Article Patrik Ronnback, Nils Kautsky, Leif Pihl, Max Troell, Tore Soderqvist and Hakan Wennhage

Ecosystem Goods and Services from SwedishCoastal Habitats: Identification, Valuation, andImplications of Ecosystem Shifts

Coastal areas are exposed to a variety of threats due tohigh population densities and rapid economic develop-ment. How will this affect human welfare and ourdependence on nature’s capacity to provide ecosystemgoods and services? This paper is original in evaluatingthis concern for major habitats (macroalgae, seagrasses,blue mussel beds, and unvegetated soft bottoms) in atemperate coastal setting. More than 40 categories ofgoods and services are classified into provisional, regu-lating, and cultural services. A wide variety of Swedishexamples is described for each category, includingaccounts of economic values and the relative importanceof different habitats. For example, distinguishing charac-teristics would be the exceptional importance of bluemussels for mitigation of eutrophication, sandy softbottoms for recreational uses, and seagrasses andmacroalgae for fisheries production and control of waveand current energy. Net changes in the provision ofgoods and services are evaluated for three cases ofobserved coastal ecosystem shifts: i) seagrass beds intounvegetated substrate; ii) unvegetated shallow softbottoms into filamentous algal mat dominance; and iii)macroalgae into mussel beds on hard substrate. Theresults are discussed in a management context includingaccounts of biodiversity, interconnectedness of ecosys-tems, and potential of economic valuation.

INTRODUCTION

The scale of human activities has increased dramatically duringthe last century, and, consequently, all ecosystems on the planethave been altered to some extent (1, 2). Many of thesealterations have reduced the capacity of ecosystems to sustainand improve human life through the provision of goods andservices. Coastal areas are especially vulnerable due to highhuman population densities and rapid economic development.Typical threats to coastal ecosystems are changed land-usepatterns, development of settlements, roads, harbors, industries,and pollution resulting from this, as well as introduction ofalien species and unsustainable extraction of natural resources,such as overfishing. In Swedish coastal waters, eutrophicationhas been the main cause of ecosystem changes (3). This hasresulted in a general shift from clear-water systems with long-lived macroalgae and seagrass to more turbid water andextensive growth of seasonal filamentous nuisance algae (4).In the Baltic Sea, the filter-feeding blue mussel has been favoredby increased phytoplankton at the expense of large algae, whichhas reduced its depth distribution due to more turbid waterconditions (5).

What will be the implications of these changes on humanwelfare? Natural systems may not be very fragile due to theirability to buffer against disturbances or change into newsystems in the face of environmental stresses. The fragility may,however, lie in the maintenance of ecosystem goods and serviceson which human societies depend: ‘‘There is no reason to expect

systems to be robust in protecting those services—recall thatthey permit our survival but do not exist by virtue of permittingit, and so we need to ask how fragile nature’s services are, andnot just how fragile nature is’’ (6).

The supply of ecosystem goods and services has usually beentaken for granted, and this has resulted in poor management ofunderlying structures and processes that facilitate its generation.We have just begun to identify the goods and services thathumans in one way or another depend upon, and the recentMillennium Ecosystem Assessment (2) provided many criticalinputs. The vast majority of research on coastal areas hasfocused on tropical ecosystems, such as mangroves, coral reefs,and seagrasses (7–9), and there is a need for more studies thatidentify the provision of goods and services from temperateregions as well. Research should also address the uncertaintyconcerning the functions and complexity necessary for sustain-ing the flow of goods and services from ecosystems, i.e., the keyrole of biodiversity at different scales (10, 11). This kind ofinformation is vital for policymakers and management institu-tions, which are frequently confronted with questions related tothe societal costs and benefits of threats, conservationprograms, and development activities affecting the integrity ofcoastal systems.

The main objective of this paper is to identify and evaluateecosystem goods and services generated by temperate coastalsystems. The majority of examples are derived from fourdominant Swedish coastal habitats: macroalgae, seagrasses,blue mussel beds, and unvegetated shallow soft bottoms. Thepaper initially provides a short description of the mainstructures and processes of these dominant habitats, followedby a conceptual platform for linking biodiversity within thesesystems to ecosystem goods and services classified into i)provisional, ii) regulating, and iii) cultural services. A widevariety of ecosystem goods and services is thereafter describedfor each category, including accounts of the relative importanceof different coastal habitats. Finally, three case studies ofecosystem shifts in temperate coastal systems are presented, andsome net changes in the generation of ecosystem goods andservices are evaluated. The results are discussed in a manage-ment context including accounts of biodiversity, interconnec-tedness among ecosystems, and the potential of economicvaluation of ecosystem goods and services.

SWEDISH COASTAL ECOSYSTEMS

Sweden has a long coastline and a large variation in coastalhabitats. A salinity gradient along the coast, from full marineenvironments in the northern Skagerrak to almost freshwater inthe Bothnian Bay, creates a multitude of different physicalconditions (Fig. 1). Along with the gradual decrease in salinity,considerable shifts in species composition of plant, algal, andfaunal assemblages occur, and several unique adaptations to thespecific salinity conditions are observed. Most of the coastalareas in Sweden have an archipelago with a complex structureof islands and fjords and a mosaic of soft and rocky bottomshores. The coastline is characterized by low tidal amplitudes

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(,0.2 m), which generally imply few intertidal habitats as wellas weak tidal currents and low physical energy in the coastalenvironment.

This paper focuses on the four major habitat types thatoccur commonly along the Swedish coast from the surfacedown to a water depth of 10 to 25 m: i) macroalgae on rockybottoms, ii) submerged vegetation (seagrass and freshwaterplants) on sediment bottoms, iii) blue mussel beds on rocky andsediment substrate, and iv) sediment bottoms without vegeta-tion (see Box 1 for detailed habitat information). Despite largedifferences in the total number of species along the salinitygradient, the general structure and function of these habitatsare rather similar from the Skagerrak and up to and includingthe Aland Sea, and, consequently, this analysis focuses on thisregion.

IDENTIFICATION OF GOODS AND SERVICES FROMSWEDISH COASTAL HABITATS

Scientific work supports a postulate that ecosystem propertiesand ecosystem goods and services depend on biodiversity (12).However, deeper ecological understanding of this complexrelationship is still limited (13). This paper adopts a typologywhere biodiversity links to three main types of services(provisional, regulating, and cultural) (Fig. 2).

