1. Chapter 12
Soil and Agriculture

2. Section 2: Soil Degradation and Conservation
Soil degradation – the deterioration of the soil characteristics needed for plant growth or other ecosystem services
Caused by erosion, desertification, and pollution
Erosion – the removal of topsoil
More than 19 billion hectares (47 billion acres) of world’s croplands suffer from erosion and other forms of soil degradation from human activities

3. Section 2: Soil Degradation and Conservation
Activities that increase erosion:
Leaving soil bare after harvests
Overgrazing rangelands
Clearing forests

4. Section 2: Soil Degradation and Conservation
Some farming practices conserve soil:
Intercropping – the planting of different crops in mixed arrangements
Crop rotation – farmers alternate crops grown in a field
No-till farming – planting new crops among remnants of previous crops

5. Section 2: Soil Degradation and Conservation
Some farming practices conserve soil:
Shelterbelts –rows of trees or other tall perennial plants that are planted along the edges of fields to slow wind

6. Section 2: Soil Degradation and Conservation
Some farming practices conserve soil:
Terracing – minimizes erosion on steep hillsides
Contour farming – plowing sideways across a hillside, reduces erosion on gently sloping hillsides

7. Section 2: Soil Degradation and Conservation
Ranching practices that lead to soil erosion:
Overgrazing – occurs when the livestock population exceeds the carrying capacity of the rangeland and too many animals eat too much of the plant cover
more soil is exposed and made vulnerable to erosion

8. Section 2: Soil Degradation and Conservation
Preventing overgrazing:
Assess the carrying capacity and enforce grazing limits on publicly owned land

9. Section 2: Soil Degradation and Conservation
Desertification – a loss of more than 10% productivity, causing land to become more desert-like
Due to:
Erosion
Soil compaction
Forest removal
Overgrazing
Drought
Salt buildup
Climate change
Depletion of water sources

10. Section 2: Soil Degradation and Conservation
Most desertification has been caused by wind and water erosion
Affects 1/3 of Earth’s land areas

11. Section 2: Soil Degradation and Conservation
Soil pollution
Irrigation – providing water other than precipitation to crops
Can result in salinization – the buildup of salts in soil
Especially a problem in dry areas

12. Section 2: Soil Degradation and Conservation
Solutions to irrigation pollution:
Avoid planting crops that require a lot of water in dry areas
Irrigate with water low in salt concentration
Drip irrigation systems – supply only enough water that is needed, as close to the roots as possible
Plant salt-tolerant plants, such as barley

13. Section 2: Soil Degradation and Conservation
Soil pollution
Pesticides – chemicals that kill organisms that attack or compete with plants we value
Can be used to kill plants, animals, fungus, bacteria, or viruses
Build up in the soil and may be harmful to animals and humans

14. Section 3: Agriculture
Green revolution – introduction of industrial agriculture and variety increased food yields worldwide
Yield – the amount of a crop produced in an area
Industrial agriculture – produces large amounts of crops and livestock through the use of mechanized farming technology, pesticides, fertilizers, and irrigation
Requires a large input of energy, water, and chemicals

15. Section 3: Agriculture Advantages of the green revolution:
Worldwide food yields increased, saving millions of lives from starvation
Production on a patch of land is now more efficient, which prevents further deforestation and habitat loss to make more farmland

16. Section 3: Agriculture Disadvantages of the green revolution:
Increased use of water, fertilizers, pesticides has worsened erosion, salinization, desertification, eutrophication, and soil pollution
Industrial agriculture is most efficient when large areas are planted with a single crop, creating a monoculture
Reduces biodiversity, crops are more vulnerable to disease and pests, and are at risk of catastrophic crop failure

17. Section 3: Agriculture
Biological Pest Control – the use of organisms to control pest populations
Uses predators, plant derived chemicals, pheromones, or beneficial bacteria
Bacillus thuringiensis (Bt) – soil bacteria that produces a protein that kills many caterpillars and larvae of some flies and beetles
Some predatory organisms may become invasive

