High Coast / Kvarken Archipelago

Fishing, mostly outside the site in the broader Baltic Sea area, remains a major pressure on several species within the site and also leads to associated food web impacts when overfishing is allowed to significantly impact trophic interactions within the ecosystem (HELCOM, 2010; 2018). Commercial fisheries exist for Baltic herring, whitefish and salmon, which are subject to ICES stock advice and have quotas enforced for some species. However other target species including sea trout, pike and perch, have not historically fallen under regulations stipulating total allowable catches.

1) Local species that are natal stocks and have a short migration range (<20 km) and reproduce in the area include perch, pike and cyprinid species. Commercial perch fishing is considered to be at maximum sustainable level, though regional differences are evident inside the area – some perch stocks are under high fishing pressure and others may not be targeted by commercial fishing depending on area (IUCN Consultation, 2024). Decreases in large predatory fishes, such as pike and perch may disrupt the functioning of the ecosystem of the archipelago, especially in the shallow bays like flads.

2) Species that have reproduction areas outside the WH site but occasionally use the site as a feeding area include salmon, sea trout and anadromous whitefish. Estimated annual recreational catches of salmon have been more variable, while the known recreational catches of sea trout have increased and are now approximately six times higher than commercial catch (ICES, 2024).

3) Species that reproduce in the WH site but also have reproduction areas beyond the boundaries and the stocks are not considered local for the WH site include herring and sea-spawning whitefish. There are several important Baltic herring spawning grounds within the site, some of which overlap with the fishing grounds. There has long been widespread concern about several of the Baltic Sea's herring stocks, which have now led to reductions in the Total Allowable Catches (TAC). For example, in 2022 the TACs for central and western herring stocks were reduced by 45% and 50% respectively (Hamrén, 2021; ICES, 2024). Herring and sprat together constitute about 95% of the total catch and are mainly caught by pelagic trawls. The fisheries for flatfishes (and cod in the past) in the Baltic Sea use both demersal trawls and gillnets (ICES, 2024). Fishing of sea-spawning whitefish is considered to be sustainable based on population size-age structure (IUCN Consultation, 2024).

For the species group 1 local fisheries management actions can have high impact, but for groups 2 and 3 management in the distribution range of specific stock are needed (IUCN Consultation, 2024).

The status of European eel remains critical. ICES has advised in 2024 that there should be zero eel catches in all habitats (ICES, 2024). Furthermore, incidental bycatches of endangered, threatened and protected (ETP) species occur in several Baltic Sea fisheries. Bycatch is an important source of mortality on marine mammals, especially the ringed seal, which occurs within the World Heritage site. Based on reported bycatch and monitoring data, the highest multiannual bycatch rates during 2017–2023 were estimated for the ringed seal in pots and traps. Bycatch of waterbirds has been reported for more than 20 species and resulted in total annual estimated removals of over 2, 000 individuals, mostly in nets. This is a significant source of mortality for diving waterbirds, e.g. long-tailed duck, scooters, and divers – especially in wintering areas with high densities of waterbirds. The highest multiannual bycatch rates during 2017–2023 were recorded for the great black-backed gull (Larus marinus) in fykenets, the great cormorant in trammel nets, and the common guillemot (Uria aalge) in longlines (ICES, 2024). While these numbers are reported for the overall area, they demonstrate the impact of fishing activities on species contributing to the biodiversity values of the World Heritage site, which utilise the World Heritage site area but are also present beyond the boundaries.

Intensive commercial fisheries has led to strained stocks, with bottom trawling outside the site causing extensive damage to the marine environment, mainly in the form of withdrawals of species, including by-catch, and increased turbidity from disturbed sediments. Although trawling for herring is considered to be pelagical trawling, it can still cause severe effects if the trawl is dragged close to the bottom. This happens if the target is standing close to the bottom. The herring is often standing close to the bottom during winter time, when also most of the fishing is done. This causes damage of the bottom and also causes by-catch of other bottom species such as viviparous eelpout (tånglake, Zoarces viviparus) (IUCN Consultation, 2025). Overall, large scale trawling outside of the WH property may well impact the fish stocks inside the property (Heron et al. 2022). Underwater noise and the introduction of organic materials are also among the consequences from fishing (Swedish Agency for Marine and Water Management, 2018).

