Soils, agriculture, and
the future of food
6
erosion
Key Words feedlots
fertilizer
food security
A horizon
genetic engineering
agriculture
genetically modified
aquaculture
(GM) organisms
B horizon
green revolution
bedrock
gully erosion
biocontrol
horizon
biological control
humus
biotechnology
industrialized
C horizon
agriculture
conservation tillage
inorganic fertilizers
contour farming
conventional irrigation integrated pest
management (IPM)
crop rotation
irrigation
croplands
leaching
deposition
low input agriculture
desertification
monoculture
drip irrigation
no-till agriculture
Dust Bowl
O horizon
E horizon
organic agriculture
organic fertilizers
overgrazing
parent material
pesticides
pollination
precautionary principle
R horizon
rangelands
rill erosion
traditional agriculture
salinization
transgenic
seed banks
waterlogged
sheet erosion
weathering
shelterbelts
soil
soil profile
splash erosion
strip cropping
sustainable agriculture
terracing
topsoil
Objectives
• Soil science fundamentals
• Soil erosion and
degradation
• Soil conservation policies
• Pest management and
pollination
• Genetically modified food
and preserving crop
diversity
• Feedlot agriculture and
Aquaculture
• Organic agriculture
Central Case: No-Till Agriculture in Brazil
• 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.
Agriculture today
We have converted 38% of Earth’s surface for agriculture,
the practice of cultivating soil, producing crops, and raising
livestock for human use and consumption.
Croplands (for growing plant crops) and rangelands (for
grazing animal livestock) depend on healthy soil.
Natural Capital
Croplands
Croplands
Ecological
Services
Ecological Services
•Help maintain water flow and
• Help
maintain water
soil infiltration
Economic
Services
Economic Services
•Food crops
• Food crops
flow and soil infiltration
protection
• •Provide
Provide partial
partialerosion
erosion
protection
•Can build soil organic matter
• Can build soil organic
matter
•Store atmospheric carbon
• Store atmospheric
carbon
•Provide wildlife habitat for some
species
• Provide wildlife habitat
for some species
• Fiber crops
•Fiber crops
• Crop genetic
resources
•Crop genetic
• Jobsresources
•Jobs
Soil as a system
Parent material, such as bedrock, is weathered to begin
process of soil formation.
Parent material = the base geological material in a
location
Bedrock = the continuous mass of solid rock that makes
up Earth’s crust
Weathering = processes that break down rocks
World soil conditions
Soils are becoming degraded in many regions.
Figure 8.1a
Soil degradation by continent
Europe’s land is
most degraded
because of its long
history of intensive
agriculture.
But Asia’s and
Africa’s soils are
fast becoming
degraded.
Figure 8.1b
Causes of soil degradation
Most soil degradation is
caused by:
• livestock
overgrazing
• deforestation
• cropland
agriculture.
Figure 8.2
Components of soil
Soil is a complex mixture of
organic and inorganic
components and living
organisms.
Humus
Dark, crumbly mass of undifferentiated material made up of
complex organic compounds
Soils with high humus content
hold moisture better and
are more productive for plant life.
Soil profile
Consists of layers called
horizons.
Simplest:
A = topsoil
B = subsoil
C = parent material
But most have O, A, E,
B, C, and R
Figure 8.8
Soil profile
O Horizon: Organic or litter layer
A Horizon: Topsoil. Mostly inorganic minerals with some
organic material and humus mixed in. Crucial for plant
growth
E Horizon: Eluviation horizon; loss of minerals by leaching,
a process whereby solid materials are dissolved and
transported away
B Horizon: Subsoil. Zone of accumulation or deposition of
leached minerals and organic acids from above
C Horizon: Slightly altered parent material
R Horizon: Bedrock
Soil characterization
Soil can be characterized by color and several other traits:
Texture (percentage sand, silt, clay)
Structure
Porosity
Cation exchange capacity
pH
Parent Material
Infiltration rate
Nutrient concentrations
Best for plant growth is loam, an even mix of sand, silt
and clay.
Erosion and deposition
Erosion = removal of material from one place and
its transport elsewhere
by wind
or water
Deposition = arrival of eroded material at a new
location
These processes are natural, and can build up fertile soil.
But where artificially sped up, they are a big problem for
farming.
Erosion and Deposition
Sand dunes around Moses Lake are all that are left of the
wind erosion in that area. The smaller particles, silt and clay
were blown eastward toward the Palouse. The deposition of
the silt and clay particles led to the formation of the Palouse
Hills. The Palouse Hills are a wind/water erosional surface.
