One Ecosystem :
Research Article
|
Corresponding author: Silvia Rova (silvia.rova@unive.it)
Academic editor: Philip Roche
Received: 23 Dec 2021 | Accepted: 02 Aug 2022 | Published: 05 Sep 2022
© 2022 Silvia Rova, Alice Stocco, Fabio Pranovi
This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Citation:
Rova S, Stocco A, Pranovi F (2022) Ecosystem services’ capacity and flow in the Venice Lagoon and the relationship with ecological status. One Ecosystem 7: e79715. https://doi.org/10.3897/oneeco.7.e79715
|
Ecosystem services (ES) are theoretically linked to healthy ecological conditions, but this relationship seems to be rather challenging to demonstrate in the real world. Therefore, shedding light on these aspects can be crucial for implementing effective ecosystem management strategies, for instance within the context of the EU Water Framework Directive (WFD) implementation. This work aims to present a spatially-explicit assessment of the ecological potential (capacity) and actual use (flow) of 12 ES in the Venice lagoon and to explore the relationships with the ecological status. Quantitative indicators of capacity and flow for each ES have been assessed and mapped and the results summarised with a set of aggregated indicators. The outcomes reveal a positive relationship between the overall capacity and flow of ES, suggesting that where the first is degraded, an overall loss of ES delivery occurs. A complex picture emerges when exploring the links with the ecological conditions, as the relationship changes with the ES and ecological status indicators considered. Structural indicators of ecological status, such as the Biological Quality Elements adopted by the WFD (assessed by MAQI and M-AMBI metrics), seem to be weakly linked with ES, while functional indicators (Kempton Q-90 diversity and secondary production) showed stronger links, especially when aggregated ES indicators are considered. Concerning different ES, it appears that the flow of the ES that are mediated by human uses (provisioning and cultural ES) is negatively related with some of the ecological status indicators. Finally, our results suggest possible limitations of the zonation adopted under the WFD, when it comes to the analysis of ES. We argue that ES could play a role in the management of the Lagoon ecosystem, as their analysis could be used to preserve the ecological functioning by managing the ‘uses’ we make of the ecosystem.
coastal ecosystems, multiple ecosystem services, BQEs, mapping, ecosystem-based management
The concept of ecosystem services (ES) has been conceived to highlight how the well-being of our society depends upon the functioning of ecosystems (
However, despite this theoretical clarity, the evidence about this linkage is still rather scarce in scientific literature (
Within this context, it becomes extremely useful to distinguish between “capacity” and “flow” of ES (
The present study intends to contribute to advance the knowledge on the ES-ecological status relationships, by focusing on the case study of the Venice Lagoon (VL), Italy (Fig.
The aims of this work are:
The assessment focuses on the quantitative mapping of 12 ES (four regulating and maintenance, four provisioning and four cultural ES) (Table
Ecosystem services assessed in the Venice Lagoon, description, capacity and flow indicators (unit of measure in brackets) and mapping methodology. Abbreviations: ES = ecosystem service, R = regulating and maintenance, P = provisioning; C = cultural.
ES category |
ES |
Description, indicators and mapping methodology |
R |
Climate regulation |
Description: Capacity to sequester carbon from the atmosphere. Capacity/flow indicator: Carbon sequestration rate (g C/m2/yr). Methodology: Average salt marshes’ C sequestration rate calculated, based on accretion rate, sediments’ bulk density and organic C concentration (from Seagrasses’ C sequestration rate estimated, based on species-specific belowground production and organic C content (from |
R |
Waste treatment |
Description: Capacity to buffer excessive nutrient loads, reducing the likelihood of eutrophication phenomena. Capacity/flow indicator: Percentage of nitrogen loads removed through denitrification (%). Methodology: the N load removed through denitrification has been estimated based on residence time, according to the equation proposed by |
R |
Erosion prevention |
Description: Capacity to mitigate the erosion of Lagoon’s sediments, contributing to the maintenance of the Lagoon’s morphology and of the channels’ navigability. Capacity/flow indicator: Sediment biostabilisation by bottom vegetation and wind fetch reduction by salt marshes (0-1 scale). Methodology: Sediment biostabilisation index (percentage increase in sediments' erosion threshold due to vegetation, from Wind fetch length calculated using the R package “waver” ( The two indicators have been scaled to 0-1 range and then averaged. |
R |
Lifecycle maintenance |
