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Chapter 10
Sustaining Terrestrial
Biodiversity: The
Ecosystem Approach
Core Case Study:
Reintroducing Wolves to Yellowstone
 Endangered

1850-1900 two million
wolves were destroyed.
 Keystone



Species
Species
Keeps prey away from open
areas near stream banks.
Vegetation reestablishes.
Species diversity expands.
Figure 10-1
Human Population
Size and resource use
Human Activities
Agriculture, industry, economic
production and consumption, recreation
Direct Effects
Degradation and destruction Changes in number and
of natural ecosystems
distribution of species
Alteration of natural chemical Pollution of air, water,
cycles and energy flows
and soil
Climate
change
Indirect Effects
Loss of
Biodiversity
Fig. 10-2, p. 192
Why Should We Care About
Biodiversity?
 Use
Value: For the
usefulness in terms
of economic and
ecological services.
 Nonuse Value:
existence, aesthetics,
bequest for future
generations.
Figure 10-3
FOOD SECURITY AND NUTRITION
 Global
food production has stayed ahead of
population growth. However:


One of six people in developing countries cannot
grow or buy the food they need.
Others cannot meet their basic energy needs
(undernutrition / hunger) or protein and key
nutrients (malnutrition).
FOOD SECURITY AND NUTRITION
 The
root cause of hunger and malnutrition is
poverty.
 Food security means that every person in a
given area has daily access to enough
nutritious food to have an active and healthy
life.


Need large amounts of macronutrients (protein,
carbohydrates, and fats).
Need smaller amounts of micronutrients
(vitamins such as A,C, and E).
FOOD SECURITY AND NUTRITION
 One
in three people
has a deficiency of
one or more vitamins
and minerals,
especially vitamin A,
iodine (causes goiter
- enlargement of
thyroid gland), and
iron.
Figure 13-2
Solutions: Reducing Childhood
Deaths from Hunger and Malnutrition
 There
are several ways to reduce childhood
deaths from nutrition-related causes:






Immunize children.
Encourage breast-feeding.
Prevent dehydration from diarrhea.
Prevent blindness from vitamin A deficiency.
Provide family planning.
Increase education for women.
Overnutrition: Eating Too Much
 Overnutrition
and lack of exercise can lead to
reduced life quality, poor health, and
premature death.
 A 2005 Boston University study found that
about 60% of American adults are overweight
and 33% are obese (totaling 93%).
 Americans spend $42 billion per year trying
to lose weight.
 $24 billion per year is needed to eliminate
world hunger.
FOOD PRODUCTION
 Food
production from croplands, rangelands,
ocean fisheries, and aquaculture has
increased dramatically.
 Wheat, rice, and corn provide more than half
of the world’s consumed calories.

Fish and shellfish are an important source of food
for about 1 billion people mostly in Asia and in
coastal areas of developing countries.
Industrial Food Production:
High Input Monocultures
 About
80% of the world’s food supply is
produced by industrialized agriculture.



Uses large amounts of fossil fuel energy, water,
commercial fertilizers, and pesticides to produce
monocultures.
Greenhouses are increasingly being used.
Plantations are being used in tropics for cash
crops such as coffee, sugarcane, bananas.
Animation: Land Use
PLAY
ANIMATION
Industrial Food Production:
High Input Monocultures
 Livestock
production in developed countries
is industrialized:




Feedlots are used to fatten up cattle before
slaughter.
Most pigs and chickens live in densely populated
pens or cages.
Most livestock are fed grain grown on cropland.
Systems use a lot of energy and water and
produce huge amounts of animal waste.
Natural Capital
Croplands
Ecological
Services
Economic
Services
• Help maintain water flow and soil infiltration • Food crops
• Provide partial erosion protection
• Fiber crops
• Can build soil organic matter
• Store atmospheric carbon
• Provide wildlife habitat for some species
• Crop genetic resources
• Jobs
Fig. 13-6, p. 276
Traditional Agriculture: Low Input
Polyculture
 Many
farmers in developing countries use lowinput 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.
SOIL EROSION AND DEGRADATION
 Soil
erosion lowers soil fertility and can
overload nearby bodies of water with eroded
sediment.



