Nord Stream pipeline did not block the development plans of Świnoujście and Szczecin ports. Environmental aspects The pipeline's greatest environmental impact is the increased consumption of natural gas imported to the EU. This conflicts with decarbonization efforts for climate protection. At a nominal capacity of per year, each pipe pair can lead to carbon emissions of of annually. The Portovaya compressor station in Russia at the beginning of Nord Stream 1, with a rating of 366 megawatts, is estimated to produce around of emissions per year, not including other compressor stations for the gas pipelines within Russia. Since the pressure loss is proportional to the square of the flow velocity, dividing an unchanged gas transport volume between two Nord Stream systems could save around of the pumping effort and presumably avoid more than of emissions annually. Using the discounted damage costs of from the German Environment Agency(), this would, after a rough estimate, enable the third tube to be amortized within around 20 years from a global point of view. The fourth tube could also possibly be amortized in the hypothetical case of overall optimization of gas flow over various pipelines between Russia and the EU. The production of over of steel for the Nord Stream 2 tubes resulted in more than of emissions, not including the concrete-coating and the associated pipeline sections onshore. Before construction, there were concerns that during construction the seabed would be disturbed, dislodging World War II-era naval mines and toxic materials including chemical waste, chemical munitions, and other items dumped in the Baltic Sea in the past decades, and thereby toxic substances could surface from the seabed and damage the Baltics' particularly sensitive ecosystem. Swedish Environment Minister Andreas Carlgren demanded that the environmental analysis should include alternative ways of taking the pipeline across the Baltic, as the pipeline is projected to be passing through areas considered environmentally problematic and risky. Sweden's three opposition parties called for an examination of the possibility of rerouting the pipeline onto dry land. Finnish environmental groups campaigned to consider a more southern route, claiming that the seabed is flatter there and so construction would be more straightforward, and therefore potentially less disruptive to waste—including dioxins and dioxin-like compounds—littered on the seabed. Latvian president Valdis Zatlers said that Nord Stream was environmentally hazardous as, unlike in the North Sea, there is no such water circulation in the Baltic Sea. Ene Ergma,