The Regime Shift from Kelp Forests to Urchin Barrens Along

question 50

Multiple Choice

The regime shift from kelp forests to urchin barrens along the west coast of the United States illustrates how human actions have caused communities to shift to alternate states. This particular shift was caused because of a decline in sea otters, most likely due to hunting. Why would the reintroduction or protection of sea otters not return the system to its original state?

• A) Hysteresis suggests that some regime shifts are incredibly difficult to reverse.
• B) Sea otters are not the only predator on sea urchins.
• C) The increase of orcas (a predator of sea otters) will continue to suppress otter populations.
• D) Urchin barrens are the climax community for coastal ecosystems.