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Biodiversity. Section #2: Biodiversity at Risk. changes in Earth’s climate & ecosystems have caused the extinction of about ½ the species on Earth. Extinctions. the loss of many species in a relatively short period of time
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Biodiversity Section #2: Biodiversity at Risk
changes in Earth’s climate & ecosystems have caused the extinction of about ½ the species on Earth Extinctions
the loss of many species in a relatively short period of time it takes millions of years for biodiversity to rebound after a mass extinction Mass Extinctions
scientists warn that we’re in the midst of another mass extinction between 1800 & 2100, up to 25% of all species on Earth may have become extinct primary cause = humans (this is different from the past) Current Extinctions
species with small populations species with limited habitats species that migrate species that need special habitats species that need lots of space species that are exploited by humans Species Prone to Extinctions
endangered species = a species that is like to become extinct if protective measures are not taken immediately threatened species = a species that has a declining population & is likely to become endangered if not protected Endangered vs. Threatened
human population growth that has lead to . . . habitat destruction & fragmentation pollution introduction of nonnative species over-harvesting of species How Do Humans Cause Extinctions?
we use more land to build homes & for harvesting resources this destroys & fragments the habitats for other species 75% of extinctions occur because of habitat loss Habitat Loss
a species that is not native to a particular region they are brought to an area where they never lived before exotic species can threaten native species that have no natural defenses Invasive Exotic Species
many countries now have laws to regulate hunting, fishing, harvesting, & wildlife trade to cut down on excessive loss of species not all threatened species are legally protected, especially in poorer countries where they might be a source of food, medicine, or income Harvesting, Hunting, Poaching
pesticides, cleaning agents, drugs, & other chemicals used by humans are making their way into food webs around the globe we often don’t know the long-term effects until its too late Pollution
bald eagles became endangered from the pesticide DDT (now illegal to use in the U.S. still manufactured here and sold around the world) the DDT caused a thinning in the eagle’s eggshells & the babies did not survive Pollution
species that are native to and found only with a limited area scientists often use the numbers of endemic species of plants as an indicator of overall biodiversity Endemic Species
tropical rain forests coral reefs coastal ecosystems islands Areas of Critical Biodiversity
only cover a small % of the Earth’s land surface (<7%) biologists estimate that over ½ of the world’s species live in these forests most of these species have not been described unknown #s of species are disappearing as tropical rain forests are cleared for farming cattle grazing Tropical Rain Forests
the Amazon has had an influx of visitors, not only tourists, but also scientists who are searching for new species to create new products, especially drugs the Brazilian government has now claimed the right to tax or patent any genetic material harvested with in its borders Tropical Rain Forests
only occupy a small fraction of the ocean, but contain the majority of biodiversity reefs provide millions of people with food, tourism revenue, coastal protection, sources of new chemicals some have placed a value of $375 billion per year Coral Reefs
threatened by human activities, particularly development along waterways, filling in swamps and marshes too much pollution is becoming a bigger problem, these ecosystems act as a buffer zone but still have limitations Coastal Ecosystems
often hold very distinct, but limited numbers of species most species have migrated from the mainland and then evolved into new species introduction of invasive exotic species can destroy the island’s species Islands
the most threatened areas of high species diversity around the world have high numbers of endemic species that are threatened by human activities most have already lost 70% of their original vegetation typical hotspots are tropical rainforests, coastal areas, & islands Biodiversity Hotspots
areas = Florida Everglades, California coastal regions, Hawaii, Midwestern prairies, Pacific NW forests species = freshwater fishes, mussels, snails, crayfish, pine trees, sunflowers, birds Biodiversity in the U.S.