While fishing presents a high threat to the biodiversity values of the site, it does not present a threat for the geological value for which the site was inscribed, although potentially fishing-related activities could impact the underwater geological formations.

The Baltic Sea is one of the most polluted areas in the world. Man-made chemicals (e.g. ‘Persistent Organic Pollutants’ (‘POPs’)) and heavy metals enter the Baltic Sea via numerous sources, including from wastewater treatment plants, leaching from household materials, leaching from waste deposits, and atmospheric depositions from industrial plant emissions (Matkowska & Rolka, 2022). Hazardous substances are having a marked effect on the wildlife, species composition and diversity all over the Baltic. The combined effects of the substances are to a large extent unknown but include persistence and associated bioaccumulation, and toxic effects.

Hazardous substances reach the site through normal water exchange with the southern Baltic atmospheric deposition, river water (especially nikel and zinc), harbours, marinas and shipping lanes, as well as re-release of accumulated substances by dredging and disposal of dredged material (IUCN, 2006, HELCOM, 2010, 2014). In the Swedish marine spatial planning the cumulative effects in the Northern Bothnian Sea and Norra Kvarken consists mostly of pollutants in sediment (synthetics approx. 20%, heavy metals approx. 29%) and phosphorous (approx. 27%), and a small part from nitrogen (approx. 7%) that is caused by several sectors, earlier emissions and other sources of pollution. Oxygen-free bottoms also account for a part of the effect (approx. 12%) (Swedish Agency for Marine and Water Management, 2018). Overall, as with any marine area the exchange and interaction with the environment outside the site is very high and cannot be regulated at site level. However, bans on mercury, dioxins, lead and other measures across the Baltic have taken place through international cooperation such as the Helsinki Convention. The overall risk of this threat is moderate to major, however is likely to be decreasing.

The Baltic Sea Action Plan (BSAP), adopted by HELCOM in 2007 and updated in 2021, is its strategic programme of measures and actions for achieving the good environmental status of the sea. One of the goals of the BSAP is a ‘Baltic Sea unaffected by hazardous substances and litter’. The BSAP has resulted in several environmental improvements such as a reduction in nutrient inputs to the sea, a better state of biodiversity and a decrease in maritime incidents and spills. It incorporates the latest scientific knowledge and innovative management approaches into strategic policy implementation and stimulates goal-oriented multilateral cooperation around the Baltic Sea region. As of 1 September 2022, about 33 % of the joint regional actions (90 out of 273) and 7 % of the national actions (29 out of 428) from the Baltic Sea Action Plan have been reported as fully implemented by all of HELCOM’s Contracting Parties. In addition to specific actions, the Contracting Parties also agreed to implement several HELCOM recommendations in support of the BSAP (Matkowska & Rolka, 2022).

From the perspective of the geological value of the site, pollution presents a low threat.

Eutrophication is still among the most influential and long-lasting environmental pressures in the Baltic Sea. Excessive inputs of nitrogen and phosphorus, which are the main triggers of eutrophication, have occurred since around the 1950s, leading to enhanced primary productivity and to indirect effects on other parts of the ecosystem. A key goal of the Baltic Sea Action Plan is to reach a Baltic Sea unaffected by eutrophication (HELCOM, 2021). The nutrients come from farmlands and forestry areas, homes and gardens, cars, cities and industries. Although the influx of nutrients from agriculture and industries are decreasing, this has not affected the nutrient levels in the sea yet (State Parties of Finland and Sweden, 2024). In the past another source was from aquaculture and although all aquaculture inside the WH area have stopped due to environmental concerns, the negative effects of excessive nutrients are still ongoing (State Parties of Finland and Sweden, 2024).