Sheet erosion: surface water or wind peel off
thin layers of soil.
Rill erosion: fast-flowing little rivulets of surface
water make small channels.
Gully erosion: fast-flowing water join together to
cut wider and deeper ditches or gullies.
Traditional Agriculture: Low Input
Polyculture
 Research
has
shown that, on
average, low input
polyculture produces
higher yields than
high-input
monoculture.
Figure 13-8
SOIL EROSION AND DEGRADATION
 Soil
erosion is the
movement of soil
components,
especially surface
litter and topsoil, by
wind or water.
 Soil
erosion increases through activities
such as farming, logging, construction,
overgrazing, and off-road vehicles.
Figure 13-9
Serious concern
Some concern
Stable or nonvegetative
Fig. 13-10, p. 279
Desertification: Degrading Drylands
one-third of the world’s land has lost
some of its productivity because of drought
and human activities that reduce or degrade
topsoil.
 About
Figure 13-12
Salinization
and
Waterlogging
 Repeated
irrigation can
reduce crop
yields by
causing salt
buildup in the
soil and
waterlogging of
crop plants.
Figure 13-13
Solutions
Soil Salinization
Prevention
Cleanup
Reduce irrigation
Flush soil
(expensive and
wastes water)
Switch to salttolerant crops
(such as barley,
cotton,
sugarbeet)
Install underground
drainage systems
(expensive)
Fig. 13-15, p. 281
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.
SUSTAINABLE AGRICULTURE
THROUGH SOIL CONSERVATION
 Terracing,
contour
planting, strip
cropping, alley
cropping, and
windbreaks can
reduce soil
erosion.
Figure 13-16
SUSTAINABLE AGRICULTURE
THROUGH SOIL CONSERVATION
 Fertilizers
can help restore soil nutrients, but
runoff of inorganic fertilizers can cause water
pollution.


Organic fertilizers: from plant and animal (fresh,
manure, or compost) materials.
Commercial inorganic fertilizers: Active
ingredients contain nitrogen, phosphorous, and
potassium and other trace nutrients.
THE GREEN REVOLUTION AND ITS
ENVIRONMENTAL IMPACT
 Lack
of water, high costs for small farmers,
and physical limits to increasing crop yields
hinder expansion of the green revolution.
 Since 1978 the amount of irrigated land per
person has declined due to:




Depletion of underground water supplies.
Inefficient irrigation methods.
Salt build-up.
Cost of irrigating crops.
THE GREEN REVOLUTION AND ITS
ENVIRONMENTAL IMPACT
 Modern
agriculture has a greater harmful
environmental impact than any human
activity.
 Loss of a variety of genetically different crop
and livestock strains might limit raw material
needed for future green and gene
revolutions.

In the U.S., 97% of the food plant varieties
available in the 1940 no longer exist in large
quantities.
Biodiversity Loss
Soil
Water
Air Pollution
Human Health
Nitrates in
drinking water
Loss and
degradation of
grasslands,
forests, and
wetlands
Erosion
Water waste
Loss of fertility
Aquifer depletion
Greenhouse gas
emissions from
fossil fuel use
Salinization
Increased runoff and
flooding from cleared
land
Pesticide residues
Other air pollutants in drinking water,
from fossil fuel use food, and air
Fish kills from
pesticide runoff
Desertification
Waterlogging
illiKng wild predators to
protect livestock
Loss of genetic diversity of
wild crop strains replaced
by monoculture strains
Sediment pollution from
erosion
Fish kills from pesticide
runoff
Greenhouse gas
emissions of
nitrous oxide from
use of inorganic
fertilizers
Surface and groundwater
pollution from pesticides
and fertilizers
Belching of the
greenhouse gas
Overfertilization of
methane by cattle
lakes and rivers from
runoff of fertilizers,
livestock wastes, and
Pollution from
food processing wastes pesticide sprays
Contamination of
drinking and
swimming water
with disease
organisms from
livestock wastes
Bacterial
contamination of
meat
Fig. 13-18, p. 285
THE GENE REVOLUTION
 To
increase crop yields, we can mix the
genes of similar types of organisms and mix
the genes of different organisms.


