When soil erodes, the most productive layers are always removed first.
As the fertility decreases, the need for fertilizers increase and the
price of food increases. Most agricultural practices remove soil more
quickly than it can be replaced.
Water can erode soil. Each year, the Mississippi transports over 325 million
metric tons of soil from the central U.S. to the Gulf of Mexico (equivalent
to about 1 mm soil over the entire central U.S.). Erosion can be reduced
by making difficult for water to flow in a straight line, especially downhill,
by using contours, strips of closely sown crops, and terraces.
Wind can erode soil. In the Dust Bowl during the 1930s, wind destroyed
3.5 million hectares of farmland and damaged another 30 million hectares.
Wind erosion can be reduced by planting trees or other plants as windbreaks
Overgrazing by livestock reduces plant cover as does deforestation. When
topsoil is washed or blown away, the fertility of the soil which remains
is reduced. Regions may eventually become barren, creating deserts. The
loss of valuable soil around existing deserts causes them to expand. The
deserts of the earth increase by 15 million acres every single year. Desertification
in Africa particularly is a serious concern.
Desertification is affecting about 100 countries. Much of Sub-Saharan
Africa (in an area known as the African Sahel) has received only two thirds
of the rain it was accustomed to earlier in the century. As a result,
more and more land has become arid and the Sahara Desert has expanded
about 41,000 square kilometers per year in recent decades (Hulme, 1993).
The average American generates about 4 ½ pounds of solid waste
a day which is the highest per capita generation of trash in the world
(although Canada's rate is close to this). America generates more than
200 million tons of trash per year (Raven, 2001) and the U.S. disposes
of enough waste daily to fill 2 Superdomes. The average amount of garbage
produced daily rose from 2.7 pounds to 4.5 pounds per person during the
period of 1960-2000. America produces 232 million tons of garbage in a
year which is twice the per capita amount as other industrialized countries.
Where will all the garbage go? Some states already have to ship their
garbage to other states at considerable expense. One memorable example
of how difficult it can be to dispose of garbage was the memorable voyage
of the ship Mobro 4000 which, after being loaded with garbage in New York
City embarked on a 5,000 mile journey in an attempt to dispose of this
garbage before finally returning back to New York. About half of the cities
in the United States have no room for additional landfill space. Philadelphia,
for example, must ship its garbage hundreds of miles away (Blatt, 2005).
About 96% of our plastic is put into an estimated 6,000 landfills and
two thirds of our paper is not recycled. About 75% of this waste is put
into landfills, 10% is recycled, and 15% is incinerated. Americans dump
8.5 million tons of refuse into rivers and oceans and industry contributes
9.5 million tons more. In the year 2000, 60 million tons of garbage were
recycled while 120 million tons were put into landfills and 40 million
tons were incinerated. The amount of recycling increased from 10% in 1980
to 32% in 2001 (Blatt, 2005). The U.S. Center for Disease Control claims
that those living within 1.5 miles of an incinerator in North Carolina
have 2.4 and 9x greater incidence of neurological and respiratory disorders
respectively. Dioxin exposure by eating beef grown near an incinerator
in Ohio were 40,000x greater than breathing the air alone. Plastics compose
7-10% solid waste by weight and 10-25% by volume. Incineration released
toxic chemicals into the environment but landfill disposal requires large
amounts of space. In 2001, 21% of the plastic bottles in the U.S. were
recycled (Kemp, 2004).
Paper and paper products are the largest source of municipal waste at
34%. To bleach paper white, chlorine is used; unfortunately, chlorine
is very reactive & may form carcinogens such as dioxins, furans, chlorinated
phenols, benzenes, chloroform and 300 others. The paper industry discharges
2 million tons of such organochlorines into the world's waterways every
year. Maine lobsters had such a high concentration in their livers that
Maine recommended that children and pregnant women not eat that part of
the lobster. Eleven of British Columbia's 14 paper pulp plants have closed
the surrounding waterways due to high concentrations of dioxin in fish,
mussels, and crabs. From 1983 to 1990, the % recycled fibers used in paper
rose form 30% to 37%. Recycling a ton of paper saves 3.3 cubic yards of
landfill space. Every year about a billion trees are cut to make disposable
In 1989 the U.S. made 75 billion aluminum cans, 42.5 billion of which
were recycled. The energy saved by recycling a single Al can is equal
to the amount of gasoline that would fill 1/3 of that can.
