FOOD AND AGRICULTURE

Chapter 15

Feeding the WorldMacronutrients- the main nutrients we need

Carbohydrates (grains and sugars)Proteins Fats

Micronutrients – nutrients we need in smaller amounts

VitaminsMinerals

What is diet?

Diet is the type and amount of food a person eats Healthy diet includes the right amounts of

both macro- and micro-nutrients Most diets worldwide are high in

carbohydrates (grains: rice, potatoes, bread)

Foods that are rich in fat and protein (meats, oils) are less common

Undernutrition- not consuming enough calories

Malnutrition- not consuming enough necessary nutrients, especially protein. 1 out of 3 people on Earth are malnourished. 1% of children in the US and 50% in SE Asia

What is a calorie?

A calorie is actually a measurement of energy.

On nutrition labels food energy is given in kilocalories (Cal.) which is equal to 1000 calories

Suggested daily Calorie intake: Depends on age, height, weight, activity level,

gender Men should average 2, 000-2,600 Cal. Women should average 1,600-2,400 Cal.

Calculators online or apps

Vitamins and Minerals Vitamin and mineral deficiencies occur more often

in people in developing countries

Iron – is needed for making proteins which transport oxygen in the blood to all body parts and to support the immune system 2 billion people lack sufficient iron which causes

anemia which causes fatigue and makes infections more likely.

Vitamin A - deficiency can cause blindness, make infections more common (Ex: HIV-AIDS, measles) estimated 124 million children in the world are

chronically deficient in vitamin A

Iodine – deficiency is the greatest cause of mental handicaps and brain damage. 1.9 billion are affected Iodized table salt is commonly

used in first world countries to ensure people get enough iodine.

Deficiency causes goiters (enlargement of the thyroid gland) and can lead to deafness.

Why are People Hungry? Food production has been increasing for

decades.However,

1. food supply is not divided equally. 2. transportation problems can occur due to politics, economics (rail road line broken) and war.3. droughts and flooding also cause food shortages.4. the world population is increasing too quickly.A widespread food shortage that causes malnutrition is a famine.

Global Outlook

Total Worldwide Grain Production (Wheat, Corn, and Rice- grains are

nutritious and do not need refrigeration)

4 staples supply most of the world’s calories: wheat, corn, rice, potatoes.

The Green Revolution The Green Revolution (1950s) was the

introduction of new farming techniques and new grains that could produce a greater yield Yield: the amount of food that can be produced in an area

This allowed more people to be fed than ever before.

These new crops require lots of fertilizers, pesticides and water. New equipment was also needed. Most subsistence farmers could not afford the necessary equipment or chemicals.

Crop acreage 25% and food production 200%!

Criticisms of the Green Revolution

Lots of water needed Sometimes in areas where fresh water is scarce

Increased use of pesticides and fertilizers (chemicals)

Emphasis on grain monocultures reduced the variety of grains grown. In India, for example, there were about 30,000 rice

varieties prior to the Green Revolution, today there are around ten.

Decreased productivity of land since land was farmed so extensively

Criticisms of the Green Revolution Did not increase food security since

famines are caused by socioeconomic problems

Monoculture= less variety eaten Many subsistence farmers couldn’t afford

the equipment and chemical needed to grow the crops.

Soil and Agriculture

There is a limited amount of arable land- fertile land that can be plowed to grow crops.

That amount is decreasing every year. As the population grows, more land is

used for housing, roads, factories… But how do we feed more people with

less land?

Amount of farmland in 1985 that was lost by 2000

SOIL Fertile soil- soil that can support rapid growth

of healthy plants. Topsoil

Most plant roots grow here Made of rock particles, water, air and organic

matter Lots of living organisms (fungi, bacteria,

earthworms and insects) help to break down the soil, allow air and water to penetrate, and decompose organic matter.

Most soil is formed from bedrock- temperature changes and moisture cause the bedrock to crack and break apart, creating smaller particles.