Erosion
Commonly caused by:
• Overcultivating, too much plowing, poor planning
• Overgrazing rangeland with livestock
• Deforestation, especially on slopes
Types of soil erosion
Splash
erosion
Rill erosion
Sheet erosion
Gully
erosion
Figure 8.11
Erosion: A global problem
Over 19 billion ha (47 billion acres) suffer from erosion or
other soil degradation.
Mississippi River…to thin to plow to thick to drink (Sam
Clemens)
Desertification
A loss of more than 10% productivity due to:
• Erosion
• Soil compaction
• Forest removal
• Overgrazing
• Drought
• Salinization
• Climate change
• Depletion of water resources
• etc.
When severe,
there is expansion
of desert areas, or
creation of new
ones, e.g., the
Middle East,
formerly, “Fertile
Crescent”.
The Dust Bowl
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.
Figure 8.14
Kansas
Colorado
Dust
Bowl
Oklahoma
New Mexico
Texas
MEXICO
Causes
Consequences
Overgrazing
Worsening drought
Deforestation
Famine
Erosion
Economic losses
Salinization
Lower living
standards
Soil compaction
Natural climate
change
Environmental
refugees
Soil conservation
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 districts worked with
farmers to disseminate scientific knowledge and help them
conserve their soil.
Preventing soil degradation
Several farming strategies to prevent soil degradation:
• Crop rotation
• Contour farming
• Intercropping
• Terracing
• Shelterbelts
• Conservation tillage
Crop rotation
Alternating the crop planted (e.g., between corn and
soybeans) can restore nutrients to soil and fight pests and
disease.
Figure 8.16a
Contour farming
Planting along contour lines of slopes helps reduce erosion
on hillsides.
Figure 8.16b
Intercropping
Mixing crops such as in strip cropping can provide nutrients
and reduce erosion.
Figure 8.16c
(c) Alley cropping
Terracing
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.
Figure 8.16d
Shelterbelts
Rows of fast-growing trees around crop plantings provide
windbreaks, reducing erosion by wind.
Figure 8.16e
Conservation tillage
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.”
Figure 8.16f
Conservation tillage
Conservation tillage is not a panacea for all crops
everywhere.
It often requires more chemical herbicides (because
weeds are not plowed under).
It often requires more fertilizer (because other plants
compete with crops for nutrients).
But legume cover crops can keep weeds at bay while
nourishing soil, and green manures can be used as
organic fertilizers.
Trade-Offs
Conservation Tillage
Advantages
Reduces erosion
Saves fuel
Disadvantages
Can increase
herbicide use for
some crops
Cuts costs
Holds more soil
water
Reduces soil
compaction
Allows several crops
per season
Does not reduce
crop yields
Reduces CO2
release from soil
Leaves stalks that
can harbor crop
pests and fungal
diseases and
increase pesticide
use
Requires
investment
in expensive
equipment
Irrigation
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.
Waterlogging and salinization
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.
Evaporation in arid areas draws water up through the soil,
bringing salts with it. Irrigation causes repeated
evaporation, bringing more salts up.
Improved irrigation
In conventional irrigation,
only 40% of the water
reaches plants.
Efficient drip irrigation
targeted to plants conserves
water, saves money, and
reduces problems like
salinization.
Figure 8.17
Solutions
Soil Salinization
Prevention
Reduce irrigation
Cleanup
Flushing soil
(expensive and
wastes water)
Not growing crops
for 2-5 years
Switch to salttolerant crops
(such as barley,
cotton, sugar beet)
Installing underground drainage
systems (expensive)
Fertilizers
Supply nutrients to
crops
Inorganic fertilizers =
mined or synthetically
manufactured mineral
supplements
Organic fertilizers =
animal manure, crop
residues, compost, etc.
Figure 8.18
Global fertilizer usages
Fertilizer use has risen dramatically in the past 50 years.
Figure 8.19b
Trade-Offs
Inorganic Commercial Fertilizers
Advantages
Disadvantages
Easy to transport
Do not add humus to soil
Easy to store
Reduce organic matter
in soil
Easy to apply
Reduce ability of soil to
hold water
Inexpensive to produce
Lower oxygen content of
soil
Help feed one of every
three people in the
world
Require large amounts of
energy to produce,
transport, and apply
Release the greenhouse
gas nitrous oxide (N2O)
Without commercial
inorganic fertilizers,
world food output could
drop by 40%
Runoff can overfertilize
nearby lakes and kill fish
Overgrazing
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.
