Chapter 14: Food & Soil Resources. T he three systems humans depend on for their food supply Croplands (77%) – land used for planting crops; vegetables, fruits, and grains Rangelands (16%)- Land used for grazing livestock; meat products
Croplands (77%) – land used for planting crops; vegetables, fruits, and grains
Rangelands (16%)- Land used for grazing livestock; meat products
Ocean fisheries (7%) - shellfish/fish (6% of protein in human diet)
Major increase in food production post-1950
9 billion humans by 2054
More food than has been produced in last 10k yrs
Is current technology capable?
Water supply (irrigation)
Ecological services (matter; energy)
3 grain crops that provide “more than ½ of the calories people consume”.
But 90% of all food only comes from
15 plants [esp. wheat, rice, corn] and
8 animals- [esp. beef, pork, chicken]
6 % protein
Traditional subsistence (20%, 44% pop.)
Low-input, human labor, "just enough"
Shifting cultivation; nomadic livestock
Higher input, "more than enough"
Monoculture cash crops (bananas, coffee, sugarcane, etc)
25% of all cropland, developed nations
Intensive traditional agriculture
Fig. 12.2, p. 263
increased production of food per unit of area of cropland; planting monocultures, increase use of pesticides, water, fertilizers, etc.
Age of Genetic Engineering
genetic engineering (GMO’s)
high energy input (8% world oil)
fertilizers, pesticides, water
dwarf varieties- 3-5x yield
Farm more land =
Increase crop yield / land area
Intensified agriculture meant monocultures, vast spreads of a single crop.
This is economically efficient, but increases risk of catastrophic failure (“all eggs in one basket”).
Wheat monoculture in Washington
Intensification of agriculture causes environmental harm:
Pollution from synthetic fertilizers
Pollution from synthetic pesticides
Water depleted for irrigation
Fossil fuels used for heavy equipment
However, without the green revolution, much more land would have been converted for agriculture, destroying forests, wetlands, and other ecosystems.
First green revolution
Major International agricultural
research centers and seed banks
Since1940’s: 2x production on the same amount of land
Agribusiness- big companies and large family farms own 75% of US food production
- 2% pop.= farmers; 9% pop.= involve in production
- Agriculture provides18% US GNP; 19% jobs (private sect); 0.3% world's labor
- 17% of world’s grain is produced in the US; ½ the world’s corn & soybean exports
Types of interplanting-
Advantages include: < energy input, erosion/weather protection, pest/herbicides not needed
Causes: water, wind, and people
Most soil degradation is caused by:
• livestock overgrazing
• cropland agriculture
A loss of more than 10% productivity due to:
• Soil compaction
• Forest removal
• Climate change
• Depletion of water resources
When severe, there is expansion of desert areas, or creation of new ones, e.g., the Middle East, formerly, “Fertile Crescent”.
Drought and degraded farmland produced the 1930s Dust Bowl.
Storms brought dust from the U.S. Great Plains all the way to New York and Washington, and wrecked many lives.
Several farming strategies to prevent soil degradation:
• Crop rotation
• Contour farming
• Conservation tillage
As a result of the Dust Bowl, the U.S. Soil Conservation Act of 1935 and the Soil Conservation Service (SCS) were created.
SCS:Local agents in conservation districtsworked with farmers to disseminate scientific knowledge and help them conserve their soil.
Alternating the crop planted (e.g., between corn and soybeans) can restore nutrients to soil and fight pests and disease.
Planting along contour lines of slopes helps reduce erosion on hillsides.
Mixing crops such as in strip cropping can provide nutrients and reduce erosion.
Cutting stairsteps or terraces is the only way to farm extremely steep hillsides without causing massive erosion. It is labor-intensive to create, but has been a mainstay for centuries in the Himalayas and the Andes.
Rows of fast-growing trees around crop plantings provide windbreaks, reducing erosion by wind.
Conservation tillage is not a solution for all crops everywhere.
No-till and reduced-tillage farming leaves old crop residue on the ground instead of plowing it into soil. This covers the soil, keeping it in place.
Here, corn grows up out of a “cover crop.”