18. Section 3: Agriculture
Pollinators – organisms such as insects, birds, bats, etc. that spread pollen from flower to flower
About 800 species of cultivated plants that rely on bees and other insects for pollination
Honeybees pollinate more than 100 crops, which make up 1/3 of the U.S. diet
Protect pollinators by reducing or eliminating pesticide use

19. Section 4: Food Production
Human population is rapidly growing, so agricultural production also needs to grow
Arable land – land suitable for farming – is running out

20. Section 4: Food Production
Food security – the guarantee of an adequate and reliable food supply for all people at all times
Depends on maintaining healthy soil and water, protecting the biodiversity of food sources, and ensuring the safe distribution of food

21. Section 4: Food Production
Food production has been increasing, but 1 billion people are still malnourished
Malnutrition – a shortage of nutrients the body needs, occurring when a person fails to obtain a healthy variety or quantity of nutrients

22. Global food crisis

23. Section 4: Food Production Genetically Modified Organisms
Any process in which scientists directly manipulate an organism’s DNA is called genetic engineering
Organisms that have undergone genetic engineering are called genetically modified organisms (GMO)

24. Section 4: Food Production Genetically Modified Organisms
85% of U.S. corn harvest and more than 90% of U.S. soybeans, cotton, and canola crops are GMO

25. What are GMOs?

26. Science, Technology, and GMOs

27. Section 4: Food Production Genetically Modified Organisms
Risks:
Evidence of health risks is inconclusive
Pesticide resistant crops are heavily sprayed with chemicals
GM genes will most likely make their way into wild plants
GM genes have been found 13 miles or more away from their growing sites

28. Section 4: Food Production Genetically Modified Organisms
Benefits:
Growing insect-resistant crops reduces the use of chemical insecticides because fewer chemicals are used

29. Section 4: Food Production Genetically Modified Organisms
ethics:
GMO crops that may benefit poor nations (increased nutrients, drought and salinity tolerance) have not been widely developed
Corporations have little economic incentive to develop such crops – farmers from poor nations cannot afford to buy GM seeds every year
The company that engineers the gene owns every copy of that gene – even if it is found in wild plants
Some feel that genetic engineering is “playing God”

30. Section 4: Food Production Industrial Food Production
Feedlots – huge pens designed to deliver energy-rich food to livestock or poultry
AKA – Concentrated Animal Feeding Operations (CAFO)
More than 1/3 of the world’s pork and poultry comes from feedlots

31. Section 4: Food Production Industrial Food Production
Advantages of feedlots:
More efficient
Do not degrade soil through overgrazing
Manure can be used as fertilizer

32. Section 4: Food Production Industrial Food Production
Disadvantages of feedlots:
Illness in feedlot animals and humans through contamination of food or water with manure
Heavy use of antibiotics
Use of steroids to promote growth
Cruelty to animals

33. Section 4: Food Production Industrial Food Production
Aquaculture – the raising of aquatic organisms
Benefits: Can be sustainable; reduces by-catch; reduces fossil fuel use
Costs: More difficult to control spread of diseases; produces a lot of waste

34. Section 4: Food Production Effects of Industrial Food Production
Loss of biodiversity
GM genes might pollinate wild plants, leading to the extinction of wild genes
Leads to monocultures in nature and on farms
In the U.S., we have lost 90% of our fruit and vegetable varieties
Seed banks – organizations that preserve seeds of diverse plants as a kind of insurance policy against global crop collapse

35. Section 4: Food Production Effects of Industrial Food Production
Energy efficiency
Production of meat requires more energy than production of plants
90% of energy is lost from one trophic level to another

36. Section 4: Food Production Sustainable Agriculture
Sustainable agriculture – agriculture that does not deplete soil faster than it forms
Ex – organic farming

37. Section 4: Food Production Sustainable Agriculture
Organic agriculture – uses no synthetic fertilizers, insecticides, fungicides, or herbicides, but instead rely on biological approaches such as composting and biological pest control
Has been increasing 10-35% each year due to consumer demand

38. Section 4: Food Production Sustainable Agriculture
Locally sourced agriculture
Average food product sold in the U.S. travels 1500 miles between the farm and shelf
Often chemically treated to ripen or preserve
Local foods may have more nutritional value
Usually more diverse
Uses less fossil fuels
Boosts local economies