorrectly lead one to believe the problem of oceanic gas in Georges Bank and the Gulf of Maine have been stalled
debris is exaggerated. by both the U.S. and Canadian governments, in large part
But even though the plastic and other debris in these because any spilled oil could damage the region’s fisheries.
gyres is typically small in size (usually only several millimeters in The danger of oil spills to fisheries, economies, and
length), it still poses threats to wildlife from ingestion and toxic- ecosystems became clear in 2010 when British Petroleum’s
ity. In many ways, smaller pieces of plastic are more dangerous Deepwater Horizon offshore drilling platform exploded,
to marine life than larger pieces, because they resemble food killing 11 workers and sinking into the ocean off the Lou-
items much more closely than do large items. So while a float- isiana coast (p. 556). Oil gushed from the underwater well
ing tire or fishing net certainly provides a striking visual impact, at rates of 1800 gallons per minute, rose to the surface, and
it’s important to realize that the oceanic plastic pollution we spread (Figure 16.17a) for three months before the underwater
cannot easily see is often of greatest concern.

Figure 16.17 Oil pollution from both large and small spills
affects the oceans. Pollution was severe (a) after BP’s Deepwa-
ter Horizon oil drilling platform exploded and disgorged millions of
gallons of crude oil into the Gulf of Mexico in 2010. (b) Non-point-
source pollution from petroleum consumption by people accounts
for 38% of total input into oceans. Sources include numerous
diffuse sources, especially runoff from rivers and coastal communi-
ties and leakage from two-stroke engines. Less oil is being spilled
into ocean waters today in large tanker spills (c), thanks in part to
regulations on the oil shipping industry and improved spill response
techniques. The bar chart shows cumulative quantities of oil spilled
worldwide from nonmilitary spills over 7 metric tons, identifying
larger spills by vessel name. Data from: (b) National Research Council,
2003. Oil in the sea III. Inputs, fates, and effects. Washington, DC: National Acad-
emies Press; and (c) International Tanker Owners Pollution Federation Ltd.

800 Atlantic Empress
Oil spilled from tankers (thousand tonnes) 500 Khark V 72,000 tonnes

ABT Summer
(a) Boat proceeds through Deepwater Horizon oil spill 700 287,000 tonnes Castillo De Bellver 260,000 tonnes
600
252,000 tonnes
Sea Empress
80,000
tonnes
Erika
Non-point-source pollution 400 20,000 tonnes
from consumption Tanker Exxon
(480,000) transport 300 Valdez Prestige
(150,000) 37,000 63,000 tonnes
tonnes
Extraction 200 Hebei Spirit
(38,000) 11,000 tonnes
Natural 100
seeps
(600,000)
0
1970 1975 1980 1985 1990 1995 2000 2005 2010
Year
(b) Sources of petroleum input into oceans (metric tons), (c) Quantity of petroleum spilled from oil tankers, 1970–2012
454 in 2003

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