Why riparian forest buffers?

What are riparian forest buffers and why do they matter?

Riparian forest buffers are woodland areas next to streams, rivers, and wetlands. Healthy riparian ecosystems can provide a number of benefits for human and ecological communities alike. They can help intercept nutrients, sediment, and pesticides from nearby areas before they enter our waterways; assist in streambank stabilization; decrease the frequency and severity of flood events; keep streams cool for their resident aquatic organisms; store carbon as they grow; provide critical habitat for wildlife; and serve as the venue for myriad cultural and recreational benefits. In the Vermont portion of the Lake Champlain Basin alone, more than 86,000 acres have been identified as potential restoration sites. 

Not all buffers are created equal. More benefits are provided by wider buffers; buffers with multiple layers of vegetation; biodiverse buffers; and buffers with downed woody debris and an intact layer of leaf litter.

Learn more about the benefits of riparian forest buffers

Nutrient retention

In order to comply with the EPA's Clean Water Act standards, annual phosphorus loads to Lake Champlain must decrease by approximately 50%, largely from non-point sources such as streambank erosion and agricultural runoff. Excessive nutrients in the lake cause eutrophication and harmful algae blooms, posing a public health risk and risks to wildlife. Restoration of riparian buffers represents one of the many strategies being applied across the Lake Champlain basin to meet these targets. Phosphorus enters waterways either as dissolved particles, or bound to sediment. Vegetated riparian areas can reduce erosion and retain nutrients, thereby limiting the amount of phosphorus entering local waterways, with positive downstream effects on water quality. While grass or shrub buffers can provide some of these benefits, and research suggests that the effectiveness of a buffer depends on many factors including soil type, hydrology, topography, and others, there is evidence that forested buffers are most effective in trapping sediment, an important source of phosphorus in Lake Champlain.

Further information: Blankenberg & Skarbøvik 2020, Fox et al. 2016Klapproth & Johnson n.d.

Erosion control

In addition to transporting excess nutrients to waterways, sediment particles can negatively impact aquatic organisms. For example, sediment that fills the gaps between streambed pebbles can affect spawning for some fish species, and excessive sediment concentrations in rivers, streams, and lakes can irritate the gills of fish. Furthermore, reduced light infiltration in rivers and streams with high sediment levels and high turbidity can impact the growth of aquatic plants. Riparian buffers composed of deep-rooted, perennial vegetation, like trees, help stabilize streambanks, minimizing erosion at times of high water flow and thus reducing the amount of sediment that ends up in our waterways.

Further information: Castro & Reckendorf 1995Zaimes et al. 2019

Flood resiliency

Maintaining healthy riparian forests is one component of managing river corridors for flood resilience. Riparian buffers, and especially forested buffers, absorb water and release that water more slowly than non-vegetated riparian areas. This slowed release of water reduces river surges during heavy rainfall. Research indicates that the greatest inflow reductions are achieved when riparian buffers are restored around all river tributaries, including ephemeral streams, but some flood regulation ecosystem services can be provided even with fewer areas restored. Additionally, by stabilizing streambanks, riparian forests can mitigate flood-related erosion.

Further information: Keeton et al. 2017, Stanton 2004Warren et al. 2018, WeConserve PA

Wildlife habitat

Riparian forests can play a critical role in providing habitat for a wide variety of species. Research shows that riparian zones, as compared to upland forests, can be home to substantially higher numbers of species of plants, beetles, birds, and other animals. The wood turtle, a species of conservation concern in the Northeast, regularly emerges from streams to forage for food in nearby forests and meadows. A network of intact riparian forests can connect larger blocks of habitat for migrating and wide-ranging species, including big game species and birds such as the Golden-winged Warbler and American Woodcock; indeed, recent research suggests that the existing focus on conserving riparian areas for a range of other benefits means that in many places they are already serving a habitat connectivity role. To ensure that they provide the highest quality habitat, riparian buffers should be designed to develop diverse structure composed of native plant species whenever possible. Read more about a project to protect Golden-winged Warblers by restoring riparian areas along Lewis Creek!

Further information: Bodie 2001, Fremier et al. 2015, Audubon Vermont Important Bird Areas

Stream environments

Mature riparian forests shade streams, keeping water cool and moderating fluctuations in stream temperature. Light intensity in a shaded portion of a stream can be 30-60% that in an exposed portion. High stream temperatures can affect aquatic organism respiration, increase the susceptibility of fish to pathogens, and inhibit fish spawning. Additionally, riparian forests are an important source of in-stream woody debris that creates important stream habitat structure, and also provide organic matter that serves as food for stream organisms. A recent study found that a forest buffer of 30+ meters alongside streams can maintain macroinvertebrate and fish communities remain near a natural or semi‐natural state. Read more about how riparian forest buffers can support brook trout populations!

Further information: Effert-Fanta et al. 2019, Kratzer 2018, Sweeney & Newbold 2014Yirigui et al. 2019WeConserve PA

Climate change mitigation

Like other forest ecosystems, forested riparian buffers can sequester and store carbon, mitigating the effects of climate change. A review of research on carbon storage in riparian buffers found that establishing riparian forests can triple the soil carbon stock, and that mature riparian forests store an average of 68–158 Mg C/ha. Furthermore, actively restoring riparian forests via plantings can substantially "jump-start" carbon sequestration because planted trees grow more quickly initially than those born of natural regeneration. Other components of the buffer can also affect carbon storage and sequestration; some research suggests that enhancing understory cover in riparian restoration projects can increase both carbon storage and wildlife benefits.

Further information: Dybala et al. 2019, Matzek et al. 2015

Culture and recreation

Because of the historical concentration of human settlements along rivers and streams used for transportation, riparian areas are often hotspots of cultural importance and archeological artifacts. Additionally, many beloved recreational areas in communities worldwide are alongside waterways. Although human use of riparian areas can have adverse impacts on these ecosystems, well-managed, cared-for riparian areas can be sites that support community connection, relaxation and perspective-building, education, recreational activities, and other non-material benefits for local populations and visitors alike.

Further information: Grizzetti et al. 2019Klapproth & Johnson n.d.