1. Announcements Fisheries problem is due now Fisheries problem is due now No class on Wednesday No class on Wednesday Problem set is due in your TA’s box by 10am on Wednesday, November 24 th Problem set is due in your TA’s box by 10am on Wednesday, November 24 th

2. Summary from Friday Economics of fishing Economics of fishing What causes overfishing What causes overfishing Biological magnification Biological magnification Aquaculture Aquaculture

3. Two minute quiz 1) With regard to fisheries, how is cost related to effort? How is effort related to population size? 2) How can government subsidies lead to overfishing? 3) Why are cheap fisheries more likely to be unsustainable than more expensive fisheries?

4. benefit matches cost at this point cost Rate of harvest (benefit or income) Cost Population Size K0 harvest (benefit or income) Effort 0%100% minimum population where fishing is economically viable

5. Unsubsidized cost Government subsidies maintain jobs, provide protein, but lead to over- fishing minimum population where fishing is economically viable Subsidized cost Rate of harvest (benefit or income) Subsidized or Unsubsidized cost Population Size K0 Effort 0%100%

6. benefit matches cost at this point cost Expensive fishery only profitable when population sizes are large, likely to be sustainable minimum population where fishing is economically viable Rate of harvest (benefit or income) Cost Population Size K0 Effort 0%100%

7. benefit matches cost at this point cost Cheap fishery profitable at small population size, likely to be unsustainable minimum population where fishing is economically viable Rate of harvest (benefit or income) Cost Population Size K0 Effort 0%100%

8. Case Study: Salmon Farming People like salmon People like salmon Wild populations are threatened Wild populations are threatened Farming used as a solution for providing people with the fish they want to eat Farming used as a solution for providing people with the fish they want to eat

9. Case Study: Salmon Farming problems with salmon farming: problems with salmon farming: escapesescapes interbreeding with wild population interbreeding with wild population genetic engineeringgenetic engineering competing with wild populations competing with wild populations farmed salmon are fed wild-caught fishfarmed salmon are fed wild-caught fish 3 pounds of wild fish for 1 pound of farmed salmon 3 pounds of wild fish for 1 pound of farmed salmon pollution from waste and left-over foodpollution from waste and left-over food disease spreaddisease spread high density of fish in cages high density of fish in cages aestheticsaesthetics

10. Marine Reserves Prime fish are larger and older Prime fish are larger and older Normal fishing removes the largest fish Normal fishing removes the largest fish eventually all big fish are caughteventually all big fish are caught quality of fish goes down quality of fish goes down reproductive success of fish goes down reproductive success of fish goes down Reserves allow some fish to grow to maturity Reserves allow some fish to grow to maturity Fishing improves Fishing improves protectedareaunprotectedarea

11. Agriculture Costs and Benefits Costs and Benefits Ecosystem Dynamics vs. Food Production Ecosystem Dynamics vs. Food Production Ecological Problems associated with: Ecological Problems associated with: tillagetillage use of chemical pesticides, herbicides, etc.use of chemical pesticides, herbicides, etc. irrigationirrigation

12. Agriculture Like fisheries: similar concerns of balancing yield and sustainability Like fisheries: similar concerns of balancing yield and sustainability Environmental impacts can be large Environmental impacts can be large Goal is to maximize productivity Goal is to maximize productivity plant growth is usually nutrient limited nutrient supply yield

13. Agriculture Benefit from crops = yield Benefit from crops = yield Cost goes up with fertilizer application Cost goes up with fertilizer application nutrient supply yield cheap fertilizer expensive fertilizer benefit

14. Fate of fertilizer Taken up by plants Taken up by plants Leached from the system Leached from the system enters systems downstreamenters systems downstream Denitrified and converted into N gasses Denitrified and converted into N gasses

15. Ecosystem Dynamics A crop field is an ecosystem! A crop field is an ecosystem! all natural biological processes can occur:all natural biological processes can occur: competitioncompetition herbivoryherbivory diseasedisease why would a farmer care?why would a farmer care?

16. Ecosystem Dynamics A crop field is an ecosystem! A crop field is an ecosystem! all natural biological processes can occur:all natural biological processes can occur: competitioncompetition herbivoryherbivory diseasedisease why would a farmer care?why would a farmer care? achieving peak yield requires that these processes be limitedachieving peak yield requires that these processes be limited

17. Ecosystem Dynamics Monoculture= one species of plant Monoculture= one species of plant encourages competition, herbivory, and diseaseencourages competition, herbivory, and disease fertilization  enhances growth of all plants, but crops are bred to be poor competitorsfertilization  enhances growth of all plants, but crops are bred to be poor competitors energy is allocated to the portions that people eat…not to roots for uptakeenergy is allocated to the portions that people eat…not to roots for uptake specialist herbivores do well in monoculturespecialist herbivores do well in monoculture disease can spread easily if all plants are the same speciesdisease can spread easily if all plants are the same species

