Chapter 12 Soil and Agriculture

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Global food crisis https://www.youtube.com/watch?v=raSHAqV8K9c

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)

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

What are GMOs? https://www.youtube.com/watch?v=sH4bi60alZU

Science, Technology, and GMOs https://www.youtube.com/watch?v=eFDyTz9K9i8

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

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

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”

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

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

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

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

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

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

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

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

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