1. Chapter 10 Section 2
Biodiversity at risk

2. Objectives
Define and give examples of endangered and threatened species
Describe ways that species are being threatened with extinction
Explain which threats are having the largest impact on biodiversity
List areas of the world that have high levels of biodiversity
Compare the amount of biodiversity in the U.S. to that of the rest of the world

3. Mass Extinctions
About 65 million years ago, changes in climate and ecosystems caused the extinction of about half the species on Earth
A mass extinction is the extinction of many different species over a short period of time
Earth has experienced several mass extinctions and it takes millions of years for biodiversity to rebound

4. Current Extinctions
Scientists are warning that we are in the middle of another mass extinction
The rate of extinction has been estimated to increase by a multiple of 50 since the year 1800.
If this is true, by the year 2100, 25% of all species on Earth will be extinct.
Humans are the primary cause of extinctions

5. Species Prone to Extinction
These types of species are especially at risk of extinction:
Small populations in limited areas
Species that migrate
Species that need a large special habitat
Species that are exploited by humans

6. Endangered vs. Threatened
Endangered species- species that is likely to become extinct if protected measures aren’t taken immediately
Threatened species- species that has a declining population and is likely to become at risk if not protected

7. How Do Humans Cause Extinction?
In the past 200 years, the human population growth has accelerated and so has the rate of extinctions
The major causes of extinction today are:
Destruction of habitats
Invasive species
Pollution
Overharvesting species

8. Habitat Destruction
As the human population grows, we use more land to build homes and harvest resources
In the process, habitats are destroyed
Habitat destruction accounts for 75% of extinction

9. Florida Panther

10. Invasive Exotic Species
Exotic Species- a species not native to a particular region
PA’s most Invasive:
Zebra Mussel-Mollusk
Chestnut Blight- Fungus
Dutch Elm Disease-Fungus
Hemlock Wooly Adelgid- Insect
Garlic Mustard-Weed

11. PA’s Invasive Species Chestnut blight Dutch Elm Disease Wooly adelgid
Zebra mussel
Garlic mustard

12. Harvesting and Hunting
In the U.S. the Passenger Pigeon, became extinct due to overhunting
The American bison nearly became extinct
Today, rare species are harvested and sold as pets, houseplants, wood, food, or herbal medicines

13. Poaching Poaching- illegal harvesting of fish, game, or other species
Many countries now have laws to regulate hunting, fishing, harvesting and the trade of wildlife
In developing countries especially, poaching is a problem

14. Pollution The following make their way into food webs: Pesticides
Cleaning Agents
Drugs
Other chemicals

15. Pollution
The long-term effect of chemicals may not be clear until after many years of use
The bald eagle is an example of a species that was endangered because of DDT
Although DDT is now illegal in the U.S., it is still manufactured around the world

16. Areas Critical of Biodiversity
Some parts of the world have a greater diversity of species than others.
Examples:
Tropical Rain Forests
Coral Reefs and Coastal Ecosystems
Islands

17. Areas Critical of Biodiversity
An important feature of these areas is that they have a large portion of endemic species
Endemic species- a species that is native to a particular place and is only found there
Ecologists often use the numbers of endemic species of plants as an indicator of overall biodiversity, because plants form the basis of ecosystems on land

18. Tropical Rain Forests Cover less than 7% of Earth’s surface
Half of the world’s species live there!
Most of these species are still unknown
Tropical rain forests are disappearing due to farming and cattle grazing

19. Coral Reefs
Coral reefs occupy a small fraction of Earth’s marine environments, but contain the majority of the biodiversity
Reefs provide millions of dollars of revenue from food and tourism
They protect coasts from waves
They are not well understood or protected
Overfishing and pollution are causing their destruction
Scientists believe if destruction continues at its current rate, 70% of the world’s reefs will disappear in the next 50 years

20. Islands
Islands are colonized by a limited number of species from the mainland
Scientists believe many of these species evolve into new species
The Hawaiian Islands have 28 endemic bird species

21. Biodiversity Hotspots
The most threatened areas of high species diversity on Earth have been labeled biodiversity hotspots
This was developed in 1980 by ecologists for endemic species that were threatened by human activities

22. Biodiversity Hotspots

23. Endangered Species World-Wide
Akiapolaau
Dragon Tree
Mouse Lemur
Monitor Lizard

24. Biodiversity in the U.S.
The California Floristic Province is home to 3,488 plant species
2,124 are endemic
565 are threatened or endangered