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2010-10-19

Wetlands increasingly effective against eutrophication

Wetlands on agricultural land have got much better at trapping nutrients which would otherwise be conveyed to lakes or the sea. Constructing wetlands is also cheaper than many other environmental measures, but they could be even more effective. This is the conclusion of a new report from Halmstad University commissioned by the Swedish Board of Agriculture.

Eutrophication is a major problem for our seas and Lakes. Its cause is ever increasing nutrient emissions, especially nitrogen and phosphorus from sources like agriculture. Constructing wetlands is a way to trap nutrients and combat eutrophication and its effectiveness has now been assessed.

The report is backed by Stefan Weisner, a professor of biology specialising in environmental science and Geraldine Thiere, a research and development engineer at the Wetlands Research Centre of Halmstad University. They studied 70 randomly selected wetlands in six Swedish counties: Halland, Skåne, Västra Götaland, Kalmar, Östergötland and Södermanland.

Wetlands

The efficiency should increase if the wetlands were designed and located optimally. Photo: Geraldine Thiere

Could be more effective


The report indicates that the effectiveness of wetlands varies. For example, the wetlands used in recent years are more effective at removing nitrogen and phosphorus. The same goes for wetlands used to trap nutrients, as distinct from those whose purpose is to increase biodiversity.

The results also indicate that efficiency should increase if the wetlands were designed and located optimally.

“If the impact is to be as great as possible, the wetlands should be located in areas where the nutrient content of the water is high; preferably with a large catchment area and connected to agricultural land,” says Weisner.

Greater environmental benefits


Another of the report’s conclusions is that wetlands are more cost-effective compared to other environmental measures; as a method, they remove the most nitrogen and phosphorus in relation to cost.

“At this point, it’s important to factor in how wetlands also provide various other ecosystem services over and above preventing eutrophication. These include helping increase biodiversity and water storage and the possibility of bioenergy production,” says Weisner.

IDA LÖVSTÅL

Stefan Weisner

Stefan Weisner, professor of biology specialising in environmental science Photo: Patrik Leonardsson

Geraldine Thiere

Geraldine Thiere, research and development engineer at the Wetlands Research Centre of Halmstad University. Photo: Annika Johansson

Updated 2018-02-21