Gema Casal1,2*
Géraldine Pérez3
Bethan C. O’Leary4,5Daisy Taylor6
Joseph Sargent7
Ian Hendy7
Rémy Simide3
Cindy C. Cornet3,6*- 1Centro Oceanográfico de A Coruña (IEO-CSIC), P. Marítimo Alcalde Francisco Vázquez, A Coruña, Spain
- 2National Centre for Geocomputation, Maynooth University, Co. Kildare, Maynooth, Ireland
- 3Institut Océanographique Paul Ricard, Ile des Embiez, Six-Fours-Les-Plages, France
- 4Department of Ecology & Conservation, Faculty of Environment, Science and Economy, University of Exeter, Penryn Campus, Penryn, United Kingdom
- 5Department of Environment and Geography, University of York, York, United Kingdom
- 6Centre for Blue Governance, Portsmouth Business School, University of Portsmouth, Portsmouth, United Kingdom
- 7Centre for Blue Governance, Institute of Marine Science, University of Portsmouth, Portsmouth, United Kingdom
Nature-based Solutions (NbS) have emerged as a cost-effective and sustainable approach to address diverse societal challenges, including biodiversity loss and the impacts of climate change to enhance ecosystem resilience and community wellbeing. However, despite some advancements, the full potential of marine and coastal (blue) NbS relying on kelp forest ecosystems remains largely untapped, partly due to insufficient resources for selecting appropriate interventions and supporting their effective implementation. As the economic, ecological, and cultural significance of kelp ecosystems becomes increasingly recognised, there is a pressing need for enhanced management strategies to protect and restore these forests. The protection of kelp, will ensure the continued provision of their valuable goods and services. This study presents the Kelp Potential Blue Interventions Support tool (Kelp PBI-Support), which uses a hierarchical tree structure to offer NbS implementation recommendations specifically adapted to kelp ecosystems and the context in which they are to be implemented. This tool enables the planification and design of blue NbS relying on kelp forest ecosystems and contributes to addressing societal challenges of climate change mitigation and adaptation. By adopting an evidence-based approach and incorporating expert knowledge, the Kelp PBI-Support acts as a decision-support system, providing standardised and customised recommendations for a range of potential interventions in kelp forest ecosystems tailored to meet the specific needs of each user. The utility of the tool is demonstrated through a case study of the Isle of Wight, located in the South of England, United Kingdom. Here, the recent designation of the area as a UNESCO Biosphere Reserve offers a strategic opportunity to improve the management of kelp forests and other marine and coastal ecosystems present to help address the societal challenges the island is facing. In this context, PBI-Support has been applied to showcase how it can inform and guide ecosystem management efforts.
1 Introduction
Nature-based Solutions (NbS) have emerged as a cost-effective and sustainable approach to address diverse societal challenges, including biodiversity loss and climate change. Mainly set up in terrestrial environments so far, their application in marine and coastal ecosystems, termed blue NbS, has been slower due to factors such as the lack of supportive tools and resources for initial planning stages (O’Leary et al., 2023; Pérez et al., 2024). Although some recent efforts have been made (Casal et al., 2025), further work is needed to operationalise NbS implementation in marine and coastal ecosystems. Blue NbS interventions, encompassing protection, restorative activities, and other sustainable management measures, require careful consideration to understand which intervention (or set of interventions) is appropriate, can be implemented, and will deliver desired outcomes (Pérez et al., 2024). Moreover, embedding diverse stakeholders across the watershed in decision-making is crucial for effective blue NbS implementation and given varied stakeholder interests, which may sometimes conflict, decision-makers must balance social, economic, and biodiversity strategies alongside associated outcomes (Hamilton et al., 2022).
Kelp forests are important marine ecosystems typically found in cold, nutrient-rich waters, primarily along rocky coastlines, covering one-third of the world’s coastline in polar, subpolar, and temperate latitudes in both hemispheres (Eger et al., 2022). These ecosystems provide valuable goods and services at local, regional, and global scales, contributing to 14 of the 18 categories of nature´s contributions to people identified by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (Díaz et al., 2018). For example, kelp forests are considered ecosystem engineers, providing spawning and nursery grounds for many species (Sjøtun et al., 1993; Rosenfeld et al., 2014) and supplying habitat for important commercial (Bertocci et al., 2015) and recreational species (Pita and Freire, 2017). This high productivity further supports local and distant food webs through exported production (Jack and Wing, 2011; Queirós et al., 2019). This means that kelp productivity supports ecosystem connectivity and trophic resilience (Zuercher and Galloway, 2019). Additionally, their high productivity means that kelp species can sequester carbon and participate to its burial in deeper water, in both natural and farmed conditions (Pessarrodona et al., 2023; Pessarrodona et al., 2024; Filbee-Dexter et al., 2024), contributing to climate change mitigation. They also alter local seawater chemistry by increasing dissolved oxygen (Murie and Bourdeau, 2020), reducing marine nutrient pollution (Kim et al., 2015), and providing environmental buffering to support juvenile and vulnerable fauna (unpublished data). Moreover, kelp forests hold cultural significance for coastal communities in the form of identity and heritage, serving as sources of traditional knowledge and spiritual significance, and inspiration for storytelling and art (Pérez-Lloréns et al., 2020).