Figure 8.22
Overgrazing
Overgrazing can set in motion a series of positive feedback
loops.
Figure 8.21
Recent soil conservation laws
The U.S. has continued to pass soil conservation legislation
in recent years:
• Food Security Act of 1985
• Conservation Reserve Program, 1985
• Freedom to Farm Act, 1996
• Low-Input Sustainable Agriculture Program, 1998
Internationally, there is the UN’s “FAR” program in Asia.
Global food production
World agricultural production has risen faster than human
population.
Figure 9.1
Global food security
However, the world still has 800 million hungry people,
largely due to inadequate distribution.
And considering soil degradation, can we count on food
production continuing to rise?
Global food security is a goal of scientists and
policymakers worldwide.
Nutrition
Undernourishment =
too few calories
(especially developing world)
Overnutrition =
too many calories
(especially developed world)
Malnutrition = lack of
nutritional requirements
(causes numerous diseases, esp.
in developing world)
Figure 9.2
The green revolution
An intensification of industrialization of agriculture, which
has produced large yield increases since 1950
Increased yield per unit of land farmed
Begun in U.S. and other developed nations; exported to
developing nations like India and those in Africa
are more productive for plant life.
Transgenic contamination?
UC Berkeley researchers Ignacio Chapela (L) and David Quist
(R) ignited controversy by claiming contamination of Mexican
maize.
They later admitted some flaws in their methods, but debate
continued, revealing the personal and political pressures of highstakes scientific research.
From The Science behind the Stories
Monocultures
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
Figure 9.4a
Crop diversity
Monocultures also have reduced crop diversity.
90% of all human food now comes from only 15 crop
species and 8 livestock species.
Biodiversity Loss
Loss and degradation of habitat from
clearing grasslands and forests and
draining wetland
Fish kills from pesticide runoff
Killing of wild predators to protect
livestock
Loss of genetic diversity from
replacing thousands of wild crop
strains with a few monoculture strains
Soil
Erosion
Loss of fertility
Salinization
Waterlogging
Desertification
Air Pollution
Greenhouse gas emissions from fossil
Fuel issue
Other air pollutants from fossil fuel use
Pollution from pesticide sprays
Water
Water waste
Aquifer depletion
Surface and groundwater
pollution from pesticides
and fertilizers
Increased runoff and
Overfertilization of lakes
flooding from land cleared and slow-moving rivers
to grow crops
from runoff of nitrates
and phosphates from
Sediment pollution from
fertilizers, livestock
erosion
wastes, and food
processing wastes
Fish kills from pesticide
runoff
Human Health
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
The green revolution
Techniques to increase crop output per unit area of
cultivated land (since world was running out of arable land)
Technology transfer to developed world in 1940s-80s:
Norman Borlaug began in Mexico, then India.
Special crop breeds (drought-tolerant, salt-tolerant, etc.) are
a key component.
It enabled food production to keep pace with population.
Green revolution: Environmental impacts
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.
Grain production
(millions of tons)
2,000
1,500
1,000
500
0
1950
1960
1970
1980
1990
Year
Total World Grain Production
2000
2010
Feeding the world
In 1983, the
amount of grain
produced per
capita leveled off
and began to
decline.
Figure 8.3
Pest management
Terms pest and weed have no scientific or objective
definitions.
Any organism that does something we humans don’t like
gets called a pest or a weed.
The organisms are simply trying to survive and reproduce…
and a monoculture is an irresistible smorgasbord of food for
them.
Chemical pesticides
Synthetic poisons that target organisms judged to be pests
Pesticide use
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.
Figure 9.5
Pests evolve resistance to pesticides
Pesticides gradually become less effective, because pests
evolve resistance to them.
Those few pests that survive pesticide applications because
they happen to be genetically immune will be the ones that
reproduce and pass on their genes to the next generation.
This is evolution by natural selection, and it threatens our
very food supply.
Pests evolve resistance to pesticides
1. Pests attack crop
2. Pesticide applied
Figure 9.6
Pests evolve resistance to pesticides
3. All pests except a few
with innate resistance
are killed
4. Survivors breed
and produce
pesticide-resistant
population
Figure 9.6
Pests evolve resistance to pesticides
5. Pesticide applied again
6. Has little effect.
More-toxic chemicals
must be developed.