In the sea, the nutrients foster the production of planktonic algae forming algal blooms, as well as short lived high yield filamentous algae species. This increased production of organic matter often has secondary and drastic negative consequences: the water becomes murkier and less transparent, fast growing, short lived species smother habitat forming perennials, the sedimentation of organic material to the sea floor increases, decomposition of organic matter increases and oxygen is consumed, thus depleting the bottom waters of oxygen. Benthic communities such as meadows of submerged aquatic vegetation are deprived of light, and benthic invertebrate communities and fish are affected by oxygen depletion, ultimately suffocating. However, possibly the most important effect of stratification in terms of eutrophication: hindering or preventing ventilation and oxygenation of the bottom waters and sediments by vertical mixing of the water, a situation that often leads to oxygen depletion. Furthermore, hypoxia and anoxia worsen the situation by affecting nutrient transformation processes, such as nitrification and denitrification, as well as the capacity of the sediments to bind phosphorus. In the absence of oxygen, reduced sediments release significant quantities of phosphorus to the overlying water. Climate change also risks increasing the nutrients carried into the sea via rivers and runoff as the precipitation increases (IUCN World Heritage Evaluation Report May 2006, HELCOM, 2010, Planning the Bothnian Sea 2012), which may be worsened further through nutrient loading in rivers such as the nearby River Kyrönjoki and clear-cutting forestry and associated flood regime alterations (IUCN Consultation, 2020). Dredging activities can also compound eutrophication by re-releasing nutrients previously trapped in the seabed into the water column (IUCN Consultation, 2020).

The HELCOM thematic assessment focussing on results for the assessment period 2016-2021 demonstrates that eutrophication is still a major problem in the Baltic Sea (HELCOM, 2023). At least 93.8 % of the region were assessed to be below good environmental status for eutrophication, including all of the open sea areas and 82.8% of the coastal waters. Nutrient inputs to the Baltic Sea have further decreased, but this has resulted in improvements in eutrophication indicator status and the overall assessment status in only a few areas, while signs of deterioration are also apparent in other areas. Deterioration is mainly driven by nutrient leakage from the sediment so that these legacy nutrients now influence the overall status.

This is in essence a threat that originates outside the site and of which the site is only a small part. The management does not have the capacity or resources to address this threat, only a change in local behaviour and international agreements can help alleviate the process (there is no way of reversing it). Any dredging should be strictly regulated and on a permission basis, however, this will cause tension with the stakeholders. The risk of this threat is high for the biodiversity values, given it's widespread occurrence, and major consequences and increasing trend. Nevertheless, eutrophication does not present a threat for the Wgeological value of the site.

Seashore properties have considerable monetary and non-monetary value to a large number of people in both areas (IUCN World Heritage Evaluation Report May 2006). A rough average of the number of secondary dwellings to permanently inhabited homes in the region is 1/1 to 0.5/1 (Planning the Bothnian Sea 2012) and the interest in secondary homes is increasing in Finland (Virtanen et al. 2023). Building of new cottages requires permission from the governing body (depending on the country) and the rules are quite strict. The dredging associated with summer houses in the High Coast are mostly done so that existing summer houses in a bay can keep their connection to the sea when the bays inlet is dredged (IUCN Consultation, 2025). Dredging associated with summer houses is a growing issue in Kvarken, where dredging for summer homes (increasing demand for second homes) has been associated with biodiversity loss in the archipelago. Small-sized dredging can be detrimental to coastal biodiversity, as dredging targets shallow, photic bays and lagoons, with diverse algal and aquatic plant communities, with limited recovery potential. Dredgings also had broad impacts on benthic faunal habitats, which maintain ecosystem processes and functions (Virtanen et al. 2023). Such dredging may also directly affect the geological values for which the site is inscribed, such as gloelakes and flads.