The goods and services provided by kelp forests are key to addressing societal challenges, such as food security through their production of comestible biomass or disaster risk reduction through the dampening of water movements (e.g., Elsmore et al., 2023; Løvas and Torum, 2001; Mork, 1996; Norton et al., 2018; Salvador et al., 2025; Smale et al., 2013). As a result, there has been growing attention toward utilising kelp forests as blue NbS, although this interest has been relatively modest compared to other coastal marine ecosystems (Eger et al., 2022; Bodycomb et al., 2023). Kelp forests have been declining globally under the combined effects of climate change and anthropogenic drivers, such as ocean warming and heatwaves (Wernberg et al., 2019; Filbee-Dexter et al., 2020; Smale, 2020; Trégarot et al., 2024), fishing and overgrazing (Ling et al., 2009; Filbee-Dexter and Scheibling, 2014; Filbee-Dexter and Wernberg, 2018), and unsustainable kelp harvesting (Loretsen et al., 2020; Vásquez et al., 2014). Therefore, blue NbS that rely on these ecosystems consist in protecting and recovering kelp forests. This is achieved through protection measures, restorative activities, and other sustainable management measures, to ensure the continuity of the goods and services they provide. For instance, initiatives such as the Kelp Forest Alliance (https://kelpforestalliance.com/), which aims to protect and restore 4 million hectares by 2040, and the Green Gravel Action Group, which restores kelp forests using the “green gravel” technique (Fredriksen et al., 2020), exemplify potential blue NbS in action. Yet, despite some progress, the full potential of blue NbS in kelp forest ecosystems remains largely untapped, partly due to a lack of resources informing the selection of suitable interventions and supporting their effective implementation. Furthermore, despite increasing interest in governance to address threats and declines in kelp forests, recent studies demonstrate that these ecosystems consistently receive less global governance attention compared to other marine habitats such as coral reefs, mangrove forests, or salt marshes (Valckenaere et al., 2023).
To assist appropriate blue NbS selection, a general conceptual framework has been developed that integrates desired intervention objectives and social-ecological context (Pérez et al., 2024). However, while this conceptual framework provides the basis for understanding how to integrate relationships among societal challenges, ecosystem services, environmental context, and ecosystem-based management approaches to identify appropriate blue NbS, it has yet to be operationalised. Addressing this challenge requires accounting for the heterogeneous and dynamic characteristics of coastal environments that hold a variety of ecosystems with distinct ecological traits and responses to multiple and diverse stressors. Building on Pérez et al. (2024) conceptual framework, we have developed the Kelp Potential Blue Interventions Support tool (Kelp PBI-Support) with the aim of providing clear steps to guide decision-makers through the initial stages of planning a blue NbS relying on kelp forest ecosystems. Taking an evidence-based approach and integrating expert knowledge, Kelp PBI-Support serves as a decision-support tool providing standardised and tailored recommendations for a portfolio of potential interventions in kelp forest ecosystems specific to each user’s needs. The use of the tool is further illustrated by its theoretical application to a case study, the Isle of Wight in the South of England Figure 1.
Figure 1. Location of the Isle of Wight and its surrounding MPAs. Source: Google Satellite 2024, the Isle of Wight Biosphere3, the United Kingdom Joint Nature Conservation Committee4 and the United Kingdom Environment Agency5.
2 Methodology
2.1 Developing the tool
To support informed decisions on kelp forest ecosystems’ management, we developed a Potential Blue Interventions Support tool, named Kelp PBI-Support. The term ‘kelp’ lacks taxonomic specificity, and its use can vary among studies regarding the Orders that are considered. While some studies referring to kelp forests only include the Order Laminariales, others broadly include other Orders of large brown macroalgae such as the Order Fucales. (Fraser, 2012). In this study, we use the former, focusing only on the Order Laminariales.
Kelp PBI-Support is based on the four-step conceptual framework for blue NbS developed by Pérez et al. (2024) but adapted to the specific characteristics of kelp forest ecosystems: Step 1: Challenge(s) orientation, Step 2: Actual and potential flow of ecosystem service(s), Step 3: Environmental context, and Step 4: Intervention options to maintain or enhance the biodiversity and the system functionality. A detailed description of each step can be found in Pérez et al. (2024). However, it is important to mention here some information about these four steps to understand the following development and adaptation of the Kelp PBI-Support:
1. Challenge orientation: pre-identifies seven societal challenges that marine and coastal ecosystems could help address, grouped into three categories: 1) “Climate change mitigation”, 2) “Climate change adaptation” (encompassing “Disaster risk reduction”, “Water security”, “Food security” and “Economic and social development”), and 3) “Those required for an intervention to be defined as NbS” (namely, “Avoid environmental degradation and biodiversity loss” and “Enhance or maintain human health”).
