Threats to Biodiversity. Habitat Loss. Happens when either natural disasters or human activities change the ecosystem so much that many species can no longer survive. Natural sources of habitat destruction: Volcanic eruptions Wildfires Droughts Severe storms Human activities:
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Habitat Loss • Happens when either natural disasters or human activities change the ecosystem so much that many species can no longer survive. • Natural sources of habitat destruction: • Volcanic eruptions • Wildfires • Droughts • Severe storms • Human activities: • Deforestation • Draining wetlands • Damming rivers
Deforestation • Forests can be logged or cleared and never replanted. • Annual deforestation rates in North America are almost three times the average rate worldwide since 1966.
Draining Wetlands • Wetlands cover 6% of Earth’s surface • Plants, turtles, snakes, mink and 1000’s more live in wetlands • Migrating birds use them to feed and rest • Plants that grow there filter sediment and pollution from water. • Often drained for farming or building homes. • 90% of wetlands around lake Ontario have been destroyed.
Alien Species • Alien species: is accidentally or deliberately brought into a new location. • Introduced species, non-native species, exotic species. • Sometimes they can become an invasive species which is a species that takes over the habitat of native species and upsets the equilibrium of an ecosystem.
Zebra Mussels • Native to Asia • Introduced to Great Lakes through ballast water • Ballast water is when cargo ships pick up water to keep them stable at sea and then dump the water in other places. • Zebra mussels out-competed native crustaceans, which in turn were a major source of food for whitefish and smelt
Round Gobies • Asian Round Goby also probably came in ballast water • Population grew exponentially since 1990’s. • We’re not sure of their impact yet, but their population is estimated in the billions in Lake Erie.
Overexploitation • The use or extraction of a resource until it is depleted. • Examples: • Passenger pigeon once 5 billion, last one died in 1900’s. • Yellowfish tuna and Atlantic cod: over-fished and reduced by 90%
Extinction • When all individuals of a species dies. • When death rate exceeds birth rate over a long period of time. • There are patterns of extinction that happened naturally: • Background extinction: apparent over long periods as ecosystems change, some species become extinct • Mass extinction: relatively sudden ecosystem change. Example: dinosaurs (caused by an asteroid?)
Environmental Stewardship • The assumption of responsibility for the welfare of the environment • All humans are responsible. • In history, most humans have not thought about sustaining ecosystems • Now, more and more we are concerned with the renewal of degraded or destroyed ecosystems through human intervention (restoration ecology)
Methods of Restoration • Reforestation: the regrowth of a forest, naturally or by planting trees or seeds in an area where a forest was cut down. • Wetlands Restoration: water returned to natural levels, soil quality returned. • Bioremediation: using living organisms to clean up contaminated areas • Plants that clean up contaminants in soil • Bacteria that clean up oil spills • Bioaugmentation: use organisms to add essential nutrients to soil • Clover added to replenish nitrogen
Controlling Alien Species • Biocontrol: use one species to control another undesired species. • Chemicals: like poisoning, it kills the species.