Figure 9.6
Biological control
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.”)
Biological control
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.
Figure 9.7
But biocontrol is risky
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.
Integrated pest management (IPM)
Combines biocontrol, chemical, and other methods
May involve:
• Biocontrol
• Pesticides
• Close population monitoring
• Habitat modification
• Crop rotation
• Transgenic crops
• Alternative tillage
• Mechanical pest removal
Pollination
Process of plant reproduction: male pollen meets female sex
cells
In many plants, animals transfer pollen to pollinate female
plants, in mutualistic interaction to obtain nectar or pollen.
Honeybee pollinating
apple blossom
Figure 9.9
Genetic modification of food
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.
Genetic engineering uses recombinant DNA
Genetic engineering (GE) = directly manipulating an
organism’s genetic material in the lab by adding, deleting,
or changing segments of its DNA
Genetically modified (GM) organisms = genetically
engineered using recombinant DNA technology
Recombinant DNA = DNA patched together from DNA of
multiple organisms (e.g., adding disease-resistance genes
from one plant to the genes of another)
Transgenes and biotechnology
Genes moved between organisms are transgenes, and the
organisms are transgenic.
These efforts are one type of biotechnology, the material
application of biological science to create products derived
from organisms.
Genetic engineering vs. traditional breeding
They are similar:
We have been altering crop
genes (by artificial
selection) for thousands of
years.
There is no fundamental
difference: both approaches
modify organisms
genetically.
They are different:
GE can mix genes of very
different species.
GE is in vitro lab work, not
with whole organisms.
GE uses novel gene
combinations that didn’t
come together on their own.
Some GM foods
Golden rice:
Enriched with
vitamin A.
But too much
hype?
Ice-minus strawberries: Frostresistant bacteria sprayed on.
Images alarmed public.
FlavrSavr tomato:
Better taste?
But pulled from market.
Bt crops:
Widely used on
U.S. crops.
But ecological
concerns?
Figure 9.12
Some GM foods
Bt sunflowers:
Insect resistant.
But could hybridize
with wild relatives to
create “superweeds”?
Roundup-Ready crops:
Resistant to Monsanto’s
herbicide. But encourages
more herbicide use?
StarLink corn: Bt corn
variety.
Genes spread to non-GM
corn; pulled from market.
Terminator seeds:
Plants kill their own
seeds. Farmers
forced to buy seeds
each year.
Figure 9.12
Transferring Genes Into Plants
Transferring genes into plants.
Click to view
animation.
Prevalence of GM foods
Although many early GM crops ran into bad publicity or
other problems, biotechnology is already transforming the
U.S. food supply.
Two-thirds of U.S. soybeans, corn, and cotton are now
genetically modified strains.
Prevalence of GM foods
Nearly 6 million farmers in 16 nations plant GM crops.
But most are grown
by 4 nations.
The U.S. grows
66% of the world’s
GM crops.
number of
plantings have
grown >10%/year
Figure 9.13
Scientific concerns about GM organisms
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?
Scientific concerns about GM organisms
These questions are not fully answered yet.
In the meantime…
Should we not worry,
because so many U.S.
crops are already GM
and little drastic harm is
apparent?
Or should we adopt the
precautionary principle,
the idea that one should
take no new action until
its ramifications are
understood?
Socioeconomic and political concerns about
GM products
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 vs. America
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.
Trade-Offs
Genetically Modified Food and Crops
Projected
Advantages
Need less fertilizer
Need less water
More resistant to insects,
plant disease, frost, and
drought
Projected
Disadvantages
Irreversible and
unpredictable genetic
and ecological effects
Harmful toxins in food
From possible plant
cell
Mutations
Faster growth
New allergens in food
Can grow in slightly salty
soils
Less spoilage
Better flavor
Less use of conventional
pesticides
Lower nutrition
Increased evolution of
Pesticide-resistant
Insects and plant
disease
Creation of herbicideResistant weeds
Tolerate higher levels of
pesticide use
Harm beneficial insects
Higher yields
Lower genetic diversity
Viewpoints: Genetically modified foods
Indra
Vasil
“Biotech crops are already
helping to conserve valuable
natural resources, reduce the
use of harmful agrochemicals, produce more
nutritious foods, and
promote economic
development.”
Ignacio
Chapela
“We should expect
fundamental alterations in
ecosystems with the
release of transgenic
crops… We are
experiencing a global
experiment without
controls.”
