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News|28 May, 2008

Climate change threatens to thwart actions against eutrophication

Natur, udsigt, Holtemmen, fra sydøst, vinter
A new report commissioned by WWF and released today, shows that agreed measures to combat eutrophication in the Baltic Sea will not be enough when predicted effects of climate change are taken into consideration.

In the report two future scenarios that include predicted effects of climate change are compared: one with no new measures against eutrophication; and one with the measures agreed in the Baltic Sea Action Plan (BSAP) adopted by environment ministers around the Baltic Sea in November last year.

“The report clearly shows that the predicted impacts of global warming evidently make the BSAP’s strategic goal on eutrophication unattainable”, says Sampsa Vilhunen from WWF. “With only limited conservation measures, eutrophication will continue to be the most serious environmental problem facing the Baltic Sea”.

“Blue-green algal blooms in the summer also clearly benefit from additional nutrients, and the warmer summers will thus increase the probability of intense blue-green algal blooms”, says Professor Harri Kuosa of the Helsinki University.

The BSAP did not account for predicted effects of climate change when adopting measures against eutrophication. The results of the report now show that, even if fully implemented, combined with the effects of climate change, the measures agreed in the BSAP will only have a limited effect on eutrophication.

“In order to succeed, the Baltic Sea Action Plan needs to include clearer and more effective policies that will also address run-off from farmland, which is today the most important source of nutrient pollution in the Baltic Sea”, says Sampsa Vilhunen from WWF.

The results of the study also show differences between different areas of the Baltic Sea. The effects of climate change will be most pronounced in the eastern Baltic, where algal biomass concentrations are already very high. The Gulf of Finland, the Archipelago Sea and the Gulf of Riga will also see higher algal biomass as a result of rapidly increasing nutrient loads carried down through rivers. The effects of this increased loading will be particularly visible in the coastal waters of Finland, Russia, Latvia and Lithuania.

“The results of the study are most reliable for the more northerly waters of the Baltic Sea. However, as the predicted increase in rainfall is expected to affect the whole catchment area, the impacts of climate change are likely to be of the same direction also in other areas of the Baltic Sea which are heavily effected by high river inflows”, says the Chief Scientist, Dr. Heikki Pitkänen of the Finnish Environment Institute (SYKE).

The scenarios presented in the report were built using a 3D-ecosystem model, which calculates water flows, nutrient concentrations and algal biomass in calculation cells that cover sea areas of 5 km x 5 km.

The full report is available at

For more information, please contact:

Sampsa Vilhunen, WWF Finland, project leader, tel +358 (0)40 5503854
Professor Harri Kuosa, advisory board member in the study, tel + 358 (0)19 280176

Notes to the editors:

The focus of the study

In the study, two scenarios were defined to examine the impacts of climate change on eutrophication in the Northern Baltic Sea. Climate Change Scenario examines how global climate change will affect eutrophication in the Northern Baltic Sea if no additional conservation measures are carried out. Climate Change and the Baltic Sea Action Plan Scenario incorporates the measures to tackle eutrophication as agreed in the HELCOM Baltic Sea Action Plan (BSAP), aiming to investigate whether the fully implemented BSAP can reach one of its main targets – “a Baltic Sea unaffected by eutrophication” – despite the impacts of climate change. The two scenarios were compared with data on the present state of the Baltic Sea.

Climate change in the Baltic Sea region

The most widely predicted consequences of climate change in the Baltic Sea catchment area are rises in average temperatures and increases in rainfall. The lack of ground frost, together with heavy winter rains, will increase nutrient flows from the catchment area into the Baltic Sea, with rivers carrying increasing amounts of the key nutrients phosphorus and nitrogen.

The average extent of the sea ice will decrease. During an average winter, sea ice has normally covered the northern half of the Baltic for several months. During the winter 2007–2008, however, the whole of the Baltic Sea remained practically free of ice. Ice cover acts as a lid over the sea, preventing wind from mixing the water. Ice cover has an important effect on the dispersal of river water, salinity stratification, and also probably on oxygen conditions near the sea bottom.

The 3D-ecosystem model

The simulated scenarios presented in this WWF report were built using YVA-SYKE 3D-ecosystem model that calculates water flows, nutrient concentrations and algal biomass in hundreds of thousands 5 km x 5 km grid cells distributed across the Baltic Sea.

Model scenarios were calculated using a historical approach and run with recorded weather information, ice maps and measured water temperatures for exceptionally warm years 1997 and 1999 (to represent post climate change weather and hydrographic conditions) and 1996 and 1998 (to represent typical conditions over the last century).

The model simulations were run for five hypothetical years and at every time step the model calculates water flows, transportation of nutrients, the consumption of nutrients by algae, and the subsequent algal growth.

Nutrients enter the modelled sea area from almost 100 separate loading points or areas – mainly rivers and industrial or municipal wastewater outlets. A nutrient load increases of 15% was chosen for riverine loads of both phosphorus and nitrogen load, as an average of the figures ranging from 5% to 25% published in related research findings. Calculations also account for nutrient deposition from the atmosphere together with rain-fall, as well as simulations of the internal nutrient loads released from bottom sediments.

Average algal biomasses were recorded for the last two growing seasons (April–September), and presented in the most commonly used indication for algal biomass: chlorophyll-a concentrations in microgrammes per litre (μg/l).

The Baltic Sea Action Plan

The Helsinki Commission (HELCOM) works to protect the marine environment of the Baltic Sea from all sources of pollution through intergovernmental co-operation between all the Baltic Sea states and the European Community. The Baltic Sea Action Plan (BSAP) is HELCOM’s programme designed to restore the good ecological status of the Baltic marine environment by 2021. The BSAP was agreed in 2007. To combat eutrophication, the BSAP aims to considerably reduce nutrient loads, especially phosphorus, which should be reduced in the Baltic Proper by 65% and the Gulf of Finland by 30%.

For more information on the BSAP see: www.helcom.f

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Effects of Climate Change on Eutrophication in the Northern Baltic Sea

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