Topic 2

1. Topic 2 Unit 3 – Environmental Chemistry

2. Dichlorodiphenyltrichloroethane = DDT Invented by Paul Hermann Muller who was given the Nobel prize. Used to kill lice that carried typhus killing allied troops in WWII. Was thought to be able to control mosquitos that carried malaria Crops thrived as pests declined. DDT – The Good News

3. Too wide spread, killed good insects as well Does not biodegrade quickly, hangs around Enters the food chain and concentrates killing larger animals like birds, made egg shells very fragile. When a chemical moves up the food chain and concentrates it is called biomagnification. Pests can become resistant to pesticide, so they no longer work. DDT – The Bad News

4. Growing crops: without the use of pesticides and commercial fertilizers using natural, renewable resources conserving water without endangering workers Organic Agriculture

5. Pesticides and Organic Farming

6. Domestic crops were selected for maximum productivity and had little natural pest resistance

7. Today’s Pests • Pests attack and eat our food crops • This problem is due, in part, to not selecting for pest resistance during domestication Based on: National Geographic, February 1980

8. DDT was invented in the 1940’s and viewed as:- miracle for farmers- safe!

9. “The most discussed of the new insecticides is dichloro-diphenyl-trichloroethane, shortened to DDT but also called Guesarol. This compound has remarkable power to kill insects, particularly body lice-the ‘cooties’ of World War I. The prevalence of typhus, carried by body lice, in the Mediterranean theater of this war has emphasized its value. DDT’s effectiveness in war may well be overshadowed by its value in peace. Painstaking investigations have shown it to be signally effective against many of the most destructive insects that feed upon crops.”Scientific American, July 1944.

10. Arial crop sprayers were used to spray tons of DDT on crops across the U.S.

11. Pests became resistant to DDT Based on: National Geographic

12. Pesticide Resistance: • In the beginning, most pests were sensitive to DDT but a few were resistant • The resistant forms survived and reproduced • In the end, most pests were resistant to DDT Based on: National Geographic, February 1980

13. BiomagnificationThe concentration of pesticides in higher levels of food chains

14. Trophic Levels Most food chains consist of four trophic levels

15. DDT in Food Chain DDT is concentrated as it moved up food chain This is because energy is lost (from respiration) as go up food chain but DDT is not Based on: Campbell et al, Biology: Concepts and Connections, Benjamin Cummings

16. Bald Eagle • Once was widely • distributed over U.S. • As a top carnivore it feeds on fish • Swoops down and captures fish off the surface of the water

17. Scientists discovered that DDT was • concentrated in the bald eagle • DDT affected the eagle’s ability to reproduce

18. Scientists found that the eagle eggs had thin egg shells and broke easily Nests contained broken, rotten eggs The number of young produced per breeding pair was reduced

19. Population of adult eagles declined to 4,000 and the eagle was listed as “Endangered”

20. The Environmental Protection Agency (EPA) banned DDT in 1972

21. Eagle reproduction before and after DDT ban - What do you notice? Based on: Grier, J., Science, 1982

22. Eagle populations increased rapidly and the eagle is now listed as “Threatened” From: Time, July 11, 1994

23. Peregrine Falcon • Occurred naturally • over most of continental U.S. • Nests on cliffs • Keen eyesight • (Ex. If human, they could read newspaper print at 110 yards) • Feeds on other birds, knocking them out of the sky at 200 m.p.h.

24. DDT & Peregrine • After DDT was introduced in the 1940s, DDT weakened the birds’ egg shells and devastated the population • By early 1970s, the entire U.S. population was down to 12 breeding pairs • Peregrines were declared federally endangered and DDT banned • Peregrines were bred in captivity and reintroduced successfully in cities

25. “In the United States at least 500 species and subspecies of plants and animals have become extinct since the 1500s.” Douglas Chadwick, H., National Geographic, March 1995

26. Endangered Species: Any species that is in danger of extinction throughout all or a significant portion of its range Threatened Species: Any species that is likely to become an endangered species within the foreseeable future Definitions – Endangered Species Act

27. OTHER COMEBACKS ESA is having some success, but there are more than 600 endangered or threatened species in the U.S. today Species removed from endangered list or reclassified as threatened Date of change 1994 Gray whale (California population) Aleutian Canada goose American alligator Brown pelican Utah prairie dot Greenback cutthroat trout 1990 1987 1985 1984 1978 Based on: Time, July 11, 1994

28. Defining “Organic” Foods produced without hormones, antibiotics, herbicides, insecticides, chemical fertilizers, genetic modification or germ-killing radiation The USDA labels such foods “certified organic” From: Newsweek, Sept. 30, 2002

29. Availability of Organic Products Based on: Newsweek, Sept. 30, 2002

30. Can organic farming help the environment? • Pesticides now kill 67 million American birds per year • The Mississippi River dumps enough fertilizer into the Gulf of Mexico to maintain a 60 mile “dead zone” devoid of fish