From Viewpoints
Preserving crop 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 preserve seeds, crop varieties
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.
Figure 9.14
Animal agriculture: Livestock and poultry
Consumption of meat has risen faster than population over
the past several decades.
Figure 9.15
Feedlot agriculture
Increased meat consumption has led to animals being raised
in feedlots (factory farms), huge pens that deliver energyrich food to animals housed at extremely high densities.
Figure 9.16
Feedlot agriculture: Environmental impacts
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?
Food choices = energy choices
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.
Grain feed input for animal output
Some animal food
products can be
produced with less
input of grain feed
than others.
Figure 9.17
Land and water input for animal output
Some animal food
products can be
produced with less
input of land and
water than others.
Figure 9.18
Aquaculture
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
Aquaculture
Fish make up half of
aquacultural production.
Molluscs and plants each
make up nearly 1/4.
Global aquaculture has
been doubling about every 7
years.
Figure 9.19
Benefits of aquaculture
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
Environmental impacts of aquaculture
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.
Environmental impacts of aquaculture
Transgenic salmon (top) can compete with or spread
disease to wild salmon (bottom) when they escape from fish
farms.
Figure 9.20
Trade-Offs
Aquaculture
Advantages
Highly efficient
High yield in small
volume of water
Increased yields
through crossbreeding and genetic
engineering
Can reduce overharvesting of
conventional fisheries
Little use of fuel
Profit not tied to price
of oil
Disadvantages
Large inputs of land, feed,
And water needed
Produces large and
concentrated outputs of
waste
Destroys mangrove forests
Increased grain production
needed to feed some
species
Fish can be killed by
pesticide runoff from
nearby cropland
Dense populations
vulnerable to disease
High profits
Tanks too contaminated to
use after about 5 years
Solutions
More Sustainable Aquaculture
• Reduce use of fishmeal as a feed to reduce depletion of
other fish
• Improve pollution management of aquaculture wastes
• Reduce escape of aquaculture species into the wild
• Restrict location of fish farms to reduce loss of mangrove
forests and other threatened areas
• Farm some aquaculture species (such as salmon and
cobia) in deeply submerged cages to protect them from
wave action and predators and allow dilution of wastes
into the ocean
• Set up a system for certifying sustainable forms of
aquaculture
Sustainable agriculture
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.
Organic farming
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
Organic produce:
Advantages for consumers: healthier; environmentally
better
Disadvantages for consumers: less uniform and appealinglooking; more expensive
Conclusions: Challenges
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.
Conclusions: Challenges
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.
Conclusions: Solutions
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.
Conclusions: Solutions
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.
Solutions
Sustainable Agriculture
Increase
Decrease
High-yield polyculture
Soil erosion
Organic fertilizers
Soil salinization
Biological pest control
Aquifer depletion
Integrated pest
management
Overgrazing
Overfishing
Irrigation efficiency
Perennial crops
Loss of
biodiversity
Crop rotation
Loss of prime
cropland
Use of more waterefficient crops
Food waste
Soil conservation
Subsidies for unsustainable
farming and fishing
Subsidies for more
sustainable farming and
fishing
Population growth
Poverty
What Can You Do?
Sustainable Agriculture
•Waste les food
•Reduce or eliminate meat consumption
•Feed pets balanced grain foods instead of meat
•Use organic farming to grow some of your food
•Buy organic food
•Compost your food wastes
QUESTION: Review
Integrated pest management may involve all of the
following EXCEPT… ?
a. Close population monitoring
b. Biocontrol
c. Exclusive reliance on pesticides
d. Habitat modification
e. Transgenic crops
QUESTION: Review
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
QUESTION: Review
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
QUESTION: Weighing the Issues
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.
QUESTION: Interpreting Graphs and Data
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
Figure 9.18b
QUESTION: Viewpoints
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.
QUESTION: Review
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.
QUESTION: Review
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.
QUESTION: Review
Erosion occurs through… ?
a. Deforestation.
b. Excessive plowing.
c. Overgrazing rangelands.
d. Two of the above.
e. All of the above.
QUESTION: Review
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.
QUESTION: Weighing the Issues
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
c. Intercropping
d. Terracing
e. Shelterbelts
f. No-till farming
QUESTION: Interpreting Graphs and Data
Grain produced per person has… ?
a. Risen steadily
b. Fallen
sharply
c. Increased
since 1983
d. Decreased
since 1983
Figure 8.3