4) TOXIC WASTES
Humans are exposed to a variety of chemicals. More than 500 synthetic
chemicals are commonly detected in human blood, breast milk, and/or body
tissue (Doyle, 2004). Between 1935 and 1995, the amount of synthetic organic
compounds increased one thousand times in the U.S. with about 1,000 new
chemicals introduced per year. The world production of synthetic organic
compounds is estimated at 400 million tons and U.S. production averages
to 1,600 pounds per person per year (Doyle, 2004). The oil refineries
of Texas are primarily responsible for that state's production of one
third of the nation's hazardous waste (Blatt, 2005). The U.S. military
produces more toxic waste than the 5 leading chemical companies combined,
is responsible for more than 20 thousand toxic sites (about 10% of the
those on the Superfund list), and the EPA is prohibited from investigating
or suing the military (Blatt, 2005).
A fourth of all Americans live near a toxic waste site and more than 600,000
children attend one of the 1,200 schools which are located within a half
mile of a toxic waste site (Blatt, 2005). Although PCBs were banned in
1976 and DDT was banned in 1974, these chemicals are still found in human
blood and in foods ranging from pork to ice cream (Doyle, 2004).
WHERE DO HARMFUL CHEMICALS COME FROM?
--WASTES AND WASTE SITES
More than 1/2 nation's industries discharge wastes in their sewage; 92
billion pounds of hazardous wastes are generated a year of which only
20% are disposed of properly; much of this waste is a threat to groundwater
supplies. In 10/95, the EPA estimated that there were 26,000 hazardous
waste sites that still posed a threat to the public water supply and awaited
These compounds are introduced into our bodies. A 1982 study in Baton
Rouge found that mother's milk could contain 34 synthetic compounds including
chloroform, dichlorobenzene, methylene chloride, benzene, and styrene.
Since then more than 100 chemical contaminants have been found in breast
milk in the U.S., including dioxins. Based on EPA studies, 9 out of 10
Americans carry dioxins, furans, chlorobenzene, benzene, and styrene in
their fatty tissues. U.S. citizens currently exposed to >65,000 synthetic
chemicals and 1,000 more are added per year. Not only might some of these
chemicals have a detrimental additive effect, some might interact with
each other to result in unforeseen effects. For example, chlorine has
a variety of uses ranging from purifying water to bleaching paper to make
it white. However, chlorine reacts with other molecules to produce new
ones: the use of chlorine to bleach paper leads to the production of many
toxic organochlorides, including dioxin. Virtually nothing is known about
the effects of mixtures of chemicals (National Toxicological Program estimates
that a minimal study on the health effects of the interactions of 25 chemicals
would require more than 33 million experiments at a cost of $3 billion).
Some Americans live at added risk because they live close to a site where
hazardous wastes are disposed of. This may be an incinerator which burns
the wastes but releases some into the air or a landfill where this waste
can potentially leak into groundwater. For example, 150,000 residents
of Chicago's southeast side live near 50 active or closed commercial hazardous
waste landfills, 100 factories (including 7 chemical factories), and 103
abandoned toxic waste dumps. It has frequently been observed that there
is a link between poverty and exposure to some of these waste sites: many
of the neighborhoods with the greatest exposure to waste sites are poor.
Each year 430 nuclear power plants in 30 countries produce 6,000-7,000
tons of spent fuel rods including 60-70 tons of plutonium.