But legume cover crops can keep weeds at bay while nourishing soil, and green manures can be used as organic fertilizers.
herbicide use for
Leaves stalks that
can harbor crop
pests and fungal
Holds more soil
Allows several crops
Does not reduce
release from soil
Southern Brazil’s farmers were suffering falling yields, erosion, and pollution from agrichemicals.
They turned to no-till farming, which bypasses plowing.
Erosion was reduced, soils were enhanced, and yields rose greatly. No-till methods are spreading worldwide.
The artificial provision of water to support agriculture
70% of all freshwater used by humans is used for irrigation.
Irrigated land globally covers more area than all of Mexico and Central America combined.
Irrigation has boosted productivity in many places … but too much can cause problems.
Overirrigation can raise the water table high enough to suffocate plant roots with waterlogging.
Salinization(buildup of salts in surface soil layers) is a more widespread problem. Salt in soils decreases the osmotic potential of the soil so that plants can't take up water from it. The salts can also be directly toxic, but plant troubles usually result primarily from inability to take up water from salty soils
Evaporation in arid areas draws water up through the soil, bringing salts with it. Irrigation causes repeated evaporation, bringing more salts up.
Not growing crops
for 2-5 years
Switch to salt-
(such as barley,
cotton, sugar beet)
Fertilizer use has risen dramatically in the past 50 years.
Inorganic Commercial Fertilizers
Easy to transport
Easy to store
Easy to apply
Inexpensive to produce
Help feed one of every
three people in the
world food output could
drop by 40%
Do not add humus to soil
Reduce organic matter
Reduce ability of soil to
Lower oxygen content of
Require large amounts of
energy to produce,
transport, and apply
Release the greenhouse
gas nitrous oxide (N2O)
Runoff can overfertilize
nearby lakes and kill fish
When livestock eat too much plant cover on rangelands, impeding plant regrowth.
The contrast between ungrazed and overgrazed land on either side of a fenceline can be striking.
Overgrazing can set in motion a series of positive feedback loops.
World agricultural production has risen faster than human population.
However, the world still has 800 million hungry people, largely due to inadequate distribution.
Considering soil degradation, can we count on food production continuing to rise?
Global food security is a goal of scientists and policymakers worldwide.
too few calories (especially developing countries)
too many calories (especially developed world)
Malnutrition = lack of nutritional requirements
(causes numerous diseases, esp. in developing world)
~ 1 in 6 people in developing nations are chronically undernourished or malnourished
Common nutritional deficiency diseases:
Marasmus and Kwashiorkor
M = diet low in calories and protein
K = severe protein deficiency
Fig. 12.9, p. 269
Loss and degradation of habitat from
clearing grasslands and forests and
Fish kills from pesticide runoff
Killing of wild predators to protect
Loss of genetic diversity from
replacing thousands of wild crop
strains with a few monoculture strains
Loss of fertility
Increased runoff and
flooding from land cleared
to grow crops
Sediment pollution from
Fish kills from pesticide
Greenhouse gas emissions from fossil
Other air pollutants from fossil fuel use
Pollution from pesticide sprays
Surface and groundwater
pollution from pesticides
Overfertilization of lakes
and slow-moving rivers
from runoff of nitrates
and phosphates from
wastes, and food
Nitrates in drinking water
Pesticide residues in drinking water,
food, and air
Contamination of drinking and
swimming water with disease
organisms from livestock wastes
Bacterial contamination of meat
Pesticide use is still rising sharply across the world, although growth has slowed in the U.S.
1 billion kg (2 billion lbs.) of pesticides are applied each year in the U.S.
Synthetic chemicals can pollute and be health hazards.
Biological control (biocontrol) avoids this.
Biocontol entails battling pests and weeds with other organisms that are natural enemies of those pests and weeds.
(“The enemy of my enemy is my friend.”)
Biocontrol has had success stories.
Bacillus thuringiensis (Bt) = soil bacterium that kills many insects. In many cases, seemingly safe and effective.
Cactus moth, Cactoblastis cactorum (above), was used to wipe out invasive prickly pear cactus in Australia.
Most biocontrol agents are introduced from elsewhere.
Some may turn invasive and become pests themselves!
Cactus moths brought to the Caribbean jumped to Florida, are eating native cacti, and spreading.
Wasps and flies brought to Hawaii to control crop pests are parasitizing native caterpillars in wilderness areas.