Artificial selection has been used for centuries to
develop genetically improved varieties of crops.
Genetic engineering develops improved strains
at an exponential pace compared to artificial
selection.
 Controversy
has arisen over the use of
genetically modified food (GMF).
Trade-Offs
Genetically Modified Crops and Foods
Projected
Advantages
Need less fertilizer
Projected
Disadvantages
Need less water
Irreversible and
unpredictable genetic
and ecological effects
More resistant to
insects, disease,
frost, and drought
Harmful toxins in food
from possible plant cell
mutations
Grow faster
New allergens in food
Can grow in
slightly salty soils
Lower nutrition
Less spoilage
Better flavor
Increased development
of pesticide-resistant
insects and plant
diseases
Need less pesticides
Can create herbicideresistant weeds
Tolerate higher
levels of herbicides
Can harm beneficial
insects
Higher yields
Lower genetic diversity
Fig. 13-19, p. 287
THE GENE REVOLUTION
• Controversy has arisen over the use of
genetically modified food (GMF).
– Critics fear that we know too little about the
long-term potential harm to human and
ecosystem health.
• There is controversy over legal
ownership of genetically modified crop
varieties and whether GMFs should be
labeled.
Mixing Genes
• Genetic engineering
involves splicing a
gene from one
species and
transplanting the
DNA into another
species.
Figure 13-19
PRODUCING MORE MEAT
• About half of the world’s meat is
produced by livestock grazing on grass.
• The other half is produced under factorylike conditions (feedlots).
– Densely packed livestock are fed grain or
fish meal.
• Eating more chicken and farm-raised fish
and less beef and pork reduces harmful
environmental impacts of meat
production.
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
How Many People can the World
Support? Food Production and
Population
• The number of people the world can support
depends mostly on their per capita
consumption of grain and meat and how
many children couples have.
– Research has shown that those living very low
on the food chain or very high on the food chain
do not live as long as those that live somewhere
in between.
Kilograms of grain needed per kilogram of body weight
Beef cattle
7
Pigs
4
Chicken
2.2
Fish
(catfish or
carp)
2
Fig. 13-22, p. 290
Aquaculture
Per capita catch
(kilograms per person)
Catch (millions of
metric tons)
Wild catch
Year
Year
Total World Fish Catch
World Fish Catch per Person
Fig. 13-23, p. 291
CATCHING AND RAISING MORE
FISH AND SHELLFISH
• Government subsidies given to the fishing
industry are a major cause of overfishing.
– Global fishing industry spends about $25 billion
per year more than its catch is worth.
– Without subsidies many fishing fleets would have
to go out of business.
– Subsidies allow excess fishing with some
keeping their jobs longer with making less
money.
Aquaculture: Aquatic Feedlots
• Raising large numbers of fish and shellfish
in ponds and cages is world’s fastest
growing type of food production.
• Fish farming involves cultivating fish in a
controlled environment and harvesting
them in captivity.
• Fish ranching involves holding anadromous
species that live part of their lives in
freshwater and part in saltwater.
– Fish are held for the first few years, released,
and then harvested when they return to spawn.
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
Solutions
More Sustainable Aquaculture
• Use less fishmeal feed to reduce depletion of other fish
• Improve management of aquaculture wastes
• Reduce escape of aquaculture species into the wild
• Restrict location of fish farms to reduce loss of
mangrove forests and estuaries
• Farm some aquaculture species in deeply submerged
cages to protect them from wave action and predators
and allow dilution of wastes into the ocean
• Certify sustainable forms of aquaculture
Fig. 13-25, p. 293
Natural Capital
Forests
Ecological
Services
Support energy flow
and chemical cycling
Reduce soil erosion
Absorb and release
water
Economic
Services
Fuelwood
Lumber
Pulp to make paper
Mining
Purify water and air
Livestock grazing
Influence local and
regional climate
Recreation
Store atmospheric
carbon
Jobs
Provide numerous
wildlife habitats
Fig. 10-4, p. 193
Types of Forests
 Old-growth
forest: uncut
or regenerated forest that
has not been seriously
disturbed for several
hundred years.


22% of world’s forest.
Hosts many species with
specialized niches.
Figure 10-5
Types of Forests
 Second-growth
forest: a stand of trees
resulting from natural secondary succession.
 Tree plantation: planted stands of a
particular tree species.
Figure 10-6
Natural Capital Degradation
Deforestation
• Decreased soil fertility from erosion
• Runoff of eroded soil into aquatic systems
• Premature extinction of species with
specialized niches
• Loss of habitat for native species and
migratory species such as birds and butterflies
• Regional climate change from extensive clearing
• Release of CO2 into atmosphere
• Acceleration of flooding
Fig. 10-7, p. 196
Case Study: Deforestation and the
Fuelwood Crisis
 Almost
half the people in the developing
world face a shortage of fuelwood and
charcoal.