2. Ecosystem services: identifies referenced ecosystem services from the System of Environmental Economic Accounting (United Nations, 2024), relevant to address the identified societal challenges potentially provided by the ecosystem of interest, namely, “carbon sequestration/storage”, “coastal protection”, “remediation of human waste or toxic substances”, “food provision”, “nursery population and habitat maintenance”, “all cultural services”.
3. Environmental context: considers spatial scale, available ecosystems, their ecological condition, and the pressures they are facing. Following Pérez et al. (2024), three levels were established for determining the spatial scale (macro, meso, and micro), considering both ecological and governance units. The macro scale refers to an ecoregional level and multiple countries from a governance perspective. The meso scale then refers to an area with common ecological drivers presenting distinctive geographic characteristics while it encompasses multiple communities in the same country. Finally, the micro scale refers to a landscape and/or seascape and one governing community.
4. Intervention options: provides a selection of interventions from a portfolio of protection, restorative, and other sustainable management measures based on the outputs from steps 1-3. Following Grorud-Colvert et al. (2021) and Pérez et al. (2024), PBI-Support considers four different levels of protection, typically within Marine Protected Areas (MPAs), based on the impact of activities allowed: minimally protected where extensive extraction and other impacts are allowed, but the site still provides some conservation benefits; lightly protected where some protection of biodiversity exists, but moderate to substantial extraction and other impacts allowed; highly protected where light extractive activities with low global impact are allowed; and fully protected where no extractive or destructive activities are allowed. Regarding restorative activities, PBI-Support considers five categories: passive, active, and partial restoration, rehabilitation, and ecosystem creation (Gann et al., 2019; Pérez et al., 2024). Passive restoration refers to management measures intentionally implemented to halt the pressure (s) that causes the degradation of an ecosystem or hinders its recovery; active restoration encompasses activities where human interferences aimed to assist or accelerate the full recovery of the native ecosystem’s functions to provide its full range of ecosystem services; partial restoration refers to activities that may not fully restore the ecological communities of the native reference ecosystem due to resource, technical, environmental, or social constraints; rehabilitation includes ecological repair activities focused on restoring ecological functions rather than the biodiversity and integrity of the native reference ecosystem while ecosystem creation includes activities where an alternative ecosystem (based on native species) is implanted/created, subject to biodiversity gain without replacing a productive ecosystem (Gann et al., 2019).
Using this conceptual framework, we adapted these general steps to suit the nuances of kelp forest ecosystems and developed a decision-support tool for use by those considering implementing blue NbS relying on them. To do so, expert knowledge, together with a non-exhaustive focused scientific literature review, was used for each ecosystem service linked with each societal challenge identified by Pérez et al. (2024) in steps 1 and 2. Expert knowledge was first used to build a decision tree based on the expected ecosystem services provided by kelp forests, thus defining the societal challenges kelp forests could help address and the factors that limit the ability of kelp forests to deliver these services. This core information was gathered during a workshop held in May 2023 as part of the MaCoBioS project, as well as through an online survey aimed at collecting expert knowledge beyond the MaCoBioS consortium (n = 37). During the exercise, the experts identified known links between societal challenges, ecosystem services, kelp forest´s ecological condition, the pressures affecting them, and potential interventions proven effective for addressing the degradation of these ecosystems, providing references whenever possible, and resulting in the first version of the decision tree. Subsequently to the workshop, this expert knowledge was extended and consolidated through searches in the scientific literature databases Google Scholar and Web of Science (title, abstract, and keywords) using key terms for societal challenges (e.g., “climate change mitigation”) and ecosystem services (e.g., “carbon sequestration”) combined with “kelp” and “kelp forests”. Searches were conducted in English between July 2023 and July 2024. This approach was complemented by the snowball method through references found in initial articles. The aim of the literature review was to find evidence of a specific ecosystem service linked with a specific societal challenge. Finally, the resultant decision tree was validated by seven external international scientists with recognised expertise in kelp forests. All the experts have led or participated in research projects related to kelp forest ecosystems and published peer-reviewed scientific literature on their ecological and social aspects.
2.2 Application to a case study: The Isle of Wight, United Kingdom
The Isle of Wight (IOW) is located off the South coast of England and measures slightly under 37 km across and 21 km from North to South (Moore, 1991; Isle of Wight Council and Royal Haskoning, 2010; Figure 1). It has over 142,300 inhabitants and an ageing population (median age of 51 years vs. 40 for England; UK Office for National Statistics, 2023). The island, a popular tourist destination since the Victorian era (Moore, 2020), is known for its unique geological features and is separated from the mainland by the Solent Strait, a strait with significant maritime traffic (May et al., 2023), including multiple ferry services with regular trips to the island and the UK’s largest export docks (Associated British Ports, 2016).
