Because the herbicide causes no direct injury to these animals, their numbers are likely to increase. The loss of nut bearing trees or shrubs may cause a temporary decrease in the numbers of squirrels and chipmunks. Herbicides that remove herb cover in forest plantations have a major indirect effect on gophers mice, and other small mammals that depend or ground cover for food and protection. Subsequent changes in mammal populations may or may not increase or decrease the expected survival of planted seedlings. An understanding of population responses of such mammals can be important in evaluating the over-all effectiveness of a vegetation management strategy, or in anticipating undesirable side effects.
Herbicides applied by aircraft in forestry unavoidably appear in small quantities in forest waters.
Many of the same materials are used in far higher concentrations as aquatic weed control agents. Thus, these traces will not cause unreasonable adverse effects if the operator makes every effort to avoid applying them to open water. In the event of spills, or accidental application of heavy dosages to open water or to water that doesn't flush out rapidly, fish may sustain a brief decrease in growth rate. Some fish may also suffer to some degree from decreases in production of certain forage algae. Even these effects can only be caused by major spills.