Post on 01-Sep-2018
Food provides
1. Energy (Calorie = amount of heat required to raise the temperature of one kilogram of water by one degree at one atmosphere pressure)
2. Materials to build body (carbon, proteins, minerals, lipids, etc.)
Humans need a variety of foods to supply their nutritional needs
Carbohydrates
Proteins
Fats
Vitamins
Minerals
The Food Pyramid
is a guide for what we
should eat daily.
Malnutrition – a condition when a person does not consume enough calories or nutrients to supply the body’s needs
Marasmus (“wasting away”)– not enough calories and protein
Kwashiorkor (“displaced child”) – severe protein deficiency, bloated belly, can cause mental retardation
Overnutrition – too many calories, results in health problems including diabetes, heart disease, stroke
How do we supply 6.8 billion people with enough food?
Agriculture = practice of
raising crops and livestock for
human use and consumption
•Cropland = land used to
raise plants for human use
•Rangeland or pasture = land
used for grazing livestock
Land devoted to agriculture
covers 38% of Earth’s land
surface
Agriculture was invented independently by different cultures
The earliest plant and animal domestication is from the “Fertile Crescent” of the Middle East
Wheat, barley, rye, peas, lentils, onions, goats, sheep
Traditional agriculture = biologically powered agriculture, using human and animal muscle power
Subsistence agriculture = families produce only enough food for themselves
Uses animals, irrigation and fertilizer, but not fossil fuels
Industrialized agriculture = using large-scale mechanization and fossil fuels to boost yields
Yield = amount of food that can be produced in a certain area Also uses pesticides, irrigation and fertilizers
Monocultures = uniform planting of a single crop
Why might monocultures be a bad idea?
Monoculture = a large expanse of a single crop
More efficient, increases output
Devastates biodiversity
Susceptible to disease and pests
Narrows human diet: 90% of our food comes from 15 crop species and 8 livestock species
Armyworms easily defoliate monocultures
The Green Revolution
Use of new varieties of crops dramatically increased per-acre yields
Spread to the developing world in the 1940s with wheat, rice, corn
Depended on large amounts of Synthetic fertilizers
Chemical pesticides
Irrigation
Heavy equipment
Soil is a thin covering over most land that is a complex mixture of eroded rock, mineral nutrients, decaying organic matter, water, air, and billions of living organisms, most of them microscopic decomposers
Soil is important because: 1. It provides most of the
nutrients needed for plant growth, and subsequently consumer growth.
2. It is the primary filter that cleanses water as it passes through.
3. It is a major component of the earth’s water recycling and water storage processes.
Components of soil 25% air (mostly N and O)
25% water
45% mineral
5% organic matter
Amounts of air and
water vary
Soil is a renewable resource Formation of soil depends on 5 factors:
1. climate 3. biologic activity 5. time
2. terrain 4. geology
It takes 15 to 100s of years to form one cm of soil!
*Parent material = the base geologic material of soil
**Bedrock = the continuous mass of solid rock comprising the Earth’s crust
*
**
Weathering produces soil Weathering = the physical,
chemical, or biological
processes that break down
rocks to form soil
Physical (mechanical)
•wind and rain
•no chemical changes in
the parent material
Chemical
•substances chemically
interact with parent
material
Biological
•organisms break down
parent material
Soil Horizons: Layers of mature soil O horizon – organic material, leaf
litter, many organisms live here
A horizon – topsoil layer, zone of accumulation of organic matter and nutrients
These top 2 horizons contain:
- the roots of most plants
- billions of living things (bacteria, fungi, earthworms, insects, etc.)
