Scientists Set Riparian Forest Buffer Standards

Avondale, PA (February 2014) – How many trees does it take to protect a stream? Scientists at the Stroud Center hoping to answer that question have, so far, set buffer width minimum standards. They’re also learning that trees along a stream channel, used for decades as a best management practice to protect streams by filtering out contaminants, may play an even more important role in improving overall stream health.

Anacostia RiverA few years ago, Stroud Water Research Center proposed that riparian forest buffers play an important role improving the health of the stream and enabling it to provide more and better ecosystem services for both humans and wildlife–the processing of natural organic matter and pollutants, for example.

In this way, a forest buffer provides a first line of defense (keeping sediment and nutrients out) as well as a secondary line of defense (keeping sediment and nutrients from moving downstream) for maintaining clean water in our streams and rivers.

According to Stroud scientists, this is both good news and bad. The Stroud Center recently published a case study showing that creating a forest buffer can in fact keep on average 43% of sediment and 27% of nutrients such as nitrogen from entering a stream. This is good news.
The bad news is that 67% and 73%, respectively, of the substances still penetrate the barrier.

OLYMPUS DIGITAL CAMERAThe Stroud Center, however, has also shown that improved stream health due to a forest buffer can increase the level of in-stream processing of nutrients and organic matter by 2-8 fold. So the case is good for their widespread use. Riparian buffers protect stream habitat, filter nutrients and sediments, and disperse concentrated runoff.

Stroud Center Director Bern Sweeney explained, “It’s important that we look at forest buffers both as a pollutant barrier and as an enhancer of in-stream function when looking to them to maintain and improve our waterways. What happens in the stream is just as important as what happens on the banks. When we consider both of these benefits, it is clear that a forest buffer provides better protection and more bang for the buck than a buffer filled with grass.”

Consideration and focus on the in-stream side of forest buffers is relatively new. However, as Sweeney points out, “by enabling streams and their ecosystems to work more efficiently, forest buffers can now be considered best management practice for both nonpoint and point source pollution. After all, if a forest buffer enables a stream to better process nitrogen, it does not matter if the molecule of nitrogen that the stream is processing comes from a farm or a wastewater treatment plant.”

Read the complete article in Stroud’s February 2014 “Upstream” newsletter, “How Many Trees Does it Take to Protect a Stream?