TOXIC METALS & CARCINOGENIC COMPOUNDS
Many of the toxic compounds are heavy metals. Cadmium can damage the liver
and kidneys and 4-8% of what we ingest stays in body. Mercury's inorganic
salts cause intestinal & kidney damage while methyl mercury attacks
brain, liver, and kidneys and causes birth defects. In Minimata Bay, Japan
in the 1950s mercury levels in water killed 52 people and caused brain
damage to 150. When Iraq mistakenly used methyl-mercury fumigated grain
for food instead of for planting, 459 people were killed and 6530 injured.
Millions of Americans drink water that is contaminated with lead. Drinking
water represents 20% exposure of adults to lead and 85% of infant exposure
to lead comes from formula mixed with tap water. Lead is a neurotoxin
that is especially dangerous to the normal brain development of children.
Lead has been linked to lower IQ, memory reduction, and a limited attention
span in children and in adults, chronic low level exposure in adults may
cause high blood pressure and kidney damage.
One region along the Mississippi River in Louisiana is known as "Cancer
Alley" because of the high rates of cancer, miscarriage, and other
health concerns (The Mississippi River is depicted in the images below).
Yellow Creek, Kentucky once had 3000 times the safe levels of cadmium,
4,000x the safe levels of chromium, and 1,500x the same levels of lead;
this caused higher cancer and birth defect rates in the area. As of the
mid-1990s, Lake Ontario received 225 tons heavy metals per year including
cadmium, chromium, copper, mercury, nickel, lead, and zinc. During the
1930s-50s, mercury was released into the Shenandoah River and bass caught
77 miles downstream still had twice the safe limits of mercury.
Fifteen thousand tons of industrial waste are legally dumped into Lake
Ontario every year. It is the 11th largest freshwater lake in the world.
New York and Ontario have issued advisories about eating the lake trout,
chinook salmon, coho slamon, brown trout, rainbow trout, walleye, white
perch, and white sucker from it. In 1994, there was a 20% increase in
health advisories against eating fish from 46 states; 7 states (New Jersey,
Maine, Massachusetts, New York, Michigan, Florida, and Missouri) had health
advisories on consuming fish from all state waters; this includes 565
bodies of water in Minnesota and 260 in Wisconsin. Forty percent of the
country's rivers, lakes, and streams still not suitable for fishing or
swimming. Legislation and cleanup have had great positive effects. The
1972 Clean Water Act has eliminated most drastic problems but not all
waters have yet met goal of being "fishable and swimmable".
The Delaware river's condition has greatly improved-it was once so polluted
that World War II pilots knew when they flew over it by the smell.
Many parts of the world have polluted water. China's Yangtze River receives
37% of China's wastewater (12.8 billion tons/year) and 17,000 tons of
harmful chemicals. The white-fin freshwater dolphin which lives there
may become extinct within the next 25 years. In Poland, 95% of the surface
water unfit to drink and some of the water from the Vistula is even unfit
to cool machinery. The Volga in Russia receives 300 million tons of solid
waste and 20 trillion liters of liquid effluent annually. Mexico's low
environmental standards allow the New River (which passes through southern
California) to be the most polluted river in North America.
These wastes often lead to very expensive cleanup costs. In 1980 the U.S.
Congress created the Comprehensive Environmental Response, Compensation,
and Liability Act (CERCLA) which includes the Superfund for the most toxic
waste sites. It has spent over $40 billion. The EPA has about 1250 sites
on a national priority list (NPL). Another 30,000 sites qualify for Superfund
laws and the individual sites have listed tens of thousands of additional
sites. There have been some tremendous success stories, such as the conversion
of the toxic Anaconda copper smelting operation in Montana into a golf
course. There is also a great deal of criticism for the Superfund, especially
the observation that about one third of the money is dedicated to legal
issues rather than actual waste cleanup.
Each year, pests destroy 45% world's food. For example, a locust can eat
3.5g (its own weight) every day and a swarm may have a billion locusts.