Soil Horizons: Layers of mature soil B horizon – subsoil, accumulates iron,
clay, aluminum and organic compounds that leach down from above
(leaching: process in which water seeps down through open spaces or pores in soil, dissolving minerals and organic matter and carrying them to lower layers)
Soil Horizons: Layers of mature soil C horizon – parent material, contains
large lumps or shelves of rock
R horizon (under C horizon)- bedrock
Soil Particles Three types, based on size:
1. Sand: 2.0-0.05 mm
2. Silt: 0.05-0.002mm
3. Clay: less than 0.002mm
Relative amounts determine soil texture
Soil Permeability Definition: the rate at which water and air move from upper to
lower soil layers
The more spaces there are between soil particles, the more permeable it is
Plants need good drainage, but not too much
Plants are like Goldilocks Sandy soil: This soil is too permeable – water runs right
through
Clay soil: This soil is too impermeable – water can’t get through
Loam: This soil is just right! (mixture of sand and clay)
Which is which?
Sand on left
Loam in middle
Clay on right
Other soil characteristics that are important to plants
Nutrient content – nitrogen, phosphorus and potassium
pH – if soil is too acidic or basic, plants can’t grow
Agriculture and Population Growth The earth has a carrying capacity for the human
population – we don’t know what it is.
We do not have unlimited land and resources to produce food for people.
2. Soil degradation soil erosion – the dislodging and movement of soil by
wind or water, occurs when vegetation is absent
Erosion increases through: excessive tilling, overgrazing, and clearing forests
Can result in desertification - most prone areas are arid and semiarid lands
The Dust Bowl
In the late 19th and early 20th centuries, settlers arrived in Oklahoma, Texas, Kansas, New Mexico and Colorado
Grew wheat, grazed cattle
Removed vegetation
A drought in the 1930s made conditions worse
Thousands of farmers left their land and had to rely on governmental help
3. Uneven food distribution around the world
Developing countries: usually faster population growth, more poverty, less infrastructure to grow and distribute food
4. Problems with irrigation
Irrigation = Artificially providing water to support agriculture
Unproductive regions become farmland
Waterlogging = over-irrigated soils Water suffocates roots
Salinization = the buildup of salts in surface soil layers
Depletion of ground and surface waters
5. Loss of biodiversity When we convert natural habitats to farms, we reduce
natural habitat
We also plant monocultures and use few species for crops
6. Negative effects of overgrazing
Soil compaction
Non-native invasive species invade
Less palatable to livestock
Out compete native vegetation
Ungrazed plot Grazed plot
7. Pollution from: Agriculture - pesticides, herbicides, fertilizers,
Livestock (on feedlots) – animal waste, excess methane is a greenhouse gas
Overapplication of Fertilizer Inorganic fertilizer use has
skyrocketed
Overapplying fertilizer can ruin the soil and severely pollute several areas
Runoff causes eutrophication in nearby water systems
Nitrates leach through soil and contaminate groundwater
Nitrates can also volatilize (evaporate) into the air
8. Resistance to pesticides Some individuals are genetically immune to a pesticide
They survive and pass these genes to their offspring
Pesticides stop being effective
Evolutionary arms race: chemists increase chemical toxicity to compete with resistant pests
Sustainable Agriculture Industrial agriculture may seem necessary, but less-intensive
agricultural methods may be better in the long run
Sustainable agriculture = does not deplete soil, pollute water, or decrease genetic diversity
Protecting soil: crop rotation and contour farming
Crop Rotation = alternating the crops grown field from one season or year to the next,
Cover crops protect soil when main crops aren’t planted
Wheat or corn and soybeans
Contour Farming = plowing furrows sideways across a hillside, perpendicular to its slope, to prevent rills and gullies
Protecting soil: terracing and intercropping
Terracing = level platforms are cut into steep hillsides, sometimes with raised edges A “staircase” to contain water
Intercropping = planting different types of crops in alternating bands or other spatially mixed arrangements Increases ground cover
Pros and cons of no-till farming Almost half of U.S. farmland
uses no-till farming
Benefits: reduced soil erosion, greater crop yields, enhanced soils
Negatives: increased use of herbicides and fertilizers
Biological control