In Haiti, 98% of country is deforested.
MIT scientist has found a way to make charcoal
from spent sugarcane.
Highway
Old
growth
Cleared
plots for
grazing
Highway
Cleared
plots for
agriculture
Fig. 10-8, p. 197
(a) Selective cutting
Fig. 10-9a, p. 198
(b) Clear-cutting
Fig. 10-9b, p. 198
(c) Strip cutting
Uncut
Cut 1
year ago
Dirt road
Cut 3–10
years ago
Uncut
Stream
Fig. 10-9c, p. 198
Harvesting Trees
Effects of clear-cutting in the
state of Washington, U.S.
Figures 10-10 and 10-11
Solutions
 We
can use forests
more sustainably by
emphasizing:



Economic value of
ecological services.
Harvesting trees no
faster than they are
replenished.
Protecting old-growth
and vulnerable areas.
Figure 10-12
Types and Effects of Forest Fires

Depending on their intensity, fires can benefit or
harm forests.


Burn away flammable ground material.
Release valuable mineral nutrients.
Figure 10-13
Solutions:
Controversy Over Fire Management
 To



reduce fire damage:
Set controlled surface fires.
Allow fires to burn on public lands if they don’t
threaten life and property.
Clear small areas around property subject to fire.
Solutions:
Controversy Over Fire Management
 In
2003, U.S. Congress passed the Healthy
Forest Restoration Act:



Allows timber companies to cut medium and
large trees in 71% of the national forests.
In return, must clear away smaller, more fireprone trees and underbrush.
Some forest scientists believe this could increase
severe fires by removing fire resistant trees and
leaving highly flammable slash.
Controversy over Logging in U.S. National
Forests
 There
has been an
ongoing debate over
whether U.S.
national forests
should be primarily
for:




Timber.
Ecological services.
Recreation.
Mix of these uses.
Figure 10-14
Solutions:
Reducing Demand for Harvest Trees
 Tree
harvesting can
be reduced by
wasting less wood
and making paper
and charcoal fuel
from fibers that do
not come from trees.

Kenaf is a promising
plant for paper
production.
Figure 10-15
American Forests in a Globalized
Economy
 Timber
from tree plantations in temperate
and tropical countries is decreasing the need
for timber production in the U.S.



This could help preserve the biodiversity in the
U.S. by decreasing pressure to clear-cut oldgrowth and second-growth forests.
This may lead to private land owners to sell less
profitable land to developers.
Forest management policy will play a key role.
CASE STUDY: TROPICAL
DEFORESTATION
 Large
areas of ecologically and
economically important tropical forests are
being cleared and degraded at a fast rate.
Figure 10-16
CASE STUDY: TROPICAL
DEFORESTATION
 At
least half of the
world’s terrestrial plant
and animal species live
in tropical rain forests.
 Large areas of tropical
forest are burned to
make way for cattle
ranches and crops.
Figure 10-17
Why Should We Care about the Loss
of Tropical Forests?
 About
2,100 of the 3,000 plants identified by
the National Cancer Institute as sources of
cancer-fighting chemicals come from tropical
forests.
Figure 10-18
Causes of Tropical Deforestation and
Degradation
 Tropical
deforestation
results from a
number of
interconnected
primary and
secondary causes.
Figure 10-19
Solutions
Sustaining Tropical Forests
Prevention
Protect most diverse and endangered
areas
Restoration
Reforestation
Educate settlers about sustainable
agriculture and forestry
Phase out subsidies that encourage
unsustainable forest use
Add subsidies that encourage
sustainable forest use
Rehabilitation of degraded
areas
Protect forests with debt-for-nature
swaps and conservation easements
Certify sustainably grown timber
Reduce illegal cutting
Reduce poverty
Slow population growth
Concentrate farming and
ranching on already-cleared
areas
Fig. 10-20, p. 207
MANAGING AND SUSTAINING
GRASSLANDS
 Almost
half of the world’s livestock graze on
natural grasslands (rangelands) and
managed grasslands (pastures).
 We can sustain rangeland productivity by
controlling the number and distribution of
livestock and by restoring degraded
rangeland.
MANAGING AND SUSTAINING
GRASSLANDS
 Overgrazing
(left)
occurs when too
many animals
graze for too long
and exceed
carrying capacity
of a grassland
area.
Figure 10-21
MANAGING AND SUSTAINING
GRASSLANDS
 Example
of restored area along the San
Pedro River in Arizona after 10 years of
banning grazing and off-road vehicles.
Figure 10-22
NATIONAL PARKS
 Countries
have established more than 1,100
national parks, but most are threatened by
human activities.