In 1 year, the offspring of 1 pair of rats can eat enough to feed 5 people.
The U.N. estimates that the food supply losses throughout the world could
feed 1 billion people. There are 100,000 different insect pests in the
U.S. alone, 600 of which are serious. Many weed plants compete with cultivated
crops and can diminish the productivity of cropland. Humans have produced
a diversity of pesticides-poisons which can kill undesired animal pests
and weedy plants. Obviously, however, there are both benefits and risks
in the use of poisons and therefore, a case can be made both for the use
of pesticides and against their use.
THE CASE FOR PESTICIDES
Without pesticides, more crops would be lost to pests and it would be
more expensive to produce the food supply. A 1990 study concluded eliminating
pesticides would cost the average household $228/year and the elimination
of fertilizers would cost $428 to the average household. While pesticides
cost $3 billion in U.S. to buy and cause an estimated $1 billion in social
and environmental damage the increased crop yields due to the use of pesticides
are worth $12 billion. In some cases, pesticide use may actually decrease
human exposure to harmful chemicals. When celery (and other fruits and
vegetables) is attacked by fungi produces its own defense chemicals which,
when eaten by humans, increase the risk of skin cancer. When pesticides
eliminate plant pests, they can reduce the amount of the plant's defensive
toxins produced. Although some pesticides pose serious threats to health,
new pesticides being developed that are safer than those used in the past.
The pesticide DDT certainly is recognized as a serious threat to human
health. Nevertheless, DDT has probably saved more lives than any other
chemical: it protected WWII soldiers from typhus and the World Health
Organization estimates that about 7 million people in the Third World
would have died since 1947 from malaria if DDT had not been used to kill
mosquitoes. Presently 1 billion are freed from the risk of malaria through
the use of insecticides.
THE CASE AGAINST PESTICIDES
1) RESISTANCE TO PESTICIDES
All individuals in every species of plant or animal vary genetically and
a small percentage may have innate resistance to a certain pesticide.
When pesticides are used, they kill nonresistant individuals first and
the percentage of pesticide-resistant individuals increases rapidly. Over
time, the populations of the pest become composed of individuals which
cannot be killed by the pesticide.
Within about 5 years, most insecticides no longer effective. Pesticide
resistance costs the U.S. about $1.5 billion per year. The same applies
to herbicides but since plants reproduce less rapidly, resistant populations
don't arise as quickly. More than 450 insect species are resistant to
DDT. Colorado potato beetles become resistant to new pesticides within
1 season. Although Sri Lanka's malaria problem was reduced because of
the use of insecticides (by 1966, Sri Lanka had only 17 malaria cases),
malaria cases later increased because of insecticide resistant populations
(by 1970, there were 4 million cases). Some cotton fields in Texas and
Peru were abandoned because no combination of pesticides could deter resistant
populations that had developed there.
2) PESTICIDES KILL OTHER SPECIES OTHER THAN THE PESTS
Pesticides usually kill the pest's natural predators and parasites and
may actually lead to increases in pest populations. In 1970, pesticide
use in the Northwest killed so many honeybees that the pollination of
fruit trees in Oregon and Washington required the air-lifting of 2 billion
3) PESTICIDE CONCENTRATION INCREASES IN THE FOOD CHAIN
Since pesticides can't be broken down quickly (chlorinated hydrocarbons
are very slow, DDT has a half-life of 10-15 years), organisms higher up
in the food chains obtain higher concentrations than can be found in any
of their food sources. Fish may contain levels of dioxin 159,000x higher
than that of the surrounding water. For example, the results from a 1960
Long Island marsh study were that the water levels of DDT were .00005
ppm (parts per million), plankton concentrations were .04 ppm, small fish
concentrations were .2 to 1.2 ppm, large fish concentrations 1-2 ppm,
and the concentrations of fish-eating birds ranged from 3 to 76 ppm. Peregrine
falcons, ospreys, and bald eagles were heading towards extinction due
to DDT concentrations in their bodies. In the mid-60s 90% of the peregrine
falcons were gone from the Western U.S. and Northern Europe and had completely
disappeared east of the Mississippi. Now, peregrines and bald eagles have
returned to the Eastern United States. The concentration of pesticides
and their health effects increases as one ascends food chains involving
aquatic invertebrates, fish, and those that eat fish whether they be egrets,
peregrinne falcons and bald eagles or humans.
