How to save an island: natural habitat restoration in the Hungarian Lower Danube

The shape and depth of the dredged arm was designed scientifically: the side-arm had to be made as self-sustaining as possible to prevent fast sedimentation. Due to natural river-dynamics, sedimentation of side-arms is unavoidable, but it is possible to slow the process down. © WWF Hungary

Just a decade ago, Liberty Island, located north of the town of Mohács, Hungary, was on the brink of disappearing. The island’s side arm had been blocked off by a rock-fill dam in 1982 and the island was badly affected by forest degradation due to commercial forestry and invasive tree species. Today, thanks to joint efforts over the last five years, the natural river flow has been restored and the native, alluvial soft-wood forest has been replanted, thus revitalising the natural habitats of the island. In addition, the restoration process has improved water quality for about 70,000 people living in the region.

Islands under risk. A natural river continuously forms new islands and side-arms, providing slower, warmer water and rambling hideouts for an extraordinarily rich range of wildlife. However, the Danube has been significantly altered over the past 150 years. A large number of side-arms have been blocked off to keep the water flowing in the main branch of the Danube for navigation. The regulated Danube no longer forms new islands and branches, leaving these unique habitats facing extinction.

A large-scale project to save Liberty Island began in 2008. It was initiated by WWF Hungary, supported by an unprecedented collaboration between the public and private sectors. WWF Hungary received more than €1 million, 60% of the total budget, from the European Community’s LIFE+ Nature programme, thanks to capital provided by Coca-Cola HBC Hungary and the Municipality of Mohács.

Actions to save the island. The first step of the project was to purchase the island and transfer ownership to the Hungarian State, which put its management into the hands of the Danube-Drava National Park Directorate. The area was turned into a nature reserve dedicated exclusively to conservation, and commercial forestry in the area was stopped for good. Secondly, the native, alluvial forest was replanted to provide an undisturbed habitat for wildlife such as rare birds of prey.

Drinking-water pipes had to be relocated before the rock-fill dam could be removed. After that, two dredging ships worked for 7 months, 12 hours a day, to remove the 160,000 m3 sediment, mainly sand, from the side-arm. The dredged material was transported to the main river branch and released there to reduce the sediment deficit of the Danube. The shape and depth of the dredged arm were carefully designed to be as self-sustaining as possible to prevent fast sedimentation. Natural river-dynamics mean sedimentation of the side-arms is unavoidable, but it is possible to slow the process down.

Benefits for nature and people. The five-year project finished in 2013 and today the side-arm flows freely again. It is 40–60 metres wide and almost 2 metres deep even in the low-water season. The relocated drinking-water pipes transport water to the nearby water purification plant, which provides drinking water for the city of Pécs and its surroundings. By making use of the healthy active biological filter of the revitalised branch, the water wells along the Danube provide cleaner water, thus requiring less purification in the waterworks. Restored to its natural shape, Liberty Island once again provides a habitat for protected species such as the European beaver and Black kite. Fish have also returned, and thus the island contributes to the ecological diversity of the Danube Basin.

The young forest will need to be taken care of for a few more years. In the side-arm, WWF Hungary will monitor sedimentation and river dynamics and will also monitor the quality of raw water extracted from the drinking water wells, ensuring that the improvement continues. Better filtration is expected to have a positive influence on the water wells within the next 3–5 years.

A unique cooperation for nature conservation goals. The success of the Liberty Island project has proved that governmental bodies, municipalities, NGOs and private corporations can join forces to provide funds and expertise for an objective beneficial to the community and nature.

Today the side-arm flows freely again: it is 40–60 metres wide and almost 2 metres deep even in the low-water season. The Liberty Island project has proved that governmental bodies, municipalities, NGOs and private corporations can join forces to provide funds and expertise beneficial to the community and nature. © Civertan Graphics Hungary

“Responsible operation and use of water means more than re-engineering the production process,” says Éda Pogány, Communications and Public Relations Director of Coca-Cola HBC Hungary. “That is why we decided to support WWF Hungary’s Liberty Island habitat restoration project, which has revived wildlife, restored the native softwoods of the island and provided better drinking water for the communities of the South Barany region.”

There are more than a hundred islands in the Hungarian stretch of the Danube still threatened by sedimentation as Liberty Island used to be. To prevent the elimination of the side-arms and to save the islands, it is urgent to start a large-scale restoration programme so that these wonderful and important alluvial habitats may be preserved.

Viktória Siposs is the project coordinator of the LIFE+ Nature project, WWF Hungary.