Transcript FOOD - Plain Local Schools

Chapter 9: FOOD
“In simplest terms, agriculture is an effort by man
to move beyond the limits set by nature.”
Lester R. Brown
President, Worldwatch Institute
L/O/G/O
9.1: Feeding the People of the World
• Ethiopa, 1985; people were starving (lack of rain,
soil degradation, war); when rain came, it washed
away millions of tons of soil into the rivers; resulted
in 6,000 sq. mi. of desert
• Events like this present frightening pictures of how
difficult it is to feed the Earth’s growing population
• Modern agricultural practices provide most of the
world’s population with enough food to survive;
however, efforts by us to feed more people in this
world are causing this environmental damage,
making it difficult to grow crops to feed all the
people
Humans and Nutrition
• We must consume organic compounds in
order to survive (carbohydrates, proteins,
lipids); we also need vitamins and minerals to
help our bodies function properly
• Food is used as a source of energy and for
building and maintaining our bodies; lack of
enough food will result in sickness or death;
starving people die from disease that our
bodies cannot fight off; malnutrition is a result
of not eating enough of the necessary
nutrients
Sources of Nutrition
• A person’s diet is the type and amount of food a
person eats.
• Healthy diets are ones that maintain a balance of
the right amounts of nutrients, minerals and
vitamins.
• Most parts of the world, people eat large amounts
of foods high in carbohydrates (rice, potatoes,
bread); foods produced in the greatest amounts
are grains (plants whose seeds are rich in
carbohydrates); aside from grains, most people eat
fruits, vegetables and small amounts of meats,
nuts and other foods rich in fats and proteins.
Diets Around the World
• Worldwide, people generally consume the same
major nutrients and eat the same basic kinds of
foods; however diets can vary from region to
region.
• More developed countries tend to eat more food
and larger proportions of proteins and fats than
people in less developed countries. ex: In US,
almost half the calories consumed come from
meat, fish and oil; In Japan, their diet traditionally
consists of a mix of rice, vegetables and seafood
The Ecology of Food
• As human population grows, farm
land replaces forests and grasslands
• Feeding all the people of the world
and still maintaining natural
ecosystems is becoming more difficult
• Different types of agriculture present
different environmental impacts and
different levels of efficiency
Food Efficiency
• The measure of the quantity of food produced on a given
area of land with limited inputs of energy and resources
• An ideal food crop would be one that efficiently produces a
large amount of food with as little negative impact on the
environment as possible.
• More energy, water and land are used to produce food from
animals than food from plants; plants are used to feed the
animals who produce food for humans; less energy is
available at each level of the food chain (10% is stored in the
animals), therefore more food can be produced for humans
when it is used for humans rather than for feed for animals
• One reason why diets around the world are largely based on
plants (it is more efficient and more can be produced per
acre); however, meat from animals provides more nutrients
per gram than most food from plants
Old and New Foods
• Researchers are investigating ancient
plants and looking at new varieties of
plants
• Looking for plants better adapted to
different climates and produce high yields
without large amounts of fertilizers,
pesticides and fresh water
• Studying plants that have not been widely
used for food in the past but may be useful
• Ex: Amaranth – sacred food of the Aztecs
and Glasswort – can be grown in saline soil
9.2: World Food Problems
• Some people become malnourished
because there is simply not enough
food for them; more food is needed
each year to feed the world’s growing
population
• World food production has been
increasing for decades, but now food
production is not increasing as fast as
human population is increasing
Unequal Distribution
• Food is not equally distributed throughout the
world; wealthy people have an abundance;
poor people have much less than they need
• Malnutrition occurs everywhere in the world;
starvation results when food cannot be
transported to where it is needed
(transportation lines break down, wars)
• During war, even if food is available, a break in
transportation can result in a famine (food
shortages in a wide spread area)
Droughts and Famines
• Droughts occur when there is a prolonged period
when the average rainfall is below average; more
likely to cause famine in places where most food is
grown locally than in places where most food is
imported
• Crops grown without irrigation may produce low
yields or fail altogether; if drought occurs, there may
be no seed to plant crops the following years (and
can continue for many years.)