The WH site brackish ecosystem has few species and are thus extra sensitive to alien species. There are also fairly large impacts of alien terrestrial mammals (State Parties of Finland & Sweden, 2024). A total of 228 non-indigenous species (NIS) have been recorded in the Baltic Sea, with about one third established permanently. The increasing trend of the annual rate of new aquatic non-indigenous and cryptogenic species records observed since the late 1990s has levelled off since the late 2010s (ICES, 2024). The main introduction pathway has been transport-stowaway, as shipping vectors (primarily ballast water and hull fouling) have contributed to more than 40% of the introductions, although some reports have estimated that the contribution of shipping is even higher. Unaided introductions – species that have been anthropogenically introduced to adjacent water bodies and have further spread to the Baltic Sea – accounted for nearly 20 % of the introductions, while 14% of the newly recorded species had an unknown mode of transport (ICES, 2024). IAS may destabilize existing ecological relationships and in the worst cases may have serious consequences on the local food web (Oguz and Gilbert 2007). Although some superior competitors and predators, for example, the American mink (Neovison vison) (UNEP-WCMC 2011), three species of the polychaete Marenzelleria and the round goby (Neogobius melanostomus), are now present in the site, there has not yet been any wide-scale economic or ecological impact following the invasion. However, the American mink (Neovison vision) as well as the introduced Raccoon Dog (Nyctereutes procyonoides) (IUCN Consultation, 2020), can have a very adverse effect on the birds breeding in the area, especially on seaducks such as the Common Eider, and thus alien predator control is currently taking place in the Kvarken archipelago. However, as with any marine area the exchange and interaction with the environment outside the site is very high and cannot be directly regulated by e.g. enclosures. Beach rose (Rosa rugosa) can also be named as a threat for the shore vegetation. Projects eradicating this IAS has been done both in Kvarken Archipelago and in the High Coast (IUCN Consultation, 2024). There is very little to no possibility for the management of the site to respond to this threat, especially after a species has already arrived, as it is an outside threat that is extremely hard to control. Nevertheless, Metsähallitus work together with local stakeholders (hunters and land owners) to address the threat from IAS, but it takes continuous work and cooperation. The High Coast management has also cooperated with the general public, hunters, fishing rights holders etc. to target mink, bisam and invasive plants (IUCN Consultation, 2025).

Although invasive alien species have a detrimental impact on the native biodiversity and pose a great challenge for management authorities, they do not impact significantly on the geological value of the site.

Marine litter is clearly visible along the coastline of the Baltic Sea. Plastics account for approximately 70 % of the waste washed ashore from the Baltic Sea (HELCOM, 2018a). Data has shown that the highest litter densities in the Baltic Sea (>200 litter items / 100 m of beach) occurred in the Gulf of Finland, Bothnian Sea, and Northern Baltic Proper (Veiga et al. 2022). The River Vistula accounts for the greatest floating macrolitter flux and annual loading into the Baltic Sea (González-Fernández et al., 2021) that results in the accumulation of more than a million macrolitter items per year. However, according to Meijer et al. (2021), limited sources of plastics exist around the Bothnian Sea and Northern Baltic Proper, indicating that plastics have been transported to these areas from elsewhere. To alleviate the problem of marine plastic pollution, knowledge of the pathways followed by the plastic debris and the locations of its accumulation is crucial. HELCOM aims to achieve a considerable reduction in the quantity of marine waste in the Baltic Sea by 2025 to prevent adverse impacts on its coastal and marine environment (Pärn et al. 2023).

Not all marine litter is visible to the human eye. Microscopic particles from various sources, e.g., degradation of plastic waste, disturb food webs by mimicking food particles, attaching to organisms’ feeding appendices and causing famine to passive filter-feeders. Some hazardous substances adsorb onto the litter particles and may cause enhanced accumulation of hazardous substances in the food web. Although, in the Baltic Sea, microplastic litter has been widely monitored in coastal, estuary and open waters common technological standards, both on sampling and analysis methods, are still under development. Existing research have shown large discrepancies between different datasets. For example, most of the trawl samples showed a MP concentration of 10-2-100 particles per cubic meter (pcs/m3), while some pump and bulk samples measured up to 102-3 pcs/m3 (She et al. 2022). Microplastics have also been found in the digestive tracts of ringed seals (Parfitt, 2021).

Increasing evidence on how the widespread use of plastic material is affecting the sea has resulted in marine litter being identified as one of the priority areas for work in HELCOM (2018). Effective management has potential to reverse the effect of the threat with regards to macro plastics, while tackling microplastics is more complex also due to long residence time. Cleaning efforts aiming at most heavily used areas help alleviate the visual intrusion.

