Visualizing Environmental Science

Human Impacts on the Ocean 285

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Human impacts on the ocean

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Impact

Very low

Low

Medium

Medium high

High

Very high

After Halperin, B.S., et al.

“A global map of human

impact on marine ecosystems.”

Science, Vol. 319, No. 5865,

pp. 948–952 (February 15, 2008).

b. Major Threats to the Ocean.

a. Mapping Human Impacts. In 2008, an international

team of marine scientists mapped effects of 17 human

activities on the ocean. Almost no location remains

unaffected, and 41 percent of the ocean has been

seriously altered by multiple activities.

Invasive species

Example: Organisms are transported and

released from ships in ballast water, which

contains foreign crabs, mussels, worms,

and fishes.

Nonpoint source pollution

(runoff from land)

Example: Agricultural runoff

(fertilizers, pesticides, and

livestock wastes) pollutes

water.

Coastal development

Example: Developers

destroy important coastal

habitat, such as salt marshes

and mangrove swamps.

Habitat destruction

Example: Trawl nets (fishing

equipment pulled along the

ocean floor) destroy habitat.

Bycatch

Example: Fishermen

unintentionally kill dolphins,

sea turtles, and sea birds.

Point source pollution

Example: Passenger cruise

ships dump sewage,

shower and sink water, and

oily bilge water.

Overfishing

Example: Populations of

many commercial fish

species are severely

depleted.

Climate change

Example: Coral reefs and

polar seas are particularly

vulnerable to increasing

temperatures.

Aquaculture

Example: Fish farms produce

wastes that can pollute

ocean water and harm

marine organisms.

Under which of the major threats

would you place the 2010 Deepwater Horizon oil spill

in the Gulf of Mexico, or floating debris from the 2011

tsunami in Japan?

Think Critically

Interpreting Data

Which regions exhibit the greatest impacts?

Which are least affected? Is there a relationship

between site location and status? Explain.