The waters around the IOW are covered by multiple, sometimes overlapping, marine protected areas. Notably, three Marine Conservation Zones (MCZ), three Special Areas of Conservation (SAC) and one Special Protection Areas (SPA) were designated between 2005 and 2019, and one SPA was proposed in 2020. The regulation and management of activities within these areas is shared between different governmental agencies, notably with the Southern Inshore Fisheries and Conservation Authority (Southern IFCA) managing all fishing-related activities, and the Marine Management Organisation (MMO) managing most of the other activities such as construction, dredging, deposit or removal of any substance or object. In 2019, the IOW was also designated as a UNESCO Biosphere Reserve due to its fulfilment of the three biosphere directives: its fulfilment of the three biosphere directives: conservation of landscapes, its commitment to socio-cultural and ecological sustainable development, its logistic support for conservation and sustainable development (UNESCO, 2013). The reserve covers the whole island and its adjacent inshore waters over 535 km2 (Sweetman and Goodyear, 2020). It is managed by a publicly appointed steering committee consisting of a mixed stakeholder group including local business owners, the public sector, industry, NGOs, local community and local governance with members of the IOW Council (Biosphere Steering Committee, 2023).
Biodiversity on land is well-documented with multiple projects established to protect, restore or manage invaluable habitats on the Island (Isle of Wight National Landscape, 2025). In contrast, knowledge gaps persist regarding the ecological condition, biodiversity and location of key habitats in coastal and marine areas, such as kelp forests or salt marshes highlighting the need for further research. The Biosphere Reserve has created opportunities for broad community engagement, led by the core steering group, through inclusive events such as the IOW Biosphere Festival, encouraging public awareness and involvement in shaping its future (Henson and Platt, 2024). As many MPAs lack fully developed management plans with activities managed in silos often coupled with zero communication, the Biosphere Reserve offers a chance to develop an integrated approach with stakeholder input and engagement, drawing upon local ecological knowledge (LEK). The IOW is therefore a good case study to illustrate how Kelp PBI-Support can guide planning in line with the shared principles of Biosphere Reserves and NbS for managing social-ecological systems as solutions to environmental and societal challenges.
3 Results and discussion
3.1 Kelp PBI-Support
3.1.1 Step 1 and 2: What societal challenge can kelp forests help to address through ecosystem services?
Kelp PBI-Support provides an evidence-based methodological approach for identifying potential blue NbS relying on kelp forest ecosystems that could help address the desired societal challenge(s) and be appropriate for an area. Thus, the first step involves identifying the societal challenge(s) a community aims to tackle, together with the ecosystem services that are relevant to address the specific societal challenge(s) (step 2) in a specific social-ecological context. Through expert knowledge and the literature review, five societal challenges were identified that kelp forests can help address through their related ecosystem services. Ecosystem services included provisioning (from [a]biotic sources), regulation and maintenance (transformation of biochemical or physical inputs to ecosystems), and cultural ([in]direct, in situ, or remote interactions). These results are summarised in Table 1.
Table 1. Identified societal challenges that kelp forests can help address, along with their relevant ecosystem services.
3.1.2 Step 3: What is the environmental context?
When selecting interventions for kelp forest ecosystems, it is crucial to consider the specific ecological and governance context. First, defining the spatial scale for NbS is important to identify the boundaries of the ecological and social governance system within which the potential intervention(s) would be applied. This aspect has been covered in detail in Pérez et al. (2024) and is not specific to kelp ecosystems, so we will not develop this idea further here.
Secondly, assessing the ecosystem’s vulnerability is essential (Pérez et al., 2024). Vulnerability refers to the extent to which ecosystems are exposed to various stressors, their sensitivity to these stressors, and their adaptive capacity to cope with and recover from their adverse effects (IPCC, 2014), e.g., how robust or resilient is the ecosystem? This adaptive capacity is closely linked to the ecosystem’s ecological condition, which is defined as “the quality of an ecosystem measured in terms of its abiotic and biotic characteristics” (United Nations, 2024) and encompasses factors like biodiversity, functional redundance, community evenness or habitat integrity (Steneck et al., 2002). Indeed, an ecosystem in poor ecological condition tends to have a lower adaptive capacity, making it more vulnerable to stressors and more prone to collapse (trophic and/or total) or regime shift (Gann et al., 2019; United Nations, 2024). Ecological condition is further used as a relative concept based on a reference ecosystem, which can either be that same ecosystem in a past state when known or an ecosystem from a different area (but with similar characteristics) known to be in “pristine condition”. Local ecological knowledge is critical with these steps. The comparison will then determine the current ecological condition of the ecosystem, relying on pre-identified relevant ecological indicators. Our literature review, combined with expert knowledge, indicates that the ecological condition in kelp forest ecosystems is primarily determined by parameters such as biomass, density, and canopy structure (Norderhaug et al., 2020; Smale et al., 2022; Strand et al., 2020; Eger et al., 2023).
Assessing vulnerability and all its dimensions in coastal ecosystems is challenging due to the complex interplay of ecological, social, and economic dimensions (Turner et al., 2003; IPCC, 2014). As such, assessing the ecological condition of an ecosystem is often easier/simpler than assessing its adaptive capacity for instance. When developing Kelp PBI-Support, we, therefore, chose to look at ecological condition rather than adaptive capacity for ease-of-use, and we defined the vulnerability of kelp forests as the degree to which these ecosystems are likely to experience negative impacts from various stressors (i.e., a combination of exposure and sensitivity), which can be driven by climate change or human activities. In other words, the user will need to evaluate, even qualitatively, the ecological condition of its focus kelp forest(s), and then reflect on what pressures could affect it, how intense these pressures are, and how negatively they impact it.
