APES Final Review
Agriculture & Aquaculture
Where our food comes from…
 Croplands (77%)
 Rangelands, pastures & feedlots (29%)
 Aquaculture (7%)
 There are 50,000 plant species that we can eat, yet 14 supply
90% of the worlds calories!!!
Food Sustainability
 14 varieties of plants
 2/3 of the world survives primarily on corn, wheat & rice alone
 Small number of species provide for meat & fish
 This all leads to food specialization
 Disease
 Environmental degradation
 Climate change
Industrialized Agriculture
 Heavy machinery
 Goal is to produce more food per area of land
 Characteristics include high fertilizer use, pesticide use,
irrigation, genetic engineering, factory-like conditions
 Monocultures
 High resource use
Case Study: Industrialized Food
Production in the United States
 Industrialized agriculture uses about 17% of all commercial
energy in the U.S. and food travels an average 2,400
kilometers from farm to plate.
Figure 13-7
Traditional Agriculture
 Labor- intensive
 Polyculture
 Usually lower resource use
 Can have a higher output than Industrialized
 Less susceptibility to changes
Traditional Agriculture: Low Input
Polyculture
 Many farmers in developing countries use low-input agriculture to
grow a variety of crops on each plot of land (interplanting) through:
 Polyvarietal cultivation: planting several genetic varieties.
 Intercropping: two or more different crops grown at the same time in a
plot.
 Agroforestry: crops and trees are grown together.
 Polyculture: different plants are planted together.
SUSTAINABLE AGRICULTURE THROUGH
SOIL CONSERVATION
 Modern farm machinery can plant crops without disturbing soil
(no-till and minimum tillage.
 Conservation-tillage farming:
 Increases crop yield.
 Raises soil carbon content.
 Lowers water use.
 Lowers pesticides.
 Uses less tractor fuel.
 Contour Farming –sloping your growing
crops, etc.
 You run terraces parallel to the ground to stop
soil from running down a steep slope. Plowing
and planting crops in rows across, rather than up
and down, the sloped contour of the land.
Terracing – (what you
use for contour farming.)
Dirt goes up to hold the
dirt in place. Broad,
nearly level terraces that
run across the land
contour. Helps to retain
water for crops at each
level and reduce soil
erosion by controlling
runoff.
SUSTAINABLE AGRICULTURE THROUGH
SOIL CONSERVATION
 Terracing, contour planting,
strip cropping, alley
cropping, and windbreaks can
reduce soil erosion.
Figure 13-16
 Strip Cropping – a row crop such as corn
alternates in strips with another crop that
completely covers the soil, reducing
erosion. It catches and reduces water
runoff and helps prevent the spread of pests
and plant diseases.
Cover Cropping (alley cropping) – several crops
are planted together in strips or alleys between trees
and shrubs that can provide shade (which reduces
water loss by evaporation) and helps to retain and
slowly release soil moisture.
Irrigation Techniques
 Conventional center-pivot irrigation- allows 80% of the
water input to reach crops
 Gravity-flow irrigation- Valves that send water down
irrigation ditches.
 Drip irrigation- Can raise water efficiency to 90-95% and
reduce water use by 37-70%.
 Floodplain irrigation- allowing the natural floods to irrigate
the crops. Soils in flood zones tend to be nutrient rich and
fertile.
The Green Revolution
 Increased food production using industrialized crop
production (heavy machinery)
 Steps of the Green Revolution
 1. Plant monocultures of high yield crops (wheat, corn, rice).
Often genetically modified.
 2. Use high amounts of fertilizers and pesticides to increase
yield
 3. Increase the number of crops grown per year
Meat consumption on the rise
 Effects:
 More densely packed feedlots
 High use of grain and or fish meal
 Increased need of grain can lead to dependance on other
countries
Trade-Offs
Animal Feedlots
Advantages
Increased meat
production
Higher profits
Less land use
Reduced overgrazing
Reduced soil
erosion
Help protect
biodiversity
Disadvantages
Need large inputs
of grain, fish
meal, water, and
fossil fuels
Concentrate
animal wastes
that can pollute
water
Antibiotics can
increase genetic
resistance to
microbes in
humans
Fig. 13-21, p. 289
PRODUCING MORE MEAT
 Efficiency of converting grain into animal protein.
Figure 13-22
Harmful Environmental Impacts of
Agriculture
 Erosion
 Degradation of soil
 Water depletion
 Water pollution
 Greenhouse gasses
 Air pollution
 Biodiversity loss
 **according to the EPA, agriculture is responsible for 75% of water
quality issues in US rivers & streams
Higher use of Biofuel
 Biofuel is a renewable energy alternative
 However, using too much biofuel aggravates the problems
brought on by agriculture.
 Are we replacing one problem with another?
Aquaculture
 Raising fish in ponds and underwater cages (43%)
 Helps with over-fishing
 Decrease contamination (ex. Mercury)
Trade-Offs
Aquaculture
Advantages
High efficiency
High yield in
small volume
of water
Can reduce
overharvesting
of conventional
fisheries
Low fuel use
High profits
Profits not tied
to price of oil
Disadvantages
Needs large inputs
of land, feed, and
water
Large waste
output
Destroys
mangrove forests
and estuaries
Uses grain to feed
some species
Dense populations
vulnerable to
disease
Tanks too
contaminated to
use after about 5
years
Fig. 13-24, p. 292
Fishing
Purse Seines
 A large purse-like net is put into the ocean and is then closed
like a drawstring purse to trap the fish.
 Tuna is a fish typically caught in purse seines
 Dolphins are a by-catch of purse seines
Long-line fishing
 Lines are put out that can be up to 80 miles long w/
thousands of baited hooks on them. These are left out freefloating for days and then the boat comes back and picks
them up.
 Pilot whales, dolphins, sea turtles, and birds are by-catch of
this technique.
Drift-net fishing
 Each net hangs as much as 50 feet below the surface and up to 34 miles
long.
 Anything that comes into contact w/ these nearly invisible nets are
entangled.
 This leads to overfishing
 Many unwanted fish and marine mammals, turtles and seabirds are
caught.