Combines biocontrol, chemical, and other methods
• Close population monitoring
• Habitat modification
• Crop rotation
• Transgenic crops
• Alternative tillage
• Mechanical pest removal
Manipulating and engineering genetic material in the lab may represent the best hope for increasing agricultural production further without destroying more natural lands.
But many people remain uneasy about genetically engineering crop plants and other organisms.
Golden rice: Enriched with vitamin A.
But too much hype?
FlavrSavr tomato: Better taste?
But pulled from market.
Ice-minus strawberries: Frost-resistant bacteria sprayed on.
Images alarmed public.
Bt crops: Widely used on U.S. crops.
But ecological concerns?
Are there health risks for people?
Can transgenes escape into wild plants, pollute ecosystems, harm organisms?
Can pests evolve resistance to GM crops just as they can to pesticides?
Can transgenes jump from crops to weeds and make them into “superweeds”?
Can transgenes get into traditional native crop races and ruin their integrity?
Should scientists and corporations be “tinkering with” our food supply?
Are biotech corporations testing their products adequately, and is outside oversight adequate?
Should large multinational corporations exercise power over global agriculture and small farmers?
Europe:has followed precautionary principle in approach to GM foods. Governments have listened to popular opposition among their citizens.
U.S.:GM foods were introduced and accepted with relatively little public debate.
Relations over agricultural trade have been uneasy, and it remains to be seen whether Europe will accept more GM foods from the U.S.
Genetically Modified Food and Crops
Need less fertilizer
Need less water
More resistant to insects,
plant disease, frost, and
Can grow in slightly salty
Less use of conventional
Tolerate higher levels of
and ecological effects
Harmful toxins in food
From possible plant cell
New allergens in food
Increased evolution of
Insects and plant
Creation of herbicide-
Harm beneficial insects
Lower genetic diversity
Native cultivars of crops are important to preserve, in case we need their genes to overcome future pests or pathogens.
Diversity of cultivars has been rapidly disappearing from all crops throughout the world.
Seed banks are living museums of crop diversity, saving collections of seeds and growing them into plants every few years to renew the collection.
Careful hand pollination helps ensure plants of one type do not interbreed with plants of another.
Consumption of meat has risen faster than population over the past several decades.
Increased meat consumption has led to animals being raised in feedlots (factory farms), huge pens that deliver energy-rich food to animals housed at extremely high densities.
Immense amount of waste produced, polluting air and water nearby
Intense usage of chemicals (antibiotics, steroids, hormones), some of which persist in environment
However, if all these animals were grazing on rangeland, how much more natural land would be converted for agriculture?
Energy is lost at each trophic level.
When we eat meat from a cow fed on grain, most of the grain’s energy has already been spent on the cow’s metabolism.
Eating meat is therefore very energy inefficient. - Hence, the “Eating Green” Challenge! Feb. 28- March 7
Some animal food products can be produced with less input of grain feed than others.
Some animal food products can be produced with less input of land and water than others.
The raising of aquatic organisms for food in controlled environments
Provides 1/3 of world’s fish for consumption
220 species being farmed
The fastest growing type of food production
Provides reliable protein source for people, increases food security
Can be small-scale, local, and sustainable
Reduces fishing pressure on wild stocks, and eliminates bycatch
Uses fewer fossil fuels than fishing
Can be very energy efficient
Density of animals leads to disease, antibiotic use, risks to food security.
It can generate large amounts of waste.
Often animals are fed grain, which is not energy efficient.
Sometimes animals are fed fish meal from wild-caught fish.
Farmed animals may escape into the wild and interbreed with, compete with, or spread disease to wild animals.
Transgenic salmon (top) can compete with or spread disease to wild salmon (bottom) when they escape from fish farms.
3 methods used to catch fish:
High yield in small
volume of water
breeding and genetic
Can reduce over-
Little use of fuel
Profit not tied to price
Large inputs of land, feed,
And water needed
Produces large and
concentrated outputs of
Destroys mangrove forests
Increased grain production
needed to feed some
Fish can be killed by
pesticide runoff from
vulnerable to disease
Tanks too contaminated to
use after about 5 years
More Sustainable Aquaculture
Agriculture that can practiced the same way far into the future
Does not deplete soils faster than they form
Does not reduce healthy soil, clean water, and genetic diversity essential for long-term crop and livestock production
Low-input agriculture= small amounts of pesticides, fertilizers, water, growth hormones, fossil fuel energy, etc.