18. Food Production The goal of agriculture is to produce food The goal of agriculture is to produce food Farmers use many techniques to limit competition, herbivory and disease Farmers use many techniques to limit competition, herbivory and disease tillagetillage herbicidesherbicides insecticidesinsecticides fungicidesfungicides These things increase yields, but also have environmental impacts These things increase yields, but also have environmental impacts

19. Tillage Plowing has been used for thousands of years Plowing has been used for thousands of years kill weedskill weeds prepare the seed bedprepare the seed bed stimulate nutrient mineralizationstimulate nutrient mineralization

20. Tillage Plowing is a powerful tool for maximizing crop production Plowing is a powerful tool for maximizing crop production Drawback: Drawback: loose, bare soil is vulnerable to erosion by wind and waterloose, bare soil is vulnerable to erosion by wind and water

21. What is topsoil? Topsoil is a semi-renewable resource Topsoil is a semi-renewable resource A horizonA horizon Good water retentionGood water retention Easy root penetrationEasy root penetration Rich in organic matterRich in organic matter Can be 50-60 cm thick in prairieCan be 50-60 cm thick in prairie Forms on the order of millimeters per year Forms on the order of millimeters per year About 1/3 has been lost from Midwest since European settlement About 1/3 has been lost from Midwest since European settlement

22. Announcements This week we will: This week we will: Finish up AgricultureFinish up Agriculture Cover ConservationCover Conservation Go over the midtermGo over the midterm Review for the finalReview for the final Fill out evaluationsFill out evaluations Have a science ethics discussion?Have a science ethics discussion?

23. Two-minute quiz A. True or false: A crop field is an ecosystem. A crop field is an ecosystem. All of the fertilizer applied to a field is taken up by plants and used for growth. All of the fertilizer applied to a field is taken up by plants and used for growth. The “dead zone” in the Gulf of Mexico is primarily caused by overfishing. The “dead zone” in the Gulf of Mexico is primarily caused by overfishing. B. Name three problems associated with aquaculture.

24. Summary from Friday Salmon as an aquaculture case study Salmon as an aquaculture case study Marine Reserves Marine Reserves Agriculture Agriculture Costs and Benefits Costs and Benefits Ecosystem Dynamics vs. Food Production Ecosystem Dynamics vs. Food Production Ecological Problems associated with: Ecological Problems associated with: tillage  erosiontillage  erosion

25. What is topsoil? Topsoil is a semi-renewable resource Topsoil is a semi-renewable resource A horizonA horizon Good water retentionGood water retention Easy root penetrationEasy root penetration Rich in organic matterRich in organic matter Can be 50-60 cm thick in prairieCan be 50-60 cm thick in prairie Forms on the order of millimeters per year Forms on the order of millimeters per year About 1/3 has been lost from Midwest since European settlement About 1/3 has been lost from Midwest since European settlement

26. How much is topsoil worth? Assume a loss of 1 inch of topsoil over 1 acre Assume a loss of 1 inch of topsoil over 1 acre 1” = 2.54 cm1” = 2.54 cm 1 m 2 = 10,000 cm 21 m 2 = 10,000 cm 2 1 acre = 4070 m 21 acre = 4070 m 2 bulk density of topsoil = 1.4 g/cm 3bulk density of topsoil = 1.4 g/cm 3 1” over 1 acre = 1” over 1 acre = 103,378,000 cm 3 = 144,729,200 g = 145 Tons103,378,000 cm 3 = 144,729,200 g = 145 Tons Topsoil costs $20 per yard 3 = 0.85 Tons Topsoil costs $20 per yard 3 = 0.85 Tons 145 Tons equals a cash loss of $3,412.00 145 Tons equals a cash loss of $3,412.00 A 50 cm thick A horizon would be worth $67,000 per acre. A 50 cm thick A horizon would be worth $67,000 per acre.

27. Can topsoil be replaced? “Topsoil” from a nursery is usually compost + subsoil (B horizon) “Topsoil” from a nursery is usually compost + subsoil (B horizon) where does the compost come from?where does the compost come from? Would dredging the Mississippi Delta work? Would dredging the Mississippi Delta work? A horizon has a mix of sand, silt, and clayA horizon has a mix of sand, silt, and clay river or wind transports particles at different ratesriver or wind transports particles at different rates how to put them back together?how to put them back together? how would you pay for dredging and transporthow would you pay for dredging and transport what about salinity?what about salinity?

28. Off-site costs of erosion Sedimentation Sedimentation fills up reservoirs, rivers, and lakesfills up reservoirs, rivers, and lakes 4 billion tons/year deposited in the U.S.4 billion tons/year deposited in the U.S. Effects: Effects: loss of water storagesloss of water storages loss of fishing groundsloss of fishing grounds loss of wetlands and estuariesloss of wetlands and estuaries loss of offshore reefsloss of offshore reefs

29. How to limit erosion Contour plowing: across a slope Contour plowing: across a slope creates lots of micro-damscreates lots of micro-dams Cover-cropping: Cover-cropping: plant something during the non-growing season to keep soil from erodingplant something during the non-growing season to keep soil from eroding No-till agriculture: don’t plow at all No-till agriculture: don’t plow at all seeds are drilled directly into soilseeds are drilled directly into soil problems?problems?

