5. other ways we screw with agriculture! (good)
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The document discusses several ways that human activities negatively impact land systems, including overgrazing, deforestation, feedlot agriculture, and unsustainable fishing practices. Overgrazing can degrade rangelands by removing too much plant cover, leading to erosion. Deforestation removes forests that stabilize soils and regulate water flows. Feedlot agriculture produces large amounts of waste and relies on chemical inputs. Unsustainable fishing has depleted fish populations in many areas. Better management is needed for rangelands and fisheries to restore soils and biodiversity.
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5. other ways we screw with agriculture! (good)
- 1. Other ways we MESS with the Land! 9/29/2013 Guru IBESS SYSTEM SOIL 1
- 2. 1. Overgrazing • When livestock eat too much plant cover on rangelands, impeding plant regrowth • The contrast between ungrazed and overgrazed land on either side of a fenceline can be striking. 9/29/2013 Guru IBESS SYSTEM SOIL 2 Figure 8.22
- 4. Overgrazing • Overgrazing can set in motion a series of positive feedback loops. 9/29/2013 Guru IBESS SYSTEM SOIL 4 Figure 8.21
- 5. Overgrazing • Livestock graze on grasslands and cleared forest slopes – 65% of drylands are grasslands • Land is often overgrazed – Barren land is eroded and degraded • In the 1800s American buffalo (bison) were slaughtered – Rangelands stocked with cattle were overgrazed – Leading to erosion and growth of unpalatable plants • U.S. western rangelands produce less than 50% of the forage they produced before commercial grazing – Yet 20% of rangelands remain overstocked 9/29/2013 Guru IBESS SYSTEM SOIL 5
- 6. Degraded rangelands • The National Public Lands Grazing Campaign documents harmful effects of livestock grazing – Competition of livestock with native animals for food – One-third of endangered species are in danger due to cattleraising practices (predator control, fire suppression) – Wooded zones along streams are trampled and polluted – Polluted streams make fish species the fastest-disappearing wildlife group • Desertification impacts 85% of North America’s drylands – The most widespread cause is livestock grazing 9/29/2013 Guru IBESS SYSTEM SOIL 6
- 7. Public lands • Overgrazing occurs because rangelands are public lands – Tragedy of the commons: the incentive is for all to keep grazing, even though the range is being overgrazed • The U.S. Bureau of Land Management (BLM) and Forest Service leases grazing rights on 2 million km2 of land – Federal land is owned by taxpayers – Animal unit = one cow-calf pair or five sheep – The grazing fee ($1.35/animal unit/month) is 10% what would be paid on private land 9/29/2013 Guru IBESS SYSTEM SOIL 7
- 8. Why are rangelands overgrazed? • The 1934 Taylor Grazing Act prohibits reducing grazing levels or keeps grazing fees below market level – The U.S. government lost $115 million in 2004 – $500 million more was lost in ecological costs (to watersheds, streams, wildlife, endangered species) • When Congress and the BLM try to raise fees, western congressmen threaten to cut the BLM budget 9/29/2013 Guru IBESS SYSTEM SOIL 8
- 9. Solutions to overgrazing • Better management could restore rangelands – Benefiting wildlife and cattle production • Conservation Stewardship Program (NRCS) – Provides information and support to land-owning ranchers to burn woody plants, reseed land, rotate cattle • The government could buy up some of the 26,000 permits – Retire rangelands – Generously pay ranchers for their permits – Use the land for wildlife, recreation, watershed protection 9/29/2013 Guru IBESS SYSTEM SOIL 9
- 10. 2. Deforestation • Porous, humus-rich forest soil efficiently holds and recycles nutrients – Also absorbs and holds water • Converting a forested hillside to grassland doubles the amount of runoff and increases nutrient leaching • When forests are cut and soils are left exposed – Topsoil becomes saturated with water and slides off the slope – Subsoil continues to erode 9/29/2013 Guru IBESS SYSTEM SOIL 10
- 11. Forests are cut at alarming rates • 13 million hectares (32 million acres) are cut per year – Mostly in developing countries • Cutting tropical rain forests causes acute problems – Heavy rains have leached soils of minerals – Parent material is already maximally weathered – So tropical soils (oxisols) lack nutrients • Clearing rain forests washes away the thin layer of humus – Leaving only the nutrient-poor subsoil – Very poor for agriculture 9/29/2013 Guru IBESS SYSTEM SOIL 11