Description: Capacity to sustain the species’ lifecycle, with particular reference to the nursery function of the Lagoon for marine migrant species. Capacity/flow indicator: Biomass of juveniles of marine migrant species (t/km2). Methodology: Sum of the biomass of juveniles of Sparus aurata, Dicentrarchus labrax and Mugilidae, as resulting from a trophic network model of the Venice Lagoon built with Ecopath-Ecosim-Ecospace referred to the period 2010-2015 ( |
P |
Artisanal fishing |
Description: Fish catches from artisanal fishing activities, which are characterised by the use of traditional fishing gears, mainly fyke nets and traps ( Capacity indicator: Biomass of target species (t/km2). Capacity methodology: Sum of the biomass of species/functional groups targeted by artisanal fishing (Atherina boyeri, Crangon crangon, Polychaeta, Decapoda, Gastropoda, Mugilidae, Solea solea, Sepia officinalis, Platichthys flesus, Knipowitschia panizzae, Pomatoschistus canestrinii, Zosterisessor ophiocephalus), as resulting from a trophic network model of the Venice Lagoon built with Ecopath-Ecosim-Ecospace referred to the period 2010-2015 ( Flow indicator: Catches from artisanal fishing (t/km2/yr). Flow methodology: Sum of the catches from artisanal fishing of the same species/functional groups included in the capacity of this ES, as resulting from a trophic network model of the Venice Lagoon built with Ecopath-Ecosim-Ecospace referred to the period 2010-2015 ( |
P |
Clam harvesting |
Description: Catches of manila clam (Ruditapes philippinarum) from mechanical harvesting activities within concession areas. Capacity indicator: Biomass of clam (t/km2). Capacity methodology: R. philippinarum biomass monitoring data (n. 220 monitoring stations) referred to the year 2016 ( Flow indicator: Catches of clam (t/km2/yr). Flow methodology: R. philippinarum yield data and spatial extension of clam harvesting concessions referred to the year 2018 (unpublished data, courtesy of San Servolo Servizi). |
P |
Recreational fishing |
Description: Fish catches from recreational fishing activities, mainly carried out from private leisure boats and from land. Capacity indicator: Biomass of target species (t/km2). Capacity methodology: Sum of the biomass of species/functional groups targeted by recreational fishing (Sparus aurata, Dicentrarchus labrax, Solea solea, Sepia officinalis, Platichthys flesus), as resulting from a trophic network model of the Venice Lagoon built with Ecopath-Ecosim-Ecospace referred to the period 2010-2015 ( Flow indicator: Catches from recreational fishing (t/km2/yr). Flow methodology: Total catches per capita (kg/fisherman/fishing trip), fishing effort (no. of fishing trips/person/year) and main fishing grounds estimated from a survey of recreational fishermen active in the VL (no. 127 questionnaires collected in the year 2019, more details in Suppl. material |
P |
Hunting |
Description: Catches of wintering birds from hunting activities, targeting mainly species belonging to Anatidae and Rallidae families. Capacity indicator: Wintering birds’ distribution (Anatidae and Rallidae) (0-1 scale). Capacity methodology: Estimate based on the number of huntable wintering birds of the families Anatidae and Rallidae from census data, considering the average of the period 2010-2019 (no. 38 monitoring stations) ( Flow indicator: Catches from hunting activities (no. birds harvested/yr). Flow methodology: Catches in hunting reserves were derived from hunting registries, considering the average of the period 2010-2019. For the rest of the Lagoon, catches were estimated, based on the total catches per capita (no. birds/person/hunting trip), the hunting effort (no. of hunting trips/person/year) and the proportion of hunters active in the Lagoon outside the hunting farms, which have been estimated from interviews to hunters active in the VL (no. 84 hunters interviewed). The total number of hunters corresponds to the members of the local hunting association (“Ambito Territoriale di caccia VE5”) in 2020 and the location of hunting blinds in the Lagoon has been obtained from the local hunting regulation plan ( |
C |
Tourism |
Description: Visits carried out in the Lagoon and its islands, including both private visits with public transport and organised boat tours (excluding mass tourism in the City of Venice). Capacity indicator: Attractiveness of the environment as perceived by visitors (0-1 scale). Capacity methodology: The relative importance of different environmental factors of attractiveness has been obtained from a survey addressed to the visitors of the lagoon (no. 517 questionnaires collected in 2019, more details in Suppl. material Flow indicator: Number of visitors (nr/yr). Flow methodology: Number of people visiting the Lagoon in the year 2019, excluding the historical centre of Venice, obtained from stakeholders operating in the tourism and transportation sectors (public transport company AVM-ACTV S.p.a., 17 private navigation companies - the major ones operating in this sector and nine ecotourism associations). The maps represent the itineraries of the trips enjoyed by visitors, thus representing the fluxes of people visiting different lagoon areas. |