• People can usually survive through one season of
crop failure (food saved from previous season or by
importing food in); if drought lasts for several years,
more serious problems can occur (ex: soil may be
less able to support the production of food crops)
The Green Revolution
• In an effort to increase crop yields, new varieties of
grain and farming methods were introduced
between 1950 and 1970, resulting in a much
greater yield (ex: Mexico increased wheat
production eight-fold; India doubled its production
of rice); changed the lives of millions of people
• Problems: need the right kind of fertilizers and
pesticides, and irrigation water for large yields of
grain; additionally, the machinery, irrigation and
chemicals required by new crop varieties can
degrade the soil if they are not used properly
The Green Revolution…con’t
• As a result, overuse of fertilizers and pesticide
have caused a decrease in green revolution
crops; grain production in US has decreased since
1990, partly because the amount of water used for
irrigation has decreased during the same period
• Subsistence farmers only grow enough for their
families and can’t afford the proper tools;
therefore, only large scale farms grow food to be
sold (they are at their max now); large use of
fertilizers and pesticides are polluting the
environment; machinery uses a large amount of
energy
Political Changes
• Making peace in war-torn countries is
essential toward supplying its people
with enough food
• Donated food can then be distributed
more effectively
• Sustainable farming techniques can
be learned
9.3: Agriculture and Soil
• Earth has a limited amount of arable land (fertile)
to grow crops; decreases every year (1/5 from
1985 to 2000)
• 371 million acres of farmland will be covered by
houses and industry; 334 million acres will become
unusable for farming because soil will be damaged
• This shortage of fertile land threatens our ability to
feed the human population
Agriculture: Traditional and
Modern
• Plowing, fertilization, irrigation and pest control
began with the earliest farmers; animals or people
pulled plows through the soil (mixes up the
nutrients, loosens soil and uproots weeds)
• Organic fertilizers (manure) enriched soil; digging
ditches supplied water; weeds were dug up by
hand – still used today in many places
• Large farms in industrialized countries use
machinery (to plow and harvest); synthetic
fertilizers are used to enrich soil; overhead drips/
sprinkles for irrigations; chemicals kill pests
Fertile Soil: The Living
Earth
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Soil that can support the rapid growth of healthy plants is called fertile
soil; most root in topsoil (rich in organic matter; loose soil comprised of
living organisms, rock particles, water, air and organic matter)
Most soil forms when rock is broken down into smaller and smaller
fragments by wind, water and chemical weathering (when minerals in
the rock react chemically with substances such as water to form new
materials); temperature changes and moisture cause rock to crack and
break apart, making smaller particles where pioneer species can take
root and grow; It can take thousands of years to form a few centimeters
of soil
Living organisms (earthworms, insects and other small animals) play an
important role in breaking up the soil; also the decomposers (fungi,
bacteria, microorganisms) when they break down detritus
One clear way to know if soil is fertile is to look for earthworms.
There are several layers of soil which lie under the topsoil; bottom layer
is called the bedrock (solid rock from which soil originally forms)
Topsoil Erosion: A Global Problem
• Soil that has been formed is being lost to erosion
• In US, about ½ of the topsoil has been lost to
erosion in the past 200 years; worldwide, 11% of
the soil has been eroded in the past 45 years
• Soil erosion is ranked as one of the most serious
ecological problems we face today
• Some farming techniques today contribute to the
erosion (blowing wind and rain washing it away)
• Harvesting removes roots and other organic matter
that holds the soil together; clearing forests for
lumber; water runoff carries away the soil
Land Degradation
• Land Degradation happens when human activity or natural
processes damage the land so that it can no longer support the
local ecosystem
• Loss of topsoil, especially in dry areas, is severe; if it
deteriorates so much the land becomes desert-like
(desertification); worldwide an area the size of Nebraska
becomes desert every year; this process is causing arable land
to disappear
• Ex: In Northern Africa, if the appropriate method of rotating the
crops and grazing their animals were observed, the land would
adequately support the people of that region; however, today,
increased overuse of the land and large numbers of grazing
animals have left the land barren. Because of the overgrazing,
the land can no longer support the plants that held the topsoil
in place, resulting in desert rather than productive farm/grazing
land
Soil Conservation
• There are many ways to conserve topsoil and reduce
erosion; soil usually erodes downhill
• Pay attention to the slope of the land when planting,
contour plowing (plowing across the slope of the hill),
leaving strips of vegetation running across the hillside, not
farming in an area where it is very hilly; terracing, multiple,
small, level fields used on a hillside; often used for wine
grapes and coffee
• Change the way farmland is plowed…ex: no-till farming rather that plowing under, plant new crops through the
remains of the old plants allowing less erosion (reduces soil
erosion to 1/10 that of traditional methods), saves time;
however, there are disadvantages to this method: soil may
become too densely packed over time and therefore, lower
crop yields over time.
