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Maintaining Sustainable Environments Requires Knowledge, Decisions, and Actions. 4.1 Intended and Unintended Consequences of human Activities within Ecosystems. Human Impact on Ecosystems: Chemical Use The use of pesticides by people, in addition to the immediate solution they are intended to produce, typically enter the food chain and produce some very undesired results. The imbalance created by the impairment or death of a species by these chemicals, affects the entire ecosystem leading to impairment or death of its predators and their predators. Migratory species are very vulnerable to the use of pesticides as they visit so many localities. Example: The devastating affect the pesticide DDT had on the people of Borneo. (pg 67). Human Impact on Ecosystems: too Little too Late? Human activity such as hunting, bioinvasion, farming, urban development, and foresting have affected species to varying degrees. __________ Threatened – when a species has dramatically declined in numbers. Ex. The wood bison and burrowing owl. Endangered __________ – when a species is in danger of extinction. Ex. The Beluga whale and Whooping crane. Extinction – when a species has been ____________ entirely eliminated. Ex. Dinosaurs Though extinction of a species is a natural phenomenon, human activity has increased the rate or altered the natural course of succession entirely. Homework!!!!!!!!! Page 71 #’s 1-6 DDT The birds were affected by DDT because they consumed animals which had absorbed DDT into their bodies, so up the food chain the DDT went. Studies revealed the peregrine was originally threatened by a pesticide the bird carried in its body that weakened the shells not permitting the young inside to fully mature. Captive breeding programs were established to assist with the bird’s reintroduction to its natural environment. A release and monitoring program have observed the success of the program. As a result of the scientific plan for the peregrine’s return, the bird’s status has been downgraded from endangered to threatened. Peregrine Falcons have also been moved to skyscrapers in major US cities where their population have thrived due to the abundance of pigeons. 4.3 There are Limitations to Scientific and Technological Knowledge. Where Did It Go????? • In dealing with environmental issues, science cannot always provide answers due to a lack of evidence or studies. – Example: The Golden Toad in Costa Rica has vanished without a clue as to why. • Frogs or amphibians are extremely sensitive • indicators of environmental changes, as the uptake of oxygen and water through their skin can increase concentrations of pollutants, and the life cycle of frogs and toads exposes them to water and airborne contaminants. Amphibians are so sensitive to changes in the environment that scientists have likened them to a canary in a coalmine. • In addition to the apparent die-offs, deformities in other species of amphibians have no clear explanation due to a lack of evidence or obvious alteration to the environment thought to be at fault. • Scientists believe many amphibians are at risk due to one of the following theories. – – – – 1 2 3 4 Climate changes Pollution Disease ultraviolet radiation 4. 4 Using Evidence from Many Sources can help Analyze a Local Environmental Problem. Ecological Footprint Ecological _______ footprint – is the amount of land needed to sustain our food, transportation, entertainment, shelter, and sanitation needs. The average Canadian requires 7.7 hectares (77 000m²). 1.7 ha actually available per person on Earth. Average ecological footprint worldwide is 2.2 ha. Humans use more of the Earth’s resources than the environment can safely support, but there are ways of reducing our ecological footprint. • Reduction in the amount of water used. • Reduction in the use of energy. • Reducing consumable materials. • Reusing products where possible. • Recycling waste materials.