The stressors affecting kelp forests are multifaceted and can even lead to their disappearance (Table 2). For instance, increased temperatures can lead to a dominant species shift associated with decreased biodiversity (Teagle and Smale, 2018), while sea urchins overgrazing can decimate kelp forests and cause phase shifts from structurally and biologically diverse habitats to “barrens” (Steneck et al., 2002). Furthermore, stressors, which operate from local to global scales (Smale et al., 2013; Wernberg et al., 2019), can interact, resulting in a combined cumulative effect. Although some studies have been published (e.g., Trégarot et al., 2024), more research needs to be done to better understand the single and combined effects of different stressors in kelp forest ecosystems. Indeed, while some studies report most interactions being additive (e.g., sum of their effects) (Strain et al., 2014), others suggest that the combined effects of two different stressors frequently result in synergistic and antagonistic interactions more than additive interactions (Wear et al., 2023). That means that the sum of their effects is often greater or less than the simple addition of their individual impacts.
Table 2. Global and local stressors affecting kelp forest ecosystems.
The rate at which kelp species can respond to climate change drivers and other localised stressors is unclear (Smale et al., 2013). Some studies suggest that their seasonal and interannual variability reflects kelp forests’ high reactivity to environmental factors and their varying capacity to resist perturbations and recover from both minor and large-scale disturbances (e.g., Ghedini et al., 2015; Scheibling et al., 2013). Rapid recovery of kelp populations following catastrophic losses may result from frequent recruitment and fast individual growth rates (Mann, 1973). Some studies also indicate that controlling local stressors can potentially affect/impact the resilience of kelp forests to other stressors (Strain et al., 2014; Morris et al., 2020a; Wear et al., 2023). Still, more research is needed to understand these processes as the tolerance to stressors and their interactions can differ depending on life stages (sporophyte vs. gametophyte), species and locations (Wear et al., 2023).
In summary, the ability of kelp forests to address the defined societal challenge(s) will depend on the ecological condition of the ecosystem as well as its exposure and sensitivity to human and natural stressors. The spatial scale together with the ecological condition and the vulnerability of the ecosystem, helps understand the environmental context (Step 3) that will define the most suitable intervention approach (es) (Step 4).
3.1.3 Step 4: What are the suitable interventions to choose?
Blue NbS build on existing ecosystem-based approaches to management, namely, protection, restorative activities, and other sustainable management measures. They aim to improve the effectiveness of such approaches by requiring a comprehensive and integrated perspective to achieve greater outcomes for cross-cutting issues (O’Leary et al., 2023; IUCN, 2020). Kelp PBI-Support directs users towards implementation of such approaches, starting, for instance, with Marine Protected Areas (MPAs) with varying levels of protection based on local pressures. When the ecosystem in an area is in good ecological condition, it can provide its full complement of services. MPAs help maintain ecosystems in good ecological condition by managing potential stressors to encourage biodiversity net gain. Such interventions appear to be an effective solution for maintaining kelp forests already in a good ecological condition while managing human activities according to the local governance objectives. For example, the Cape Rodney-Okakari Point Marine Reserve was established in 1977 in northern New Zealand, where overfishing led to historical kelp declines (Peleg et al., 2023). The MPA, a no-take zone, enabled the recovery of predatory fish populations, which helped control sea urchin numbers and reduce their destructive grazing over kelp forests. The reserve sites showed a clear successional trajectory towards stable kelp forests, unlike the fished sites (Peleg et al., 2023). Another example in the East Atlantic would be the Iroise Marine Natural Park (https://parc-marin-iroise.fr/), a MPA in western Brittany, France, established in 2007. This MPA was created to promote a sustainable use of the regional marine resources, including kelp species such as Laminaria digitata (Couceiro et al., 2013). More than 50% of the yield of Laminaria digitata in France comes from the area of Molène located within this MPA (Alban et al., 2011). Efforts to protect and restore kelp forests in the MPA involve collaborative governance with local stakeholders, government agencies, marine professionals, and the community (Mazé et al., 2022). This collaborative approach ensures that conservation measures are well-integrated with sustainable local economic activities such as traditional fishing and seaweed harvesting.
Alternatively, when an ecosystem is in poor ecological condition, Kelp PBI-Support directs the user towards restorative activities, the type of restoration depending on the capacity to stop or reduce the pressure(s) and the level of restoration possible. The spectrum of restorative activities aims to restore a degraded ecosystem for one specific function through restoring it to a good ecological condition with all associated ecosystem services, depending on the project goal. Restorative activities are ideally based on a reference ecosystem that provides the specific condition an intervention aims to achieve (McDonald et al., 2016). These activities can be effective for recovering damaged kelp forests to good ecological condition, as these ecosystems show strong resilience once the main pressure(s) is/are halted (e.g., Filbee-Dexter and Scheibling, 2014).
