Announcements – Oct 9, 2006

1. Announcements – Oct 9, 2006 Review # 2 one week from today. Exam # 2 one week from Wednesday (on October 18th)

2. Harvesting methods • Clear-cutting: economical, but leads to erosion, loss of plants and animals • fewer roads needed • reforestation necessary (conifers) • Patchwork clear-cutting: smaller, unconnected clearcuts • good for deer, rabbits • reduces need for reforestation

3. Harvesting methods 3) Selective harvesting: individuals trees taken • Less economical • More roads • Leaves a more “natural” forest Debate over “Healthy Forest Initiative” • Bush policy to decrease risk of forest fires by allowing selective logging and stream-lining legal process • Fire Prone Trees ≠ Desirable Timber Trees

4. Rangeland ecosystems Rangelands – lands too dry to support crops, but receive enough precipitation to support grasses and drought-resistant shrubs • wildlife are usually introduced species

5. Rangeland costs • Economic & energy – usually low • common use lands, breed animals, walk • Environmental – high • selective grazing can change plant diversity, increase non-native grasses • over-grazing • desertification – process of converting arid and semi-arid lands to desert (loss of productivity)

6. Possible desertification

7. Desertification in China

8. Points to know • Know the 3 main ways humans impact the environment (pollution, movement of exotics & resource use) • What is pollution? What determines how much of it there is? • What are 3 types of material pollution? What are 3 types of energy pollution? • What three types of costs are associated with exploitation of resources? Which ones are immediate or delayed and why? • What are some problems with loss of biodiversity and extinction? What is a fundamental challenge in trying to prevent extinction? • Know 4 types of resource exploitation in terrestrial ecosystems • What are some limitations of recycling mineral materials? • Why is tropical deforestation a big problem? • What is desertification? What causes it?

9. Human Impacts II Lecture Objectives: • Introduce human impacts on freshwater systems • Learn about human impacts on marine systems

10. Freshwater Ecosystems • Invasive Species (e.g., zebra mussel, lamprey) – already covered • Pollution - will discuss later • Habitat Modification • Channelization • Dams • Draining wetlands • Changes in terrestrial landscape

11. Channelization • Channelization – the dredging and straightening of stream channels • Why? • Divert water for irrigation • Drain fields for agriculture • Increase “usable” land • Prevent flooding 1961 Kissimmee River, FL Present

12. Problems with Channelization • Altered flow regimes • Many species not adapted to different flows • Loss of habitat • Within the stream • Dredging removes snags, habitat complexity • Total stream area • Floodplains low- and no-flow in remnant channels & encroaching exotics led to low O2 & fish kills

13. Dams and stream modifications • Long history of modifying rivers • Egypt had irrigation ditches by 3200 B.C. and dams by 2760 B.C. • Dams built per year steadily increased from around 1800 to a peak in the 1970’s.

14. Dams and stream modifications • 75,000 dams over 2m tall, plus 2.5 million smaller dams in the U.S. alone

15. Effects of Dams • Benefits: • Water supplies • Navigation • Hydropower • Flood Control • Decreased frequency, but increased severity

16. Physical Effects of Dams • Alterations of flow • Prevents movement of sediment, nutrients downstream • Slower flows upstream • leads to settling of sediment • reservoirs can fill by as much as 80% in 12 years • More unpredictable flows downstream • Disturbs normal flood-pulse in spring • Interchange of nutrients between river and floodplains

17. Biological Effects of Dams • Interrupts fish migration (e.g., salmon) • Fish ladders can help • Still can have 10-20% fish loss during outmigration

18. Biological Effects of Dams • Loss of important spawning/foraging habitat in floodplain • Net economic loss - river fisheries more productive than reservoir fisheries • Changes in plant communities, reduced species richness below dams

19. Human Health Effects of Dams Aswan Dam, Egypt – completed in 1970 Schistosomiasis (Bilharzia ) Parasite passes from humans to snails to humans Irrigation from lake provided more habitat for snails

20. Wetlands • Wetlands – Transitional habitats between aquatic and terrestrial environments, where water table is at or near the surface • Includes marshes, swamps, bogs, estuaries, temporary ponds, etc. • Estimated loss of 53% of total wetlands in U.S. • 9.2 million acres lost between 1950’s-1970’s • 2.6 million acres lost between 1970’2-1980’s • current loss of 124,000 acres per year

22. Wetland Loss • Wetlands provide important ecosystem services • 1. Mitigate flooding • 2. Retention of sediments, nutrients, pollutants • Natural sewage treatment plants • 3. Wildlife habitat • 20% of threatened and endangered species associated with wetlands • Important habitat for waterfowl

23. Wetlands: restoration • No-net loss of wetlands rule ~1989 • Developers must recreate wetlands they destroy in construction • Are new wetlands really the same?