Provisional Services

The production functions of coastal ecosystems generate manynatural resources that humans use, including food, rawmaterials, genetic and medicinal resources, etc. (Table 1).

Food resources extracted by subsistence and commercialactivities (fisheries, gathering, hunting, and aquaculture) are themost well-known ecosystem goods generated by coastalsystems. Fish and shellfish species are supported via theprovision of food resources, shelter from predation, andhydrodynamic retention of immigrating larvae (14, 15). Coastalhabitats provide significant support to total marine finfishfisheries landings in Sweden. Species utilizing coastal ecosys-tems as nursery, feeding, or breeding ground comprise 77% byweight and 80% by value of commercial landings, and 77% byweight of recreational landings (Table 2). Fishes are highlymobile animals that commonly exhibit several habitat shiftsduring their life cycle, and the degree of habitat specificity variesamong fish species. The consequences of habitat loss on apopulation level therefore require detailed information. Docu-mented habitat association for commercial and recreational fishspecies indicates that vegetated habitats (macroalgae andseagrasses) are most frequently used, followed by unvegetatedshallow soft bottoms (Table 2). Vegetated habitats are used ashabitat during at least some stage in the life cycle by species like

Figure 1. Type of coastline, major habitats, salinity, and species numbers in the major basins of the seas surrounding Sweden. Dominantcoastline types are indicated as rocky/archipelago or sandy/sediment shores. Large-scale distribution and species composition of majorhabitat types are indicated in small maps (bottom type and depth at site determines local distribution). Species numbers include marinemacrofauna (excluding fish and insect larvae) (H. Kautsky pers. comm. Data from national and regional monitoring and inventories ofphytobenthos. Department of Systems Ecology, Stockholm University) and macroscopic flora (93) on rocky and vegetated sedimentbottoms ,25 m, and they decrease with salinity from the west coast to the inner parts of the Baltic Sea.

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herring, cod, eel, perch, pike, etc., whereas unvegetated soft

bottoms are strongly associated with flatfishes, such as plaice,flounder, and turbot. Mussel beds seem to be of limited value as

habitat for commercial and recreational fish species, althoughthis finding partly reflects the lack of studies from this habitat.

Crustaceans like brown shrimp (Crangon crangon) and grass

shrimp (Palaemon adspersus) are dominant on sandy bottoms andin seagrass beds, respectively (16). Although, not commercially

harvested in Sweden, these species are important in the coastalfisheries inGermany,Netherlands, andDenmark. On the Swedishwest coast, the edible crab (Cancer pagurus) and the lobster

(Homarus vulgaris) are important species for the local commercialand recreational fishery. These species mainly occur on hard

bottoms with a complex community structure, and the distribu-tion of this habitat is most likely a limiting factor for the

population size. The west coast also supports local harvesting ofblue mussels, mainly from unvegetated shallow sediment bottoms.

Raw materials such as construction material, fuel, skin, and

fertilizers would today only have marginal economic values in

developed countries such as Sweden. There are, however,

numerous examples of historical uses of raw material fromSwedish coastal waters, and in many locations, these uses have

contributed to the development and strengthening of identity

and cultural traditions among coastal communities. Historically,

fish oil extracted from coastal fish populations (stickleback and

herring) has been an important product, and already in 1745,

Linnaeus (17) reported extensive use of bladderwrack and othermacroalgae as fertilizer in agriculture. One example of a current

raw material is the continuous input of wild mussel larvae

providing the basis for mussel farming on the west coast. The

most valuable raw material linked to Swedish coastal waters is

fishmeal production. More than 160 000 t of fish for reduction

was landed in Sweden in 2004, comprising 61% by weight and20% by value of total (finfish and shellfish) marine commercial

Figure 2. Linking biodiversity to the provision of ecosystem goods and services.

Table 1. Provisional services (ecosystem goods) supported by production functions and associated processes and components in Swedishcoastal systems.

Production functionsProcesses/components Ecosystem goods

Food FishPhotosynthesis and food web dynamics Crustaceans (shrimps, crabs, crayfish, and lobster)

Molluscs (mussels and gastropods)AlgaeGame and birds

Raw materials Construction (e.g., insulation material and sand/gravel)Photosynthesis and food web dynamics Manufacture (e.g., skin)

Fuel (train oil)Seed (fry and larvae) and broodstock to aquacultureFish meal and fish oilFodder and fertilizers

Chemical and medicinal resources Drugs and pharmaceuticalsBiochemical substances of natural biota Chemical models, test organisms, etc.

Agar

Genetic resources Genetic support to cultured biota (cross-breeding, genetic engineering, etc.)Genetic material and evolution

Existence of and variety within biota with potential ornamental uses Resources for fashion, handicraft, jewelry, souvenirs, pets, decoration, etc.

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landings (18). Sprat (45%) and herring (21%) dominate landingsof fish for reduction, and especially herring is supported bycoastal habitats. In the Baltic Sea, herring spawns and utilizesvegetated rocky and soft bottom habitats as nursery grounds (19,20). On the west coast, highest densities of herring have beenobserved on soft bottoms (including eelgrass) (21).

Coastal ecosystems also have the potential to generatechemical and medicinal resources, either by direct provision ofchemicals that can be used as drugs or pharmaceuticals orindirectly by providing the chemical code (model) needed tosynthesize chemicals and drugs in laboratories. Macroalgae asFurcellaria lumbricalis are used for industrial agar production.The algal supply became rather depleted in the 1980s (22), butstill some 10 000 t yr�1 are harvested for industrial productionin Denmark and Estonia. Gene technology has developed gluebased on byssus threads from blue mussels. This glue couldpotentially be used in medicine, antifouling paints, etc., since itis very strong, nonsynthetic and attaches to wet surfaces (23).Another promising and potentially valuable finding is the recentidentification of chemical defenses in, for example, corals, seasquirts, and eelgrass (24) that prevent the settlement ofbarnacles, which are the main fouling organisms on boat hulls,oil platforms, and cooling water intakes. Globally, this foulingcosts more than 1.4 billion USD annually due to increased fueland pumping costs, corrosion, etc., but not including theenvironmental costs due to impacts from use of toxicantifouling paints (24). An antifouling paint based on suchnatural products has the advantage of being very specific andhaving limited side effects on the environment.

