cunningham - cunningham - saigo: environmental science 7 th ed. agriculture and food

Cunningham - Cunningham - Saigo: Environmental Science 7th Ed.

Agriculture and Food


Outline

• Nutrition and Food Supplies• Soil

Structure Erosion

• Agricultural Resources Water Energy

• Genetic Engineering• Sustainable Agriculture


Subsistence agricultureCommercial agriculture


NUTRITION AND FOOD SUPPLIES

• World food supplies have more than kept up with human population growth over the past two centuries. 1950 - 2.5 billion people - average daily

diet was less than 2,000 calories/person. 2001- 6.0 billion people - world food supply

can provide more than 2,500 calories/person.


Nutrition

• The most common dietary problem in wealthy countries is over-nutrition. In NA and Europe, average daily caloric

intake is 3,500 calories.• Sub-Saharan Africa has not kept food

production up to pace of population growth.• Collapse of Soviet Union also led to significant

collapse in food production.


Chronic Hunger and Food Security

• About 1 in 5 people in the developing world are considered chronically hungry. 200 million children

- Can lead to permanently stunted growth, mental retardation, and other developmental disorders.

Poverty is the greatest threat to food security (The ability to obtain sufficient food on a daily basis).


Chronic Hunger and Food Security


Essential Nutrients

• Malnourishment - Nutritional imbalance caused by a lack of specific dietary components. In poorer countries, people often cannot

afford to purchase an adequate variety of foods, including meats and vegetables.


Risk of Inadequate Nutrition


Famines

• Famines are characterized by large-scale food shortages, massive starvation, social disruption, and economic chaos. Mass migrations often occur because

productive capacity has been sacrificed. Environmental conditions are immediate

trigger, but politics and economics are often underlying problems.

- Arbitrary political boundaries block historic access to refuge areas.


Famines

• Aid policies of rich countries often serve to distribute surplus commodities and produce feeling of generosity. Food camps have serious drawbacks:

- Stress and crowding- Lack of sanitation- Close contact to epidemic diseases


MAJOR FOOD SOURCES

• Three crops deliver majority of world’s nutrients: Wheat, Rice and Corn

- Potatoes, barley, oats and rye are staples in cool, moist climates.

- Cassava, sweet potatoes, and other roots and tubers are staples in warm wet climates.


Meat and Milk

• Meat and Milk distribution highly inequitable. Core makes up 20% of world population,

but consumes 80% of meat and milk. 60% of production occurs in lesser

developed countries. 90% of grain grown in NA is used to feed

livestock.


Meat

• Every 16 kg of grain and soybeans fed to beef cattle in feedlots produce about 1 kg of edible beef. If we ate the grain directly, we would obtain

21x more calories and 8x more protein than we get from eating the beef.


Seafood

• Seafood is an important protein source.• Since 1989, 13/17 major fisheries have

declined or become commercially inviable.• Between 1970-1990, number and average

vessel size of world fishing fleet doubled. Now have twice the capacity needed to

extract total annual sustainable harvest.- Catching $70 billion cost $124 billion.

1/4 animals considered by-catch.


SOIL: A RENEWABLE RESOURCE

• Soil - A complex mixture of weathered minerals, partially decomposed organic materials, and a host of living organisms. At least 20,000 different soil types in the US.

- Vary due to influences of parent material, time, topography, climate, and organisms.

Can be replenished and renewed.


Ways we use and abuse soils

• Approximately 11% of the earth’s land area is currently in agricultural production. Up to four times as much could potentially

be converted to agricultural use.- Much of this additional land suffers from

constraints.


Soil Degradation


Land Resources

• In developed countries, 95% of recent agricultural growth has been from altered agricultural practices (pesticides - fertilizer). Less land cultivated in NA now than 100

years ago.• Many developing countries are reaching limit

of lands that can be exploited for agriculture without unacceptable social and environmental costs.


Land Degradation

• Estimated nearly 3 million ha of cropland ruined annually via erosion, 4 million ha transformed into deserts, and 8 million ha converted to non-agricultural uses.


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, or biodiversity is diminished.

- Water and wind are the driving forces for vast majority of soil degradation.


Land Degradation


Erosion• Erosion is an important 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.


Mechanisms of Erosion

• Rill Erosion - Small rivulets of running water gather together and cut small channels in the soil.

• Gully Erosion - Rills enlarge to form bigger channels too large to be removed by normal tillage.

• Streambank Erosion - Washing away of soil from established streambanks.


Mechanisms of Erosion

• Wind can equal or exceed water as an erosive force, especially in a dry climate and on flat land. Intensive farming practices:

- Row crops leave soil exposed- Weed free-fields- Removal of windbreaks- No crop-rotation or resting periods- Continued monocultures


CHEMICALINPUTS

Fertilizers

Pesticides

Fungicides

Herbicides(weed killers)


Fertilizer

• Lack of nitrogen, potassium, and phosphorus often limits plant growth. Adding nutrients via fertilizer usually

stimulates growth and increases crop yields.- 1950 - 90 Average of 20 to 91 kg/ha

fertilizer used. Manure and nitrogen-fixing bacteria are

alternative methods of replenishing soil nutrients.


