Download case study: how losing a keystone species can collapse an ecosystem

© Victoria Chapman & Associates
CASE STUDY: HOW LOSING A KEYSTONE SPECIES CAN COLLAPSE AN ECOSYSTEM
Sea otters live in Pacific Ocean kelp
beds. They prey on sea urchins,
crabs, abalone, fish, and other sea
life. In the 18th and 19th centuries,
fur trappers hunted sea otter
populations to near extinction.
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Without sea otters to
prey on them, sea urchins
multiply and overgraze
kelp and other seaweeds.
They nip off the holdfasts
that anchor kelp to rocks,
creating a barren sea floor.
The many species that rely
on kelp forests for food
and shelter disappear.
Kelp
Sea urchins
Kelp
holdfast
Surviving populations of sea otters have been
reintroduced to some of their former home sites. With the
return of the sea otter, the kelp forests have grown back.
The sea otter is a keystone species. When it is removed,
the kelp forest community changes drastically.