By the year 2010 it has been estimated that the majority of the human population on the planet will live in urban areas, and already today approximately 75 percent of Europeans live in urban areas. An increasing population means an increasing production of Nitrogen.
Equally, the Swedish capital Stockholm is steadily growing, and is by 2030 expected to increase its population by almost 240 000 inhabitants compared to today´s population of approximately 1,9 million.
In the report “Tradeoffs between Environmental Goals and Urban Development: The Case of Nitrogen Load from the Stockholm County to the Baltic Sea", Stockholm Resilience researchers Åsa Jansson and Johan Colding, present solutions on how to reduce the total Nitrogen load to the Baltic Sea.
Wetland an efficient option
The report, which was published in Ambio Volume 36 2007, presents several options to effectively reduce Nitrogen cost. This includes wetlands creation, fertilizer reduction, catch crops, and wastewater plants, and combinations of these options.
Wetlands, in particular, are often considered important ecosystems in the context of Nitrogen retention.
- Wetland use represents quite an efficient local option that spatial planners should consider to a much greater extent, Jansson and Colding state.
- If present wetlands in the Stockholm County would be maximally utilized and a sufficient amount of wetland area restored or reconstructed to reduce the Nitrogen load to the 2900 ton Nitrogen level stated in the environmental goals of the county, our estimates indicate that an additional 80 percent wetland area would have to be added to the present.
This represents a wetland area increase of total land area from 0.5 percent to about 3 percent, or an additional 150 square kilometres wetland. It illustrates the potential of using wetlands as N filters in Stockholm County, the researchers state.
Better sewage plants not enough
According to the report, treatment plants would do little for improving the Nitrogen loads to the Baltic Sea. Investments in technical solutions to improve sewage treatment plants around the growing cities of the Baltic Seas hould be combined with wetland options.
- Our results indicate a significant increase of total Nitrogen input to the Baltic Sea in both urban development scenarios when Nitrogen reduction in the sewage treatment plants are kept at present levels, Jansson and Colding say.
Major sewage treatment plants in the county all emit purified sewage water directly into the Baltic Proper, suggesting that spatial urban planning, should not be restricted to local and regional scales, but needs to be conducted on national and even international scales in the case of managing the ecosystem service of Nitrogen retention in Stockholm County.
However, the scale of effective management could differ, depending on what ecosystem service you are focusing on and the scale of operation of that service.
- We propose that it may be potentially rewarding to invest in spatial urban planning projects in other countries for increased cost effectiveness and sustainability.
Bodies such as the Helsinki Commission (HELCOM) and the European Union (EU), can provide suitable platforms for exchange of information and communication, the researchers say.