The highest level of recovery possible should always be pursued (Nelson et al., 2024). This level must be determined according to local specifics, balancing social, economic, and environmental goals. Restoring a kelp forest to its former state involves halting all pressures responsible for its loss and damage, although this is not always the objective since certain activities like fishing may be necessary to continue and only some kelp forest functions may be desired to be recovered. For instance, South Korea developed an extensive Marine Restoration Program running from 2009 to 2030 to stop the decline of kelp forests caused by sea urchin overgrazing on the east coast and coastal development and habitat loss on the south coast and Jeju Island. They employed a combination of methods, including active restoration (transplanting juvenile kelp, seeding, and urchin removal) to allow the ecosystem to recover almost all its ecosystem services, and rehabilitation (deploying concrete artificial reefs in areas with low sea urchin density) to regain habitat function (Eger et al., 2020). Another example is the Sussex Kelp Restoration Project that aims to rewild ca. 200 km2 of lost kelp forest along the coast of Sussex in an ongoing effort following the disappearance of ca. 96% of kelp forests in the region by the end of the century due to a combination of increased inshore trawling, advances in fishing technology, and the “Great Storm” of 1987 (Sussex Kelp Restoration Project, 2023). The project came together after a successful campaign that saw the adoption of the Sussex Nearshore Trawling Byelaw in 2021, banning all trawling activities within 0.75–4 km of the coast, while still allowing sustainable inshore fisheries using only static fishing methods, to monitor and further support the kelp forests recovery in the area. As such, when the pressure can be reduced, passive and active restoration and ecosystem creation can be considered, while or if the pressure cannot be halted or reduced, Kelp PBI-Support recommends partial restoration or rehabilitation. Finally, Kelp PBI-Support directs the user towards the implementation of other sustainable management measures to regulate a specific pressure outside any MPA or restorative activities to gain biodiversity and ecosystem services. Such implementation can take various forms, e.g., anchoring or pollution regulations, but always seek to halt one or multiple pressures (CBD, 2018). For example, in Norway, sea urchin population regulation within kelp forests has shown remarkable results in avoiding overgrazing and letting the algae grow to restore the canopy density (Eger et al., 2022; Miller et al., 2022; Norderhaug et al., 2020). Several studies have also found that the improvement of water quality (e.g., reducing sediment load and nutrient concentrations) could be effective to prevent habitat shifts from canopy to mat-forming algae (Falkenberg et al., 2013; Strain et al., 2015). Experimental restoration projects include reseeding kelp through cultivation techniques, with juvenile plants being transplanted to degraded areas, such as the green gravel trials in Norway (Filbee-Dexter et al., 2022).
The concepts underpinning Kelp PBI-Support are summarised in Figure 2 and the resulting decision tree itself can be accessed here: https://macobios.vercel.app/en/tree.
Figure 2. Overview of the concepts underpinning Kelp PBI-Support for defining recommended blue NbS options in kelp forest ecosystems. The different steps of the tool bring you from the left (societal challenges) to the right (intervention options) of the diagram.
3.2 Application of PBI-Support to the Isle of Wight case study
3.2.1 Step 1 and 2: What societal challenges does the Isle of Wight face?
While all societal challenges identified in Kelp PBI-Support could apply to the IOW, three stand out as particularly significant and of greater concern to its inhabitants: disaster risk reduction, water security, and economic and social development (Figure 3).
Figure 3. Utilisation of the Kelp PBI-Support decision tree for the Isle of Wight case study fully illustrated through one of the three societal challenges the island is facing (“Disaster risk reduction”). Options which are not selected (Step 1–3) or not proposed (Step 4) are greyed out.
The IOW coastline is ca. 168 km long (estuaries included) and varies greatly in morphology, weathering and landslide activity (Isle of Wight Council and Royal Haskoning, 2010). More particularly, the southern coastline is often exposed to storms from the Atlantic and the English Channel, hence experiencing rapid coastal erosion compared to the more sheltered northern coastline (Isle of Wight Council and Royal Haskoning, 2010). The southern cliffs’ erosion often deposits into the littoral system, offering limited protection to the base of the cliffs (Isle of Wight Council and Royal Haskoning, 2010). This protection is often short-lived, however, with sediment deposits continuously being removed and transported away from the coast (Isle of Wight Council and Royal Haskoning, 2010). This has had major consequences for life on the island and, notably, for its road network (Isle of Wight Council and Royal Haskoning, 2010), which could prove very costly to protect and maintain1.
