Global Environmental Issues • Global Warming – Greenhouse Effect • Water Pollution • Eutrophication • Acid Rain • Deforestation • Habitat loss • Over exploitation • Bioaccumulation
Global Warming – Greenhouse Effect • Greenhouse gases help to maintain the earth’s temperature at a level suitable to support life • Human activities are increasing the amount of greenhouse gases in the atmposphere, which cause more heat to be trapped • Predicted effects of global warming include: • Higher sea levels • Higher temperatures • Variable climatic conditions • These changes are expected to cause a significant impact on agriculture and ecosystems.
Pollution • Water pollution - A change in water quality that impacts on living organisms • Types and effects of water pollution include: • Nutrients and eutrophication • Toxic materials, through mining • Organic chemicals • Sediments can disrupt aquatic ecosystems Atmospheric Pollution: -CFC’s chlorofluorocarbons, can reach the stratosphere and destroy ozone gas. - Gas emissions – leads to Acid Rain
Eutrophication • an excessive amount of nutrients in a body of water, usually caused by runoff of nutrients (mainly phosphorous in freshwater and nitrogen in saltwater) from the land, which causes a dense growth of plant life, leading to a decrease in oxygen supply, which causes the death of animals.
Acid Rain • The burning of fossil fuels leads to atmospheric emissions of NOx and SO2 • These gases react with water and oxygen to make sulfuric and nitric acids. Sunlight increases the rate of these reactions • Rain, snow and fog can be polluted with these acidic compounds, which is then deposited at the earths surface • The effects of acid rain can: • Damage forests and soils • Causes acidification of lakes and other water bodies • Disturb wildlife • Cause the decay of building and other structures • Impact on human health
Deforestation • The deforestation of tropical rainforests is a major global problem-each year millions of hectares are lost • Deforestation rates in some countries continue to increase despite worldwide pressures • Rainforests are destroyed for wood products, and to make way for agricultural activities, mining and dams • The impacts of deforestation include: • Loss of livelihood for local inhabitants • Variable environmental conditions (susceptability to flood, aggravated droughts, soil erosion etc) • Loss of biodiversity and disturbance to ecosystems • Loss of carbon sink
Habitat loss • due to destruction, fragmentation or degradation of habitat—is the primary threat to the survival of wildlife in the United States. Habitat fragmentation: terrestrial wildlife habitat has been cut up into fragments by roads and development; Aquatic species’ habitat has been fragmented by dams and water diversions. Habitat destruction: A bulldozer pushing down trees is the iconic image of habitat destruction. Other ways that people are directly destroying habitat, include filling in wetlands, dredging rivers, mowing fields, and cutting down trees. Habitat degradation: Pollution, invasive species and disruption of ecosystem processes so the habitats become degraded that they no longer support native wildlife
Introduced Species • Any organism that was brought to an ecosystem as the result of human actions • Can pose a threat to the stability of an ecosystem if they prey on or crowd out the native species Purple loosestrife Burmese python
Overexploitation • Overexploitation of species affects the loss of genetic diversity and the loss in the relative species abundance of both individual and/or groups of interacting species. • Overexploitation may include over fishing and over harvesting. • Removing ground cover and degrading fertile land initiates desertification • Water washes away nutrients, the land becomes inhospitable • The process is accelerated by expanding populations and the need to overuse fragile areas of land
Bioaccumulation(biomagnification) • Bioaccumulation is defined as the increase in concentration of a substance(s) in an organism Biomagnification is simply the increase in concentration of a substance in a food chain, not an organism. DDT, PCBs