Chapter 10 Section 2 Biodiversity at risk

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

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

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

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

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

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

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

Florida Panther

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

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

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

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

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

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

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

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

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

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

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

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

Biodiversity Hotspots

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

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