The IOW is associated with three coastal water bodies, two in the south (Dorset/Hampshire and IOW East) and one in the north (Solent), and five transitional water bodies, all on the northern coast of the island (Western Yar, Newton River, Medina, Wootton Creek, and Eastern Yar) (Figure 1). While Dorset/Hampshire and IOW East are assessed as having good ecological condition, all others are classified as being in moderate ecological condition (United Kingdom Environment Agency)2. All are impacted by high chemical pollution from polybrominated diphenyl ethers (PBDEs) and mercury and its compounds. Other notable indicators of moderate ecological conditions are related to biological quality elements (salt marsh, infaunal quality index and opportunistic macroalgae) and dissolved inorganic nitrogen, the later one at least being associated with poor nutrient management from agriculture and sewage discharge, and potentially from urban and transport pollution. Furthermore, while all designated bathing waters on the IOW were classified as either “Good” or “Excellent” in the last assessment in 2024, it is worth noting that some experienced a degradation, being retrograded from “Excellent” to “Good” (Ryde on the north coast, and Sandown and Bembridge Beach on the southeast coast) since the beginning of the monitoring. Despite this positive overview, NGOs such as Surfers Against Sewage regularly report on sewage pollution alerts for the United Kingdom coastline, as well as collect reports of sickness after swimming from citizens. In their 2023 Water Quality Report, for instance, they stated that the Bathing Water at Gurnard in Cowes had 649 spills, ranking 9th in the 20 most polluted United Kingdom bathing waters that year (Ross et al., 2023).
Finally, the IOW is one of the UK’s smallest local authorities, with limited financial resources, making large-scale economic development challenging (McInnes et al., 2003). Its economy primarily depends on micro-businesses serving the tourism and construction sectors, where employment is often seasonal with much lower wages than in neighbouring counties (Cox et al., 2016). The island’s separation from the mainland, combined with the seasonal nature of tourism, influences the cost of goods and services, affecting affordability for the local community (Cox et al., 2016). This situation is further exacerbated by high levels of second-home ownership and private rentals on the island (Cox et al., 2016). The IOW also lacks a university or higher education institution, meaning many young people must either relocate to pursue further education or regularly commute to the mainland (Cox et al., 2016). These financial and educational barriers are cited as major factors driving the outmigration of 15–29-year-olds from the island (Cox et al., 2016).
3.2.2 Step 3: What is the environmental context on the Isle of Wight?
As the IOW encompasses various parishes and ecosystems affected by shared ecological drivers, though with varying pressure levels depending on local factors such as substrate type and wave energy, the case study can be classified at the “meso” scale.
Several kelp species are distributed along the IOW’s coastline, particularly along the southern shores where rocky and mixed sediment habitats are common. The four dominant species are Laminaria digitata, Laminaria hyperborea, Saccharina latissima and Saccorhiza polyschides (Collins et al., 1990), all of which are characteristic canopy-forming species of the Northeast Atlantic. Laminaria ochroleuca, a warmer water kelp species, has also been documented on the Island’s coast (Smale et al., 2015) showing the effects of warming sea temperatures on the IOW kelp ecosystems.
However, the ecological state of kelp forests around the IOW is considered to be poor in comparison to forests found further west on England’s south coasts. Surveys conducted by the University of Portsmouth in 2023 revealed that many areas of kelp forests on the Island’s southern coast are fragmented and stressed by several environmental factors (personal communication) arising from a range of local and regional pressures.
The broader trend of rising sea temperatures in the Northeast Atlantic (Venegas et al., 2023) is driving thermal conditions around the island beyond the functional range of both Laminaria hyperborea and Laminaria digitata (Smale et al., 2019). Local episodes of mass coastal erosion (Isle of Wight Council and Royal Haskoning, 2010) also threaten kelp communities, with large amounts of clay and other soft sediments regularly deposited into the shallow waters along the island’s southern coastline. These sediment deposits, particularly severe near sites of large landslides, greatly increase water turbidity, thereby reducing sunlight availability essential for kelp photosynthesis. Frequent landslides also alter intertidal topography, potentially displacing and translocating kelp populations. Furthermore, repeated incidents of sewage discharge and agricultural runoff into coastal waterways (Environment Agency2) also endanger these communities. Increased nutrients in the water column can promote the growth of epiphytic and smothering algae, such as Ulva intestinalis, which can overgrow seabed areas and diminish suitable habitats for kelp sporophyte settlement.
3.2.3 Step 4: What suitable interventions do kelp PBI-Support propose for the Isle of Wight?
Given the poor ecological condition and high pressures on kelp forests around the IOW, Kelp PBI-Support offers the following interventions as potential blue NbS to help address local societal challenges: Fully or Highly protected MPAs, restoration activities ranging from passive recovery to ecosystem creation, and other sustainable management measures (Figure 3; Table 3).
Table 3. Interventions, existing and potentially suitable following Kelp PBI-Support, for the Isle of Wight case study where kelp forests are estimated to be in poor ecological condition. X indicates where an intervention is not present on the IOW.
While MPAs already exist around the IOW, their current level of protection falls short of Kelp PBI-Support’s recommendations, as they are classified as “lightly” or “minimally” protected. However, activities typically regulated through MPAs, such as fishing and dredging, known threats to kelps elsewhere (e.g., trawling impacts in Sussex’s kelp forests), do not appear to be the primary drivers of kelp degradation around the IOW. Instead, pressures such as sedimentation and anthropogenic nutrient inputs have been identified as the main causes. This situation may be partly due to the regulation of fishing and dredging through other mechanisms, such as the Southern IFCA fishing bylaws and the MMO regulations controlling dredging and other potentially damaging activities. As a result, the combination of existing MPAs and other management measures may be achieving a similar objective as the “fully” and “highly” protected MPAs recommended by Kelp PBI-Support.
