Let nature do the work

The climate in Sweden has become more unpredictable, with rising sea levels, heatwaves, and extreme weather events increasing the risk of flooding and drought.

The City of Stockholm has developed a biodiversity action plan outlining strategies to strengthen . Stockholm’s stormwater strategy aims to improve water quality and includes guidelines for better utilisation of stormwater to address the challenges posed by climate change in an increasingly dense urban environment.

The water and greenery in Stockholm Royal Seaport serve many vital functions. A well-designed blue and green infrastructure not only supports ecosystem services and valuable synergies but also provides recreational spaces, which is beneficial for the health and well-being of residents. Facilitating cultivation at both the community level and at scale promotes local food production.

Strengthening dispersal zones

The location of Stockholm Royal Seaport between the northern and southern parts of the Royal National City Park is crucial for connecting these areas. The park boasts one of the largest contiguous oak habitats in the Nordic region, rich in natural values and especially protected trees. It is home to various plants, animals, and insects known as conservation species, some of which are red-listed or protected under the species protection ordinance. As cities expand and become denser, green corridors and green spaces play a crucial ecological role. They enhance natural values as parks and public spaces strengthen dispersal connections. Old oaks are preserved, and new ones are planted along these corridors. One of the park paths features a frog tunnel that connects to moist corridors and ponds, thus enabling safe passage for frogs, essential for maintaining well-functioning ecosystems in nearby areas.

An insect study was conducted to monitor the function of green corridors and green roofs as dispersal pathways between the Royal National City Park and Hjorthagsberget. The results showed that a large, preserved oak played a particularly important role in aiding the spread of insects. Flowers and the moist corridor were crucial for pollinator species. The green roofs had a minimal effect on attracting insects. The survey provided valuable insights that assists in the future development of Stockholm Royal Seaport and other parts of the city.

An ecological survey carried out in Loudden, (a former oil terminal), protected water salamanders were discovered living in a pond near a number of oil tanks. Before the area's remediation began, the water salamanders were captured and relocated to a newly created pond at Kaknäs. The rare and protected narrow-leaved lungwort has also been given a new habitat on the roofs of the terminal building in Värtahamnen and at the Bergius Botanic Garden. Plans are underway to reintroduce the narrow-leaved lungwort to Värtahamnen after the remediation is complete. The area also hosts other red-listed species such as the Eurasian Eagle Owl, Herring Gull, Lesser Black-backed Gull, and the Great Capricorn Beetle.

Multi-functional green infrastructure

Parks, streets, and residential courtyards are designed to be efficient, where multiple functions interact within the same space. Greenery creates pleasant places for people to gather, provides shade, and reduces temperatures during warm days. It also reduces the risk of flooding and promotes biodiversity through a rich variety of plants. To date, about 140,000m² of new green space has been created, equivalent to more than 20 football pitches. This includes 26,400m² of green roofs, 47,300m² of courtyards, and 33,450m² of .

Several small parks have been established, and new bridges and pathways have simplified access to the Royal National City Park. Every resident in Stockholm Royal Seaport has access to a park within 200 metres of their home, which promotes health and well-being. The 2023 residents’ survey showed that approximately 90 per cent of residents visit a park or natural area several times a week during the summer months.

Planting a variety of plants increases the chances of survival for trees and other vegetation, even if one species is affected by disease or decay. So far, a total of 640 new trees of around 20 different species have been planted in public open spaces, including 120 oaks. In 2023, 16 new trees and more than 40 bird and debris nest boxes were installed in parks, including in the Brofästet area along Husarviken and at the brick gasometers Gasklocka 1 and 2. In other parts of Gasverket, the requirement to preserve its industrial character has resulted in less space for greenery. The design of Jaktgatan was awarded the Swedish Architects’ Landscape Prize in 2019.

Developers are required to meet certain standards set out in the Stockholm Royal Seaport’s . The index is a planning tool used to ensure that high-quality, multifunctional green solutions are implemented on courtyards and roofs. The design of a residential courtyard, including its size and shape and potential to utilise walls and roofs for vegetation, affects how much eco-efficient area it is possible to create. The majority of developers meet these requirements. To date, green roofs have been mostly made of sedum with a thin layer of soil, and the Green Space Index has been further developed to enhance the conditions for more robust green roofs. The trend is towards designing roofs for social activities, demonstrating an increased awareness of the recreational value of green spaces.

The Green Space Index is applied in land allocations on City of Stockholm land throughout Stockholm and other municipalities.

A potential study for large-scale and small-scale urban farming will be developed in 2024 as part of an innovation project funded by JPI Europe. The results of the study may help to expand the Green Space Index with productive ecosystem services.

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Stormwater management

In Stockholm Royal Seaport, stormwater is treated as a resource that adds aesthetic value and is used for irrigation, while also being purified and delayed. Due to the site’s previous industrial use, infiltration of stormwater is not permitted. This precaution is taken to prevent the spread of contamination after the land has been remediated.

Space for stormwater management is included as a prerequisite in the design process. The stormwater strategy outlines principles for the area’s stormwater management. This strategy describes a local, integrated system where stormwater is managed through a combination of green roofs in conjunction with courtyards, parks, and green corridors with ponds and plant beds, as well as a delay and discharge requirement for residential blocks.

The plant beds along the streets consist of pumice and biochar soil. This helps to store and delay water flow while directing excess water to the nearest recipient. During heavy rainfall, ponds and moist corridors capture water that would otherwise cause flooding, while parks and other green areas act as natural water reservoirs. This green infrastructure functioned well during a period of exceptionally heavy rainfall in 2022. Stormwater solutions and heavy rainfall management continue to attract media attention; see the two examples below.

Stormwater management poses particular challenges in two areas: Gasverket and Värtahamnen. These are flat, low-lying areas with buildings of special cultural interest. The preservation of the industrial character of Gasverket has required the use of large impervious surfaces with limited vegetation. In Värtahamnen, low points have been identified where stormwater typically accumulates. To manage this, a stormwater tunnel has been constructed to rapidly divert water during periods of heavy rainfall.

Extended periods of drought impose new requirements in terms of irrigating vegetation. An innovation project, “Grey becomes Blue”, has explored the use of greywater for irrigation. Funded by the County Administrative Board, the project has shown positive results. The delay and purification capacity of the plant beds will need to be evaluated in the future.

Improved water quality and bottom sediments

Stockholm Royal Seaport borders Lilla Värtan to the east and Husarviken to the north. Elevated levels of pollutants have been found in the bottom sediments of Husarviken, originating from the time when Gasverket was operational. An early investigation of the contaminated bottom sediments determined that they should not be remediated to prevent the release of heavy metals. Consequently, access to the water is restricted, with only sun decks installed, lacking facilities for swimming. However, there are plans to enable swimming in the Kolkajen phase.

The ecological connections associated with the area’s aquatic environments, especially the shorelines, play a significant role in the ecosystems. As part of the detailed development plans for Kolkajen and Ropsten, marine biological surveys have been conducted in Lilla Värtan. These investigations show that the presence of benthic animals, plants, and fish is very limited.

The planned remediation in the water area around Kolkajen and Ropsten will eventually reduce the amount of pollutants in the sediments and thereby improve the quality of the surface water in Lilla Värtan. Moreover, the extensive land remediation being carried out will reduce the amount of pollutants reaching Lilla Värtan and Husarviken from the groundwater. This, in turn, leads to improved water quality. The plans also include a marine park in Kolkajen, designed with consideration for the plants and animals living in the water.

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