Pesticide Problems

• Non-Target Species Up to 90% of pesticides never reach

intended target.• Pesticide Resistance

Resistant members of a population survive pesticide treatment and produce more resistant offspring.

- Pest Resurgence


Pesticide Resistance


Environmental Persistence and Mobility

• Many persistent organic pollutants were banned globally in 2001. Use was banned or restricted in

developing countries for years, but between 1994 and 1996, the US shipped more than 100,000 tons of DDT and POP’s annually.

- Many returned to US in agricultural products and migrating wildlife.


DDT pesticide effect on birds;U.S. recovery since ban

Still exported to Periphery


Human Health Problems

• WHO estimates between 3.5 and 5.0 million people suffer acute pesticide poisoning, and 20,000 die, each year. At least two-thirds resulting from

occupational hazards in developing countries.

Long-term health effects difficult to conclusively document.

- PCB’s have been linked to learning deficiencies in children.

Intake during mother’s pregnancy.


Alternatives to Pesticide Use

Crop Rotation Mechanical Cultivation Flooding Fields Habitat Diversification Growing in Pest-Free Zones Adjusting Planting Times Plant Mixed Polycultures


ENERGY

• Farming in industrialized countries is highly energy-intensive. Between 1920-1980, energy use rose

directly with mechanization of agriculture, and indirectly with spraying of chemicals.

Altogether, US food system consumes 16% of total energy use.

- Most foods require more energy to produce, process, and transport than we yield from them.


Energy


NEW CROPS AND GENETIC ENGINEERING

• Most of world food comes from 16 widely grown crops. At least 3,000 species of plants have been

used for food at some point in time.- Many new or unconventional varieties

might be valuable food supplies. Winged-bean Triscale


Green Revolution

• Most major improvements in farm production have come from technological advances and modification of a few well-known species. Corn yields jumped from 25 bushels per

acre to 130 per acre in last century.- Most of gain accomplished through

conventional plant breeding. Also seen rise of dwarf varieties.

• Green Revolution - Spread of new varieties around the world.


Green Revolution


“Green Revolution”benefits

• Core exports high-yield “miracle” seeds

• Needed oil-based fertilizers, pesticides

• Asian rice crop up 66% in 1965-85

• Favored areas with good soil, weather


“Green Revolution”


“Green Revolution”drawbacks

• Favored farmers who could afford seeds, inputs, machines, irrigation

• Indebted farmers lost land, moved to cities

• New “monocrops” lacked resistance to disease/pests

• Environmental contamination, erosion

• Oriented to export “cash crops,” not domestic food


Genetic Engineering

• Genetically Modified Organisms (GMO’s) Contain DNA possessing genes borrowed

from unrelated species.- Can produce crops with pest-resistance

and wider tolerance levels.- Opponents fear traits could spread to

wild varieties, and increased expense would largely hurt smaller farmers.

70% of all processed foods in NA contain transgenic products.


Genetic Engineering


Biotechnology: Using organisms to…

• Make or modify products

• Improve plants or animals

• Develop new microorganisms

• Crossing different species Genetic engineering


Genetically Modified Organisms (GMO)

Consumer concernsbegan in Europe,

now in U.S. too


Biotechnologybenefits in agriculture

• Increase yields

• Increase pest resistance

• Grow crops in new areas


Biotechnologydrawbacks in agriculture

• High costs (available to few)

• Monocrops have less tolerance to disease

• Possible health effects, contamination of crops

• Corporate patents on life forms


Bovine GrowthHormone (BGH)


Starlink corn


Monarch butterfliesand corn pollen

Possibleeffects of

Bt-modifiedcorn pollen


Cloning

First calf cloned inWisconsin, 1997.

Many clones dieof complications.

Ethical andeconomic conflicts


SUSTAINABLE AGRICULTURE

• Soil Conservation Managing Topography

- Contour Plowing - Plowing across slope to slow flow of water.

- Strip Farming - Planting different crops in alternating strips along land contours.

- Terracing - Shaping land to create level shelves of earth to hold water and soil.


Soil Conservation

• Providing Ground Cover Annual row crops cause highest rates of

erosion because they leave soil bare for much of the year.

- Leave crop residue after harvest.- Plant cover crops after harvest.


Soil Conservation

• Reduced Tillage Minimum Till - Chisel plow Conserv-Till - Coulter (Disc) No-Till - Drilling

• Often farmers using conservation tillage must depend relatively heavily on pesticides. Traditional tillage helped control weeds

and pests.


Summary

• Nutrition and Food Supplies• Major Food Sources• Soil

Structure Erosion

• Agricultural Resources Water Energy

• Genetic Engineering• Sustainable Agriculture

cunningham - cunningham - saigo: environmental science 7 th ed. agriculture and food

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