What's Left to Eat?

Chemicals: Messing Around in Nature's Lab

To combat insects and other pests, farmers rely more and more on what you might call chemical warfare. Pesticides have won some impressive battles. But our health and environment could wind up as casualties.


Plants don't get around much. To reproduce, therefore, they depend on animal pollinators. These critters, mainly insects, unwittingly carry pollen from place to place, fertilizing the next generation of plants. Without animal pollinators, U.S. food production would drop by about 30 percent.

eat06_side1_120x180 "The blue orchard bee," says the USDA's Agricultural Research Service, "is one of nature's best pollinators." Source: Agricultural Research Service, USDA

Few pollinators do the job better than bees. North America is home to some 1,500 wild species, but most have vanished from farmland. A key cause of their disappearance is the widespread
use of chemical pesticides. Engineered to kill, these poisons weaken bees' immune system and impede their ability to reproduce.

Lacking wild bees, farmers in the U.S. and Canada increasingly rely on managed pollination. Basically, that means having professional bee-keepers deliver bees
to a particular field.
It's a ten-billion-dollar business each year. That's a hefty price tag, isn't it, for some-thing nature used to provide for free?

eat06_side2_120x168 The white box contains a hive of bees. Source: USDA ARS


"An apple a day keeps the doctor away."

People have said that for ages. For a long time, they were right. Those apples nestled in the bottom of many lunch bags can be great, low-fat sources of fiber and nutrients. But nowadays, apples (or pears or carrots or radishes...) can sometimes be a source of not-so-great chemicals used on many modern farms.


Apples. Source: USDA
Source: USDA


Those manufactured chemicals fall largely into two groups: pesticides and fertilizers. Use of these substances has skyrocketed since the 1940s. So has our knowledge of their impact. Without even realizing it, many humans and other animals have been getting involuntary overdoses of various agricultural chemicals. Among other effects, this has meant higher cancer rates for humans, and bizarre mutations for fish and amphibians.


Put simply, a pesticide is a substance or mixture that kills pests. A pest, at least from the farmer's perspective, is anything that harms the crops. Pests can include mice, insects and other critters, weeds, fungi, and microorganisms such as bacteria and viruses.

Before the 1940s, farmers generally used pesticides made from natural ingredients, such as dried flowers or plants. Of course, "natural" doesn't always equal "safe" or better. Pesticides made from tobacco, for instance, proved harmful to humans, and were banned.

Since the forties, agriculture has increasingly relied on pesticides created in laboratories, and they are big business. Farmers around the world use three million tons of pesticides each year. In 1960, the average farmer used 2.8 pounds of pesticide per acre. By 1995, he or she used 9.6 pounds per acre. In the U.S. alone, pest-fighting farmers can choose from some 25,000 different brands. That vast selection has four main categories. Fungicides kill fungi, herbicides kill weeds, insecticides kill insects, and rodenticides kill (you guessed it) rodents.

There's just one problem with those tidy categories. A pesticide doesn't exactly know what it's supposed to kill. So it often disrupts or destroys other life-forms too—even those that help the farmer. Take earthworms, for example. Squiggling through dirt, they create tiny passages for air and water. That makes the soil much healthier. Yet some pesticides destroy the worms' central nervous system causing them to die from lack of oxygen. Using this pesticide just once can wipe out
60 to 99 percent of the earthworms in the soil.


Source: Olympic National Park
Source: Olympic National Park



Well, at least those mighty chemicals are wiping out pests, right? Not exactly.

Strange as it may sound, crop losses due to insects have actually increased since the advent of chemical pesticides. In the 1950s, U.S. farmers lost roughly 7 percent of their crops to insects. Today insects devour 13 percent of American crops.

How could this be true? Scientists say two things are happening. For starters, you just read about how most pesticides take a one-size-fits-all approach. So they often kill the pests' predators. That can have the perverse effect of boosting pest populations.

An even bigger problem is that insects, weeds, and other pests can be awesome adapters. As a result, many species have developed resistance to pesticides. Back in the fifties, fewer than 20 insect species were resistant to pesticides. Today more than 500 are. There are also some 300 weeds and more than 150 fungi known to be pesticide-resistant. And these numbers are rising fast.


Pesticide use in the United States. Source: U.S. Geological Survey
Pesticide use in the United States.
Source: U.S. Geological Survey


In response, farmers try combining different pesticides in order to create a more toxic blend. They also try bigger and bigger doses. Of course, those tactics can leave the farmer with pests that seem more invincible than ever. What weapon does the farmer have then? More pesticides. Experts call this the pesticide treadmill. In the 1950s, American farmers used about 15 million pounds of pesticide a year. Nowadays they use more than 125 million pounds.

Do the math. U.S farmers now use eight times as many pesticides as in 1950. Yet insects now destroy twice as many crops. Odd definition of progress, isn't it?


Fertilizers are the other main chemicals used in agriculture. A fertilizer is any substance that makes soil more plant-friendly—or, in formal terms, fertile. They do this by adding nitrogen, phosphorus, potassium, and other nutrients to the ground. Plants need these for their metabolism, or growth.

There are two major types of fertilizers. Organic fertilizers are derived, either directly or indirectly, from living things (aka organisms). Such fertilizers include plant products and animal manure. Inorganic fertilizers, in contrast, are derived from rocks and minerals, or are manufactured. They're also called synthetic fertilizers or chemical fertilizers. Despite some companies' claims, petroleum-based fertilizers are also inorganic.