2006- World

population reaches 6.5

billion

1998- U.S. probe

Pathfinder lands on Mars

1795- Eli Whitney invents the cotton gin

1614- Native American princess

Pocahontas marries John

Rolfe

1507- German geographer and

mapmaker first to call the new world

‘America’

Soil Composition Mineral Particles (45%)

Weathered rock Provides essential nutrients for plants

Organic Material (5%) Animal dung, dead remains of plants and

animals, humus Water (25%) Air (25%)

Soil Horizons O-horizon

Surface litter, decomposed organic matter

A-horizon Topsoil: organic matter,

living organisms, rock particles

B-horizon Zone of leaching: dissolved

materials moving downward Lighter material

C-horizon Subsoil: larger rock particles

with organic matter and inorganic matter

Weathered RockSolid Bedrock

Nutrient Cycling

Nutrients are cycled between plants, organisms and soil

Example Bacteria and fungi

decompose plant and animal wastes

They are transformed into CO2, soil nutrients and water

Soil Properties Soil Texture- size of particles in the soil

Relative proportion of sand, silt and clay Sand: 2mm-0.05mm Silt: 0.05mm-0.002mm Clay: >0.002mm

Soil texture affects soil properties Coarse textured soil (sand)

Will not hold water well- flows through easily, feels gritty

Medium textured soil (silt)- found in floodplains, main soil component in

mud.make excellent farm land, but erodes easily.

This is the soil blown away in dust storms and carried down stream in floods.

Retains water well, with slow drainage. Fine textured soil (high in clay)

Poor drainage Low oxygen levels in soil, but high in important

plant nutrients

The Soil Texture Triangle

Use the percentages of the components of soil to find the name for that type of soil.

For example, 30% sand, 30% clay and 40% silt:

Clay loam

What is Loam??? Soil that has approximately the same

percentages of clay, silt and sand. Great for gardening and agricultural uses

because it retains nutrients and water while still allowing the water to flow freely.

Found in a majority of successful farms in regions around the world

Feels soft and rich and is easy to work over a wide range of moisture conditions.

Soil Properties

Porosity and Permeability

Porosity is a measure of how much of a rock is open space. This space can be between grains or within cracks or cavities of the rock.

Permeability is a measure of the ease with which a fluid (water in this case) can move through a porous rock.

Soil Problems Soil Erosion- one of the most serious ecological

problems wearing away of topsoil by wind and water Water, wind, glaciers, deforestation, poor

agriculture techniques, mining, and overgrazing. Why a problem?

Causes a loss in soil fertility as organic material and nutrients are eroded

More fertilizers must be used to replace nutrients lost to erosion

Erosion and the resulting sedimentation is the #1 pollutant of our waters!

½ the US topsoil has been lost in the last 200 years and 1/10 of world’s topsoil has been eroded in the last 45 years

Soil Problems Soil Salinization

Accumulation of salt in the soil.

Irrigation takes water from rivers and groundwater that contain more salts than rainwater.

Water evaporates and the salt is left behind.

Stunts crop growth, lowers yields and can eventually kill plants.

Soil Problems

Desertification loss of topsoil creates an

infertile soil and the land becomes desert-like.

Case Study: the Sahel region in northern Africa.

The increased population led to overuse of the land. More crops had to be planted and the land could not lie fallow (rest). Soil lost fertility and most trees were cut for fuel. The land is becoming a desert.

Soil ConservationTo control erosion: Contour Plowing

Plowing around hill instead of up-down

Decreases soil erosion Strip Cropping

Alternating strips of different crops along natural contours

Terracing Creating terraces on

steep slopes to prevent erosion

Strip Cropping

Terracing

Soil Conservation

No-tillage leaves the soil undisturbed in the winter; it saves on fuel costs, machinery wear and tear, and labor time.

