Special Environmental Concerns: Protecting Ground Water and Endangered Species


Learning Objectives:

Be able to name activities that threaten ground water and endangered species. Determine whether pesticides will reach ground water and learn what actions will help avoid that. Explain why the location of your use site is important and whether it is subject to limitations. Describe how water affects movement of pesticides, how solubility and pesticide persistence affect movement into ground water and how soil type affects movement. Define biological diversity, endangered species and habitat.

New efforts are underway by the Environmental Protection Agency, as well as by other federal and state agencies, to protect natural resources. Two major environmental concerns that all pesticide users must now consider are ground water and endangered species. Limitations and instructions that affect users and are devised to protect these resources are not always listed on pesticide labels. It is the responsibility of each user to find and follow instructions in regard to these resources.

Despite common misconceptions, ground water usually occurs in irregular spaces in rock and soil. It is not usually found in large quantity and it moves slowly, often only a few feet over the course of a year. Large quantities of ground water that can add to a well are called an aquifer. The other exception is ground water in limestone areas.  Contamination of these sources is an issue as these are sources for drinking and irrigation.

Ground water is replenished through rain, snow, irrigation, lakes and streams. When water falls above ground, it evaporates, moves across the surface or moves down into the soil. Once water is absorbed, it may provide irrigation to plants. Some stays in the top layers of soil, but some also move down to the water table. The water table is a saturated zone in the top layer of groundwater.

Pesticides can travel with water all the way to the water table. Several factors determine if this will happen: practices of pesticide users, whether water is present at the side during application, the pesticides’ characteristics, type of soil, and the distance of the ground water from the surface. If you are aware of these factors, you can prevent most opportunities for ground water contamination.

The primary way to avoid ground water contamination is to follow label instructions exactly. Other good practices include: avoiding overdosing, reducing risks associated with application methods, preventing back-siphoning, keeping storage facilities at least 100 feet away from water sources, locating mix and load sites 100 feet from ground water lings and disposing of unused chemicals in accordance with all regulations.

Once a surface has been treated, prolonged periods of standing water or soaking rains will move pesticides downward to ground water. Therefore outdoor treatments should be postponed during periods with forecasts for heavy rain.

It is also important to prevent irrigation water containing pesticides from flowing into other water sources.

Movement of pesticide chemicals to ground water is dependent on solubility, absorption and persistence. Certain pesticides dissolve easily and move quickly into water systems. Other pesticides attach to soil and are unlikely to move from the soil to a water source. Persistent pesticides break down so slowly that they remain in the system for long periods.

Each of these components is interrelated. Even a persistent pesticide would resist movement to ground water if it is strongly attached to soil. Highly soluble, persistent pesticides that are not absorbed are the most likely to move to ground water.

Labeling will NOT reveal these characteristics and it is necessary to contact the Soil Conservation Service, Cooperative Extension Service or your trade association to obtain this necessary information.

The local Soil Conservation Service can also help you determine the makeup of the soil in your area. This is essential as the soil is another important factor in the dissolution and movement of pesticides. Texture, permeability and organic matter of the soil determine how the pesticide is affected.

Sand, silt and clay in the soil are indications of the soil texture. Hard and sandy soils will allow pesticides to be moved more rapidly while finer textured soils slow the rate of movement. Pesticides may attach to organic matter in the finer textured soils.

How fast water moves in a particular soil is measured by soil permeability. Highly permeable soils require greater precautions to prevent ground water contamination.

Since pesticides cling more readily to organic matter, soil with it slow the movement. Soil with vegetation is more likely to stop the downward flow of pesticides.

The distance from the soil surface to the water table determines the depth of ground water. Pesticides are more likely to reach ground water only a few feet below the surface. Water tables are not as deep in humid areas as they are in arid ones. Water table depths vary throughout the calendar year depending upon the amount of rain, snow or irrigation, evaporation and vegetation, frozen ground, and by how much ground water is removed artificially.

Again, the Soil Conservation Service is the best source for geological information impacting pesticide distribution and disposal.

During the spring and fall, water tables are closer to the surface. When evaporation and plant uptake are heavy during the hot months, the water table moves down. It also moves down when surface water cannot break through frozen soil.

Another important variable is the permeability of geological layers between soil and ground water. Some layers, like gravel deposits, are highly permeable and allow easy flow of pesticides to ground water. In areas with hard clay or limestone, the pesticide flow could be stopped completely or aided dramatically by naturally formed caverns or rivers.

Surface water flows easily to sinkholes. This is dangerous from a contamination standpoint, as even moderate rain will easily carry pesticides directly to groundwater.

Some pesticides have restricted uses due to the possibility of soil contamination. Certified applicators must take responsibility and be prepared to reduce all risks through extra precautions, particularly when using techniques like soil injection. Some pesticides will carry specific labels to aid in precautionary steps.

A plant or animal in danger of extinction is called an endangered species. There are two classifications: “endangered species,” and “threatened species.” In this application, endangered species is used as a collective term for both.

The Endangered Species Act requires the EPA to be sure endangered species are protected from pesticides. Their goal is to eliminate or reduce the threat from pesticides. This is achieved by limitations placed on pesticide use in known habitats or in habitats where certain species are being re-introduced.

The areas of land, water and air space that endangered species need to survive are called habitats or critical habitats. This would include any territory where normal population behavior takes place, like feeding and breeding.

Carefully read all labels for specific limitations related to endangered species. They will direct you to other sources for necessary details. Limitations are generally imposed based on a specific geographic location. If a site has an endangered species habitat or if an endangered species uses that habitat, pesticide use will be restricted.

Identifying current endangered species habitats falls to the U.S. fish and Wildlife Services. Habitats for aquatic species often include areas around the bodies of water to prevent contamination by drifts, runoff and leaching.

Habitats are identified as accurately as possible to prevent unnecessary restrictions. Each location need to be checked as one property may fall under the restrictions while a nearby location may not.

The Endangered Species Act protects hundreds of animals and thousands of plants, including those that are only recognizable by a trained specialist. Whether they are recognizable or not, it is essential that each survive in order to maintain biological diversity. Without such diversity, mankind would not survive.

Diversity is necessary in agriculture as each crop grown today once began as a wild species. Crossbreeding with wild species creates more durable plant hybrids. It is necessary to create new hybrids with better resistance to insure against devastation from natural disaster.

Most of today’s medicines are dependent on obscure plant and animal resources. Scientists are continually discovering and developing the resources for miracle cures. It is imperative that these species are preserved.

The extinction of any species may have profound effects. One particular plant species falling to extinction can cause a chain reaction that would devastate an entire environment.

Although extinction is a natural process, man’s activity has sped up the process and can jeopardize the balance of interdependence of species. Stability of a system is based on the diversity of its inhabitants. The more diverse an ecosystem, the less likely it is to be upset by the loss or addition of certain species.

Pesticides directly affect endangered species in a number of ways. They can kill them directly or indirectly by disrupting a habitat. Drift, runoff and other applications may contaminate water sources that species are dependent upon. Predators that are endangered may be threatened by accumulation in its prey.

Certified applicators must fulfill their role of responsible application and handling to prevent harm to endangered species. Careful attention to labeling is an excellent starting point for fulfilling that obligation.

The Fish and Wildlife Service can prosecute persons who harm endangered or threatened species. This includes pesticide users. EPA personnel also have authority to be sure pesticide users observe labeling restrictions.