Creation and restoration of marine gardens

What

This NbS involves forming the urban coastal or constructed landscapes and terrain and actions needed to improve the environmental conditions in the sea. This will allow creation or restoration of diverse and robust marine habitats and communities for site-specific native species. The NbS can be used to rewild existing so called “urban marine deserts”, as well as to avoid creating deserts when building new structures in the sea.  

 

Coastal graphic: Before

Coastal ecosystem before NbS have been implemented

Coastal graphic: After

Coastal ecosystem after NbS have been implemented

 

Where

This NbS is relevant in urban areas, and in industrial parks or other areas where artificial structures are built into the sea. The NbS is relevant for all Nordic countries.  

Why

Traditionally, the marine landscape and marine life is not considered when planning and building structures in the sea, hence, marine deserts are created. The main aim of the NbS is to enhance marine life and biodiversity (SDG 14), as well as to support human health and wellbeing (SDG 3) by providing a varied landscape, a healthy land-sea crossing ecosystem, opportunities for nature experiences, and getting closer to the sea and to marine life.  

The NbS has the potential to contribute to mitigate the intertwined nature and climate crisis, by creating structures and textures that promote marine native species, such as kelps, seagrass species, and oysters. In turn, these contribute to climate regulation and adaptation by storing carbon and reducing shoreline erosion (SDG 13).  

Restoring lost habitats or building new habitats, will benefit local biodiversity and ecosystem services, including improved water quality (SDG 6). The water quality will be improved by the kelps and seagrass’s ability to use nutrients for growth, and for trapping sediments. Oysters and blue mussels have great ability to clean the water for plankton and other particles. The NbS can be used in education and promotion of a highly needed ocean literacy.  

How

Creation or restoration of soft and hard bottom marine gardens are one of several possible NbS that can be used to rewild urban/constructed coastal areas. The construction of these costal landscapes needs to be formed to deliberately create room for geological and biological diversity, using the local landscape and native species as a template (i.e. a nature-inclusive approach). 

The landscape must be shaped based on the needs of key local species. To identify these species, it is important to gather site-specific knowledge about the native species and to assess their need for space, habitat type, and living conditions. These needs should be used as a template for the site-specific solutions for the soft and hard bottom gardens. It is particularly important to form the landscape and to facilitate the living conditions for native foundation species that facilitates the presence of other species. Such habitat forming species could be seagrass, macroalgae and/or animal species. The focused species should:

  • have a high potential to form robust and species-rich communities within the area
  • provide important ecological functions 

The aim should be to create facilitation cascades between marine neighborhoods. This means that the habitats formed by the foundation species have a mutual positive impact on each other, causing positive feedback mechanisms and persistence of the communities.   

The gardens can be planned at different scales, from small tidal pools to gardens/ecosystems at a landscape scale. The design of the gardens on the upper shores should be amphibious and future climate proof, i.e. it should be able to withstand flooding and future extreme weather, like heavy rainfall and heat waves. Amphibious and climate-smart designs will be more resistant to such events than today’s constructed coastal landscapes. Furthermore, it is crucial to use marine-life-friendly materials when constructing marine gardens.  

Rinde & Sørensen’s rewilding manual provides a step-by-step approach from planning through implementation and monitoring of the NbS, to succeed with urban seashore rewilding. The approach is general and applies to rewilding of other ecosystems. A key to success is to provide sufficient room for nature, and to allow the dynamics of nature to unfold over time. In addition, innovative design, management plans, and adaptive management are important to succeed. 

There are several other NbS that can be used to restore soft and hard bottom marine gardens: 

  • Kelp farming on how to facilitate for hanging gardens of kelp 

  • Eelgrass restoration on recommendations for how to succeed in creating/restoring seagrass beds within a formed soft bottom garden 

  • Sea urchin removal on the removal of urchins living on artificial structures deployed in shallow water as a method to promote recovery of kelp and rockweed in northern Norway

Potential outcomes

The direct ecological effects of a restored or newly built soft or hardbottom garden include:

  • Increased primary and secondary production from the established habitat forming vegetation (maerl, seagrass, kelp, and/or rockweed species), and from the epiphytes living on these habitat forming species, and of the associated fauna living on and among the plants/algae.
  • Increased biodiversity and more complex food webs compared to the urban deserts, including more trophic levels, and coupling between land and sea by means of birds using the gardens for gathering food
  • Recovery of lost ecological functions provided by established vegetation (e.g. maerl and seagrass beds, and rockweed and kelp forests) and the filtering animals (e.g. mussels or ascidians).
  • New or restored habitats can provide important habitat corridors within systems that have lost most of their historic natural ecosystem extent.
  • Improved water quality 

