Transcript Document
HUMAN IMPACT • One-third of all plant and vertebrate species live on just 1.5% of Earth’s land • Every year, humans destroy an area of tropical rain forest equal to the size of West Virginia Introduced Species • Introduced species – #2 cause of extinction and loss of Earth’s biodiversity; border questions • Kudzu, a Japanese plant HUMAN IMPACT ON ECOSYSTEMS • Burning of fossil fuels is the most likely cause of global warming Impact on the Carbon Cycle • The increased use of fossil fuels – raises the level of CO2 in the atmosphere Impact on the Nitrogen Cycle • Sewage treatment facilities and fertilizers – add large amounts of nitrogen and phosphates to aquatic systems, causing heavy growth of algae Impact on the Water Cycle • Destruction of tropical rain forest – alters local and global weather patterns – the water cycle Deforestation and Chemical Cycles: A Case Study • The Hubbard Brook Experimental Forest is a study site for nutrient cycling in a forest ecosystem Altered Completion of tree cutting Control The Release of Toxic Chemicals to Ecosystems • Humans are adding new toxics to ecosystems and they often cannot be degraded by microorganisms • Biological magnification DDT concentration increase of 10 million times DDT in fish-eating birds 25 ppm DDT in large fish 2 ppm DDT in small fish 0.5 ppm DDT in zooplankton 0.04 ppm DDT in water 0.000003 ppm • It was once thought that the atmosphere could absorb our gaseous waste products; smog Depletion of Atmospheric Ozone • The ozone layer – absorbs UV radiation, preventing most of it from striking organisms in the biosphere • Our protective ozone layer (a) Ozone hole (b) Thickness of ozone layer – started thinning due to the build up of CFCs (chlorofluorocarbons) Monthly averages for October • The consequences of ozone depletion – are quite severe for all life on Earth The Loss of Species • The current mass extinction – caused by human activity – broader and faster than other past extinctions • At the current rate of destruction over one half of all plant and animal species will be gone by the end of this century The Three Main Causes of the Biodiversity Crisis • 1. Human destruction of habitat Introduced Species • 2. Introduced species Overexploitation • 3. Overexploitation of wildlife Why Biodiversity Matters • Humans rely on biodiversity for – food, clothing, shelter – oxygen, soil fertility, medicinal substances CONSERVATION BIOLOGY • Conservation biology – a goal-oriented science that seeks to counter the loss of biodiversity Biodiversity “Hot Spots” • A biodiversity hot spot – a relatively small area with an exceptional concentration of species Equator Tropical forest hot spots Chaparral hot spots • Endemic species – found nowhere else; common in hot spots – highly sensitive to habitat degradation Conservation at the Species Level • Much of the discussion of the biodiversity crisis centers on species • The U.S. Endangered Species Act – an endangered species is “in danger of extinction throughout all or a significant portion of its range” Conserving Species amid Conflicting Demands • Conservation biology – deals with relationships between biology and society • Competing demands for habitat are always an issue Sustainable Development • Sustainable development – balances human needs with the health of the biosphere • The goal of sustainable development – the long-term prosperity of human societies and the ecosystems that support them Habitat Fragmentation • Population fragmentation – the splitting and consequent isolation of portions of populations by habitat destruction Corridors • A movement corridor – a narrow strip or series of small clumps of quality habitat connecting otherwise isolated populations An artificial corridor • Corridors – promote dispersal and help sustain populations – especially important to species that migrate between different habitats Zoned Reserves • A zoned reserve – an extensive region of land that includes one or more areas undisturbed by humans • The areas surrounding zoned reserves are buffer zones that support both agriculture and tourism