Key species have large effects on ecosystems and can cause collapse if removed. Sea otters were key to kelp forests by eating sea urchins that eat kelp, providing habitat. Wolves were removed from Yellowstone in 1926, allowing elk populations to increase and reduce forest cover and wetlands until wolves were reintroduced, though elk are influenced by multiple factors like disease and other predators as well.

1. KEYSTONE SPECIES

2. KEYSTONE SPECIES
Species that have a large effect on an ecosystem
Take them away and the system collapses

3. THE CASE OF THE CALIFORNIAN
SEA OTTER

4. KELP FORESTS
• Sea otters eat sea urchins
• Sea urchins eat kelp
• Kelp forests act as ecosystems for many species and as nurseries for
young fish
• Hunting sea otters for fur impacted on the kelp forest ecosystems.
Sea urchins eating kelp

5. THE WOLVES OF YELLOWSTONE
PARK
• Grey wolves (Canis lupus)
were considered a pest species
• Hunted throughout western
US
• Exterminated from
Yellowstone 1926

6. THE
CONSEQUENCES
• Wolves hunt elk
•  Elk populations increase
•  Forest cover decreases
•  Decrease in wetlands
North American Elk (Cervus elaphus)

7. YELLOWSTONE NORTHERN ELK
POPULATION
Culling
of elk
stops

8. NOT SO SIMPLE
• Though wolves are important predators on elk they are not
the only factors
• Disease
• Drought
• Fire
• Other predators (e.g. grizzly bears)