- 12. Animal agriculture: Livestock and poultry •Consumption of meat has risen faster than population over the past several decades. 9/29/2013 Guru IBESS SYSTEM SOIL 12 Figure 9.15
- 13. 3. Feedlot agriculture •Increased meat consumption has led to animals being raised in feedlots (factory farms), huge pens that deliver energyrich food to animals housed at extremely high densities. 9/29/2013 Guru IBESS SYSTEM SOIL 13 Figure 9.16
- 14. Feedlot agriculture: Environmental impacts •Immense amount of waste produced, polluting air and water nearby •Intense usage of chemicals (antibiotics, steroids, hormones), some of which persist in environment •However, if all these animals were grazing on rangeland, how much more natural land would be converted for agriculture? 9/29/2013 Guru IBESS SYSTEM SOIL 14
- 15. Food choices = energy choices •Energy is lost at each trophic level. •When we eat meat from a cow fed on grain, most of the grain’s energy has already been spent on the cow’s metabolism. •Eating meat is therefore very energy inefficient. 9/29/2013 Guru IBESS SYSTEM SOIL 15
- 16. Grain feed input for animal output •Some animal food products can be produced with less input of grain feed than others. 9/29/2013 Guru IBESS SYSTEM SOIL 16 Figure 9.17
- 17. Land and water input for animal output •Some animal food products can be produced with less input of land and water than others. 9/29/2013 Guru IBESS SYSTEM SOIL 17 Figure 9.18
- 18. 4. Aquaculture •The raising of aquatic organisms for food in controlled environments •Provides 1/3 of world’s fish for consumption •220 species being farmed •The fastest growing type of food production 9/29/2013 Guru IBESS SYSTEM SOIL 18
- 19. Aquaculture •Fish make up half of aquacultural production. Molluscs and plants each make up nearly 1/4. •Global aquaculture has been doubling about every 7 years. 9/29/2013 Guru IBESS SYSTEM SOIL 19 Figure 9.19
- 20. Benefits of aquaculture •Provides reliable protein source for people, increases food security •Can be small-scale, local, and sustainable •Reduces fishing pressure on wild stocks, and eliminates bycatch •Uses fewer fossil fuels than fishing •Can be very energy efficient 9/29/2013 Guru IBESS SYSTEM SOIL 20
- 21. Environmental impacts of aquaculture •Density of animals leads to disease, antibiotic use, risks to food security. •It can generate large amounts of waste. •Often animals are fed grain, which is not energy efficient. •Sometimes animals are fed fish meal from wild-caught fish. •Farmed animals may escape into the wild and interbreed with, compete with, or spread disease to wild animals. 9/29/2013 Guru IBESS SYSTEM SOIL 21
- 22. Environmental impacts of aquaculture •Transgenic salmon (top) can compete with or spread disease to wild salmon (bottom) when they escape from fish farms. 9/29/2013 Guru IBESS SYSTEM SOIL 22 Figure 9.20
- 23. Trade-Offs Aquaculture Advantages Disadvantages Highly efficient Large inputs of land, feed, And water needed High yield in small volume of water Produces large and concentrated outputs of waste Increased yields through crossbreeding and genetic engineering Destroys mangrove forests Increased grain production needed to feed some species Can reduce overharvesting of conventional fisheries Fish can be killed by pesticide runoff from nearby cropland Little use of fuel Profit not tied to price of oil Dense populations vulnerable to disease High profits Tanks too contaminated to use after about 5 years 9/29/2013 Guru IBESS SYSTEM SOIL 23
- 25. Spotter airplane Trawler fishing Fish farming in cage Purse-seine fishing trawl flap trawl lines sonar fish school trawl bag fish caught by gills Drift-net fishing float buoy Long line fishing lines with hooks 9/29/2013 Guru IBESS SYSTEM SOIL 25
- 26. 100 Catch (millions of metric tons) 80 60 40 20 0 1950 1960 1970 1980 1990 2000 Year 9/29/2013 Guru SOIL TotalIBESS World Fish Catch SYSTEM 26
- 27. 25 Per capita catch (kilograms per person) 20 15 10 5 0 1950 1960 1970 1980 1990 2000 Year 9/29/2013 World Fish Catch Per Guru IBESS SOIL SYSTEM Person 27
- 28. 800 80 Abundance 70 600 60 50 400 40 Abundance (kilograms/tow) Harvest (thousands of metric tons) Harvest 30 200 20 0 1960 9/29/2013 10 1970 1980 Guru IBESS Year SYSTEM 1990 SOIL 2000 28
- 29. Problems and consequences • Problem • Consequence – Overgrazing – Desertification, erosion nutrient loss – Water Pollution – Groundwater contamination, ^BOD, Eutrophication, etc • Slaughter • Wastes • Riparian grazing – Land use – Habitat loss & fragmentation, decreased biodiversity • Fencing, deforestation – Uses more water 9/29/2013 – Water shortages / depletion Guru IBESS SYSTEM SOIL 29