Nutrients are absorbed into the soil as the plants decompose.

crop rotationPlanting a series of different crops in the same field over a period of years. Ex: corn/soybeans

It lessens insect damage and disease, retains essential nutrient and minerals, decreases erosion, and helps maintain soil fertility

Preserving Soil FertilityAccomplished through the use of both organic and commercial inorganic fertilizers Organic fertilizers: Animal manure, crop

residue, bone meal and compost Slow acting

Inorganic fertilizers Manufactured from chemical compounds Soluble in water

Fast acting, short lasting Mobile- easily leach and pollute groundwater

o Agroforestry uses both forestry and agricultural techniques to improve degraded areas and offer economic benefits.

o Trees can serve as windbreaks, control erosion, provide shade, recharge ground water, increase biodiversity (birds and other pollinators!)

Sun Coffee vs Shade Coffee

COFFEE GROWN IN THE SUNLIGHT

COFFEE GROWN UNDER THE SHADE OF TREES

Planted in higher density

Needs more fertilizers and pesticides

So much coffee was produced that the demand decreased and prices decreased

Increased erosion and toxic runoff

Soil lacks nutrients

Lower yield No need for fertilizers

and pesticides because the birds and insects take care of disease and hungry insects

Greater biodiversity Soil is healthy

and can produce coffee yearly

How do we deal with pests?

In NA, insects destroy 13% of all crops. Worldwide, insects destroy 33% Pest= any organism that occurs where

you don’t want it or in large enough numbers to cause damage.

Pesticides Chemicals that kill pests. They can be very effective, but also have

many drawbacks. Can remain in the soil 10,20 or more years

after the spraying has stopped. Can cause illnesses in people as well as

wildlife. Can cause pollution Pests can evolve resistance

DDTdichlorodiphenyltrichloroethane

Used during WW II to kill mosquitoes in order to prevent malaria and typhus. It is not water soluble so it accumulates in

the tissues of organisms. Got in the waters, then fish, then birds.

Caused bird eggs to be too thin so they broke when sat on

Contributed to the declining numbers of bald eagles, bats, peregrine falcons

Banned in 1972, but many countries still use it.

Biomagnification

PESTS CAN DEVELOP RESISTANCE

SOME INSECTS HAVE A GENE THAT ALLOWS THEM TO SURVIVE THE CHEMICAL. THEY REPRODUCE AND PASS ON THE RESISTANT GENE.

DDT Why Are We Concerned About DDT?

Even though DDT has been banned since 1972, it can take more than 15 years to break down in the environment.

What harmful effects can DDT have on us? Damages the liver Temporarily damages the nervous system Can cause liver cancer Damages reproductive system

How are we exposed to DDT? By eating contaminated fish and shellfish Infants may be exposed through breast milk By eating imported food directly exposed to DDT By eating crops grown in contaminated soil

Rachael Carson- Silent Spring1962

American biologist and ecologist

Researched effects of modern agricultural practices

Highlighted the dangers of pollution and chemicals used in agriculture

Considered a pioneer of the modern environmental movement.

Rachael Carson

Another way to control pests is Biological Pest Control

Biological Pest Control is using living organisms or naturally produced chemicals to control pests. Release a natural predator or pathogen like disease-

causing organisms such as the bacterium Bacillus thuringensis (Bt) which kills caterpillars that eat certain crops

Plant defenses- breed plant varieties that can produce their own defenses like chemical compounds to repel pests and physical barriers like tougher skin.

Chemicals from plants- using plant chemicals as a natural pesticide such as chrysanthemums

Disrupt Insect Breeding by treating crops with pheromones- confuse them!

Genetically Engineered foods

Biotechnologists use genetics to develop plants with desirable traits. Like…Pest resistanceDrought toleranceRipen slowlyIncrease vitamin or mineral contentIncrease crop yieldsTolerance of extreme climates (temperatures)Example: Flavr Savr tomato- ripens more slowly

Did You Know?

91% of soybeans grown in the United States are GMOs. 88% of cotton is genetically modified. 75% of corn has been genetically modified.

Many products such as corn meal, soy meal, coke, baking soda, and vegetable oil are made with GM foods

Most corn is grown for livestock feed.

Sustainable Agriculture

Farming that conserves natural resources and helps keep land productive

Planting productive, pest-resistant crops that require little energy, pesticides, fertilizer, water