The degradation of wetlands has led to drops in the size of many waterbird populations – even in Finland, the land of a thousand lakes. A recent study proves that measures that reduce overgrowth in the wetlands are a much-needed help to increasingly rare waterbirds.

More than half of the world’s wetlands have been lost due to human action during the past century, and many of the remaining areas have suffered from eutrophication and pollution. A recently published study examined potential methods for restoring wetlands.

 “Cattle grazing along the shores of the wetlands significantly increased the amounts of both migratory birds who rest in the area and birds who nest there. Rehabilitation increased the amounts of both common and endangered species – one in three bird species in Finland are currently endangered," says researcher Petteri Lehikoinen from the University of Helsinki’s Finnish Museum of Natural History (Luomus).

The results are significant, as the rehabilitated wetlands were among the most valuable such areas for birds in Southern Finland even before rehabilitation, and now their value for birds has increased many times over.

Increasing open areas in overgrown wetlands through grazing, mowing and dredging has resulted in a boost to the number of dabbling ducks, waders, rails and bitterns. Rehabilitation has also brought back colonies of black-headed gulls, which provide vital protection for nesting ducks against predators.

Every euro helps

A comprehensive cost analysis of the rehabilitation showed that every euro spent on the project was useful. Researchers consider it particularly important that the efficacy of the rehabilitation is analysed to discover better and more cost-effective rehabilitation methods.

Improving habitats is necessary, as environmental changes in wetlands are thought to be the primary reason for the diminishing number of many species of waterbird. Many species were classified as endangered in the latest conservation status evaluation.

 “Eutrophication in particular has made wetlands less hospitable for waterbirds. Overgrowth, the overabundance of fish in the Cyprindae family and water turbidity resulting from eutrophication reduce both the habitable area and the food which waterbirds need,” explains senior researcher Markku Mikkola-Roos from the Finnish Environment Institute.

Significance increased by climate change

Wetland rehabilitation is also necessary because the significance of Finnish wetlands as bird habitats will increase with climate change. Many migrating waterbirds already arrive in Finland earlier and leave later than usual, meaning that they spend a longer amount of time in the north.

If the degraded wetlands cannot maintain the current waterbird population, bird populations may plummet as a result.

Climate change has also been estimated to increase nutrient pollution and the eutrophication of waterways as winter rains become more common, further increasing the need for wetland rehabilitation.

The study was conducted in cooperation between the Finnish Environment Institute and the University of Helsinki’s Tvärminne Zoological Station and the Finnish Museum of Natural History, and it is available on the website of the esteemed international publication series Scientific Reports.

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