Human Impact on the Biosphere Intro to Environmental Science

Human Impacts Humans are using energy and altering the environment at astonishing rates We are altering natural processes before we even understand them

Developing vs. Developed In developing countries (LDCs), per capita resource use is fairly low but growing, as is population size In developed countries (MDCs), population growth has slowed but per capita resource use is very high

Pollutants Substances with which an ecosystem has had no prior evolutionary experience or adaptive mechanisms. Depends on concentration, location, and timing.

Air Pollutants Carbon oxides Sulfur oxides Nitrogen oxides Volatile organic compounds(VOCs) Photochemical oxidants Suspended particles

Industrial Smog Gray-air smog Forms over cities that burn large amounts of coal and heavy fuel oils; mainly in developing countries Main components are sulfur oxides and suspended particles

Photochemical smog Brown-air to orange smog Forms when sunlight interacts with primary release chemicals Nitrogen oxides are major culprits Hot days contribute to formation as does thermal inversion

Thermal Inversion Weather pattern in which a layer of cool, dense air is trapped beneath a layer of warm air cool air warm inversion air cool air

Acid Deposition Caused by the release of sulfur and nitrogen oxides Coal-burning power plants and motor vehicles are major sources

Ozone Thinning In early spring and summer ozone layer over Antarctica thins Seasonal loss of ozone is at highest level ever recorded South America Antarctica

Effect of Ozone Thinning Increased amount of UV radiation reaches Earth’s surface UV damages DNA and negatively affects human health UV also affects plants, lowers primary productivity

Protecting the Ozone Layer CFC production has been halted in developed countries, will be phased out in developing countries Methyl bromide will be phased out Even with bans it will take more than 50 years for ozone levels to fully recover

Generating Garbage Developed countries generate huge amounts of waste Paper products account for half the total volume Recycling can reduce pollutants, save energy, ease pressure on landfills

Land Use Almost 21 percent of Earth’s land is used for agriculture or grazing About half the Earth’s land is unsuitable for such uses (non-arable) Remainder could be used, but at a high ecological cost

Green Revolutions Improvements in crop production Introduction of mechanized agriculture and practices requires inputs of pesticides, fertilizer, fossil fuel Improving genetic character of crop plants can also improve yields

Deforestation Removal of all trees from large tracts of land 38 million acres logged each year Wood is used for fuel, lumber Land is cleared for grazing or crops

Effects of Deforestation Increased leaching and soil erosion Increased flooding and sedimentation of downstream rivers Regional precipitation declines Possible amplification of the greenhouse effect

Regions of Deforestation Rates of forest loss are greatest in Brazil, Indonesia, Mexico, and Columbia Highly mechanized logging is proceeding in temperate forests of the United States and Canada

Reversing Deforestation Coalition of groups dedicated to saving Brazil’s remaining forests Smokeless wood stoves have saved firewood in India Kenyan women have planted millions of trees

Destroying Biodiversity Tropical rainforests have the greatest variety of insects, most bird species Some tropical forest species may prove valuable to humans Our primate ancestors evolved in forests like the ones we are destroying

Desertification Conversion of large tracts of grassland to desertlike conditions Conversions of cropland that result in more than 10 percent decline in productivity

The Dust Bowl Occurred in the 1930s in the Great Plains Inappropriate cultivation techniques, overgrazing and prolonged drought left the ground bare 1934 winds produced dust storms that stripped about 9 million acres of topsoil

Ongoing Desertification Sahel region of Africa is undergoing rapid desertification Causes are overgrazing, overfarming, and prolonged drought One solution may be to substitute native herbivores for imported cattle

Water Use and Scarcity Most of Earth’s water is too salty for human consumption Desalinization is expensive and requires large energy inputs Irrigation of crops is the main use of freshwater

Negative Effects of Irrigation Salinization, mineral buildup in soil Elevation of the water table and waterlogging Depletion of aquifers

Ogallala Aquifer Extends from southern South Dakota to central Texas Major source of water for drinking and irrigation Overdrafts have depleted half the water from this nonrenewable source

Aquifer Problems

Water Pollutants Sewage Animal wastes Fertilizers Pesticides Industrial chemicals Radioactive material Excess heat (thermal pollution)

Wastewater Treatment Primary treatment –Use of screens and settling tanks –Addition of chlorine to kill pathogens Secondary treatment –Microbes break down organic matter Tertiary treatment removes additional toxic substances; rarely used

Water Wars? Per capita amount of freshwater available is decreasing International conflicts over water use and quality have already occurred Building dams or dumping pollutants effect countries downstream

Energy Use Only 10 percent of energy used in developed countries is from renewable sources Less developed countries rely more heavily on renewable sources (primary biomass)

Fossil Fuels Coal, oil, natural gas Main energy source of developed countries Burning of fossil fuels contributes to global warming

Oil Reserves are declining Many reserves are in ecologically fragile wilderness areas Environmental costs of extracting and transporting reserves from such areas are high

Coal Extensive reserves exist Mining is very destructive Burning coal releases sulfur dioxides that cause acid deposition

Nuclear Energy Used extensively in some energy- poor developed countries Little support in the United States Emits fewer air pollutants than burning coal, but creates radioactive wastes Potential for meltdown

Chernobyl Accident Core meltdown at a nuclear power plant in the Ukraine 31 immediate deaths, radiation sickness and death for others Cloud of radiation spread by winds across Europe Long-term health impacts downwind

Solar-Hydrogen Energy Photovoltaic cells use sunlight energy to split water Hydrogen gas produced in this way can be used as fuel or to generate electricity Clean, renewable technology

Wind Energy An indirect use of solar energy Wind farms are arrays of turbines Can supplement needs of some regions but is not dependable enough on it own

Fusion Energy is released when atomic nuclei fuse This process produces solar energy Attempts to mimic this process on Earth require use of lasers, magnetic fields Not yet a commercially viable energy source

Changes in the World of Life Adaptations of species have changed the environment Photosynthetic organisms that arose during the Proterozoic altered the atmosphere by adding oxygen Change is natural

Humans and Change Unlike previous species, human have the capacity to observe and make decisions about the changes they bring about

The Big Picture Environment Socio-politics Economics

References Modified from presentation of Prentice Hall Publishers, 2002