Fertilizer sales in the United States. Source: U.S. Geological Survey
Fertilizer sales in the United States.
Source: U.S. Geological Survey


Like synthetic pesticides, chemical fertilizers can boomerang—hitting the farmer right in the soil. By changing the chemistry of the soil, inorganic fertilizers slowly turn the ground acidic. Repeated overdoses of chemical fertilizers, especially in arid places, can make soil too salty. Synthetic fertilizers also mess with soil ecology. The chemicals in them kill microbes, insects, and worms that keep soil healthy. Put this all together, and you wind up with farmland that is actually less fertile than before.

That's not all. Chemical fertilizers make it mighty tempting to stop crop rotation. Ages ago, farmers figured out that various crops add or subtract different soil ingredients. Corn, for example, gobbles up nitrogen. Soybeans, on the other hand, draw nitrogen from the air and put it into the soil. Knowing such facts, farmers grew different crops in different fields each year. The corn-soybean rotation is probably the most common example of playing "musical fields" in American agriculture.

Mind you, rotating crops is a bit of a nuisance. It's much simpler to keep planting the same thing in the same place. Chemical fertilizers make it possible to do just that—at least in the short run. Over the long haul, however, nutrient shortages get worse and worse. Can you guess what the solution is? Yep, more fertilizers. It's another grim treadmill—expensive for farmers, damaging for soil.


Agricultural chemicals have another nasty habit as well: They keep showing up where they're not wanted. Some studies estimate that less than one percent of all pesticides—at most—ever reach their targets. So what happens to all the rest? It gets carried off by air or water into ecosystems near and far.

Pesticides waft over a California farm. Source: USDA
Pesticides waft over a California farm.
Source: USDA

Water-soluble chemicals, moreover, wind up in runoff water that flows into streams and rivers, ponds and lakes. The Environmental Protection Agency estimates that agriculture accounts for 70 percent of the pollution in American rivers and streams. Each year, millions of Americans drink water laced with pesticides gone astray.

Many of these runaway chemicals are POPs (persistent organic pollutants). Most ordinary compounds decay sooner or later. Not POPs. They stick around for ages, perhaps even forever. Over time, POPs can wind up hundreds of miles from where they started.

Even some non-POPs are frequent fliers. Excess nitrogen, for instance, can wind up in the sea. There it really rattles the food chain. The nitrogen is a feast for wee plants known as phytoplankton. Populations boom. They, in turn, sustain supersize groups of bacteria, which also consume enormous amounts of oxygen. That creates hypoxia, an oxygen shortage
that kills fish and other water dwellers.

Chronic hypoxia creates a dead zone, which is exactly as charming as it sounds. Dead zones can be massive. Near the mouth of the Mississippi River, you'll find a dead zone larger than New Jersey. And it's still growing.


There's another place where all these chemicals are showing up uninvited—the human body. We breathe them with our air, drink them with our water, and eat them with our food. Each day, experts estimate, a million American kids eat unsafe amounts of pesticides. Children are especially vulnerable to chemical overexposure because, pound for pound,
kids eat, drink, and even breathe more than adults do.

For children and adults alike, all those chemicals can cause big problems. Pesticides, don't forget, are designed to kill living things. The World Health Organization estimated in 2001 that three million cases of severe pesticide poisoning occur each year in the developing world. Of them, about 220,000 lead to death. Hospital records suggest that those bleak figures may actually be low.

Frogs. Source: U.S. Geological Survey
If farm chemicals (and other environmental problems) can do this to frogs, what are they doing to us?
Source: U.S. Geological Survey

Pesticides affect human health in varied ways:

  • They raise the risk of cancer and reproductive problems.
  • Many chemicals are hormone disruptors that impede the body's normal systems and cause endocrine disorders.
  • They weaken the immune system, leaving one more likely to fall sick.
  • Some chemicals trigger serious mutations, or changes in the genetic structure.

In the face of such problems, some governments have banned certain pesticides. The United Nations estimated in 2000 that half a million tons of banned pesticides have been stockpiled. Of course, a nation's laws may not protect citizens from chemicals that hitchhike aboard imported food or in rain clouds.


Farmers have also begun to see the need to break their chemical dependency. After all, massive use of pesticides menaces both their health and their profits. And consumers
have become increasingly interested in organic food. So farmers are rediscovering the value of fish heads, manure, and other traditional fertilizers. Dutch farmers recently found that Tabasco sauce makes a handy, nonlethal way to deter rabbits and rodents from nibbling on crops.

Efforts at producing safer food are paying off. Sales of organic foods have jumped 20
percent each year since 1990. The amount of farmland cultivated organically doubled between 1992 and 1997.


Organic farming. Source: USDA magazine
Learn more about the rise of organic farming from Amber Waves, a USDA magazine.


click to download image [PDF]
USDA flyer
The USDA flyer encourages Great Plains dwellers to use integrated pest management against a pest plant. Learn more from TEAM Leafy Spurge.

Even non-organic farmers are rethinking their chemical use. One current trend is integrated pest management. Farmers use global positioning systems (GPS) and other cutting-edge technologies to determine exactly which pesticides and fertilizers are needed where. They then tailor site-specific doses that involve much smaller amounts of synthetic chemicals.

Agriculture, you can see, does have alternatives to chemical warfare—if we're hungry enough for them.


health_iconShould I stop eating vegetables and fruit?

science_iconHow do we know what chemicals do to our bodies?


Is our water use all wet? back_eatnext_eat What does genetic engineering have in store for us?

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