Biological control (Biocontrol) = uses a pest’s natural predators to control the pest Reduces pest populations
without chemicals
Cactus moths control prickly pear
Bacillus thuringiensis (Bt) = soil bacteria that kills many pests
Salinization prevention
It is easier and cheaper to prevent salinization than fix it
Do not plant water-guzzling crops in sensitive areas
Irrigate with low-salt water
Irrigate efficiently, supplying only water that the crop requires
Drip irrigation targets water directly to plants
Integrated Pest Management (IPM)
IPM uses multiple techniques to suppress pests
Biocontrol
Chemicals, when necessary
Population monitoring
Habitat alteration
Crop rotation and transgenic crops
Alternative tillage methods
Mechanical pest removal
Within 4 years of using IPM in Indonesia, rice yields rose 13%, and
$179 million saved by phasing out subsidies
Genetically Modified Organisms (GMOs)
Genetic engineering = laboratory manipulation of genetic material
Genetically modified organisms = organisms that have been genetically engineered by …
Recombinant DNA = DNA created from multiple organisms
Genetic engineering has both benefits and risks Benefits of genetic engineering:
Increased nutritional content
Increased agricultural efficiency
Rapid growth
Disease and pest resistance
Negatives of genetic engineering: Risks are not yet defined or well understood
Protests from environmental activists, small farmers, and consumer advocates
Eating animal products has significant impacts As wealth and commerce increase, so does consumption of meat,
milk, and eggs
Global meat production has increased fivefold
Per capita meat consumption has doubled
Domestic animal production for food increased from 7.3
billion in 1961 to 20.6 billion in 2000
Energy choices through food choices 90% of energy is lost every time
energy moves from one trophic level to the next
The lower on the food chain from which we take our food sources, the more people the Earth can support.
Some animals convert grain
into meat more efficiently than others
Environmental ramifications of eating meat Land and water are needed to raise food for livestock
Producing eggs and chicken meat requires the least space and water Producing beef requires the most
When we choose what to eat, we also choose how we use resources
Organic agriculture
Organic agriculture = Uses no synthetic fertilizers, insecticides, fungicides, or herbicides Relies on biological approaches (composting and biocontrol)
People debate the meaning of the word “organic”
Organic Food Production Act (1990) establishes national standards for organic products
The USDA issued criteria in 2000 by which food could be labeled organic
Aquaculture
World fish populations are plummeting Technology and increased
demand
Aquaculture = raising aquatic organisms for food in a controlled environment Aquatic species are raised in
open-water pens or land-based ponds
The benefits and drawbacks of aquaculture
Benefits: A reliable protein source
Sustainable
Reduces fishing pressure on overharvested wild fish stocks
Energy efficient
Drawbacks: Diseases can occur, requiring
expensive antibiotics
Large amounts of waste
Farmed fish may escape and introduce disease into the wild
Government intervention The Soil Conservation Service
Started in 1935, the Service works with farmers to develop conservation plans for farms Assess the land
Prepare an integrated plan
Work closely with landowners
Implement conservation measures
Conservation districts = districts operate with federal direction, authorization, and funding, but are organized by the states
What can you do?
Eating to Save the Earth: Food Choices for a Healthy Planet by Linda Riebel and Ken Jacobsen
As a consumer, you can:
Use locally grown food, or grow your own! – uses less fuel for transportation
(Example: a single fast food meal comes from Texas (meat), Nebraska (corn to feed cow), Washington (cheese), California (lettuce and tomato), Idaho (wheat for bun and potatoes), Louisiana (salt), Pennsylvania (ketchup), Ohio (ketchup pouches), Arkansas (french fry box), Iowa (corn syrup for soft drink))
Buy organic – few or no pesticides or chemicals added
Go vegetarian (or nearly) – use little or no meat, dairy, eggs
Use less processed foods - stay close to the food’s natural state
Buy products with less packaging
Branch out and buy unusual products to support diversity
Consider purchasing products that support fair trade
Try not to waste food
Educate yourself and think critically
http://well.blogs.nytimes.com/2007/10/22/five-easy-ways-to-go-organic/?em&ex=1193544000&en=39941565969220ef&ei=5087%0A