Enriching the Soil
• Traditional fertilizers: organic matter such as manure and leaves
were added to the soil; as it decomposes, it adds nutrients to the
soil and improves the texture of the soil
• Inorganic fertilizers that contain nitrogen, phosphorous, and
potassium have changed farming methods; without these
fertilizers, world food production would be less than half of what it
is today
• Over the past 50 years, use of such fertilizers has rapidly
increased; if soil erosion would occur in areas where these
fertilizers (inorganic) are being used, waterways will be at risk of
being polluted
• A modern method of enhancing soil is to use both organic and
inorganic fertilizers by adding compost (partly decomposed organic
material) and chemical fertilizers to the soil
• Compost can be purchased (composted cow manure) in stores;
yard waste and crop waste can be used
Salinization
• Salinization is the accumulation of salt in the soil; salt is in the
soil naturally, but when it is irrigated with water from rivers or
groundwater, it builds up and makes the land unusable;
rainwater contains less salt than groundwater
• Major issue in places such as California and Arizona which
have low rainfall and have naturally salty soil; soil is salty
because the water used for irrigation is saltier than rainwater,
when it evaporates it leaves behind the salt; over time it will
become too salty to plant
• Ways to slow soil salinization: irrigation canals, water soil
heavily prior to planting seeds, plant salt tolerant crops or trees
to reclaim the land (shade trees will reduce evaporation from
the soil surface; fallen leaves add organic matter to the soil)
• Total restoration of the land takes decades
9.4: Pest Control
• In North America, 13% of all crops are destroyed
by insects; tropical climates enough greater
damage; Kenya lose 25% of their crops from
insects; worldwide, 33% of the world’s potential
food harvest is destroyed
• Wild plants have more protections from pests than
do crop plants; wild plants are scattered, therefore,
harder to find, have evolved defenses and have
pest predators living in or around them; crops
plants are all in one location, a one-stop food
source
Pesticides
• Over the last 50 years, many new chemical
pesticides have been developed and
farmers have begun to rely on them to
protect their crops; used to kill insects,
weeds and other crop pests
• Unfortunately, the new pesticides affect a lot
more than just the pests that they were
designed to kill
• They can also harm people, wildlife and
beneficial plants and insects
Pesticide Resistance
• If large amounts of pesticides are
used frequently, over time, the pest
problem will become worse.
• Pest populations evolve to become
resistant and survive through
exposure to that particular pesticide
• More than 500 species of insects
have developed resistance to
pesticides since the 1940’s
Health Concerns
• Many pesticides can cause people to get sick
• Ex: California has seen an increase in cancer
rates among children in areas which grow fruits
and vegetables with high pesticide use; people
applying the pesticides have to follow safety
guidelines to protect themselves from contact
with these chemicals
• Workers in pesticide factories may become ill,
as well as the people living near these
factories, from accidental chemical leaks
Pollution and Persistence
• Pesticides can become problematic for humans and
wildlife because they are persistent (don’t break down
rapidly into harmless substances when they enter the
environment), they accumulate in the water and soil
• Ex: DDT – used in the 1940”s to kill mosquitoes
(malaria, lice that spread typhus); DDT is very
persistent, gradually accumulates in bodies of water,
absorbed by fish, and then eaten by birds; resulted in
increased levels of DDT in bodies; eggs were so thin
they broke when sat on (penguins, pelicans, peregrine
falcons, eagles); many became endangered
• DDT banned in U.S.; but continues to remain in the
environment
Biological Pest Control
• Because resistance evolves so rapidly, farmers and pestcontrol companies are using fewer pesticides and
practicing some form of pest management
• Turning to biological pest control (using living organisms or
naturally produced chemicals to control pests); every pests
has enemies in the wild and those enemies can be used to
control pest populations (ex: In India (mid-1800’s),
American prickly pear cactus had been introduced into
India to feed insects that are used to make a valuable red
dye; Cactus had no natural enemies, grew and spread.