Biotechnological research and genetic engineering are todayincreasingly used to manipulate genetic resources in, forexample, cultivated terrestrial plants (25). These geneticmanipulations can be essential in improving qualities such astaste, resistance to pests and diseases, and adaptation to certainenvironmental conditions like cold climate. For example,antifreeze protein genes derived from Antarctic fish areregarded as promising in increasing freezing resistance infarmed vegetables, salmon, etc. (26). From the Baltic Sea itmight be possible to derive low-salinity-tolerance genes.

Regulating Services

The capacity of ecosystems to regulate essential ecologicalprocesses through structures, functions, and biogeochemicalcycles generates many ecosystem services (Table 3). Manyregulating functions involve a high degree of complex processes

distributed across broad spatial and temporal scales. Thequantification of associated ecosystem services is thereforebased on research fields ranging from studies of the net flow ofcarbon and nutrient cycling to the dynamics of weather andclimate patterns.

Resilience is the ability of a social-ecological system toundergo, absorb, and respond change and disturbance whilemaintaining its functions and controls (27). The correspondingecosystem service can be considered as insurance values, oroption values in the presence of irreversible or catastrophicchanges. A general conclusion is that high marine biodiversityincreases stability and recovery potential of ecosystems (11),which can be attributed to different compensation mechanisms:portfolio effect (fewer fluctuations of ecosystem functioning insystems with many species) (28), density effect (in species-richenvironments, ecosystem functioning is sustained until a largeproportion of the species is lost) (29), and response diversity orfunctional effect (differences in behavior and taxonomicalbackground between species allows for diverse responses toenvironmental changes) (30). When and under what conditionsthese operate, in isolation or simultaneously, are still poorlyunderstood factors and need further studies (13).

The reproduction function is a prerequisite for the mainte-nance of biodiversity at all scales, although marginal reductionsin the reproductive capacity for individual species could becompensated by extensive plantation, seeding, or restockingprograms (Table 3), usually at a very high cost. Reproduction inand recolonization of areas where habitat-forming species havedisappeared are usually the bottlenecks in habitat recovery afterdisturbance. For example, bladderwrack eggs are heavy and fallmore or less vertically to the bottom (31), which means thatmacroalgal recolonization in areas far away from an existingpopulation is very slow. Eelgrass propagation is dominated byclonal shoots (32), which also hampers distant colonization. Theproblem for seagrass recolonization may be further aggravatedby the fact that erosion of the fine-trapped sediment often takesplace after vegetation loss, resulting in the substrate becomingtoo coarse and too mobile for recolonization. The mussels arenot limited in the same way because they produce enormousamounts of pelagic larvae that spread far with currents. InSweden, small-scale restocking experiments have been carriedout on macroalgae (Fucus vesiculosus) in the Baltic Sea (33), andin the US and Australia, large programs have been launched forcompensation of seagrass losses. Published costs for plantingseagrass range from about 25 000 to 50 000 USD hectare�1 in

Table 2. Swedish landings and market value of the most important commercial and recreational fish species with documented coastal habitatassociation. Landings include weight, market value (first sale of landed weight) and relative importance (%) to total Swedish marinecommercial and recreational finfish fisheries in 2004 (excluding fish for reduction) a. Habitat association: MA¼macroalgae; SG¼seagrass; MB¼ blue mussel beds; US ¼ unvegetated shallow soft bottoms.

Commercial landed weight Commercial market value Recreational landed weight

Species (t) (%) (103 x USD) (%) (t) (%) Habitat association

Herring (Clupea harengus) 53 833 55 15 116 39 3454 19 MAb,c, SGc, MBd, USd

Cod (Gadus morhua) 14 297 15 25 616 8 1730 10 MAb,c, SGe

Mackerel (Scomber scombrus) 4423 5 5467 2 2851 16 MAc, USc

Saithe (Pollachius virens) 1902 2 1604 5 MAc

Eel (Anguilla anguilla) 450 0.5 2963 1 388 2 SGe

Plaice (Pleuronectes platessa) 359 0.4 969 0.3 USf,g

Whiting (Merlangus merlangus) 120 0.1 192 0.1 MAc, SGe, USc

Flounder (Platichthys flesus) 105 0.1 74 0.2 MAb, SGe, MBd, USc,g

Turbot (Psetta maxima) 25 0.03 144 0.03 USg

Sea trout (Salmo trutta) 8 0.01 21 729 4 MAc, SGe, USc

Perch (Perca fluviatilis) 2360 13 MAb, SGb,h

Pike (Esox lucius) 2236 13 MAb, SGb

TOTAL 75 522 77 52 165 80 13 748 77

Sources: a (18), b (100), c (21), d (101), e (68), f (102), g (103), h (95).

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the US, but values in the range of 80 000 USD hectare�1 may bemore reasonable over the entire life span of such projects (34).

Biological interactions and feedback mechanisms enablebiological control of nuisance species, controlling the outbreakof diseases and pest species. For example, the filtering ofphytoplankton by mussels has the potential to mitigate algalblooms in the Sound between Sweden and Denmark (35) orentire coastal areas of the Baltic Sea (36). Mussels thus reducewater turbidity, which positively affects the depth distributionof macroalgae and seagrass (4), besides improving water qualityfor recreational users. Furthermore, grazers such as gastropodsand isopods have an important role in controlling the growth ofopportunistic fast-growing epiphytes on seagrass and macro-algae (37). These grazers can also control the formation offilamentous algae on hard substrate, which prevents thecolonization by macroalgae (37). Extensive growth of filamen-tous algae can also negatively affect fisheries recruitment of,e.g., herring, through the release of toxic exudates or by causingoxygen depletion for fish eggs (38). Intermediate-sized fishes canin turn control grazers and thus reduce the risk of excessivegrazing on biotope-forming species, i.e., seagrass and macro-algae. For example, overexploitation of fish stocks maysignificantly increase the abundance of isopods like Idothea,which are then able to graze heavily on Fucus and can destroythe bladderwrack communities over large areas in the Baltic Sea(39, 40). The development and use of a variety of chemicals,each targeting specific nuisance species, might be a potential butvery expensive technical substitute to the biological controlservice (Table 3).

Nutrient cycling via the continuous storage and recycling ofmacronutrients and trace elements is a critical function in orderto maintain ecosystem productivity. Seagrass and algal bedsgenerally function as net transformers of nutrients to organicmatter, whereas sediment and mussel beds are more importantin the mineralization of organic matter into nutrients (41). Theimmense economic importance of this service can be illustratedby the fact that the technical response would be to activelyfertilize all individual habitats across wide spatial scales. Thereis currently no limitation of macronutrients for Swedish coastalsystem, and many habitats rather show signs of eutrophication

(3). Coastal ecosystem productivity is, however, still totallydependent on the continuous provision of efficient nutrientcycling, provided free of charge.

