1. Agriculture Unit Notes

2. Food and Nutrition Foods humans eat are composed of several major types of biological molecules necessary to maintain health : Carbohydrates – Sugars and starches metabolized by cellular respiration to produce energy Proteins – Large, complex molecules composed of amino acids that perform critical roles in body Lipids – Include fats and oils and are metabolized by cellular respiration to produce energy Vitamins and Minerals

3. Agricultural Land Use Agriculture now covers more of Earth’s surface than forests. – 38% of planet’s land surface is used for agriculture 26% pasture/rangeland 12% cropland

4. Using Land For Agriculture Humans need: – Most women need ~2,200 kilocalories / day – Men, ~ 2,900 kilocalories / day Biologists estimate that there are roughly 30,000 plant species with parts that humans can eat Majority of our food supply (90%) is derived from only 15 plant and 8 animal species Three grains, wheat, rice, and corn, provide almost half of the calories consumed by people – These three species are all annual plants 2 out of 3 people on Earth survive primarily on grains World food supplies have more than kept up with human population growth over the past two centuries. – During the past 40 years, population growth has averaged 1.7% per year, while food production increased an average 2.2%.

5. Principle Types of Agriculture There are two Principle Types of Agriculture 1. Traditional Agriculture – Low Input Polyculture Human and animal labor used to produce only enough food for farming family’s survival 2. Industrialized agriculture High Input Monocultures Produce huge output of single crops (monocultures) or livestock (which are often fed monoculture products)

6. Traditional Agriculture: Low Input Polyculture Many farmers in developing countries use low-input agriculture to grow a variety of crops on each plot of land (interplanting) through: – Polyvarietal cultivation Planting several genetic varieties. – Intercropping/Polyculture Two or more different crops grown at the same time in a plot.

7. Polyculture Agriculture Advantages of polyculture: Crops mature and ready to harvest at different times Provides food throughout the year Soil constantly covered, preventing erosion Less need for fertilizer and water because roots are at different depths, using more of soil and increasing efficiency Creates habitats for natural predators of pest species, reducing need for pesticides and herbicides

8. Industrial Food Production: High Input Monocultures Requires large amounts of energy, water, fertilizers, antibiotics, and pesticides; three of which come from fossil fuels Produce huge output of single crops (monocultures) or livestock (which are often fed monoculture products) Accounts for roughly 25% of the world’s cropland Mostly in developed countries, but it is spreading into developing nations

9. Sources of Protein -- Livestock One of the principal uses of animals in agriculture is to transform plant material into high-quality protein In traditional agriculture, livestock graze land, taking nutrients in and then they defecate and return some of the nutrients to the same field In industrial agriculture, livestock are fed grains (corn particularly, which they are not “designed” to do) and not necessarily in a field, so the manure does not fertilize a field Per capita meat consumption has increased 29% between 1950 and 1996 1/5 th of the world’s population consume roughly half of the world’s grain production through livestock

10. Pesticides – Agricultural Chemicals Industrial agriculture relies on pesticides to produce their crops. A pesticide Is a poison used to destroy pests, such as insects, rodents, or weeds Pesticides can also harm: Beneficial plants and insects, wildlife and people

11. Pesticide Resistance – Over time, spraying large amounts of pesticide to get rid of pests usually makes the pest problem worse. – Pest populations may evolve resistance – Most surviving individuals have characteristics that allowed them to tolerate the pesticide. Survivors pass on genetic characteristics for tolerance. Subsequent pesticide applications become less effective. – More than 500 species of insects have developed resistance to pesticides since the 1940s.

12. Problems with Pesticide Use Pesticide resistance is a problem associated with the widespread use of pesticides. Most pesticides are not species-specific, and kill beneficial species as well as pest species. – Many kill predator and parasitic insects that normally control pest insects. – Insecticides may change the population structure of the species present so that a species not previously a problem may become a serious pest. Pesticides are designed to kill organisms, so they may also be dangerous to humans. Short-term and long-term health effects to persons applying pesticides and the public that consumes pesticide residues in food are also concerns.

13. Why Are Pesticides So Widely Used ? Food Production Worldwide, pests destroy 35% of crops. This represents an annual loss in U.S. of $18.2 billion. Economic Concerns Pesticides increase yields and profits. Health Reasons Insecticides curtail many diseases.

14. Land Degradation Definitions of degradation are based on both biological productivity and expectations of what land should be like. – Generally, land is considered degraded when Soil is impoverished or eroded Run-off is contaminated Biodiversity is diminished. Water and wind are the driving forces for vast majority of soil degradation.

15. Erosion Erosion is a natural process, resulting in redistribution of the products of geologic weathering, and is part of both soil formation and soil loss. – Worldwide, erosion reduces crop production by equivalent of 1% of world cropland per year. – Erosion results in sediment loading of rivers and lakes, siltation of reservoirs, and smothering of wetlands and coral reefs. Wind can equal or exceed water as an erosive force, especially in a dry climate and on flat land.

16. Genetic Engineering and Agriculture Genetic engineering – Removes DNA from one organism and splices it into the chromosomes of another. – Produces genetically modified organisms (GMOs) with new traits. Can produce crops with pest-resistance and wider tolerance levels to frost, drought, low nutrient soils, salty soils, etc. Can improve protein or vitamin content of crop Can incorporate oral vaccines into foods such as bananas for use in developing nations Animals can be modified to grow faster or produce pharmaceuticals in their milk. – It differs from traditional breeding methods in that desirable genes from any organism can be used, not just those from the species of plant or animal being improved Can also be called transgenic organisms

18. The Problems With Monocultures Biodiversity loss Loss of habitat through conversion of grasslands and forests along with wetland draining Fish kills from agricultural runoff Extermination of predators Loss of genetic diversity due to monocultures Genetic pollution from bioengineered or selectively bred organisms that “escape” and interbreed with native species Spread of diseases from agroecosystems to natural ecosystems Water – Aquifer depletion – Increased runoff, due to land clearing and plowing – Sediment pollution from runoff – Fish kills from pesticide runoff – Surface and groundwater pollution from pesticides, antibiotics, and fertilizers – Over-fertilization of lakes, rivers, and coastal ocean from fertilizers, livestock wastes, and food processing wastes