Plants were finally controlled by the introduction of an
American beetle that eats cactus
• Generally, do no harm anything but the particular pest it is
designed to control, resistance takes longer to evolve
Pathogens
• Releasing a natural predator or parasite is
one method of biological control
• Pathogens (organisms causing disease) is
another method
• Ex: Bacillus thuringensis (bacterium) kills
larvae (caterpillars of moths and butterflies)
Plant Defenses
• Cross breeding some plant varieties
to produce crops that have their own
defenses
• Tomato plants labeled “VNT” means
they are resistant to certain fungi,
worms and viruses
• Ex: production of chemical
compounds that repel pests; tougher
skin
Chemicals from Plants
• Another type of biological pest control is
to make use of plants’ defense
chemicals (Ex: extracting chemicals
from the chrysanthemum and sell it as
a pesticide)
• They are biodegradable (can be broken
down by bacteria and other
decomposers) and are designed for use
in the home because they do not harm
humans or pets
Disrupting Insect Breeding
• Growth regulators are chemicals that interfere with
some stage of a pest’s life cycle (ex: dogs – flea
pills prevent flea eggs from developing)
• Pheromones - chemicals produced by an organism
that affect the behavior of another - are also used
• Ex: female moths find mates by releasing
pheromones that attract males, farmers treat crops
with those pheromones to confuse the males
(interferes with mating)
• Another example: treat male insects with x-rays,
making them sterile; when they mate, eggs do not
get fertilized
Integrated Pest Management
• This is a modern method of controlling pests on crops (see
handout)
• Not designed to eliminate pest populations but to reduce pest
damage to a level that causes minimal economic damage;
program is designed for specific crops; can include a mix of
farming methods (biological pest control and chemical pest
control)
• Used at specific times in the growing season, fields are monitored
at all times during the growing season, when significant pest
damage is found, pest is identified and program to control the pest
is created
• Biological methods are the first methods used to control the pest
(natural predators, pathogens, parasites of the pest)
• Cultivation controls can also be used
• As a last resort, insecticide may be used; changed over time so
they do not have the ability to evolve resistance
Engineering a Better Crop
• Plant breeding has been used since agriculture began;
farmers select best tasting tomato plants, least pest
damage, save seeds and use them the next year;
consequently, these plants are more likely have genes
for large, tasty tomatoes and resist pest
• A faster way to get the same result is to use genetic
engineering (genetic material in a living cell is modified
for medical or industrial use); they will isolate genes
from one organism and implant it into another to get the
desirable trait they are looking for (ex: pest resistant)
• Plants resulting from genetic engineering are called
genetically modified plants (GM)
• (See handout for steps used to produce a GM plant)
Implications of Genetic Engineering
• In US, we now eat and use genetically
engineered agricultural products every day
• Many have not been fully tested for
environmental impacts; could cause
problems in the future (ex: genes are
sometimes transferred from one species to
another in the wild)
• GM corn plant could pass its genes to a wild
corn plant; then, that corn plant could not be
eliminated by a pesticide
Sustainable Agriculture
• How can we feed the world’s population
without depleting the world’s resources?