Dredging operations (both large and small scale) and the disposal of dredged material reintroduce sediment- bound TBT and other POPs to the marine environment (IUCN World Heritage Evaluation Report May 2006). Developmental pressures include dredging of shallow areas and continual dredging of boat channels creates some disturbance (UNEP-WCMC 2011). Due to land rise dredging is very common in the area, especially on a small scale. Small scale operations, while under regulations e.g. on dumping of the dredged materials, do not need permission from any authority and are not followed up upon however must inform the authorities. The companies doing the work also need no certification, and illegal dumping of the materials straight into the sea is common. Due to the nature of the areas that need dredging (shallow, enclosed bays in the process of rising out of the sea) this practice is more common in Kvarken than in the High Coast. Such dredging may directly affect the geological values for which the site is inscribed, such as glolakes and flads. Moreover, the effect of the recirculated nutrients can have major implications for the surrounding ecosystem as they may contain toxic elements. Currently management has no legal way of regulating the small scale dredging and any such regulation of the stakeholders rights to dredge will also create serious tension between management and stakeholders. As such, addressing this threat requires short and long term impact assessments on dredging activities, which specifically consider the OUV of the site.

The side effects of eutrophication such as reduced water clarity and increased sedimentation of organic matter have benefited some algal species (primarily filamentous algae) while perennial species such as bladder- wrack (Fucus) have declined. This has caused changes in the invertebrate community (Korpinen and Jormalainen 2008; HELCOM 2010). In the site, Fucus radicans is also the only endemic species in the region. Common bream (Abramis brama) is also expanding in range, especially on shallow sea bays (IUCN Consultation, 2020). Other effects caused by eutrophication and overfishing of top predatory species have resulted in an increase in numbers of Three spined Sticklebacks (Gasterosteus aculeatus) populations, which threaten other spices such as Pike (Esox Lucius) and Perch. This further straightens the eutrophication effect (Candolin & Voigt, 2020). The County administrative board has had projects creating or restoring breeding habitats for pike and perch that are out of reach for sticklebacks. One was a joint project with WWF and two other areas in Sweden (IUCN Consultation, 2025).

The risk of this threat is high to the site's biodiversity values, based on its widespread occurrence and increasingly negative consequences. As this is a result of the general eutrophication of the Baltic Sea and originates outside the site, the management does not have the capacity or resources to address this threat. The threat to the geological value is considered low.

Effects of climate changes are already evident in the Baltic Sea, and global warming is expected to lead to further hydrological changes in the near future. Projected changes include acidification, increased sea level, decreasing ice cover extent, and changed precipitation patterns, leading to altered composition of nutrients, and interactions with other pressures (HELCOM, 2018). Climate related changes should be considered in all aspects of management. The apparent uplift rate in the World Heritage site depends on the sea level rise and will most likely change in future. It will be important to keep for example flads in good condition, since the formation of new ones is likely to stop or at least slow down as sea level rise affects apparent land uplift (IUCN Consultation, 2025).

The land uplift maximum is near the city of Umeå, where the current absolute uplift is about 10 mm/year, and during the last century the uplift rate relative to the sea has been almost 9 mm/year (Poutanen, M. et.al., 2014). In addition to the threat posed by climate change to the geological processes climate change will further unbalance sea salinity, causing impacts to saline sensitive species and systems, particularly given the low saline concentration to begin with.

This increased production of organic matter often has secondary and drastic negative consequences: the water becomes murkier and less transparent, the sedimentation of organic material to the sea floor increases, decomposition of organic matter increases and oxygen is consumed, thus depleting the bottom waters of oxygen. Benthic communities such as meadows of submerged aquatic vegetation are deprived of light, and benthic invertebrate communities and fish are affected by oxygen depletion, ultimately suffocating (HELCOM, 2010; 2023b).Locally, this threat can be managed by effective ditching of dredging materials in specific areas such as enclosed bays and floods (IUCN Consultation, 2020), however as the primary drivers of this threat lie outside the site, overall management of this threat is difficult to control.