Page 532 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

496 part III The earth–atmosphere interface
F cus Study 16.1 Pollution Coastal Oil Spills: A Systems Perspective
an oil tanker splits open at sea and re- leases its petroleum cargo. This is carried by ocean currents toward shore, where it coats coastal waters, beaches, and animals. in response, concerned citizens mobilize and try to save as much of the spoiled envi- ronment as possible (Figure 16.1.1). But the real problem goes far beyond the immedi- ate consequences of the spill. What are the spatial and systems relationships between an oily bird, coastal restoration, energy demand and consumption, and ongoing global climate change?
Prince William Sound, Alaska
in Prince William Sound off the southern coast of alaska, in clear weather and calm seas, the Exxon Valdez, a single-hulled supertanker operated by exxon Corpo- ration, struck a reef in 1989. The tanker
spilled 42 million litres of oil. it took only 12 hours for the Exxon Valdez to empty
its contents, yet a complete cleanup is impossible, and cleanup costs and private claims have exceeded USD $15 billion. Scientists are still finding damage and residual spilled oil. eventually, more than 2400 km of sensitive coastline were ru- ined, affecting three national parks and eight other protected areas in alaska.
The death toll of animals was massive: at least 5000 sea otters died, or about 30% of resident otters in the affected areas; about 300000 birds and uncounted fish, shellfish, plants, and aquatic micro- organisms also perished. While some species, such as the bald eagle and common murre, have recovered, the Pacific herring is still in significant de- cline, as are the harbour seals. Sublethal effects—namely, mutations—are now
appearing in fish. More than two decades later, oil remains in mud- flats and marsh soils beneath rocks.
On average, 27 oil-releasing accidents occur every day, 10 000
a year worldwide, ranging from a few disastrous spills to numerous small ones (Figure 16.1.2a). Fifty spills equal to the Exxon Valdez or larger have occurred since 1970. in addition to oceanic oil spills, people improperly dispose of crankcase oil from their automobiles in a volume that annually exceeds all of these tanker spills.
Louisiana Coast, Gulf of Mexico
The largest oil spill in U.S. history occurred in 2010 in the gulf of Mexico (Figure 16.1.2b). Somewhere between 50 000 and 95 000 barrels of oil a day, for 86 days, exploded from a broken wellhead on the seafloor; this is 8 to 15 million litres a day, or the equivalent of a 1989
Exxon Valdez oil spill every 4 days. The differences in the spill-rate estimates are a consequence of the concerted efforts of the oil company to cover up the true nature of the spill because of potential financial liabilities.
The Deepwater Horizon well, at an ocean depth of 1.6 km, was one of the deepest drilling attempts ever, and much of the technology of the operation remains untested or unknown. Scien- tists are analyzing many aspects of the tragedy to determine the extent of the biological effects on the open water, beaches, wetlands, and wildlife of the gulf (Figure 16.1.2c). The seafloor in the affected region is essentially dead, covered in oil. early reports of the effectiveness of microbial digestion in cleaning up the oil in the water column were greatly exaggerated; these pro- cesses perhaps eliminated only 10% of the spill mass.
Questions Going Forward
The immediate effect of global oil spills on wildlife is contamination and death. But the issues involved are much bigger than dead birds. exercising the perspec- tive gained from the systems approach of this text, let us ask some fundamental questions concerning international de- mand for and trafficking in oil:
• Why was the single-hulled oil tanker in vulnerable alaskan waters? Why is it necessary to drill in ultra-deep water in the gulf using untested technology and equipment?
• Should we support increased efforts to discover and extract oil and gas resources in the Beaufort Sea region? How would the cold climate and geo- graphic isolation increase the com- plexity of a response to an oil spill?
• The Canadian demand for oil on a per capita basis is one of the highest in
▲Figure 16.1.1 Oily birds. Brown Pelicans (Pelecanus occidentalis) struggle as they wait for cleaning after the 2010 BP oil spill in the gulf of Mexico. [Jim Celano/reuters.]
• Human activities are an increasingly significant input producing coastal change.
All these inputs occur within the ever-present influ- ence of gravity’s pull—exerted not only by Earth, but also by the Moon and Sun. Gravity provides the poten- tial energy of position and produces the tides. A dynamic
equilibrium among all these components produces coast- line features.
The Coastal Environment
The coastal area and shallow offshore environment is the littoral zone, from the Latin word litoris, for