Agriculture as an ecosystem

1. Agriculture as an ecosystem

2. Great diversity in Natural habitats

3. Crops – low species diversitylow genetic diversity

4. Green revolution

5. Machine Crops

6. Machine Crops _genetically uniform

7. Machine Crops– dwarf, responsive to fertilizer, fast growing…... E.g. Miracle rice

8. Chief beneficiaries

9. Machine Crops_require large amount of chemical fertilizer

10. Machine Crops_large scale irrigation Irrigation

11. Machine Crops_require pesticides

12. Impact of Agriculture: Soil degraded_Dust bowl

13. Impact of Agriculture: Land clearing for farming

14. Impact of Agriculture: Soil erosion

15. Impact of Agriculture: Soil erosion

16. Impact of Agriculture: Salinization

17. Impact of Agriculture: Overgrazing

18. Impact of Agriculture: Ecological disruption

19. Impact of Agriculture: create weeds and pests

20. Weeds – competitors of crops

21. Factors contributing to pest problem

22. Pests and Pest control

23. Insect pests

24. Chemical control

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

26. Potato famine of Ireland was caused by genetically uniform crops and lack of pesticides to protect them Blight hits potatoes, 1845 Based on: Population Reports, May 1992

27. 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

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

29. Arial crop sprayers were used to spray tons of DDT on crops across the U.S. Photo courtesy of Texas Parks and Wildlife Department

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

31. 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

32. Bio-magnificationThe concentration of pesticides in higher levels of food chains

33. Trophic Levels Based on: Mader, S., Inquiry Into Life, McGraw-Hill Most food chains consist of four trophic levels

34. Energy Available to Consumers at Next Trophic Level Energy Lost by Death and Decay Energy Lost by Respiration Energy Lost by Excretion Energy Lost by Egestion of Feces Energy Ingested

35. 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

36. Overview of Lesson • Pests, DDT and biomagnification • DDT, eagles and falcons • Species endangered • Organic foods

37. 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 Photo courtesy of Texas Parks and Wildlife Department

38. Scientists discovered that DDT was • concentrated in the bald eagle • DDT affected the eagle’s ability to reproduce Photos courtesy of Texas Parks and Wildlife Department

39. 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

40. Population of adult eagles declined to 4,000 and the eagle was listed as “Endangered” Photo courtesy of Texas Parks and Wildlife Department

41. The Environmental Protection Agency (EPA) banned DDT in 1972 (USA) Photo courtesy of Texas Parks and Wildlife Department

42. Eagle reproduction before and after DDT ban Based on: Grier, J., Science, 1982

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

44. Peregrine Falcon • Occurred naturally • over most of continental U.S. • Nests on cliffs • Keen eyesight • (if human, could read newspaper print at 110 yards) • Feeds on other birds, knocking them out of the sky at 200 m.p.h. Photo courtesy of Texas Parks and Wildlife Department

45. DDT & Peregrine • After DDT was introduced • in 1940s, DDT weakened • the birds’ egg shells, • devastating 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 Photos courtesy of Texas Parks and Wildlife Department

46. poisoning

47. Good insects

48. Red Fire ant

49. Red fire ant

50. Prickly pear Prickly pears were imported into Australia in the 19th century for use as a natural agricultural fence, but quickly became a widespread weed, rendering 40,000 km² of farming land unproductive. The Cactoblastismoth, a South American moth whose larvae eat prickly pear, was introduced in 1925 and almost wiped out the infestation. This case is often cited as a "textbook" example of successful biological pest control. The same moth, introduced accidentally further north of its native range into southern North America, is causing serious damage to some native species in that area.