Contaminant-rich runoff from adjacent agricultural land is diluted by rainfall within the buffer zone. Generally less effective for dissolved nutrients and pesticides, although excellent nitrate removal from shallow groundwater may be obtained under wetland conditions. Ineffective on contaminants in tile drainage water and drainage ditches that bypass the buffer. Periodic harvesting of vegetation may be required where nutrient loads are high in order to remove the nutrients it contains, maintain vigorous plant growth, and promote additional nutrient uptake. Bare, unshaded, sediment-laden channels are poor habitat for fish and other aquatic organisms.
Shade reduces light intensity and water temperature.
Plant litter as well as insects and other invertebrates on plants are food for fish. Larger plant debris and roots can form stable shelter for aquatic organisms. Shade is particularly important for cold water fisheries occurring in warmer climates. Water temperature control may depend on extent of buffers within the watershed. Expansive cultivated cropland may provide insufficient cover and food for upland game, songbirds, and other wildlife, especially in winter.