Biodiversity is life

Biodiversity is our life

Chapter 10 Section 2

Biodiversity at Risk Objectives

• Define and give examples of endangered and threatened species.

• Describe several ways that species are being threatened with extinction globally.

• Explain which types of threats are having the largest impact on biodiversity.

• List areas of the world that have high levels of biodiversity and many threats to species.

• Compare the amount of biodiversity in the United States to that of the rest of the world.

Biodiversity at Risk

Key Terms:

Endangered species Threatened species

Exotic species Poaching

Endemic species

Major Extinction Events A sixth extinction?

Major Extinction Events

• Mass extinction – extinction of many species in a relatively short period of time.

• The rate of extinction is estimated to have increased by a multiple of 50 since 1800.

• Between 1800 and 2100 up to 25% of all species on Earth may become extinct.

• Sixth extinction?

• Endangered species are those likely to become extinct if protective measures are not taken immediately.

• Threatened species are declining in population and likely to become endangered if not protected.

Major human causes of extinction:

• Habitat destruction and fragmentation

• Introduction of non-native species

• Pollution

• Over-harvesting of species

(Human population growth affects rate of extinctions.)

Habitat destruction and fragmentation

It is estimated that habitat loss causes about 75% of current extinctions.

Habitat fragmentation - habitat broken up by roads, canals, fences, etc.

Habitat destruction and fragmentation

• Example: Florida Panther, which is the most endangered species in North America. Habitat loss is the major reason.

Introduction of non-native species

• Invasive exotic species are not native to a particular region.

• Can threaten native species that have no natural defenses.

• Example: invasive fire ants threaten livestock, people, and native species in southeastern United States.

Introduction of non-native species

Kudzu Fire Ants

Pollution: Pesticides, cleaning agents,

pharmaceuticals, other chemicals used by humans

Example: Bald eagle and DDT

Over-harvesting of species

• Poaching – harvesting wildlife illegally.

• Thousands of species are harvested and sold as pets, houseplants, wood, food, and herbal medicine.

• Many countries have laws to regulate hunting, fishing, harvesting, and trade of wildlife.

Poaching

Example: Bison numbers went from 60 million before North America was settled by Europeans to only 300 in 1906. Many killed for their tongues (considered a delicacy) and bodies were left to rot. Current population is 200,000 +.

Areas of Critical Biodiversity

• Endemic species – species native to and found only within a limited area.

• Number of endemic species of plants are an indicator of overall biodiversity because plants form the basis of terrestrial ecosystems.

Areas of Critical Biodiversity

Tropical Rain Forests

• Less than 7% of Earth’s land surface; 50% or more of biodiversity

• Threats: clearing for farming, cattle grazing, logging

Areas of Critical Biodiversity

Coral Reefs and Coastal Ecosystems

• Provide food, tourism revenue, coastal protection, sources of new chemicals

• Nearly 60% of coral reefs are threatened

• Threats: development along waterways, overfishing, pollution.

Example: Great Barrier Reef near Australia is the largest and maybe oldest reef (2000 km/1,250 miles long and 3,400 individual reefs).

Areas of Critical Biodiversity

Islands • Colonized by a limited number of species

from mainland;

• Colonizing species evolve into several new species

Hawaiian Islands have 28 species of endemic birds (honeycreepers) endangered because of invasive exotic species. Threats: cattle and feral pigs that destroy habitat, rats that eat eggs and young birds, and introduced birds that have out-competed the honeycreeper for habitat.

Biodiversity hotspots

• Biodiversity hotspots – most threatened areas of high species diversity.

• High number of endemic species threatened by human activities.

• International conservationists have identified 25 biodiversity hotspots.

Biodiversity hotspots

• Most have lost at least 70% of their original vegetation.

• Most are tropical rain forests, coastal areas, or islands.

Biodiversity hotspots Example: Island of Madagascar

• Only 18% of original forests remain

• 80% of 10,000 flower plant species are endemic

• 91% of 300 reptile species are endemic

• All 33 species of lemur are found only in Madagascar

Examples of U.S. biodiversity hotspots:

• Florida Everglades

• California coastal region

• Hawaii

• Midwestern prairies

• Forests of the Pacific Northwest

The U.S. has an unusually high number of species of freshwater fishes, mussels, snails, crayfish, pine trees, and sunflowers.