C |
Recreational navigation |
Description: Recreation in the Lagoon by pleasure-boat owners. Capacity indicator: Attractiveness of the environment as perceived by pleasure-boat owners (0-1 scale) Capacity methodology: The relative level of appreciation of different Lagoon areas has been obtained from a survey to recreational boaters, active in the Lagoon (no. 233 questionnaires collected in 2019, more details in Suppl. material Flow indicator: Number pleasure-boats trips (nr/yr) Flow methodology: The fluxes of pleasure-boats have been estimated, based on the average behaviour of boaters, as obtained from a survey (no. 233 questionnaires collected in 2019, more details in Suppl. material |
C |
Information for cognitive development |
Description: Environmental education activities carried out in the Lagoon and its islands by students of every level (guided tours, naturalistic excursions and educational workshops, excluding cultural visits to the City of Venice). Capacity indicator: Attractiveness of the Lagoon as perceived by visitors, accounting for the accessibility to disabled people (0-1 scale). Capacity methodology: The map is obtained by averaging the attractiveness map produced for the capacity of tourism ES and a map of accessibility for disabled people, characteristic that is necessary for the organisation of educational activities with schoolchildren and students. The rationale is that not all the Lagoon is accessible to disabled people and, thus, considering educational activities, the attractiveness of inaccessible areas is much lower. The accessibility map (0/1 scale, meaning not accessible/accessible) includes areas reachable by land and areas with landing places and itineraries that are accessible for disabled people. Flow indicator: Number of students joining environmental education activities (nr/yr). Flow methodology: The number of students of every level who practise environmental education activities in different areas of the Lagoon (guided tours, naturalistic excursions, educational workshops) has been mapped, based on data and interviews to the six major ecotourism cooperatives and associations that offer environmental education activities to students in the area). |
C |
Traditions |
Description: Recreation in the Lagoon through venetian rowing activities (“voga alla veneta”). Venetian rowing is an ancient local rowing technique tailored to the characteristics of the Venice Lagoon ecosystem, in which rowers are standing and facing forward on traditional boats with flat bottom, allowing a safe navigation also in shallow waters. Originally developed for transportation within the Lagoon, it is nowadays practised as a recreational activity that allows the enjoyment of the Lagoon ecosystem also outside the navigable routes. Capacity indicator: Areas with bathymetry suitable for practising venetian rowing activities (0/1 scale). Capacity methodology: The average bathymetry suitable for venetian rowing activities has been obtained from interviews with rowing associations. The map of suitable areas corresponds to all the Lagoon areas with bathymetry ≥ 90 cm (0/1 scale, corresponding to unsuitable/suitable, respectively), excluding the inlets. Flow indicator: Number venetian rowing boats trips (nr/yr). Flow methodology: The number of boat trips with traditional venetian rowing boats has been estimated, based on interviews to all venetian rowing associations active in the lagoon (no. 31 associations). From each association, we obtained the average number of boat trips per day in spring-summer and autumn-winter periods and the areas where the trips occur. |
A set of aggregated indicators has been calculated, based on the results of the assessment (Table
Aggregated ES indicator |
Description |
Sum of ES capacity |
Sum of the capacity of all ES. |
Sum of ES flow |
Sum of the flow of all ES. |
Sum of Dir ES flow |
Sum of the flow of direct ES (i.e. regulating and maintenance ES). |
Sum of Med ES flow |
Sum of flow of mediated ES (i.e. provisioning and cultural ES). |
For what concerns the ecological status of the Lagoon, on one side, we used the two biological quality elements (BQE) suggested by the WFD (MAQI and M-AMBI); on the other, two functional indicators extracted by a food web model (Kempton Q-90 index and Secondary Production).
The WFD requires that the ecological status of transitional waters environment, as the VL, is assessed by monitoring macrophytes and benthic macroinvertebrates, by using the metrics MAQI (Macrophyte Quality Index,
Kempton Q is a community diversity index which measures the slope of the cumulative species abundance curve (
This set of indicators covers different aspects of the Lagoon ecosystem health, following the recommendation of previous studies (e.g.
The monitoring of the BQE occurs in 103 monitoring stations distributed across the Lagoon (Fig. 85 for MAQI and 75 for M-AMBI), whose values are averaged at the “water body” level, that is, the management units defined by the management plan “Hydrographic district of Oriental Alps” (
Fig.