24. Human Impacts on Marine Systems • Many threats to words oceans • We will focus on: • Overfishing • Aquaculture • Coral reefs

25. Oceanic Fisheries • Worldwide, 25% of animal protein • 70% of world’s marine fisheries are overexploited or in danger of becoming overexploited

26. Oceanic Fisheries • Number of fish caught rose steadily until 1990’s, but per capita number caught decreased • Human population growing faster than increase in catch • Leads to increased demand and overfishing • many species commercially extinct - no longer economically profitable to harvest

27. Sustainable harvest • Ideal strategy: harvest population to maximize growth rate • determines how quickly fish can be removed, while still maintaining healthy stock • too little or too much harvest, population grows slowly • keep population at half carrying capacity • Most fisheries harvest too much

29. Why overfish? • Economics - Tragedy of the Commons • Each group tries to maximize individual returns at expense of common resource • Quota problems • Often a fixed number, not percentage • Harvesting constant number of decreasing population leads to severe impacts

30. Why overfish? • Technological “Improvements” • e.g., Bottom trawlers vs. hook and line • problem of bycatch - killing non-target animals

31. Overfishing Example: Bluefin Tuna • Large, wide ranging, fast animal • Grows to 1500 lbs. • Swims up to 50 mph • Can migrate across oceans • One of most valuable and over-exploited fish • Single fish sold for $172,000 in Tokyo fish market auction - sashimi • Adult population declined 90% since 1975 • 250,000 to about 22,000

32. Overfishing: Bluefin Tuna

33. Overfishing: Bluefin Tuna • International Commission for the Conservation of Atlantic Tunas (ICCAT) responsible for management • Manages tunas and tuna-like species (marlins, swordfish) • Supposed to manage for maximum sustainable yield • Has scientific committee • Compile catch statistics and models population trends

34. Overfishing: Bluefin Tuna • Commission’s managers repeatedly ignored scientists’ advice • e.g., 1981 own scientific committee concluded Atlantic tuna population depleted, quotas should be set close to zero • Set 1160 metric ton quota for “scientific study”

35. Overfishing: Bluefin Tuna • Population continued to decline, but doubled quota • Early 1990s - Sweden wanted to list bluefin on CITES (Convention on International Trade in Endangered Species)

36. Overfishing: Bluefin Tuna (cont.) • Lobbying by U.S., Canada, and Japan, forced Sweden to accept compromise • 50% reduction in catch • Population still extremely low • Why did efforts fail? • 1. Lack of commitment by Commission • conflicts of interest - some work for seafood industry • 2. Quota problem - number not percent • 3. Lack of international support • 4. Non-member nations

37. Audubon Society Seafood Ratings • Yellow – some concern over status, manag. • Longline caught Mahimahi • Pacific cod • Rainbow trout • Maine lobster • Squid (calamari) • Canned tuna • Red – severe overfishing, poor management • Atlantic cod • Shrimp • Atlantic flounders and soles • Sharks • Farmed salmon • Orange Roughy • Chilean seabass (toothfish) Green – abundant, well managed Farmed mussels and clams Alaska salmon Troll caught Mahimahi U.S. farmed Tilapia Pole/troll caught yellowfin, bigeye, albacore tuna http://www.audubon.org/campaign/lo/seafood/seafood_wallet.pdf

38. Is Aquaculture the answer? • Aquaculture - breeding and raising of fish and shellfish for food • Rapidly increasing industry • Provides 1/4 world’s marine fisheries

39. Aquaculture • Arguments for aquaculture • 1. Not depleting natural fish stocks • 2. No bycatch • 3. More efficient • Problems • 1. Still depleting natural fish populations • Feeds often include fishmeal from wild populations • 2-5 kg wild fish to produce 1 kg raised fish • especially problematic for carnivores fish (e.g. salmon)

40. Aquaculture • Problems (cont.) • 2. Fish wastes • aquatic pollution, disease spread • 3. Genetic diversity • raised fish escape and breed with wild fish • reduces genetic diversity • can cause migration problems • 4. Can still be bycatch • if wild fish used to stock pens/ponds • Milkfish in Philippines • 85% of fry collected NOT milkfish

42. Aquaculture • Problems (cont.) • 5. Habitat destruction - loss of mangroves, coastal wetlands habitats • provide nursery habitat for fish/shellfish • protect coast from storms • help control floods • trap sediments • filter and clean water of excess nutrients • Solutions? • Reduce fishmeal in feeds, raise more herbivorous fish (e.g. Tilapia), regulations on building new facilities

43. Coral Reefs • One of most diverse and productive ecosystems • Support at least 1/3 marine fish • Protect coasts from storms • Uptake carbon

44. Threats to Coral Reefs • Most threatened marine habitat • Major problems include: • 1. Trawling and dynamite fishing - breaks up reefs

45. Threats to Coral Reefs 2. “Bleaching” - death/loss of algae • Triggered by stress • elevated temperatures • pollutants • Frequency and severity have increased in the last decade

46. Threats to Coral Reefs • Problems (cont.) • 3. Runoff • sediments, pollutants • 4. Aquarium industry • collect best coral, animals • 5. Global warming • rising sea levels - corals need shallow water • rising temperatures • corals exist in very narrow temperature range • Solutions - creating marine reserves, control development, regulate collecting

47. Why should I care about coral reefs? • Tourism • Countries w/reefs get about 50% of their GNP from reef activities • Beach protection from waves • Medical uses • AZT, 50% of cancer research, bone-grafting • Biodiversity • 1% of ocean floor houses 25% of marine species

48. Points to know • What is channelization? Why is it done and what problems can it cause? • What can be the problems with dams and flood control? How do they affect sediment & water flows, fish migration, and floodplains? • What is a wetland and how much has been lost in the U.S.? What ecosystem services do they provide? • Why is oceanic fishing important (2 reasons)? Name 3 reasons for overfishing. What does the bluefin tuna example tell us about the effects politics & conflict of interests on fishing policies? • What are the pros and cons of aquaculture? • Why should you care about the destruction of coral reefs?