The breakdown and removal of pollutants is linked tonutrient cycling as sediment, vegetation, and animals constituteimportant storages that provide stabilizing effects on ecosys-tems (36). Pollutants may be stored in shallow coastal sedimentsor be transported after resuspension to deeper offshore habitats.Algae and seagrass can also store or transfer pollutants betweenhabitats. In addition, fisheries and harvesting of mussels oralgae will remove large amounts of nutrients from the sea andcan thus counteract eutrophication (42, 43), or removesignificant amounts of organic contaminants like polychlori-nated biphenyls (PCBs) and dioxins (44). This is especiallyevident with filter feeders like blue mussels in the Baltic Sea,which constitute 80% of the total animal biomass in coastalareas of the Baltic proper (45, 46). On the Swedish west coast,mussel farming has even been found to be a much more cost-effective measure for removing nutrients from marine waterscompared to conventional sewage treatment (47).

Many ecosystem properties and functions influence theefficiency of energy transfer from solar energy to species thatare either harvested directly by humans (goods) or performfunctions valued by humans (services). Increased speciesdiversity improves the efficiency of energy transfer to higherlevels in the food chain (11), thereby potentially diversifying andincreasing the productivity of ecosystem goods and services.Low efficiency relates to cases where energy is routed intopathways that support limited, if any, production of goods andservices. Therefore, large losses of energy through sedimenta-tion of organic matter and sequestering in the sediment, ordeposition of macrovegetation into bacterial decomposition willimply reduced production of goods and services. Filter-feedingorganisms such as mussels constitute a key functional group inunvegetated habitats by incorporating carbon produced inother systems into the food web of the local habitat. Forexample, blue mussels consume about 35% of the annual pelagicprimary production (phytoplankton) in the northern Balticproper (41). Plankton that would otherwise stay in suspensionare actively filtered and deposited as detritus on the bottom,

Table 3. Regulating services supported by ecosystem functions and associated processes and components in Swedish coastal systems, andthe identification of potential human responses to replace shortage of specific ecosystem services.

Regulating functionsProcesses/components Ecosystem services Human response to shortage

Biological maintenance of resilience Resilience against natural andBiogeochemical processes governed by biodiversity anthropogenic disturbances

ReproductionSexual and asexual reproduction

Maintenance of plant, algal, and animalpopulations

Plantation, seeding, andrestocking

Biological control of nuisance species Control of pathogens and pests Chemical useTop-down population control (e.g., algal blooms)

Reduction of herbivory and predation

Nutrient cycling Maintenance of ecosystem productivity FertilizationStorage and recycling of macronutrients and trace elements

Breakdown and removal of xenic nutrients and compounds Mitigating eutrophication Water-treatment technologyAssimilation and transformation of pollutants Pollution control and detoxification

Energy transfer Efficient energy transfer to higherPhotosynthesis, food web dynamics trophic levels

Environmental disturbance prevention Control of wave and current energy, Artificial seawallsStructures dampening disturbances i.e., storm and flood protection

Waterways as medium for transport

Sediment formation and retention Erosion and siltation controlVegetation structure and root matrix Maintenance of productive sedimentsStorage and recycling of organic matter, rock weathering Mitigating effects of sea-level rise

Gas and climate regulation Ultraviolet (UVb) protection by O3

Photosynthesis, respiration, and biogeochemical cycles CO2/O2 balanceLand-cover properties Maintenance of air quality

Global climate influence (e.g., CO2 sink)Maintenance of favorable local climate

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where it provides energy input for invertebrates (36, 48), whichin turn improves the food base for fish.

Environmental disturbance prevention and sediment forma-tion and retention relate to the ability of structures withinecosystems to protect against storms and floods, controlerosion, mitigate effects of sea-level rise, etc. The three-dimensional structures of macroalgae and seagrasses functionas hydrodynamic barriers and erosion controls. In Norway,studies have shown macroalgae (kelp) to cause significant wavedamping and reduction of wave breaking (49). Seagrass rootsand rhizomes stabilize bottom sediments (50), which reducesturbidity and coastal erosion. For example, the removal ofseagrasses for tourism development in Mauritius resulted inincreased water turbidity and beach erosion that eventuallyimpacted the island’s important tourism industries (51). The lowtidal amplitudes (,0.2 m) of Swedish coastal areas somewhatreduce the relative importance of these services compared tocoastlines characterized by much higher tidal amplitudes.

Biogeochemical processes and land-cover properties governthe gas and climate regulation function, which maintainsservices such as oxygen production, clean air, and climateinfluence on local as well as global scales (2). Primaryproduction provides the basis for the gas regulation function,and half of the global primary production originates frommarine systems (52). Shallow coastal systems have much higherproductivity compared to pelagic systems, although, from aglobal perspective, the latter is much more important for totalgross production due to vast coverage. Vegetated habitats(macroalgae and seagrasses) generally function as oxygenproducers and carbon dioxide sinks, and the opposite appliesto mussel beds and unvegetated soft bottoms, which importmuch of the energy (carbon) used by oxygen-consuminganimals (41).

Cultural Services

The existence of and variety within coastal ecosystems providehumans with almost unlimited opportunities for aesthetic andrecreational experiences, cultural and artistic inspiration, as wellas spiritual and religious enrichment (Table 4). Propertiessituated close to the coast are relatively more attractive. Forexample, Swedish tax authorities have assessed permanentresidential houses situated �250 m from the coast of the Islandof Gotland in the Baltic Sea to be 24% more valuable than otherhouses (53). The corresponding figure for holiday residentialhouses is 56%. Property values have elsewhere been shown to benegatively affected by reduced marine water quality (54, 55).Furthermore, swimming, fishing, sailing, and other recreationalactivities dependent on coastal ecosystems are common inSweden. For example, in a survey of the adult Swedishpopulation in 1995 about recreational uses of the Baltic Sea, amajority (51%) of the respondents reported that they hadbathed in the Baltic Sea during the summers of 1993 or 1994(56). Fishing is another major recreational activity amongSwedes: 1.8 million persons (28% of the adult Swedishpopulation) contributed about 3000 million SEK (1 USD ’

7.8 SEK) in expenditures during 30 million fishing days in 2004,of which 38% took place in Swedish marine waters (57). Severalstudies have shown that recreational values and the coastaltourism industry are affected by changes in water quality andfishing opportunities along the Swedish coast (58–60). Suchrecreational values are linked to several types of habitats.Unvegetated shallow sandy soft bottoms provide particularlysuitable beaches, but rocky shores are also used extensively forbathing. Recreational fishing depends on fish recruitmenttaking place in several different types of habitats, with vegetatedhabitats supporting the majority of important species (Table 2).

