When the National Forest System was established in 1905, its primary mandate was to restore the watershed functions of forests. Over a century later, it’s hard to believe that most of the southern landscape—from the Coastal Plains of the Atlantic Coast, through the Southern Appalachians, and down to the Mississippi Delta— was literally treeless just a century ago. So many trees have been planted and forest ecosystems restored that the desolate landscapes and contaminated rivers of the past have largely been forgotten.

In today’s South, the loss of forestland is driven mainly by sprawling residential and commercial CLEANING UP OUR ACT Planting Trees to Clean Water development, with untold thousands of acres cleared each day to build new houses, shopping malls, and roads. As development spreads, so do concerns about reduced infiltration of rainfall, loss of ground-water recharge, increased stormwater runoff, and downstream channel erosion. In addition, intensive agricultural practices often translate into farming up to the edges of streams, resulting in waterways devoid of trees and other vegetation in their riparian zones and along their banks. This causes runoff containing fertilizers, pesticides, animal wastes, and soil sediments to enter surface waters unabated.

Working Trees for Water Quality

How can the water-filtering functions of a forest be restored onto small but significant segments of land? Research from the National Agroforestry Center and other SRS units working on issues ranging from phytoremediation to constructed wetlands shows that making what may look like small changes at the local level can make a real difference in water quality. A glance at the table of contents for this issue of Compass may have you asking just what these stories about riparian buffers, cows among trees, phytoremediation, and restoring wetlands have in common. The answer: They all involve strategically locating tree plantings where they can help to maintain or improve water quality and quantity in landscapes that are impacted by human activities.

This issue of Compass opens with an introduction to agroforestry, a wide array of practices—riparian buffers, windbreaks, alley cropping, specialty forest products, silvopasture—that can promote water quality. These practices can also improve landowner income while providing wildlife habitat and a wide range of conservation benefits. With emerging markets for energy from woody biomass, trees grown in agroforestry plantings can also be harvested for renewable energy. The stories that follow discuss the economics of adopting agroforestry in the South, and offer examples of successful practices from other parts of the world.

We switch gears to show how SRS research has contributed to better designs for phytoremediation, including the use of trees to clean up contamination that ranges from sewage to nuclear waste. Next we look at the efforts of SRS researchers to restore the Carolina bays that clean water along the Southern Coastal Plain and to construct wetlands to purify stormwater runoff from suburban developments.

What is common to all of these situations is the role of research in understanding the geological, physical, and chemical interactions of soil, trees, and water that determine the effective functioning of these practices—and in coming up with the right trees and the right designs to make them work.

As research continues to fine-tune these practices, it becomes more and more apparent that what may seem almost too simple—planting trees— remains the most effective approach for ensuring water quality.