New Reforestation Study

The study on the potential for reforestation on disused farmland to improve water quality focused on Ohio, but the researchers’ findings could be applied to a wide range of agricultural areas, including the Oxnard Plain at the far western end of the Santa Monica Mountains. Currently the only trees in much of the Oxnard agricultural area are old eucalyptus windbreaks, but a credit program to replant disused land with native trees could help reduce soil loss, improve water quality, and create habitat. Photo by Suzanne Guldimann

In the July 12 issue of the Messenger Mountain News we reported on how planting a trillion trees may be the best and simplest way to slow global warming. Now, a new study by UC Santa Barbara professor of environmental biogeochemistry Arturo Keller published in the journal PLOS ONE, links reforestation of marginal, degraded or abandoned agricultural land with the potential to improve water quality. 

The study proposes a program that provides incentives for facilities that discharge pollutants to work with local farmers to plant trees in exchange for water quality credits.

“While there is a general belief that reforesting marginal, often unprofitable, croplands can result in water quality benefits, to date there have been very few studies that have attempted to quantify the magnitude of the reductions in nutrient (N[itrogen] and P[hosphorus]) and sediment export,” the report finds. “In order to determine the magnitude of a credit for water quality trading, there is a need to develop quantitative approaches to estimate the benefits from forest planting in terms of load reductions.”

Keller and the study’s co-author, Jessica Fox, of the Electric Power Research Institute, in Palo Alto, focused on the Ohio River Basin, where agricultural runoff impact drinking water for a wide swath of the Midwest, and the growing “dead zone” in the Gulf of Mexico, which the National Oceanic and Atmospheric Administration has predicted could encompass a 7,829-square-mile area this summer.

“While we have intuitively known that reforestation can be a very positive action, to date, determining how much bang for your buck you can get in terms of water quality has not been reliably quantified,” Keller told The Current, UCSB’s official news site. “Here we present an approach for identifying areas where reforestation will be most effective for improving water quality, using a widely available USDA model and data sets that anyone can access.”

An incentive program to reforest poor-quality and disused farmland would also help sequester carbon as well as improve water quality.”

The study’s authors suggest that a reforestation incentive program could be adapted for almost any area where agriculture chemicals impact water quality. 

“The potential for targeted forest planting to reduce nutrient loading demonstrated in this study suggests further consideration of this approach for managing water quality in waterways throughout the world,” the study finds.

The authors of the study acknowledge that creating a well-managed water quality trading program is not simple, and involves a number of critically important elements, including soil type Best Management Practices, verification of the BMP, and ongoing validation of credit legitimacy, but the study finds that a program of this type would not only help reduce nutrient and sediment loads but would help sequester carbon and potentially create habitat.

“Trees retain soil and sediments almost completely, compared to open fields, and take up the available nitrogen and phosphorus, as well as store carbon,” Keller said. “Quantifying these effects can now be used to give tradable credits for improving water quality.”

For more information visit, The abstract for the study is available online at


Suzanne Guldimann
Suzanne Guldimann

Suzanne Guldimann is an author, artist, and musician who lives in Malibu and loves the Santa Monica Mountains. She has worked as a journalist reporting on local news and issues for more than a decade, and is the author of nine books of music for the harp. Suzanne's newest book, "Life in Malibu", explores local history and nature. She can be reached at

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