Besides economic values due to present human use of coastalecosystems, there are also values associated with futuregenerations’ use and the mere existence of these ecosystems.For example, a survey found that Swedes refer to other persons’future use of the Baltic Sea to a greater extent than to own useof the sea when asked to state their motives for a positivewillingness to pay for a program reducing marine eutrophica-tion effects (61).

The information functions of coastal ecosystems provide thebasis for environmental education, scientific research, andmonitoring activities (Table 4). Monitoring of environmentalstatus, whether conducted on local, regional, or global scales, isfounded on the provision of ecological indicators. Long-termenvironmental records are also kept free of charge by naturalsystems. The ‘‘mussel watch’’ program is probably one of themost widespread environmental indicators used in national andinternational monitoring programs all over the world forpollution records. Many countries, including Sweden, also usethe depth distribution and species composition of vegetation(macroalgae and seagrasses) as key indicators in monitoringprograms.

ECOSYSTEM SHIFTS AND THEIR IMPLICATIONS FORGOODS AND SERVICES

The causal relationships between individual threats andecosystem changes are rarely straightforward due to the varietyof and interactions among threats. Disturbances of coastalsystems can act over long time, resulting in gradual changes ofthe systems’ structure and functions, such as altered trophicstates caused by long-term increased nutrient inputs. Due to theresilience of ecosystems, it is generally very difficult to measureeffects of gradual changes. However, when disturbances arestrong or have been acting over a long time, the system mayshift into an alternative state (62, 63), and changes in structureand functions that provide goods and services become morestraightforward to measure. In the following three case studies,we evaluate some net changes in goods and services caused byecosystem shifts.

Loss of Seagrass Beds into Unvegetated Substrate

Over the last two decades, a 60% reduction in the distribution ofeelgrass has been observed in the Swedish Skagerrak archipel-

Table 4. Cultural services supported by ecosystem functions inSwedish coastal systems.

Cultural functions Ecosystem services

Community-support functionsof ecosystems

Cultural identity and sustainedlivelihood of human coastalcommunities

Aesthetically attractivelandscape features

Enjoyment of scenery (scenic roads,housing, etc.)

Existence of and varietywithin nature with potentialrecreational uses

Use of natural ecosystems forecotourism, fishing, diving,swimming, sunbathing, sailing, etc.

Existence of and varietywithin nature with culturaland artistic value

Use of nature as inspiration(motive) in books, films, painting,folklore, national symbols,architecture, advertising, etc.

Existence of and varietywithin nature with spiritualand historic value

Use of nature for religious or historicpurposes, i.e., heritage value ofecosystems

Existence of and varietywithin nature

Preservation of nature for ethicalreasons (e.g., existence values)

Information functions withscientific and educational

Use of natural systems for scientificresearch, school excursions, etc.

value Monitoring of global change andindicators of ecosystem health

Long-term environmental record

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ago (64). Along most sections of the coast, both the upper andthe lower depth distributions have been reduced, and in someareas, seagrass meadows have vanished completely. Althoughsimilar declines have been observed worldwide, this has notbeen documented in the Baltic Sea, possibly due to lack ofhistoric data (65).

Ecosystem services linked to regulating functions such asreproduction, environmental disturbance prevention, as well assediment formation and retention, are all negatively affected byseagrass loss (Table 5). Seagrass removal or degradation alsotriggers feedback mechanisms, speeding up the ecosystem shiftand locking the system into an alternative, stable domain. Theremoval of the hydrodynamic barrier (seagrass) causes sedimentloss, which increases turbidity, which reduces light penetrationand causes a further decline of seagrasses. Such shifts have beenobserved in the Wadden Sea, where seagrass loss has beeninitiated by a combination of factors (e.g., disease and a changein disturbance regimes) and has led to wide-scale sediment lossand exposure of gravel and rock bottoms (66). The shift fromsoft sediments to harder substrate will severely hamper thepotential for seagrass recolonization.

The ecosystem service of efficient energy transfer from solarirradiation to species supporting goods and services is impairedby the loss of seagrass through various mechanisms (Table 5).While seagrass systems can be self-sustained in terms of carbonproduction, unvegetated bottoms are dependent on the importof pelagic microalgae into the system to sustain high produc-tivity (67). The physical structure of seagrass beds also supportssediment retention and accumulation of organic matter. Theorganic content in sediments of extensive seagrass beds is onaverage three times higher compared to areas where the seagrassbeds have been lost (68). When the vegetation structure androot matrix are lost, the carbon content of the sedimentdecreases as wave and current exposure transport the finefractions of the sediment to deeper benthic systems. Conse-quently, the pool of carbon as a fuel in the shallow sedimentsystem is reduced. In the colder and deeper waters, carbon willhave a lower value because production capacity is reduced dueto lower turnover rates.

The production of goods such as genetic, medicinal, andchemical resources, as well as fish and shellfish, will significantlydecrease as seagrass habitats are lost (Table 5). Eelgrass is abiotope-forming species, and its three-dimensional structurecreates a multitude of niches. The abundance and production offish food organisms are generally higher in a seagrass habitatcompared to unvegetated bottoms (69). Small-sized fish such as

gobies are important food for many commercial fish speciesduring the low-productivity winter season (70), and gobies havebeen shown to have four to six times higher densities andbiomasses in eelgrass beds compared to sediment bottomswhere seagrass has disappeared (68). Again, seagrass lossimpairs the efficiency of energy transfer to goods harvested byhumans. The loss of seagrass beds also results in a reduction inthe diversity of coastal fish species and in a change in speciesdominance (68). For example, many species of the familySyngnathidae are unique to the seagrasses, and loss of thishabitat will also result in a loss in genetic diversity of the fishassemblage. Furthermore, the recorded 60% loss in thedistribution of seagrass on the Swedish west coast lowers therecruitment of cod to commercial fisheries, because densities ofjuvenile cod are reduced by 94% in alternative sandy habitatsfree of vegetation (68).

