Riparian Forest Buffers

Technological improvements have reduced the impact of pesticides on the aquatic environment

Diagram showing how surface runoff is transformed as it travels through a forest bufferThe chemical, physical and biological properties which determine the effect of pesticides on water resources and the fate of these pesticides in the environment have been advanced significantly in the years since Rachel Carson's Silent Spring. Wide spectrum pesticides, which kill a wide variety of non-target organisms and remain active for a long period time, are no longer used. For example, DDT is a wide spectrum chlorinated hydrocarbon with a half life of ten years (i.e. the time required for one half of a compound to decay). DDT, and other pesticides like it, have been banned in the United States because they concentrate in the fatty tissue and tend to accumulate in the food chain where they can interfere with the reproduction and survival of many non-target species.

Many complementary insecticides such as Organophosphate and Carbamate have half lives of only a few days to several weeks, are not fat soluble, and are often much more specific in the targets they affect. While these insecticides do not accumulate up the food chain and are safer environmentally, they are very soluble in water and usually quite toxic to fish.

In contrast, most herbicides currently in use break down by the end of the growing season and are relatively less toxic to fish than insecticides. However, if herbicides reach surface waters, many species of aquatic plants can be killed. Along with shorter half lives, newer pesticides utilize more effective stickers (the chemical which keeps them in place) and are thus effective in much lower concentrations. This makes them easier to control and adds less chemical to the environment. In addition, biological controls (viruses and bacteria that occur in nature) are being refined and adopted for use as natural microbial pesticides, such as Bacillus thuringiensis for the control of gypsy moth.