• Low-input farming – farming without using a lot
of energy, pesticides, fertilizers and water
• Ex: organic farming – farming without the use
of synthetic materials, use manure, compost
and keep the land planted at all times
(reducing erosion), alternating crops
• Aquaculture – “fish farming” or raising fish in
artificial environments
Section 9.5: Animals and Agriculture
• We have seen that the total energy needed to grow plants
for food is much less than the energy needed to raise
animals as food.
• Most people will include some animal proteins in their
diets because they contain more essential amino acids
than proteins found in plants; animal proteins have been
the basis of life for centuries; many populations have
traditionally obtained most of their proteins from fish and
seafood.
• Ancestors hunted and fished; today, animal proteins are
obtained from domesticated species (about 50 species
are domesticated – bred and managed for human use)
ex: chicken, sheep, cattle, honey bees, silkworms, fish,
shellfish, goats, pigs, water buffalo
Food from Water
• Fish are an important food source for
humans
• Harvesting fish has become an
important industry worldwide
• Damage to ecological systems can
occur when too many fish are
harvested over a long period of time.
Overharvesting
• Catching or removing too many of any one
organism from a population without giving
them time to be replenished is called
overharvesting.
• Governments are now attempting to stop
overharvesting by creating no-fishing zones
so the fish populations can recover;
surrounding areas have seen improvements
after a few years
• These areas are necessary if fish markets
throughout the world are to prosper
Aquaculture
• Fish and other aquatic organisms provide up to 20% of the
animal protein consumed worldwide; however,
overharvesting is reducing the number of fish and other
organisms in the oceans
• Aquaculture (raising of aquatic organisms for human use
and consumption) is rapidly increasing and will continue to
be an important source of protein in the human diet
• Not a new idea; began in China about 4000 years ago;
they lead the world in using aquaculture
• Different methods of aquaculture include: oyster farms
and fish farms-ponds that contain fish at specific stages of
development by using clean water to bring in oxygen and
remove CO2 and fecal matter, grow until maturity and then
are harvested
Aquaculture…con’t
• Another type of aquaculture is known as ranch. Fish, like
salmon, as raised until they reach a certain age, then are
released into the wild. Salmon return to their birthplace to
reproduce, when they return, they are captured and
harvested.
• Most of the catfish, oysters, salmon, crayfish and rainbow
trout eaten in the US are products of aquaculture;
worldwide, about 23% of seafood comes from
aquaculture
• This method can cause environmental damage is not
managed properly (ex: aquatic organisms can create a
large amount of waste, can deplete local water supplies,
wetland areas can be destroyed when aquaculture
operations are located within them)
Livestock
• Domesticated animals that are raised to be used on a
farm or ranch or to be sold for profit are called livestock
• Global livestock populations have changed dramatically
in the last 40 years; meat production per person has
increased worldwide since 1950
• Pig farming produces most of the meat consumed in
developed countries; in developing countries. Livestock
also provided leather, wool, eggs, meat and many other
functions
• Some livestock are used as draft animals (to pull carts
and plows), while others provide manure as the main
source of plant fertilizer or as a fuel for cooking
Ruminants
• Cattle, sheep and goats are ruminants (cud-chewing
mammals that have three or four chambered stomachs
• Cud is the food these animals regurgitate from the first
chamber of their stomachs and chew again to aid
digestion; also have microorganisms in their intestines
which allow them to digest plant material
• Humans have created hundreds of breeds of cattle suited
for specific environments; they are most common in North
America, India and Africa; not always slaughtered for meat
• In Africa, herders drink milk and blood from their cattle,
rarely kill them for meat; India has almost 1/5 of the
world’s cattle, they are sacred to Hindus and are not killed
or eaten, they are used for milk, dung and as draft animals
Poultry
• Chicken populations worldwide have increased by
a greater percentage than any other population of
livestock since 1961.
• In more-developed countries, chickens and turkeys
are usually raised in factory farms; these farms
have been criticized because of the cramped,
artificial environments these animals live in
• Fewer ducks and geese are raised worldwide than
chickens but in some areas ducks and geese are
economically important. Chinese use ducks for
meat and for their waste; waste is used to fertilize
rice paddies
Thank You!
L/O/G/O