The unvegetated habitat following seagrass loss will natu-rally provide some goods and services, but these will be ofmarginal value in the concerned depth interval compared toshallower soft sediments (see below).

Algal Mats in Shallow Soft Bottom Habitats

Soft bottom sediments make up ;70% of the surface areawithin the 0–1 m depth range on the Swedish west coast (71),which makes it a key ecosystem in the coastal zone. Filamentousmacroalgal mats have increased in occurrence on shallow softbottom sediments during the last decades, and may now cover30–50% of the habitat (72, 73). Filamentous algae are favoredby elevated nutrient conditions, and there are strong links to thegeneral eutrophication of coastal waters over the same period.The presence of filamentous algae can have considerable effectson the provision of ecosystem goods and services from thesystem (Table 5). Algal mats reduce the density and biomass ofbenthic macrofauna (74), trap particulate organic matter in thewater column, incorporate algal mat biomass into the sediment,and reduce water circulation (63). Put together, these changeslower the oxygen levels both in the sediment and water columnand may reduce the system’s capacity to mitigate eutrophicationwith impaired rates of remineralization and denitrification oforganic matter (63).

Algal mats negatively affect seafood production. Thereduced oxygen levels and lowered food abundance affecthigher trophic levels, including fish. Feeding success is alsosignificantly reduced for juvenile cod (Gadus morhua) foragingin bays with algal mats covering .30% of the sedimentcompared to bays without vegetation (75). Furthermore, theproliferation of algal mats leads to a drastic shift in speciescomposition, and commercially important fish species likeplaice (Pleuronectus platessa) are replaced by noncommercialfish (sticklebacks) and crustaceans (76). Juvenile plaice areabsent from potential nursery grounds with algal mats, andstudies have shown that the fisheries recruitment of plaice mayhave been reduced by 30–40% on the Swedish Skagerrak coast(77). An ecological-economic fishery model has estimated thedirect profit losses in Danish plaice fisheries to at least 3000million SEK, given a time horizon of 55 years and a 1%discount rate (78).

Algal mats also affect cultural ecosystem services throughreduced aesthetic and recreational attraction (63). The visualimpact of algal mats, the smell of decomposing algae, and thephysical disturbance on recreational activities such as swimmingand fishing, constitute a threat to the Swedish coastal tourismindustry. The costs of mechanical harvesting of algal mats insome bays in the northernmost municipality of the Swedish westcoast have been estimated to about 660 000 SEK y�1, or 500 000SEK t�1 nitrogen removed (79). Other studies have confirmed

Table 5. Net changes in the provision of some ecosystem goodsand services following ecosystem shifts. Case A: seagrass beds! unvegetated substrate; B: shallow soft bottoms ! algal matcover, and C: macroalgae ! blue mussel beds.

Net impact and type of Case Case Caseecosystem goods and services A B C

Provisional Services� Reduced fisheries production x x x� Reduced potential production of chemical,

medicinal, and genetic resources x x

Regulating Services� Reduced storm and flood protection x x� Reduced erosion and siltation control x� Loss of productive sediments x� Reduced efficiency of energy transfer x x� Reduced capacity to mitigate eutrophication x� Improved capacity to mitigate eutrophication x

Cultural Services� Reduced aesthetic values x x� Reduced recreational values x x

540 Ambio Vol. 36, No. 7, November 2007� Royal Swedish Academy of Sciences 2007http://www.ambio.kva.se

the importance of aesthetic conditions to recreationists, who puta high economic value on improved water quality and clarity inSwedish coastal waters (58–60).

Shift from Perennial Macroalgae to Mussel Beds on Rocky

Substratum

In the Baltic Sea, the load of phosphorous has increased aboutfive times, and the nitrogen load has increased about three timessince the 1940s, causing eutrophication and favoring someorganisms and systems at the expense of others (3).

The reduced light conditions in outer archipelago areas ofthe Baltic proper, has reduced the depth distribution (from 11 to8 m) of bladderwrack (Fucus vesiculosus) since the 1940s, whichcorresponds to 50% reduction of its biomass (80). Similarreductions have been observed in other areas far from localpollution sources and are probably representative for the Balticas a whole. Locally, complete disappearance of Fucus hasoccurred, e.g., in the inner Stockholm archipelago, probablydue to both decreased light conditions as well as increasedepiphytic growth and sediment dust on the rocks preventingalgal recolonization. Some of the Fucus communities are nowslowly recovering, especially in areas that have been cleanedthrough sewage diversion or reduction of pulp mill effluents,and there are also signs of increasing depth penetration as aresult of a generally improved eutrophication status in theBaltic proper.

The species-rich Fucus community is the ‘‘forest’’ of theBaltic Sea, and there is no other large, long-lived, and belt-forming vegetation that can replace it on hard bottoms in case itdisappears. The massive loss of Fucus during the last decadeshas certainly impaired the generation of numerous ecosystemgoods and services (Table 5). The control of wave and currentenergy along coastlines has been reduced. Genetic, chemical,and medicinal resources are also affected, since Fucus isregarded as the most species-rich community in the Baltic Sea(81). Furthermore, the decline in bladderwrack in many coastalareas, both in Sweden and in Finland, has negatively affectedthe available spawning and nursery grounds of coastal fishspecies such as perch and pike, resulting in declining fisheriesproduction (39, 80, 82).

Blue mussels have, in contrast, been favored by increasednutrient loads to the Baltic Sea because the increasingphytoplankton production provides food and limits thedistribution of bladderwrack, which competes for space. Thedeeper rocky bottoms on which the bladderwrack used to groware now instead largely covered by blue mussels (80). Bluemussels have increased their distribution by about 20% since the1970s at the same time as Fucus has retreated in its depthdistribution in the Asko area. The mussels have in turnstimulated growth of filamentous red algae that can formextensive drifting mats and beach casts after detachment andhave negative effects on tourism. Beach casts can be up to 7000tonnes per shore kilometer and day under certain conditions(83). Campground owners’ profit losses, due to beach cleaningon the island of Oland, amount to at least 1 million SEK y�1

(60). These losses do not account for lost recreational valuesamong visitors because of the remaining nuisance. Thick layersof drifting algae may also periodically cover bottoms, causingoxygen depletion and reduction of animals, including fish (75).Drifting macroalgal mats can also cause major economicimplications for coastal fisheries through fouling of fishing gear.