30. Use of Pesticides/Herbicides Cost Cost expensive to buy and disperseexpensive to buy and disperse Health Health many are toxic to humansmany are toxic to humans Ecological Effects Ecological Effects when washed downstream, can affect other ecosystemswhen washed downstream, can affect other ecosystems can select for resistant strains of pestscan select for resistant strains of pests

31. Irrigation Crops grow well in warm climates Crops grow well in warm climates sunlightsunlight appropriate temperaturesappropriate temperatures good soilgood soil Water often limits growth  irrigation Water often limits growth  irrigation

32. Salinization Common result of irrigation Common result of irrigation Salts precipitate out of solution in soil Salts precipitate out of solution in soil Occurs when: Occurs when: climate is warm and dryclimate is warm and dry water table is highwater table is high salts are presentsalts are present Problem: too much salt kills plants Problem: too much salt kills plants primary cause: plants are unable to take up waterprimary cause: plants are unable to take up water secondary cause: toxicity of Na + and Cl -secondary cause: toxicity of Na + and Cl -

33. Mechanism of Salinization Irrigation: most water contains a small amount of salt Irrigation: most water contains a small amount of salt accumulation over timeaccumulation over time Surface soils dry up, and water from deeper soil moves upwards Surface soils dry up, and water from deeper soil moves upwards Evaporation: leaves salts on surface Evaporation: leaves salts on surface

34. Food Production How can farmers reduce environmental impacts while still keeping yields high? How can farmers reduce environmental impacts while still keeping yields high? limit monoculturelimit monoculture intercrop or rotate cropsintercrop or rotate crops plant a variety of genotypesplant a variety of genotypes currently, some fields have a single clone of corncurrently, some fields have a single clone of corn control pests with natural predatorscontrol pests with natural predators use ladybugs to control aphidsuse ladybugs to control aphids use chemicals only when necessaryuse chemicals only when necessary

35. Conservation Long term management plans can be used to conserve resources Long term management plans can be used to conserve resources Resource Management can include: Resource Management can include: management of materialsmanagement of materials management of plants or animals that are used for food, fiber, or other purposesmanagement of plants or animals that are used for food, fiber, or other purposes

36. Resource management There are 3 different classes of resources: Renewable Renewable airair Semi-renewable: renewable if not over-harvested Semi-renewable: renewable if not over-harvested waterwater soilsoil fish populationsfish populations Non-renewable Non-renewable fossil fuelsfossil fuels certain mineralscertain minerals

37. Resource management Biological resources are fragile! Biological resources are fragile! Populations can easily be over-harvested Populations can easily be over-harvested fisheries are often over-fishedfisheries are often over-fished

38. Conservation keystone species keystone species “flagship species” “flagship species” long-term land protection: reserves long-term land protection: reserves single-species management

39. Announcements Professor Levine’s announcement Professor Levine’s announcement This week we will: This week we will: Finish up ConservationFinish up Conservation Go over the midtermGo over the midterm Review for the finalReview for the final Fill out evaluationsFill out evaluations Have a science ethics discussion?Have a science ethics discussion?

40. Two-minute quiz A. True or false: A flagship species must be a keystone species. A flagship species must be a keystone species. Coal is a renewable resource. Coal is a renewable resource. Cover cropping can reduce erosion during the non-growing season. Cover cropping can reduce erosion during the non-growing season. B. Name two problems caused by sedimentation.

41. Summary from Monday Replacement of Topsoil Replacement of Topsoil costcost feasibilityfeasibility Sedimentation Sedimentation Limiting Erosion Limiting Erosion Pesticides and Herbicides Pesticides and Herbicides Irrigation and Salinization Irrigation and Salinization Resource Management and Conservation Resource Management and Conservation

42. Designing a reserve Shape and Size Shape and Size determine minimum viable area (MVA) needed for each populationdetermine minimum viable area (MVA) needed for each population estimates of energy use by trophic levelestimates of energy use by trophic level territorialityterritoriality landscape structurelandscape structure one large or several small?one large or several small?

43. A larger area can support more animals

44. Edge effect circular reserves have less edge circular reserves have less edge edge effects include gradients in: edge effects include gradients in: lightlight moisturemoisture windwind noisenoise pollutionpollution outside may be unprotected outside may be unprotected

45. Shape determines edge effect

46. One large or several small? minimize edge effects minimize edge effects more complete food chains more complete food chains lower risk of inbreeding lower risk of inbreedingBUT… at risk from environmental disaster and disease at risk from environmental disaster and disease may be easier to accomplish politically may be easier to accomplish politically can create corridors so than animals can interbreed can create corridors so than animals can interbreed

47. = limited protection = full protection