For many years the disparity in values placed by different people on naturally growing plant species in both non-cropland such as in rights-of-way and in crop fields has been apparent. For example, agencies responsible for highway maintenance have preferred to destroy most growths of woody species located on roadsides because they were an obstacle to snow removal or ditch drainage. Some agriculturists have advanced land-use practices aimed at eliminating all non-crop vegetative growths whether herbaceous or woody located anywhere on the farm. Conversely, wildlife managers not only have stressed the importance of leaving all non-crop vegetation but have advocated the planting of more shrub species.