4) ALTERNATIVES TO PESTICIDES
Chemical poisons are not the only way of reducing crop loss due to pests.
1) The rotation of crops removes the pest's food source and populations
cannot be maintained in an area.
2) Natural predators can be introduced/encouraged into an area.
3) The release irradiated male insects (which are sterile) can reduce
pest populations. As they compete for females with healthy males, the
reproductive fitness of the population decreases.
4) The use of chemical pheromones can interfere with insect mating or
lure males to traps.
5) The use of insect hormones can interfere with insect development.
--TOXIC COMPOUNDS FROM PLANTS
PLANTS ARE FED UP!! For millions of years there have been bugs which gnaw
and gnaw and gnaw and gnaw and gnaw of the plants of the world. Do you
have any idea how frustrating this must be for plants? Since they are
in danger of being eaten and are unable to run away, typical plants put
really nasty chemicals into their leaves so that any animal that eats
a large quantity of this plant is going to pay a price. Plants are fighting
back. Of course, animals try to adapt to these chemicals-the liver makes
enzymes which can detoxify many of these compounds and the tongue can
detect many of these compounds and signal the brain with a "bitter"
taste. Our nervous system is prepared to reject things that taste bitter-this
is actually a self defense mechanism to limit our exposure to toxic chemicals
We are exposed to some of these chemicals every day. Even in plants which
have been cultivated for a long time, such as coffee and broccoli, there
are toxic compounds present (resulting in their slightly bitter tastes).
The average person's spice rack contains many potentially toxic chemicals.
These compounds are at a very low concentration and certainly do not produce
any measurable health risk, but nevertheless we are constantly exposed
WHY ARE TOXIC COMPOUNDS TOXIC?
There are a variety of ways that a chemical compound can interfere with
the normal functioning of living organisms. Heavy metals can bind to proteins
and change their shapes. The effects of this heavy metal would depend
on which proteins it interacted with. Some chemicals can interact with
(or block) the enzymes which catalyze the normal reactions in living cells.
Some irritants can induce inflammatory reactions and make us more susceptible
to asthma. There are many ways that chemicals can affect living things.
There are two effects of chemicals which warrant special consideration:
the actions of teratogens and carcinogens.
An embryo (such as that of a frog pictured below) can be damaged by chemicals
which do not affect adults.
Teratogens are chemicals which cause birth defects. Some teratogens can
be ingested directly such as alcohol (which can cause the skeletal and
mental changes observed in infants with fetal alcohol syndrome), components
of cigarette smoke (which can increase the risk of birth defects ranging
from cleft palate to anencephaly, the rare lethal condition in which fetuses
develop without a cerebrum), and thalidomide (whose use as a prescription
medication in Europe led to the birth of ten thousand of infants whose
limbs did not develop properly). Some teratogens are chemical toxins from
environmental sources. For example, dioxins which leaked into the groundwater
at Love Canal were responsible for the higher than normal incidence of
birth defects. In 1979, only 2 of 17 pregnancies resulted in normal, live
births pregnancies among those who had stayed in Love Canal. The National
Research Council has blamed environmental factors for 5,000-7,500 birth
defects/year with the possibility being contributors in an additional
Exposure to teratogens is most dangerous during the 1st 2 months of pregnancy
when an embryo's organ systems are first developing.
Endangered plants often survive in areas in which phosphorus and nitrogen, suggesting that the addition of these nutrients to environments is a factor threatening these species (Wassen, 2005).