Organic agriculture= no synthetic chemicals used. Instead, biocontrol, composting, etc.
Small percent of market, but is growing fast
1% of U.S. market, but growing 20%/yr
3–5% of European market, but growing 30%/yr
Advantages for consumers: healthier; environmentally better
Disadvantages for consumers: less uniform and appealing-looking; more expensive
Chemical pesticides pollute, and kill pollinators, and pests evolve resistance.
GM crops show promise for social and environmental benefits, but questions linger about their impacts.
Much of the world’s crop diversity has vanished.
Feedlot agriculture and aquaculture pose benefits and harm for the environment and human health.
Organic farming remains a small portion of agriculture.
Human population continues to grow, requiring more food production.
Soil erosion is a problem worldwide.
Salinization, waterlogging, and other soil degradation problems are leading to desertification.
Grazing and logging, as well as cropland agriculture, contribute to soil degradation.
Biocontrol and IPM offer alternatives to pesticides.
Further research and experience with GM crops may eventually resolve questions about impacts, and allow us to maximize benefits while minimizing harm.
More funding for seed banks can rebuild crop diversity.
Ways are being developed to make feedlot agriculture and aquaculture safer and cleaner.
Organic farming is popular and growing fast.
Green revolution advances have kept up with food demand so far. Improved distribution and slowed population growth would help further.
Farming strategies like no-till farming, contour farming, terracing, etc., help control erosion.
Government laws, and government extension agents working with farmers, have helped improve farming practices and control soil degradation.
Better grazing and logging practices exist that have far less impact on soils.
Loss of prime
Subsidies for unsustainable
farming and fishing
Biological pest control
Use of more water-
Subsidies for more sustainable farming and
Integrated pest management may involve all of the following EXCEPT… ?
a. Close population monitoring
c. Exclusive reliance on pesticides
d. Habitat modification
e. Transgenic crops
What do seed banks do?
a. Lend money to farmers to buy seeds
b. Pay farmers to store seeds
c. Buy seeds from farmers
d. Store seeds to maintain genetic diversity
e. None of the above
Which is NOT a benefit of aquaculture?
a. Provides a reliable protein source
b. Reduces pressure on natural fisheries
c. Produces no waste
d. Uses fewer fossil fuels than commercial fishing
e. All of the above are benefits
Can we call the green revolution a success?
a. A huge success; it has saved millions from starvation because it increased food production to keep pace with population growth.
b. Not a success; its environmental impacts have outweighed its claimed benefits.
c. A success; its environmental impacts are balanced by the fact that it saved huge areas from deforestation.
With 500 kg of water, you could produce … ?
a. 2 kg of protein from milk
b. Protein from 50 chickens
c. 750 kg of protein from beef
d. 15 eggs
Should we encourage the continued development of GM foods?
a. Yes; they will bring many health, social, and environmental benefits.
b. No, we should adopt the precautionary principle, and not introduce novel things until we know they are safe.
c. Yes, but we should proceed cautiously, and consider each new crop separately.
Which statement is NOT correct?
a. Soil consists of disintegrated rock, organic matter, nutrients, and microorganisms.
b. Healthy soil is vital for agriculture.
c. Soil is somewhat renewable.
d. Soil is lifeless dirt.
e. Much of the world’s soil has been degraded.
The A horizon in a soil profile… ?
a. Is often called the “zone of accumulation.”
b. Is often called “topsoil.”
c. Contains mostly organic matter.
d. Is the lowest horizon, deepest underground.
Erosion occurs through… ?
b. Excessive plowing.
c. Overgrazing rangelands.
d. Two of the above.
e. All of the above.
Drip irrigation differs from conventional irrigation in that … ?
a. It is much less efficient.
b. It can cause salinization.
c. Water is precisely targeted to plants.
d. About 40% is wasted.
You are farming an extremely steep slope that is sunny and very windy. What strategies would you consider using?
a. Crop rotation
b. Contour farming
f. No-till farming
Grain produced per person has… ?
a. Risen steadily
b. Fallen sharply
c. Increased since 1983
d. Decreased since 1983