The observed system shift from macroalgae to musselhabitats in the Baltic Sea has caused major effects on theproduction of ecosystem goods and services, but total netimplications are not possible to calculate due to limitedscientific information. Net gains include improved biological

Box 1.

MacroalgaeOn hard substrate there are about 100 species of brown algae inthe North Sea but only some 20 species in the Baltic Sea (93). Alarge number of seaweeds are belt forming as well as structurallyand functionally important on the west coast (Ascophyllum sp.,Fucus spp., Sargassum sp., Laminaria spp., Halidrys sp., and anumber of red algae), but only two larger algae form belts in theBaltic proper (F. vesiculosus and F. serratus). In the Skagerrak-Kattegat and the Belt Sea area, macroalgae are generally canopy-forming from the surface down to 15 m, and in some areas to waterdepth of 30 m, while in the Baltic proper, the benthic vegetationreaches down to about 25 m (1–8 m of canopy forming) (81). Themacroalgal belts in the Skagerrak harbor around 200 species ofassociated invertebrates and serve as important feeding ground formore than 40 fish species (21, 94). In the Baltic proper, this is themost species-rich community, containing some ten species ofalgae and 30 macroscopic animal species, including mussels,snails, crustaceans, bryozoans, and even insect larvae (81).

Seagrass BedsEelgrass (Zostera marina) is the only rooted plant that has beenable to colonize fully marine areas in Sweden. In the Skagerrak-Kattegat area, it forms dense meadows on intermediately exposedand protected sediment bottoms from 1 to 6 m (95). Meadows inthe Baltic proper have lower blade density and occur in moreexposed areas covering sandy bottoms between 3 and 8 m (93). Ithas its largest extension off the southern coasts of Sweden andhas its northernmost limit in the Aland Sea area (96). The fauna ofthe seagrass system is either associated with the vegetation orliving in or above the sediment. The importance and function ofthese faunal groups may vary between areas, but they often makemajor contributing in the food web up to fish (67, 96).

Blue Mussel BedsIn the Skagerrak-Kattegat area, the blue mussel (Mytilus edulis)beds are restricted to shallow soft and hard bottom communitiesdue to high predation, but may still form habitat patches (,100 m2)on sheltered shallow (0–2 m) soft sediment bottoms with goodwater exchange. In the Baltic proper, where competitors for spaceand predators are largely lacking due to low salinity, the musselsdominate, with dense belts normally starting at a few meters depthand often extending to 30 m or until the bottom gets too muddy toallow the mussel to attach. The benthic animal biomass in theBaltic proper is totally dominated by the blue mussel, whichaccounts for 90% of the total animal biomass on hard bottoms (45).Patches and beds of blue mussels add additional structures thatincrease the habitat complexity of soft and hard bottom substrate,which enhance the number of niches for the benthic flora andfauna, leading to substantial increase in biodiversity (speciesrichness, abundance, and biomass) compared to surroundingareas (48).

Unvegetated Soft BottomsShallow soft bottom systems are generally considered as low-diversity and high-production compared to deeper (below 20–25 m)sediment bottoms. Few species have adapted to this variableenvironment, but populations generally have high densities (97). Inthe Skagerrak-Kattegat area, soft bottoms that are absent ofvegetation are the dominant habitat type in the depth 0–10 m,covering about 60% of the coastal area (98). The shallowest part(0–3 m) has the highest production, mainly due to hightemperature, unlimited food availability, and a dominance ofsmall-sized, fast-growing fauna. The shallow soft bottom systemsare mainly fuelled by plankton and organic matter transported bycurrents from the pelagic system, supporting high production ofmacrofauna (67). This macrofauna provides the food base forfishes, including commercially important species (99).

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control of nuisance species such as phytoplankton, andamelioration of eutrophication effects such as algal bloomsand poor water quality. From a societal perspective, it is,however, questionable if this can compensate for net losses ofproduction, regulating, and cultural functions due to reductionsof the macroalgal community (Table 5).

DISCUSSION

Ecosystem management is based on understanding of hownatural systems work and how human activities may influencethese systems. Management is also about identifying the valueswe wish to protect and the economic costs or gains ofpreservation. This suggests that the evaluation of ecosystemgoods and services, from both economic and ecologicalperspectives, is a necessary ingredient in practical policy.

Biodiversity has a fundamental role in providing the basis forall ecosystem goods and services, although detailed understand-ing of the complex underlying mechanisms is still limited (10,12). Some general aspects of biodiversity do, however, linkdirectly to goods and services. First, genetic and speciesdiversity influences the probability of making a commercialdiscovery in some industries. Such biodiversity has been valuedbecause of the importance of an existing or future potentialinput to production processes in agricultural and pharmaceu-tical industries (84, 85). Second, biodiversity can also be viewedas providing an insurance value by enabling opportunities forrisk spreading and avoidance of economic losses, for example,by using different species or different genetic structures of aparticular species in cultivations (86). Such a value can also befound whenever biodiversity contributes to increased ecosystemresilience (11, 28–30) and thus stabilization of the provision ofecosystem goods and services. Third, stated preference valua-tion methods such as contingent valuation might indicate thatpeople are willing to make trade-offs for the existence ofbiodiversity. However, while there are numerous valuationstudies on, for example, preservation of single or multiplespecies and human use of natural areas and landscape diversity,few of them have considered variability explicitly (85). Somegeneral aspects of biodiversity can thus be valued directly.However, finding arguments for increasing or stabilizing thesupply of ecosystem goods and services is likely to be a saferway of maintaining the production status of habitats and theirassociated biodiversity in comparison to trying to valuebiodiversity itself.

In this paper, we have identified a wide range of ecosystemgoods and services of importance to stakeholders and resourceusers across the entire socio-economic spectra (Tables 1, 3, and4). Each of the four dominant Swedish coastal habitats cansupport the majority of these goods and services, although therelative importance of habitats differs. Distinguishing charac-teristics would, for example, be the exceptional importance ofblue mussels for mitigation of eutrophication, sandy softbottoms for recreational uses, and seagrasses and macroalgaefor fisheries production and control of wave and current energy.To date, the available scientific information is insufficient forevaluating entire habitats and the relative importance amonghabitats. Future research should focus on quantitative assess-ments of how critical functions and underlying patterns,processes, and structures that generate ecosystem goods andservices are affected by disturbance regimes. Researchers shouldalso address the fragility of ecosystem services, i.e., how close isthe system to some alteration that would substantially changeservice flow. Ecosystem resilience can mask the effects thatgradual changes have on goods and services. The negativeimplications of disturbances are usually only obvious oncesevere degradation has occurred, sometimes leading to entire

regime shifts. Unfortunately, the alternative state may then belocked in a stable domain (undesirable resilience), leading to theloss of ecosystem goods and services and major concerns forsuccessful restoration. Three examples of system shift, allinfluenced by increased nutrient loading to coastal areas, wereanalyzed in this paper. Significant net changes in the provisionof many ecosystem goods and services were identified (Table 5).Undesirable resilience was also evident in the case of seagrassloss and filamentous algal mats covering shallow soft bottoms.In both cases, negative feedback mechanisms sustain the newsystems not preferred by society.

