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Despite high public concern in California for the protection of wildlife and native habitat, very little information is available about the effects of herbicides on wildlife that the state's road maintenance agencies use.
The information that is available gives rise to concern about the effects of chemicals used by these agencies. Herbicides narrow the range of plants varieties. Perhaps worse, they also cross biological lines to injure and kill species which are not  the intended target. Fish, birds and frogs - all species known to be suffering serious decline in the Golden State - are also known to be harmed by herbicides used by public road agencies.
It's hard to see the sublethal, or non-fatal consequences herbicides have on wildlife. Behavior changes, weight loss, impaired or unsuccessful reproduction, high offspring mortality or deformed embryos can result from herbicide contamination. Affected wildlife become easy prey for predators or lose their ability to adapt to environmental changes. Scientists are increasingly concerned about these less-than-acute exposures which, because they are subtle, are difficult to observe. But a toll is exerted on wildlife.
In a report from Oregon, a fish biologist outlined these subtle problems for salmon species that are in serious decline on the West Coast. The report noted that observations recorded in laboratory and stream studies have revealed serious changes in behavior. These include: interruption of schooling activity, inhibition of normal migration to the sea and, especially in salmon, avoidance of polluted water. Disturbances to behavior patterns impair fish survival because they interrupt the life cycle and disrupt reproduction.
Studies have also established a strong link between herbicide pollution and impacts to the olfactory, or smell, function - by which fish carry out their most critical survival and reproduction tasks. Diuron, for instance, has been found to affect how fish swim. It also affects social activities of fish such as grouping. Even slight variations in water quality can make herbicides more or less toxic to fish. In a study of glyphosate toxicity to Pacific salmonids and rainbow trout, there were significant variations in the toxic effects glyphosate had on the same fish species when different water types were used.
Though little is understood about the consequences of herbicide pollution on fish survival, even less is known about when herbicides are dispersed in the air, and how they harm the animals that fly there.
Searches are rarely conducted for birds killed by sublethal herbicide exposures. This is partly due to the difficulty involved in tracking dead birds. But the number of birds lost to pesticides, including herbicides, adds up. According to the National Audubon Society, of the roughly 672 million birds exposed to pesticides in the United States each year, 10 percent - or 67 million - are killed. This estimate does not include indirect losses caused by adult failure to return to eggs and young birds in the nest or of weakened birds which cannot escape predators.
 Birds can be imperiled by herbicides when they drink from polluted puddles of water, preen feathers contaminated by spray drift or breathe vapors of evaporating herbicides. As is true for fish and all other wildlife, the timing of an exposure can have a great influence on the toxicity of the herbicide. The problem is that life-like exposures are difficult or impossible to replicate in a laboratory. Birds are more susceptible, for example, during nesting season or when food is hard to come by.
Like birds, frogs depend on very complex and subtle behavior patterns in order to survive, but what has been happening to frogs lately - which many scientists think is linked to the sublethal effects of herbicides and other chemicals - is anything but subtle. Large numbers of frogs are being found with gross abnormalities and are now considered to be in serious decline internationally.
Diuron and glyphosate, the two most popular roadside weed killers, were recently discovered to be among the likely culprits in the destruction of frog populations. Diuron effects the survival and growth of frog embryos and tadpoles and also causes malformations at levels that are found where the chemical has pooled. Tests of the surfactant most often mixed with glyphosate in formulations used on roadsides caused effects to frogs so great the Australian government banned spraying of the formulation anywhere near water.
Clearly, as public agencies, our road departments have a duty to protect wildlife for the current and future benefit of all Californians. Because viable alternatives are available, continuing to use chemicals that threaten wildlife - and all life - cannot be defended.
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