Special Reports

When wetland projects pollute

Developers and government regulators say it would be too expensive to significantly monitor the long-term results of stream restoration projects. But researchers monitoring one wetlands restoration project have found that the projects can have unintended consequences.

Since 2005, Duke professor Emily Bernhardt's team and Martin Doyle, a professor from UNC-Chapel Hill, have been testing the effects of a private wetland restoration in Tyrrell County. The 440-acre site sits on former farmland that was ditched and drained to grow corn and soybeans.

The site drains into the Little Alligator River, which flows into the Alligator River and eventually empties into the Albemarle Sound.

Monitors throughout the site collect data on water levels and water chemistry. What they've shown is that the site does a good job of absorbing nitrogen, a common pollutant that is likely coming from an adjacent farm.

But the restoration is releasing phosphorus, another pollutant that the state is trying to keep out of public waters. Years of farming left significant deposits of phosphorus-rich fertilizer in the soil, and returning the site to a wetland is releasing the phosphorus into the river.

At some point, the existing phosphorus will finally be gone, and then the restoration will be expected to retain any phosphorus that enters the wetland, Doyle said.

The state's ecosystem restoration program has targeted the Neuse and Tar-Pamlico river basins for phosphorus reduction and has spent millions on wetland restorations and pollutant-absorbing buffers along rivers and agricultural ditches.

But state and federal regulations do not require the kind of monitoring that would show whether a project is helping or hurting. The Tyrrell County wetland site shows that if restorers don't understand what's in the soil, they can create projects that release pollutants.