BI 105A Environmental Biology

1. BI 105AEnvironmental Biology Professor Jill Nissen Montgomery College Fall 2006

2. Regional and Global Atmospheric Changes Chapter 21

3. Earth’s Atmosphere • The troposphere is the layer of the atmosphere closest to the Earth’s surface • The stratosphere is the layer above the troposphere • The stratosphere contains a layer of ozone that is critical to life because it absorbs most of the sun’s damaging UV radiation

4. The Greenhouse Effect Greenhouse Effect The natural trapping of heat in Earth’s atmosphere Greenhouse Gases Warm Earth’s atmosphere by absorbing some of the outgoing infrared (heat) radiation. Enhanced Greenhouse Effect The land and oceans are warmed as some of this trapped heat is transferred back to Earth’s surface.

5. Greenhouse Gases The five main greenhouse gases are: • Carbon dioxide • Methane • Nitrous oxide • Chlorofluorocarbons (CFCs) • Tropospheric (surface level) ozone The concentrations of these gases are increasing in the atmosphere due to: • Burning of fossil fuels (factories and vehicles) • Deforestation • Agricultural activities • Other man-made gas emissions

6. What is Global Warming? Global Warming The gradual increase of temperature of the Earth’s lower atmosphere as a result of the increase in greenhouse gases since the Industrial Revolution. Source: http://data.giss.nasa.gov/gistemp/graphs/

7. Effects of Global Warming • Melting ice and rising sea levels • Changes in precipitation patterns • Effects on organisms • Effects on human health • Effects on agriculture

8. Global Warming and Sea Level Rise Thermal expansion has already raised the oceans 4 to 8 inches, but that's nothing compared to what would happen if Greenland's massive ice sheet were to melt. These maps show that a 1-meter (3-foot) rise would swamp cities all along the U.S. eastern seaboard: Source: http://www.geo.arizona.edu/dgesl/index.html

9. Global Warming and Precipitation Some areas will have more frequent droughts, while other areas will have heavier precipitation

10. Global Warming and Hurricanes Hurricane forecast models indicate that increased CO2 and warmer temperatures will result in more intense hurricanes The frequency of the strongest (category 5) hurricanes roughly triples in this scenario: Source: http://www.gfdl.noaa.gov/~tk/glob_warm_hurr.html

11. Global Warming and Organisms Global warming affects organisms and their habitat around the world. Some species may become extinct or survive in a greatly reduced range Some species may prosper and expand their ranges (weeds, pests, and disease-carrying organisms)

12. Global Warming and Organisms Shrinking sea ice affects the entire Antarctic food web: • Krill (tiny shrimp-like organisms) feed on marine algae found in and around sea ice • Krill is a main source of food for penguins, whales, seals, and fish • As water warms, sea ice melts, and the krill population declines, causing food shortages

13. Global Warming and Human Health Increase in Heat Related Illnesses • Heat Stroke – Internal body temperature raises above 105°F • Heat Exhaustion – Caused by overexposure to heat, can also lead to dehydration Increase in Diseases Transmitted by Mosquitoes • Malaria • West Nile Virus • Dengue Fever

14. Global Warming and Human Health Increase in Allergies and Asthma • Increased CO2 leads to increased plant growth and more pollen • Increased moisture leads to more mold

15. Global Warming and Agriculture Changes that may seem minor can completely alter the climate and what can grow and survive • Dramatic changes in distribution and quantities of crops • More unpredictable farming • Increased instance of pests and diseases

16. Dealing with Global Warming • Mitigation – finding ways to lessen the effects or postpone global warming • Develop cleaner fuels or alternative fuels • Improve fuel efficiency in vehicles • Curb deforestation and plant more trees • Fertilize the ocean with iron to stimulate plant growth • Adaptation – creating strategies to adapt to global warming • Relocate people in coastal areas • Build structures to protect coastal land • Substitute temperate crops for tropical crops

17. Ozone Depletion • Ozone (O3) is a natural component of the stratosphere that shields Earth from the sun • The total amount of ozone is slowly declining globally and scientists have observed that the hole in the ozone layer grows each year

18. Dangers of UV radiation • Ozone depletion leads to higher levels of UV radiation reaching earth’s surface • Exposure to UV radiation can cause melanoma (skin cancer), cataracts, and weakened immunity

19. Chlorofluorocarbons and Stratospheric Ozone Depletion The primary chemicals responsible for ozone depletion are chlorofluorocarbons (CFCs). CFCs were developed in the 1930s and commonly used as • coolants in refrigerators and air conditioners • aerosol propellants in spray cans • foaming agents in making plastic-foam containers In 1974 it was demonstrated that CFCs could destroy the ozone layer

20. CFC Free? • In 1978, The U.S. banned the use of CFC propellants • In 1987, The Montreal Protocol was signed into effect to limit CFC production (183 countries ratified the agreement) • Although we are not adding new CFCs to the atmosphere, these products have a lifespan of 80-120 years and will continue to deplete the ozone layer for years to come

21. Acid Deposition • Acid deposition is a type of air pollution that includes sulfuric and nitric acids in precipitation and in dry particles that settle out of the air

22. What Causes Acid Deposition? • Acid deposition occurs when nitrogen oxides (from vehicles and factories) and sulfur dioxide (mainly from factories) are released into the atmosphere • These gases react with water vapor in the atmosphere to produce sulfuric and nitric acids

23. The pH Scale • The acidity or basicity of a substance is measured on the pH scale. • The pH scale ranges from 0 to 14: • A pH of 7 is neutral • A pH between 0 to 7 is acidic • A pH between 7 and 14 is basic

24. Acid Deposition Affects Freshwater Fish Populations • Living organisms require a steady pH • Normally, rainfall is slightly acidic with a pH from 5 to 6 • The pH range of acid rain is from 2.5 to 4.5 • A field study conducted in the Adirondacks in the 1980’s found that lakes with a pH of 5.0 or less were likely to have no fish populations

25. Other Effects of Acid Deposition Acid deposition • Corrodes metal and building materials • Causes declines in bird reproduction • Leads to forest decline Sandstone statue from 1702 photographed in 1908 (left) and 1969 (right) Source: http://www.atmosphere.mpg.de/enid/0,55a304092d09/Climate_in_brief/-_Climate_in_Cities_2t9.html

26. Forest Decline • Acid Rain weakens trees by damaging their leaves, and by altering soil chemistry which limits the nutrients available to them and exposes them to toxic substances • Forest decline Is the gradual deterioration and eventual death of trees • Yellowed needles in conifers is one symptom of forest decline:

27. Controlling Acid Deposition • Reducing emissions of sulfur dioxide and nitrogen oxides curbs acid deposition: • Installing scrubbers in smokestacks • Increased use of mass transit • Cars that run on clean fuels

28. Review Objectives Global Climate Change• Describe the enhanced greenhouse effect and list the five main greenhouse gases.• Discuss some of the potential effects of global climate change, including rising sea level, changes in precipitation patterns, effects on organisms, effects on human health, and effects on agriculture.• Give examples of ways to mitigate and adapt to global climate change. Ozone Depletion in the Stratosphere• Define ultraviolet (UV) radiation.• Distinguish between tropospheric and stratospheric ozone and describe the importance of the stratospheric ozone layer.• Define stratospheric ozone thinning and relate some of the harmful effects of ozone depletion.• Define chlorofluorocarbons and explain how they and other chemicals attack ozone. Acid Deposition• Explain how acid deposition develops and relate some of the effects of acid deposition.• Describe the pH scale.• Define forest decline and relate its possible causes.