At the supermarket, there are usually two sections in the produce aisle. In one, all the fruits and vegetables, from apples to zucchini, are labeled “organic.” Often these products cost more than ones that look the same but don’t have the organic label.
The big price tag can lead people to assume organic food is better than conventionally grown food. But, in the United States, the label simply means that the food has met guidelines set out by the U.S. Department of Agriculture.
For instance, organic fruits, vegetables and other crops must not have been treated with synthetic fertilizers, certain pesticides or sewage sludge. Meat, eggs and milk must come from animals that have been raised according to specific health and welfare standards. Also, farmers may not treat these animals with antibiotics or growth hormones and must raise them on organic feed. Products with multiple ingredients must contain 95 percent or more organic content.
What benefits the organic label might signify, though, has not always been clear.
For years, scientists have been trying to tease out whether organic foods are themselves different than those grown conventionally. Research is beginning to show organic foods can be better — and not only for the people who eat it. Growing foods organically also can help the environment, new data show.
Pesticides are good travelers
On a farm, pests and weeds can destroy a crop. So most U.S. farmers apply chemicals called pesticides to limit the damage.
Conventional farmers can apply any pesticide approved for use in the United States. Organic farmers cannot use all of those same chemicals. That doesn’t mean organic farmers allow insect pests and weeds to live peacefully among their crops. They too can use pesticides and weed killers. They just have a smaller list from which to choose.
But none of these chemicals will necessarily stay put. Some share of them will tend to move off through the soil, air or water. Eventually, these pesticides end up in streams where they can mix, creating a mystery soup.
Scientists have been studying how far and how fast pesticides can move through the environment. These data may then point out which animals are at risk of being exposed to the pollutants.
For instance, researchers recently looked at pesticides commonly used on California farms. They found the pesticides in Pacific chorus frogs living in national parks, forests and other locations high in the Sierra Nevada mountains. In some cases, the frogs lived more than 100 kilometers (62 miles) from the nearest farms that had used the chemicals.
“This is the first time we’ve detected many of these compounds, including fungicides, in these remote locations,” says Kelly Smalling. She’s the study’s lead author. She’s also a hydrologist with the U.S. Geological Survey (USGS) in Lawrenceville, N.J. A hydrologist studies the movement, distribution and quality of water. Her team published its findings in the July 2014 issue of Environmental Toxicology and Chemistry .
Discovering that pesticides contaminate frogs is bad news. Earlier research had found that pesticide exposure could cause problems for the frog’s immune system. And this could alter how the frogs developed. It might even cause male frogs to adopt some female traits.
Smalling and her colleagues think their study supports the idea that pesticides used in conventional agriculture may play some role in the falling numbers of many species of frogs and toads.
But amphibians aren’t the only animals in decline. Honeybees also are in trouble. A problem called colony collapse disorder causes seemingly healthy bees to suddenly abandon their hives. The queen bee remains. Without the worker bees, though, the hive eventually dies.
A May 2014 study published in the Bulletin of Insectology looked at 18 beehives for almost a year. As they go around collecting pollen, bees may pick up any pesticides that had been sprayed onto the plants they visited.
To probe possible effects of these chemicals, scientists looked at hives whose bees had been exposed to two pesticides: imidacloprid (Ih-MEED-uh-KLOH-prid) and clothianidin (Klo-thee-AN-ih-din). Neither can be used on organic farms. The scientists compared bees in these hives to those in hives free of these chemicals. And they found that even small amounts of the two pesticides triggered a biological change that led to bee deaths.
This suggests the pesticides create unintended problems for growers. Farmers need bees to pollinate many crops, including almonds, cherries and broccoli. If too many bees die, less pollination may occur. And this can shrink farm harvests.
But without using chemicals like these, an influx of pests and diseases also may shrink those harvests. So even organic farms are allowed to use some pesticides. These chemicals just supposed to pose less of a risk to bees and other beneficial wildlife.
Still, those chemicals approved for use on organic farms are not necessarily harmless. One 2010 study in PLOS ONE, for example, looked at organic pesticides applied to soybeans. These chemicals controlled a type of insect known as an aphid. The study found that organic pesticides were more poisonous to the aphid’s natural enemies than conventional pesticides were. That means these organic pesticides may have a worse overall impact on this environment that will conventional ones.
Dirt poor, dirt rich
Pesticides help growers by poisoning some of the farmers’ worst enemies: insects, weeds and disease. But there’s another family of farm chemicals that also help growers: fertilizers. To grow, plants need nutrients, especially the elements nitrogen and phosphorus. And fertilizers add nutrients to the soil.
Organic farmers cannot use these elements if they come from synthetic (human-made) sources, such as ammonia salts. Instead, the farmers need to find natural fertilizers. For instance, they may plant beans. These plants naturally increase nitrogen levels in the soil. Crops that are planted after the beans are gone can now use that nitrogen.
With rich, healthy soil, crops also may need fewer pesticides or fertilizers, farmers are finding. And because they don’t have to use as much of these chemicals, naturally fertilized soils can cut the amount of pollution linked to the frequent overuse of nitrogen and phosphorus.
“Having nitrogen in a plant form, as compared to a liquid form [used] in more conventional agriculture, tends to be less leaky,” notes Meagan Schipanski. As an agronomist at Colorado State University in Fort Collins, she studies soil and crop production. By “leaky,” she means that liquid nitrogen is easily washed out of the soil and carried off the farm. The reason plant-deposited nitrogen tends to stay put is because it “is attached to carbon molecules,” she explains. “There’s a molecular bond there” to hold it in place.
Both nitrogen and phosphorus can build up in nearby waterways. This is called nutrient pollution. Plants and animals need nutrients to thrive. But when large amounts of these elements end up in lakes and oceans, they can cause large growths of algae. Those growths are called algal blooms . They can kill fish and other aquatic life.
The problem can be made worse by unpredictable rains. This may be happening in the Midwest, says Lisa Nowell. As a chemist with the USGS in Davis, Calif., she studies how pesticides and other chemicals affect water quality. In 2012, the Midwest experienced a drought. The following year it rained. A lot. Rivers overflowed their banks. Towns and fields flooded. All that rain risks washing away fertilizers and other chemicals that had collected in the soil, Nowell says.
Indeed, she says: “Preliminary data show really high concentrations of both nutrients and atrazine and other herbicides in the streams. It was kind of phenomenal. And that can cause real problems downstream.” The atrazine (AT-truh-zeen) she mentioned is one of the most common weed killers used in the United States.
Organic farms tend to produce less of that kind of pollution. One reason: These farms often work to build soil that retains more water and that produces less runoff.
Organic farmers also use compost. This soil-enriching mix is usually made from decomposed plants , food waste and manure. Compost provides nutrients for plants. It also is rich in microscopic life. Research suggests these microbes are important for the health of soils — and plants.
Rick Carr is a compost-production specialist at the Rodale Institute in Kutztown, Pa. He says, “We know that if you have diverse microorganisms in your soil, that’s going to lead to better soil health.” Scientists have found evidence that healthy soils help suppress plant diseases. Healthy soils also can help plants take up nutrients and can hold water in the root zone, where plant’s most need it.
Carr is researching how microbes in compost can help fight plant diseases. Being full of microbes, “Soil is alive and it’s doing things,” Carr says. “So we’re really relying on the soil. We’re taking care of the soil so it can take care of our plants.”