Restoration of peatlands: Flooding is not the ideal solution

Restoration of peatlands: Flooding is not the ideal solution - Leibniz Institute of Freshwater Ecology and Inland Fisheries

land next to a river with cages and scientific equipment — An inundated riparian peatland in northeast Germany after 12 years of rewetting mainly colonized by Typha latifolia and instrumented with an automated chamber system for greenhouse gas flux measurements (Dominik Zak)

Intact peatlands are habitats for many rare animal and plant species and important sinks for greenhouse gases. Many peatlands that have been converted to agricultural land should therefore be restored. A current study with IGB participation discusses different strategies for this. The authors make clear that the most commonly used method of flooding former peatlands is problematic: it can cause large amounts of methane, a greenhouse gas, as well as nutrients to be released into the environment. Removing the topsoil or slowly rewetting could have more ecological sense in many cases.

Peatlands, whose areas once accounted for more than ten percent of the land in some regions of Europe, are important biodiversity hotspots and store carbon as well as nutrients. But most peatlands have been drained and used for agricultural purposes, such as cropping or grazing. With the beginning of the 1990s, a rethinking began: People started rewetting large areas of peatlands to restore their original function. "At that time, people simply rewet them and thought the ecosystems would restore themselves in short-term," reported Dr. Dominik Henrik Zak. The scientist and peatland specialist is now working at Aarhus University in Denmark and is also a guest scientist at IGB. He is investigating the rewetting of peatlands for many years. In a study published today in the Journal of Applied Ecology, "A call for refining the peatland restoration strategy in Europe," he and co-author Robert J. McInnes call for greater attention to be paid to the ecological and also social consequences of the chosen method when restoring peatlands.

For example, the most common and cost-effective method used to date, large-scale flooding of former peatlands, also has undesirable effects: very large quantities of greenhouse gases are released, and nutrient inputs into the environment can also increase rapidly. "The soil is degraded and mineralized. When water comes on top of it, a shallow lake is first formed, and the phosphorus bound in the soil is released. The phosphorus concentrations of such flooded peatlands are thereby 100 to 1000 times higher than in near-natural peatlands. The concentrations are so high because the peat is highly decomposed and mineralized, and the soils are often overfertilized if they were previously intensively farmed. In addition, large amounts of methane, which has a particularly strong impact on the climate, are released under these conditions," explained Dominik Zak. Moreover, it takes more than 50 years for conditions similar to those in nature to develop and for plants typical of peatlands, such as mosses and sedges, to become dominant.