As Daniel Conley points out, reducing nutrient input is the most important measure for rescuing the Baltic Sea from eutrophication (Nature 486, 463–464; 2012). But its restoration also depends strongly on political support. With ecological models indicating that recovery could take 50–100 years, such support must continue for decades. This will happen only if accompanied by evidence of steady progress.

The Baltic Sea's nutrient load can be reduced by improving agricultural practices, but huge nutrient stores in the soils will slow progress. Yet the European Union wants high water quality to be achieved by 2015 in coastal waters (Water Framework Directive) and by 2020 in open sea areas (Marine Directive).

Patience is not enough: we need ways to accelerate recovery and early demonstrations of improved water quality, at least in some enclosed coastal waters. There has been some progress near Stockholm after upgrades to sewage treatment, even as conditions deteriorated in the open Baltic Sea.

The foundation BalticSea2020 (www.balticsea2020.org/english) will reduce land-based nutrient inputs to a eutrophic bay in the Stockholm archipelago and use aluminium chloride to increase phosphorus binding by the bay's hypoxic sediments. This will reduce nutrient levels and algal production within years. Submerged vegetation and spawning sites for predatory fish will also be restored.

Such timely local recoveries could help to sustain political support for nutrient reductions for long enough to save the Baltic Sea.