Local people invade park for wood, cropland,
and other natural resources.
Loggers, miners, and wildlife poachers also
deplete natural resources.
Many are too small to sustain large-animal
species.
Many suffer from invasive species.
Case Study: Stresses on U.S.
National Parks
 Overused
due to
popularity.
 Inholdings (private
ownership) within
parks threaten
natural resources.
 Air pollution.
Figure 10-23
 Suggestions
for
sustaining and
expanding the
national park
system in the
U.S.
Figure 10-24
NATURE RESERVES
 Ecologists
call for protecting more land to
help sustain biodiversity, but powerful
economic and political interests oppose doing
this.



Currently 12% of earth’s land area is protected.
Only 5% is strictly protected from harmful human
activities.
Conservation biologists call for full protection of
at least 20% of earth’s land area representing
multiple examples of all biomes.
NATURE RESERVES
 Large
and medium-sized reserves with buffer
zones help protect biodiversity and can be
connected by corridors.
 Costa
Rica has
consolidated its parks
and reserves into 8
megareserves
designed to sustain
80% if its biodiversity.
Figure 10-10B
NATURE RESERVES
A
model biosphere
reserve that
contains a protected
inner core
surrounded by two
buffer zones that
people can use for
multiple use.
Figure 10-25
NATURE RESERVES
 Geographic
Information System (GIS)
mapping can be used to understand and
manage ecosystems.


Identify areas to establish and connect nature
reserves in large ecoregions to prevent
fragmentation.
Developers can use GIS to design housing
developments with the least environmental
impact.
NATURE RESERVES
 We
can prevent or slow down losses of
biodiversity by concentrating efforts on
protecting global hot spots where significant
biodiversity is under immediate threat.
 Conservation biologists are helping people in
communities find ways to sustain local
biodiversity while providing local economic
income.

34 hotspots identified by ecologists as important and
endangered centers of biodiversity.
Figure 10-26
NATURE RESERVES
 Wilderness
is land legally set aside in a large
enough area to prevent or minimize harm
from human activities.
 Only a small percentage of the land area of
the United States has been protected as
wilderness.
ECOLOGICAL RESTORATION
 Restoration:
trying to return to a condition as
similar as possible to original state.
 Rehabilitation: attempting to turn a
degraded ecosystem back to being
functional.
 Replacement: replacing a degraded
ecosystem with another type of ecosystem.
 Creating artificial ecosystems: such as
artificial wetlands for flood reduction and
sewage treatment.
ECOLOGICAL RESTORATION
 Five
basic science-based principles for
ecological restoration:





Identify cause.
Stop abuse by eliminating or sharply reducing
factors.
Reintroduce species if necessary.
Protect area form further degradation.
Use adaptive management to monitor efforts,
assess successes, and modify strategies.
Will Restoration Encourage Further
Destruction?
 There
is some concern that ecological
restoration could promote further
environmental destruction and degradation.


Suggesting that any ecological harm can be
undone.
Preventing ecosystem damage is far cheaper
than ecological restoration.
WHAT CAN WE DO?
 Eight





priorities for protecting biodiversity:
Take immediate action to preserve world’s
biological hot spots.
Keep intact remaining old growth.
Complete mapping of world’s biodiversity for
inventory and decision making.
Determine world’s marine hot spots.
Concentrate on protecting and restoring lake and
river systems (most threatened ecosystems).
WHAT CAN WE DO?



