1. Extinction

2. Passenger Pigeons 1850’s – Billions of birds 1914 – Extinct
Commercial Hunting
Clearing of Forests (destroyed habitat and food)
“Stool Pigeon”

3. Humans and the Rate of Extinction
Extinction of passenger pigeon was sudden, but not an isolated event
Species extinction rates are increasing as the human population grows
Between 8000 B.C. and 1600 A.D. the species extinction rate was approximately 1 species every 1000 years. Between 1600 – is approximately 1 species every 4 years
Projection for the future: 1 species every 30 minutes
Many threatened species are found in the tropical rainforest, however the problem also exists in Canada
Number of species at risk of extinction is growing, at the rate of about 80 species per year.

4. Brief History of Extinction
Several large scale disasters have destroyed a number of species
First mass extinction: 438 million years ago (marine organisms)
Another mass extinction of marine organisms – 360 millions years ago
Largest mass extinction – 245 million years ago. (approximately 80% of all species died)
208 million years ago – mass extinction marked the beginning of the age of dinosaurs
It removed the competition which allowed the success of early reptiles, which were then no larger than a small dog
Most famous mass extinction – 65 million years ago (end of dinosaurs)
Most common theory for the mass extinctions: asteroids colliding with earth
Evidence (crater off the Yucatan Peninsula of Mexico, 9.6 km deep and 300 km wide)

5. Other Causes of Extinction
Approximately 500 million species have inhabited the planet, more than 90% of these have become extinct or evolved into a new species
Climate changes and pressure of competition from other species force organisms to adapt or die
If one species disappears, it could cause a domino effect in the food chain
Eventually (hundreds of millions of years), all species will encounter conditions to which they cannot adapt and will become extinct. However, humans are significantly speeding up the process.
The Banff longnose dase (a small minnow) was recently declared extinct. It was unable to compete with the guppies, swordtails and other tropical fish released accidentally into warm marsh waters below the hot springs in Banff National Park

6. In Canada’s arctic, climate change has been blamed for the demise of the Peary Caribou. Changes in snow cover, caused by global warming, have caused changes in local plant communities. Lichens and mosses, the preferred food choice, are being replaced by plants that previously grew more south.
In fir, pine, and spruce forests from BC to Newfoundland, logging, oil exploration, and expanding of cities have reduced the size of ecosystems, endangering forest-dwelling species such as spotted owls, woodland bison, and woodland caribou.
The expansion of agriculture has also been identified as a major contributing factor in extinction. The decline of the monarch butterfly has been linked to the use of herbicides used to control milkweed, the monarch caterpillar’s only source of food.
The burrowing owl, which lives on the prairies, is threatened because the burrows it nests in have been plowed under and rodents (it’s food) have been exterminated.

7. Effects of Extinction
Biodiversity – the number of species in an ecosystem; biological diversity
The reduction of biodiversity in an ecosystem can cause a “domino effect” on the entire ecosystem
Example: overhunting of sea otters
Overhunting of sea otters along the Pacific coasts of Asia and North America removed the main predator of the sea urchin. As the number of sea urchins grew, the amount of kelp declined, and so did the fish that relied on the kelp bed ecosystem for habitat and food.
Sea otters very nearly became extinct due to hunting pressure.

8. Example: The Whooping Crane
Restoring the Balance
Not easy to do!
Reintroduction of Sea Otter into Pacific Northwest
Example: The Whooping Crane
In the past three decades, the number of whooping cranes has increased from 14 to 183 (1940 – 1999).
Chemical pesticides were the original human threat to the crane, but it was already struggling.
The cranes fly between their summer homes in the north, to their winter homes on the Gulf of Mexico. A long flight. Along the way they are vulnerable to hunting and accidents.
Whooping crane reproduces VERY slowly. Two eggs/year, and only one will mature. The first born eats the other egg to reduce competition for food.
Once the number of whooping cranes is low, it is very difficult for the species to increase its numbers.

9. What is the Value of Wolves?
Read “What is the Value of Wolves” (Pages 20-21) Read the three different views on what should have been done in Yellowstone Park and pick a side, or come up with your own view. Discuss with your table partner. Do you have the same views? Different views? Has your opinion changed at all after talking with your partner?

10. Bees are the Bees Knees
bees-went-extinct

11. Assignment ½ page Why are bees going extinct?
What will happen, short term and long term, if the bees go extinct?
What can you do to help/prevent the bees from becoming extinct?