Keystone species For BSc Msc BS Honour

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)