Conservation Commission

Wetland Buffers

A buffer is an undisturbed and naturally vegetated upland area next to a wetland or surface water. Buffers ideally consist of three types of plants - trees, shrubs and ground cover. A 100 foot buffer provides a pollutant removal rate of at least 60% which is considered an acceptable level of protection for water quality.

How do buffers work?

The vegetation in the buffer intercepts rainfall and meltwater from snow, slows it down and allows it to gently trickle into the soil.

The vegetation and plant material which collects on the ground traps sediment before it can reach the water supply.

Chemicals, fertilizers, pesticides and pathogens are partially absorbed or made less toxic by plant roots, decaying plants, and beneficial microbes.

These actions pretreat the water entering the wetland, so it stays
healthier and provides cleaner drinking water for everyone.

Why is a buffer of natural vegetation recommended?

Natural vegetation is not "groomed" or disturbed. This allows leaf litter and deadfall to remain in place to rot naturally as well as for roots to grow without disturbance. These buffers are more effective at slowing the flow of water, trapping sediment and removing pollutants. In addition, natural vegetation contains a wide variety of plants which perform different water cleaning functions.

All Buffers Are Not Equal - What Works Best?

• Worst Of All:
  NO PLANTS - Such a buffer, perhaps an area of crushed rock, is preferable to an area disturbed by building or paving, but little protection to the adjacent wetlands occurs. Soil is eroded, water is not pretreated, and wetlands become choked with algae. The result is increased siltation and disruption of life cycles of both wetland plants and animals so that eventually the wetlands can no longer function to purify the water.


• Somewhat More Effective:
  GROUNDCOVER BUFFERS - Groundcover includes grasses, ferns and many other low growing plants. Buffers of primarily groundcover, which look much like an overgrown meadow, protect the water entering the aquifer by diminishing erosion, trapping some sediment, absorbing phosphorus, and enabling some water to percolate through the soil. They lack efficiency at trapping excess nutrients, utilizing nutrients, rendering nitrates harmless, neutralizing acid rain, enabling the breakdown of pesticides and petroleum products, and binding metals so that they do not enter the drinking water supply.


• More Effective:
  NATURALLY VEGETATED BUFFERS - Buffers of natural vegetation include a wide range of plant life including groundcovers, shrubs and a few small trees. Such buffers are more effective than a newly overgrown meadow. Leaf litter and a layer of humus slow water flows, trap sediment and remove nitrogen. More nutrients are removed from the water percolating into the aquifer. Pesticides and some petroleum products are slowly broken down by microbial activity. The leaf canopy has some efficiency at neutralizing acid rain. More metals are bound to soil particles, thus keeping them out of the drinking water supply.


• Most Effective:
  FORESTED BUFFERS OF NATURAL VEGETATION - These buffers do the best job of protecting the drinking water. Tree roots create spaces that promote water infiltration. Leaves in the canopy can neutralize acid rain. A forest can filter up to 80% of phosphorus and nitrogen which makes it the most efficient buffer for converting toxic chemicals to less toxic forms. These actions result in cleaner water and better refilling of the aquifer.

Buffers Protect Water Quality In The Wetlands As Well As In Our Drinking Water Supply By:

• filtering water and trapping sediment
• trapping excess nutrients in the soil
• utilization of some nutrients by the plants
• converting nitrates to gaseous nitrogen by the microorganisms in the soil
• slowing the flow of rainwater and meltwater
• rendering harmless pathogens such as bacteria, viruses, and parasites
• chemical breakdown by subsoil microbes of pesticides and petroleum products
• binding of some metals such as copper and zinc to soil particles, thus keeping these metals out of the drinking water supply
• neutralizing of acid rain by leaves in the canopy above

Without Natural Buffers Our Drinking Water
Is Not Protected.

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