Kelp PBI-Support further identified restoration activities as potential intervention options, though none have yet been implemented around the IOW. Feasibility studies are underway, exploring options such as deploying hard substrates, with or without kelp alginates from genetically diverse spore pools, to promote kelp recruitment, or installing artificial structures to restore nursery habitats for some fish species such as cuttlefish. Research projects are also investigating the ecosystem services provided by other seaweed species, such as the extensive Ascophyllum nodosum and Halidrys siliquosa forests, which naturally co-occur with kelp and appear more resilient, as well as by other marine and coastal ecosystems, in order to adopt a more holistic approach to addressing societal challenges on the IOW. For these restoration efforts to succeed, they must be coupled with measures to halt existing pressures on kelps, particularly the regulation of wastewater discharges and agricultural run-offs, which are well-recognised stressors impacting not only kelp forests but many other critical ecosystems.
4 Conclusion
Kelp PBI-Support relies on a hierarchical tree structure to provide tailored recommendations for appropriate NbS options considering the context in which they will be implemented. Its goal is to improve the management of kelp ecosystems to benefit both the ecosystem and society. Kelp PBI-Support operates on the principle that the suitability of an intervention in a particular context depends on the ecosystem’s condition and surrounding human activities and impacts. On the IOW, while many management measures are already in place, the recent designation as a Biosphere Reserve offers an opportunity for a more integrated and coordinated approach to managing kelp forests and other marine and coastal ecosystems, such as seagrass beds and salt marshes, informed by Kelp PBI-Support’s recommendations. As demonstrated in this case study, Kelp PBI-Support serves as a decision-support tool that helps local stakeholders contextualise results, supporting practitioners and decision-makers in the initial stages of planning or re-evaluating management strategies. Its structure fosters a better understanding among different stakeholder groups of the rationale behind recommended intervention option(s) and facilitates dialogue to identify shared objectives and actions.
Data availability statement
Publicly available datasets were analyzed in this study. This data can be found here: The datasets are included in the manuscript and correspond to research articles.
Author contributions
GC: Conceptualization, Data curation, Writing – original draft, Writing – review and editing. GP: Conceptualization, Writing – original draft, Writing – review and editing. BO’: Conceptualization, Writing – original draft, Writing – review and editing. DT: Writing – review and editing. JS: Writing – review and editing. IH: Writing – review and editing. RS: Writing – review and editing, Visualization. CC: Visualization, Writing – review and editing.
Funding
The author(s) declared that financial support was received for this work and/or its publication. This work was supported by the European Union’s Horizon 2020 research and innovation programme under grant agreement No 869710 “Marine Coastal Ecosystems Biodiversity and Services in a Changing World” (MaCoBioS). GC contributions were partially supported by the Ramón y Cajal Programme (Grant RYC2023-044898-I) funded by the Agencia Estatal de Investigación (AEI) within the Spanish State Plan for Scientific and Technical Research and Innovation 2021–2023.
Acknowledgements
The authors are grateful to Prof. Stein Fredriksen (University of Oslo) for his valuable contribution to the development of Kelp PBI-Support’s decision tree. In particular, for sharing his expertise and advice on kelp forest ecosystems during the early stages of this work.
Conflict of interest
The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
Generative AI statement
The author(s) declared that generative AI was not used in the creation of this manuscript.
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Footnotes
1https://consult.environment-agency.gov.uk/solent-and-south-downs/isle-of-wight-coastal-defence-schemes-information/
2https://data.catchmentbasedapproach.org/search?q=Event%20Duration%20Monitoring%20-%20Storm%20Overflows
4https://jncc.gov.uk/mpa-mapper/
5https://experience.arcgis.com/experience/73ed24b6d30441648f24f043e75ebed2/page/Classification/
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Keywords: conservation, isle of wight, marine and coastal ecosystems, protection, restoration
Citation: Casal G, Pérez G, O’Leary BC, Taylor D, Sargent J, Hendy I, Simide R and Cornet CC (2026) Developing a decision-support tool to inform blue nature-based solutions relying on kelp forest ecosystems. Front. Environ. Sci. 13:1627459. doi: 10.3389/fenvs.2025.1627459
Received: 12 May 2025; Accepted: 29 December 2025;
Published: 06 February 2026.
Edited by:
Chong Jiang, Guangdong Academy of Science (CAS), ChinaReviewed by:
Kristina Cordero-Bailey, University of the Philippines Los Banos, PhilippinesShyni Anilkumar, National Institute of Technology Calicut, India
Copyright © 2026 Casal, Pérez, O’Leary, Taylor, Sargent, Hendy, Simide and Cornet. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
*Correspondence: Gema Casal, Z2VtYS5jYXNhbEBpZW8uY3NpYy5lcw==; Cindy C. Cornet, Y2luZHkuY29ybmV0QHBvcnQuYWMudWs=, Y2luZHkuY29ybmV0QGluc3RpdHV0LXBhdWwtcmljYXJkLm9yZw==