It should also be emphasized that the coastal ecosystemsevaluated in this paper are strongly linked through biogeo-physical interactions, suggesting that they cannot easily betreated as separate units from a management perspective.Analogous to the tropical seascape, composed of mangroves,seagrasses, unvegetated shallows, and coral reefs (87), dominanttemperate systems exhibit connectedness via nutrient andcarbon fluxes, faunal migrations, etc. The use of one functionin any system may influence the availability of other functions,and their associated goods and services, in the same or adjacentsystems in the temperate seascape. The capacity of ecosystemsto provide goods and services in a sustainable manner shouldtherefore be determined under complex system conditions,subject to dynamic modeling (88, 89).

The interconnectedness of certain ecological functions, andassociated ecosystem services, also highlights the potential riskfor economic double counting. Ecosystem functions andservices do not always show a one-to-one correspondence.Sometimes a single ecosystem service is the product of two ormore processes, whereas in other cases, a single processcontributes to more than one service. For example, theefficiency of nutrient cycling, energy transfer, and sedimentformation functions influences the productivity of services suchas mitigation of eutrophication and goods such as fish andshellfish, and cannot easily be valued separately. These types offunctions have therefore also been classified as supportingservices (2).

Numerous publications from the last decade have illustratedthe values of ecosystem goods and services and indicated howthey might be estimated (25, 59, 90, 91). Changes in theprovision of many of the ecosystem goods and servicesidentified in this paper can also be economically valued,although such a valuation typically requires substantialinformation on ecosystem dynamics, the role of ecosystems incommercial sectors, such as fisheries, and the preferences ofindividuals. Furthermore, the value of services such asmitigation of eutrophication and climate regulation dependmuch on the scale at focus in the analysis. The loss of a small(,1 hectare) blue mussel patch or area of bladderwrack mayonly have marginal effects on water quality, whereas the loss ofmussel beds or bladderwrack in a large bay or the entire BalticSea would have major implications. Extreme caution is alsoneeded whenever the objective is to estimate the total value ofan entire ecosystem, or whether some habitats are moreimportant than others from a societal perspective, if this is atall a relevant question. It could be argued that a majorreduction in the provision of critical ecosystem services such asresilience against disturbances, maintenance of ecosystemproductivity, as well as maintenance of clean, breathable airand favorable climate, would imply an infinite loss in economicand social values, because they constitute a prerequisite forhuman survival and wellbeing. This fact is also emphasized bythe dearth of human-made substitutes or responses for manyregulating functions (Table 3). It should also be stressed that theoccasional potential to replace one ecosystem service with atechnological substitute usually implies a fossil-based alterna-

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tive requiring extensive engineering and maintenance costs. Thissubstitution can also never replace the multitude of ecosystemservices provided free of charge by solar powered, self-repairing,and resilient ecosystems (87).

Spatial and temporal ecosystem dynamics influence thequantity of generated goods and services, which in turn limitsthe potential for transferring values across time and space. It isalso reasonable to question the natural state of manyecosystems, which makes it very difficult to detect and valuechanges or deviations from the natural regime. This problem ofshifting baselines has received considerable attention during thelast years, e.g., in fisheries (92). Context-specific research shouldpreferably provide the basis for any evaluation of managementalternatives or the implications of threats and disturbances.

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104. Acknowledgments: This study is part of the research program MARBIPP (MarineBiodiversity: Patterns and Processes) financed by the Swedish EnvironmentalProtection Agency, which we kindly acknowledge. We thank the anonymous reviewersfor constructive comments to an earlier manuscript and Robert Kautsky for illustratingthe map.

105. First submitted 22 June 2006. Accepted for publication 28 November 2006.

Patrik Ronnback has a PhD in systems ecology, and hisresearch interests relate to the field of ecological economicsand sustainability analyses of fisheries, aquaculture andecosystem services in coastal ecosystems in Sweden as wellas in developing countries. His address: Department ofSystems Ecology, Stockholm University, SE-106 91 Stock-holm, Sweden.E-mail: pat@systems.ecology.su.se

Nils Kautsky is professor of marine ecotoxicology. He has longexperience of working with ecology and management of coastalmarine ecosystems in Sweden as well as in the developingcountries. His address: Department of Systems Ecology,Stockholm University, SE-106 91 Stockholm, Sweden.E-mail: nils@system.ecology.su.se

Leif Pihl is professor in marine fish ecology, and his researchconcerns the ecology of coastal ecosystems. His address:Department of Marine Ecology, Gothenburg University, Kristi-neberg Marine Research Station, SE-450 34 Fiskebackskil,Sweden.E-mail: leif.pihl@kmf.gu.se

Max Troell is an associate professor, and his research focuseson sustainable aquaculture and evaluation of ecosystemservices in tropical and temperate coastal systems. Hisaddress: Beijer International Institute of Ecological Economics,Royal Swedish Academy of Sciences, SE-104 05 Stockholm,Sweden.E-mail: max@beijer.kva.se

Tore Soderqvist is an environmental economist at the Swedishconsultancy Enveco, and associate professor of Economics atthe Stockholm School of Economics. Economic valuation ofenvironmental change in an interdisciplinary setting is one ofhis main spheres of activity. His address: Enveco Environmen-tal Economics Consultancy Ltd., Oxholms-grand 3, SE-127 48Sweden.E-mail: tore@enveco.se

Hakan Wennhage is an associate professor, and his researchfocuses on recruitment processes in coastal fish populations inrelation to natural and anthropogenic changes in habitat quality.His address: Department of Marine Ecology, GothenburgUniversity, Kristineberg Marine Research Station, 450 34Fiskebackskil, Sweden.E-mail: h.wennhage@kmf.gu.se

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