The ecological outcomes of a hard bottom garden of kelp or rockweed would be like the outcomes of a restored kelp forest, and the outcomes of a soft bottom garden with eelgrass, would be like a restored eelgrass bed. The water-cleaning capacity of one adult blue mussel is 60 l per day. Hence a garden that allow establishment of a blue mussel reef, provide efficient water cleaning as well as increased biodiversity from the fauna living among the mussels. Blue mussel beds provide a well-known link between ocean and land through feeding birds. A varied landscape with healthy ecosystems in the sea and on land, promote human health and well-being through close to nature experiences. 

ATTENTION

  • The landscape, including depth, terrain attributes, and substate type, need to be shaped and chosen based on the needs of the targeted local habitat forming species. The same should be done to improve the environmental conditions.
  •  It is important to secure good environmental conditions for the marine life, and to consider the needs for habitat as well as living environment along the whole life cycle of the species. This includes sufficient light for plants and algae, and oxygen for animals. The latter depend on urban water treatment as well as solutions that promote sufficient water circulation.
  • Due to lack of experiences with rewilding actions in the sea, it is important to test solutions, and to change and adapt the solutions if needed.  
  • It is essential to include maintenance of the blue gardens, and measures such as removing alien species, waste, and filamentous algae should be considered.  
  • A holistic and long-term approach is needed to succeed, including a cross disciplinary approach from the planning phase until implementation, monitoring, and adaption.  

How much do we know?

There are several relevant restoration manuals for the Nordic countries. These include: 

Costs 

The costs will depend on scale, habitat type(s), region, and context. See the eelgrass restoration page for information about potential costs. Additional costs to facilitate for an eelgrass meadow in an urban area include planning and preparing the terrain that should hold the meadow, as well as material costs. Preparation of the terrain can involve just setting off sufficient suitable space for the meadow, and to add sand or mud if needed to form a suitable substrate for the plants. However, it can also involve reconstructing the landscape and to form a suitable habitat for the meadow.  

Reconstructing the landscape involves costs such as removing material (natural as well as constructed), and costs of new material and the construction work. In a reconstructed landscape, the soft substrate needs to be prevented to become flushed away by currents and waves (e.g. by forming a sheltered basin). In both cases, the sea floor needs to receive sufficient light for the eelgrass plants photosynthesis (i.e. the site cannot be placed too deep, or in the shadow of high buildings).  

On a small scale, hard bottom gardens can be established by just transporting stones with rockweed from adjacent natural environments. Or it can involve reconstructing the landscape to form hard bottom gardens on a larger spatial scale, and to facilitate settlement and survival of native benthic species by forming suitable growth surfaces on walls, pillars and floors in built constructions. The costs of the living shoreline project in San Fransico, was 2.1 million dollars; $ 400k for design and permitting, $ 450k for construction, and $1.25M for monitoring. 

Plats: Litangen lagune, Kragerø, Agder fylke, Norge 

Vilken ekosystemtyp(er): Kust, saltvattenlagun 

Titel/namn på NbS: Skapande av marina stadsdelar 

Sammanfattning: I samarbete med Urbant HAV tog projektet fram ett förslag till marin landskapsarkitektur och naturbaserade återförvildningslösningar för ett gammalt kvartsbrott som man ville omvandla till ett område med fritidshus och rekreationsändamål runt en saltvattenslagun. Vi föreslog att man skulle underlätta för tre huvudtyper av marina stadsdelar baserat på kraterns terrängegenskaper och djupzoner. 

Relevanta länkar: NIVA Open Access Archive: Litangen Lagune – marin landskapsarkitektur og naturbaserte villgjøringsløsninger. En tverrfaglig rapport laget av NIVA og Urbant HAV 

Plats: Oslo, Norge  

Vilken ekosystemtyp(er): Kust, urban havsstrand 

Titel/namn på NbS: Skapande av marina stadsdelar 

Sammanfattning: Projektet föreslog mångfaldsfrämjande åtgärder såsom mångfaldsfrämjande reparation av konstruerade strandlinjer och en mångfaldsfrämjande marin landskapsarkitektur för sex områden längs Oslos urbana havsstränder. Rekommendationerna betonade skapandet av goda marina grannskap som kan samverka på ett positivt sätt för att skapa en ekologisk kaskad och robusta och hälsosamma ekosystem. Rinde et al. 2019. 

