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 alongside crops.

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 diapers.
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.


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).

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 cleanup.

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.

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.

apple tree

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.

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.
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 honeybees.
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.

aquatic invertebratesfish

egretperegrinne falcon

bald eagle
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.

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 in plants.
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 to them.

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.

frog embryo
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 150,000.
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).