Chapter 9: Food

“Growing crops is easier than building castles, yet there are many castles in our

world and not enough crops.". - Petak Saeoung

Discussion:

Why do you think it is so difficult to provide adequate food for all of the world’s people?

Besides using chemical pesticides, how might farmers keep insects from destroying crops?

Feeding the People of the WorldFeeding the People of the WorldEthopiaEthopia - 1985Thousands of people were starvingLack of rain, soil degradation, & warThen rains came and washed millions of tons of soil into the rivers.What People EatFood staples:Asia - RiceChina & India - Grains (noodles & breads)Central America - Corn (tortillas)Europe - PotatoesWhat could Irish officials have done to prevent the potato famine that occurred in Ireland in the 1800s?More diverse crops

3 Major nutrients in human foods:

1.CarbohydratesFound in: breads, cereals, potatoes, beans

2.Proteins Found in: meat, fish, eggs, dairy products,

beans

3.Lipids / FatsFound in: butter, oils, fatty foods

MalnutritionCondition caused by not consuming enough necessary nutrients; causes health problems and possibly death1 out of every 3 people on Earth are malnourished; mostly the very young or very old

Example: Malnutrition- due to severe protein deficiencyMost victims of these diseases are ChildrenSymptoms: bloated abdomen, diarrhea, loss of hair, liver damage, wide eyes, thin bodyIf left untreated can cause mental retardation and stunted growth; can reverse with a balanced diet

Why do people go hungry?1.The World’s population is increasing

fast than its’ food supply2. Food supply is not equally divided3. Difficulties in transporting food to

those who need it4. Droughts leading to crop failure and

famine.

Famine = widespread food shortage that causes malnutrition in many people.

How can we make a difference?

THE GREEN REVOLUTION

Between 1950-1970 new varieties of grains & new farming techniques were introduced into Asian & Latin American countries

- These new varieties had a much greater Yield – amount produced per unit area.

New grain did not grow well because it required special fertilizers and more water than older varieties.

Subsistence Farmers = grow only enough food to feed their family; could not afford necessary chemicals

Most of the increased production came from Larger Farms that grow food to be sold

The pesticides and fertilizer's polluted the environment.

Agriculture and Soil

Arable Land - fertile land that can be plowed to grow crops

Amount of arable land is decreasing each year

FERTILE SOILCan support the rapid growth of healthy plantsTopsoil is loose surface layer of soil in which the roots of most plants grow

Fertile topsoil is composed of: rock particles, water, air and organic matter (dead plant & animals and animal excrement)

Living organisms in soil (fungi, bacteria, earthworms) break up the soil and let water and air into itMost soil forms when Bedrock cracks and breaks apart

It can take thousands of years to form a few centimeters of soil

ErosionErosion is the wearing away of topsoil by wind and water

Topsoil is needed to grow crops

In the US, about 1/2 of the topsoil has been lost to erosion in the past 200 years

Ranked as one of the most serious ecological problems we face

Farming practices that contribute to topsoil erosion:

PlowingHarvestingClearing of forests to produce lumber

DesertificationProcess by which soil fertility deteriorates and lands become desert like

Worldwide, an area the size of Nebraska becomes desert each yearEx: Sahel region of northern Africa

PROBLEMS:several crops planted/yearFallow periods shortened or eliminatedmore animals put out to grazetrees and shrubs cut down

Soil Conservation1. Contour Plowing•plow across the slope of a hill

•tiny ridges help prevent soil from, washing down hill

•can also leave strips of vegetation running across hillside

2. Use Organic Material instead of inorganic fertilizers- Compost-Animal manure

3. No till farming - seeds of the next crop are planted in slits that are cut into the soil and through the remains of the previous crop.- Roots of old crop hold soil in place- As old crop decays, organic matter

is added to the soil

Sustainable Agriculture

Low Input Farming does not use a lot of energy, pesticides, fertilizer or water

1.Organic Farming - Grow plants without any synthetic pesticides or inorganic fertilizers- Use manure & compost- Alternate crops to reduce pest populations2. Aquaculture (“Fish-farming”)

Salinization- Accumulation of Salt in the soil-Plants cannot grow in salty soil

Causes of Salinization:1. Water for irrigation is taken from rivers or groundwater which contain more salt than rainwater

- When water evaporates it leaves salts behind2. Irrigation causes level of groundwater to rise, drawn up by Capillary Action

Preventing Salinization:1.Line irrigation canals to prevent water from seeping into the soil and raising the

groundwater level

2. Water the soil heavily to wash out salts before seeds are planted

3. Plant salt-tolerant crops which absorb salts from soil

4. Plant salt-tolerant trees- Help to reclaim the soil and prevent

evaporation of water thereby slowing the upward movement of groundwater

- Roots of trees penetrate the soil and allow rainwater to sink in and wash out the salts

PEST CONTROL- Worldwide, pests destroy 1/3 of all crops.- Wild plants have more protection from pests than crop plants.

1. Grow scattered apart2. Pest predators3. Evolved defenses (poisonous plant fluids)

3 Main Types Pesticides:1. Chlorinated hydrocarbons 2. Organophosphates3. Carbamates

Drawbacks of Pesticides:

1. Health Concerns- high Cancer Risk-accidental chemical leaks in factories

2. Pollution and Persistence-persistent pesticides do not break down rapidly into harmless chemicals; they accumulate in the water and soil

DDT used in 1940s to kill mosquitoes and lice1. DDT accumulated in the water2. Fish absorbed DDT3. Birds ate the fish4. Birds layed eggs with thin shells that broke when the birds sat on them5. Penguins, pelicans, peregrine falcons, and eagles were endangered and even wiped out as a result

** DDT was eventually banned in the U.S.

Resistance-Ability to tolerate a particular pesticide

1. A few insects contain a gene that protects them from the pesticide.2. Those insects survive and pass that gene onto their offspring.3. The resistant insects continue to reproduce while the others die off. **More than 500 species of insects have developed resistance to pesticides since the 1940s.

Biological Pest Control1. Predators and Pathogens

- Release a natural predator, parasite, or pathogen into the area where the pest lives

Parasitoids. This wasp is laying its egg inside an aphid where its young will develop. Parasitoid immatures develop on or inside a host, killing it as they mature. They emerge as adults and continue the cycle.

Predators. Lady beetles are well-known examples of predatory insects. A predator consumes many prey during its lifetime. The predators listed in this guide feed on insects and mites.

Pathogens. This nematode is just one example of a pathogen which may kill its host. Other pathogens include bacteria, viruses, fungi and protozoa. This section also includes antagonists which control plant diseases.

Weed Feeders. Weeds can be attacked by arthropods, vertebrates, and pathogens. This weevil feeds only on one particular type of weed called purple loosestrife.

2. Plant defenses - Crossbreed plant varieties to produce crops with their own defenses such as a tougher skin

3. Chemicals from Plants

4. Disrupt Insect Breeding- Treat crops with Pheromones (insect hormones)- Treat males with x-rays, make them sterile, then release them-After mating, females will produce eggs that do not develop

5. Home remediesA. Cockroaches- Put honey in the bottom of a jar and set it upright-Line the cracks where roaches enter your home with bay leaves; the smell of bay leaves repels roaches

B. Ants- Squeeze fresh lemon or lime juice into the holes or cracks and leave the peels where you've seen ants-Scatter mint around your shelves and cabinets

C. Fleas and Ticks- Feed the animal brewer's yeast or vitamin B- Spray animal with a mixture of rosemary and water