Relevanta länkar: NIVA Open Access Archive: Reetablering av biologisk mangfold i Oslos urbane sjøområder 

Plats: Grønlikaia, Oslo, Norge 

Vilken/vilka ekosystemtyp(er): Kustnära, urbana 

Sammanfattning: Projektet undersökte möjligheter och begränsningar för hur naturliga ekosystem och ekologiska processer kan stärkas i området och införlivas i den planerade utvecklingen. Bedömningarna baserades på kartlagd och dokumenterad information om berggrund och lösa massor, klimat- och miljövariabler, registrerade naturvärden såsom viktiga naturtyper för biologisk mångfald, skyddade områden och artregistreringar, topografi, landskap och historisk utveckling samt viktiga landskapselement i området. 

Relevant referens: Hanslin HM, Sørensen ET, Rinde E (2022) Landskapsøkologiske vurderinger for Grønlikaia. NIBIO Rapport 8 (77). 40s. 

Plats: San Fransisco Bay, USA 

Vilken ekosystemtyp(er): Kustnära, ålgräs och ostronbäddar 

Titel/namn på det nationella stödprogrammet: Restaurering av habitat i ålgräs- och ostronbäddar 

Sammanfattning: San Francisco Bay Living Shorelines Project omfattar restaureringen av tidvattenshabitat av inhemskt ålgräs och inhemska ostronbäddar på tre platser i San Francisco Bay. I projektet testas de bästa restaureringsteknikerna och användningen av NbS-metoder som en strategi för anpassningar till klimatförändringarna. Målet är att skydda San Francisco-buktens strandlinje och samtidigt skapa biologiskt rika och mångsidiga livsmiljöer som är motståndskraftiga mot förändrade miljöförhållanden.  

Relevanta länkar: The San Francisco Bay Living Shorelines Project 

Gagnon K, Rinde E, Bengil E, Carugati L, Christianen M, Danovaro R, Gambi C, Govers L, Kipson S, Meysick L, Pajusalu L, Tüney Kızılkaya I, van de Koppel J, van der Heide T, van Katwijk M, Bostrom C (2020) Facilitating foundation species - the potential for plant-bivalve interactions to improve habitat restoration success. J. App. Ecol.  

Gagnon K, Alan V, Bakran-Petricioli T, Bengil EG, Carugati L, Christianen MJ, Christie H, Danovaro R, Da Ros Z, Gambi C, Lo Martire M, Govers LL, Gräfnings M, Kipson S, Martin G, Meysick L, Pajusalu L, Rinde E, Tüney Kızılkaya İ, van der Heide T (2019) Manual of restoration measures in soft bottoms based on surveys and experiments. Marine Ecosystem Restoration in Changing European Seas (MERCES). MERCES Work Package 2. Deliverable 2.1 November 2019. 36 s. 

Hanslin HM, Sørensen ET, Rinde E (2022) Landskapsøkologiske vurderinger for Grønlikaia. NIBIO Rapport 8 (77). 40s.  

Hudson, R., Kenworthy, J. and Best, M. (eds) (2021). Saltmarsh Restoration Handbook: UK and Ireland. Environment Agency, Bristol, UK. 

Infantes E, Rinde E, Kvile KØ (2022) Restaurering av ålegrasenger. En praktisk veileder utviklet for Oslo kommune. NIVA-rapport 7693-2022.  

Moksnes PO, Gipperth L, Eriander L, Laas K, Cole S, Infantes E. 2016. Handbook for restoration of eelgrass in Sweden - National guideline. Swedish Agency for Marine and Water Management, Report number 2021:5, 111 pages (excluding appendices). 

Rinde E, Sørensen ET, Walday MG, Fagerli CW, Christie HC, Staalstrøm A, Barkved LJ, Simmons H, Borchgrevink HB (2019) Reetablering av biologisk mangfold i Oslos urbane sjøområder. NIVA rapport nr 7426-2019. 68 s. 

Rinde E, Sørensen ET (2022) Manual for villgjøring av urbane sjøområder. NIVA-rapport 7806-2022 (M2454|2023). 54 s. 

Rinde E, Sørensen ET, Gitmark JK, Kile MR, Kvile KØ (2022). Litangen lagune – marin landskapsarkitektur og naturbaserte villgjøringsløsninger. En tverrfaglig rapport laget av Urbant HAV og NIVA. NIVA-rapport 7776-2022. 

Verbeek J, Louro I, Christie H, Carlsson PM, Matsson S, Renaud PE (2021) Restoring Norway's underwater forests. A strategy to recover kelp ecosystems from urchin barrens. SeaForester, NIVA & Akvaplan-niva, Report, 2021.