Ensure that the full range of the earths
ecosystems are included in global conservation
strategy.
Make conservation profitable.
Initiate ecological restoration products to heal
some of the damage done and increase share of
earth’s land and water allotted to the rest of
nature.
What Can You Do?
Sustaining Terrestrial Biodiversity
• Adopt a forest.
• Plant trees and take care of them.
• Recycle paper and buy recycled paper products.
• Buy sustainable wood and wood products.
• Choose wood substitutes such as bamboo furniture
and recycled plastic outdoor furniture, decking, and
fencing.
• Restore a nearby degraded forest or grassland.
• Landscape your yard with a diversity of plants
natural to the area.
• Live in town because suburban sprawl reduces
biodiversity.
Fig. 10-27, p. 219
Solutions: Steps Toward More
Sustainable Food Production
• We can increase food security by slowing
populations growth, sharply reducing poverty,
and slowing environmental degradation of the
world’s soils and croplands.
PROTECTING FOOD
RESOURCES: PEST
MANAGEMENT
• Organisms found in
nature (such as
spiders) control
populations of most
pest species as part
of the earth’s free
ecological services.
Figure 13-27
PROTECTING FOOD
RESOURCES: PEST
MANAGEMENT
• We use chemicals to repel or kill pest
organisms as plants have done for millions of
years.
• Chemists have developed hundreds of
chemicals (pesticides) that can kill or repel
pests.
– Pesticides vary in their persistence.
– Each year > 250,000 people in the U.S. become
ill from household pesticides.
Advantages
Save lives
Disadvantages
Promote genetic
resistance
Increase food
supplies
Kill natural pest enemies
Profitable to use
Create new pest species
Work fast
Pollute the environment
Safe if used
properly
Can harm wildlife and
people
Fig. 13-28, p. 295
The ideal Pesticide and the
Nightmare Insect Pest
• The ideal pest-killing chemical has these
qualities:
– Kill only target pest.
– Not cause genetic resistance in the target
organism.
– Disappear or break down into harmless
chemicals after doing its job.
– Be more cost-effective than doing nothing.
Superpests
• Superpests are
resistant to
pesticides.
• Superpests like the
silver whitefly (left)
challenge farmers
as they cause >
$200 million per
year in U.S. crop
losses.
Figure 13-29
Pesticide Protection Laws in the
U.S.
• Government regulation has banned a
number of harmful pesticides but some
scientists call for strengthening pesticide
laws.
– The Environmental Protection Agency (EPA),
the Department of Agriculture (USDA), and
the Food and Drug Administration (FDA)
regulate the sales of pesticides under the
Federal Insecticide, Fungicide and
Rodenticide Act (FIFRA).
– The EPA has only evaluated the health effects
What Can You Do?
Reducing Exposure to Pesticides
• Grow some of your food using organic methods.
• Buy organic food.
• Wash and scrub all fresh fruits, vegetables, and wild foods you pick.
• Eat less or no meat.
• Trim the fat from meat.
Fig. 13-30, p. 299
Other Ways to Control Pests
• Biological pest
control: Wasp
parasitizing a
gypsy moth
caterpillar.
Figure 13-31
Other Ways to Control Pests
• Genetic
engineering can
be used to
develop pest and
disease resistant
crop strains.
 Both
tomato plants were exposed to
destructive caterpillars. The genetically
altered plant (right) shows little damage.
Figure 13-32
SOLUTIONS: SUSTAINABLE
AGRICULTURE
• Three main ways to reduce hunger and
malnutrition and the harmful effects of
agriculture:
– Slow population growth.
– Sharply reduce poverty.
– Develop and phase in systems of more
sustainable, low input agriculture over the next
few decades.
Solutions
Sustainable Organic Agriculture
More
High-yield
polyculture
Organic fertilizers
Biological pest
control
Integrated pest
management
Efficient
irrigation
Perennial crops
Crop rotation
Water-efficient
crops
Soil conservation
Subsidies for
sustainable farming
and fishing
Less
Soil erosion
Soil salinization
Aquifer depletion
Overgrazing
Overfishing
Loss of
biodiversity
Loss of prime
cropland
Food waste
Subsidies for
unsustainable
farming and
fishing
Population
growth
Poverty
Fig. 13-33, p. 302
Solutions
Organic Farming
Improves soil fertility
Reduces soil erosion
Retains more water in soil
during drought years
Uses about 30% less
energy per unit of yield
Lowers CO2 emissions
Reduces water pollution
from recycling livestock
wastes
Eliminates pollution
from pesticides
Increases biodiversity
above and below ground
Benefits wildlife such as
birds and bats
Fig. 13-34, p. 302
What Can You Do?
Sustainable Organic Agriculture
• Waste less food
• Eat less or no meat
• Feed pets balanced grain foods instead of meat
• Use organic farming to grow some of your food
• Buy organic food
• Eat locally grown food
• Compost food wastes
Fig. 13-35, p. 303