In order to be able to capture different nuances of the relationship between ecological status and ES, we have considered both the capacity and flow of individual ES and the aggregated ES indicators described above. Their relationships with each of the four ecological status indicators (MAQI, M-AMBI, Kempton Q-90 and Secondary Production) have been tested using Spearman’s rank correlation and subsequent significance test, adjusted for multiple comparisons using Holm’s correction (considering each ecological status indicator as a separate set of tests).
We have chosen to evaluate these relationships under two different spatial settings: by considering the water bodies adopted by the Directive and by disregarding them, in order to broaden the analysis beyond these spatial units given the greater variation in size that characterises them. The BQE values in water bodies were calculated as the average of the data from the sampling stations falling within each water body, according to the methodology required by the WFD. For the other ecological status indicators (Kempton Q-90 and Secondary Production), as well as for individual ES and aggregated ES indicators, in order to have a number of observations per water body comparable to that of the BQE, the data were subsampled in the locations corresponding to the BQE monitoring stations. The average values in the water bodies were calculated on the basis of this subsample. To test the relationship between ecological status indicators and ES without considering the subdivision of the Lagoon into water bodies, we used as samples the values of ecological status and ES corresponding to the locations of the BQE monitoring stations, without averaging the data by water body.
Finally, we have tested the relationship between the aggregated ES’ capacity and flow, by calculating the Spearman’s rank correlation (and subsequent significance test) between the sum of capacity and the sum of flow. In this case, the test has also been repeated under different spatial settings:
These two latter settings are equal to those used to analyse the ES-ecological status relationship.
All the analyses have been carried out in R statistical software (
The maps of ES capacity and flow in the VL are shown in Figs
The carbon sequestration rate for salt marshes and seagrass meadows ranges between 64 and 258 g C/m2/yr, while for waste treatment, we estimate that denitrification processes can remove about 12% of nitrogen loads. Erosion prevention shows the important role played by salt marshes and seagrasses to prevent sediment erosion and thus to maintain the Lagoon morphology, while the lifecycle maintenance map shows that juveniles’ biomass is greater in the northern part of the Lagoon, which is characterised by a a greater surface of intertidal and shallow areas (
We estimate that total catches of artisanal fishing are equal to almost 700 tonnes/yr, while clam harvesting amounts to about 1900 tonnes/yr, concentrated in the small areas directly managed by fishers. It should be noted that harvest of clam in these areas often exceeds the capacity, because clam juveniles are usually re-allocated there from other areas of the Lagoon, for growing. We estimate that catches from recreational fishing amount in total to about 140 tonnes/yr, mainly concentrated at the three inlets, while for hunting, the greatest share of catches occurs in the hunting farms and a smaller share in the hunting blinds located in the confined areas of the Lagoon. Finally, for what concerns the flow of cultural ES, we estimate a total flow of visitors to the northern Lagoon as high as 2.4 million visitors/yr, while for recreational navigation, we estimate that fluxes of leisure boats can be as high as 400,000 boat trips/yr in the most congested channels located in front of the inlets. Environmental education in the Lagoon has been enjoyed by almost 14,000 students in a single year, the majority of which have visited areas located in the northern part of the Lagoon. The fluxes of venetian rowing boats are as high as nearly 215,000 boat trips/yr in total, mainly concentrated around Venice downtown where most of the rowing associations are located.
The maps of the ES aggregated indicators are shown in Fig.
The relationships between the sum of capacity and sum of flow, in the different spatial settings considered, are shown in Fig.
Scatterplot between the sum of ecosystem services’ (ES) capacity and the sum of ES flow, considering (A) submerged and intertidal pixels; (B) data subsampled in the WFD monitoring stations and (C) average values in the water bodies defined in compliance with the Water Framework Directive (WFD).
Fig.
Spearman’s rank correlation between ecological status indicators (MAQI, M-AMBI, Kempton Q-90 and Secondary Production) and ES (A: capacity and flow of single ES, B: ES aggregated indicators), computed using the water bodies as spatial units. Symbols near the correlation coefficient represent the significance level (+: p-value < 0.1; *: p-value < 0.05; **: p-value < 0.01; ***: p-value < 0.001), adjusted for multiple comparisons using Holm's correction. Significant correlation coefficients (p-value < 0.05) are coloured in blue or red, representing positive and negative correlations, respectively.
Fig.
Spearman’s correlation between ecological status indicators (MAQI, M-AMBI, Kempton Q-90 and Secondary Production) and ES (A: capacity and flow of single ES, B: ES aggregated indicators), computed without using the water bodies as spatial units. Symbols near the correlation coefficient represent the significance level (+: p-value < 0.1; *: p-value < 0.05; **: p-value < 0.01; ***: p-value < 0.001), adjusted for multiple comparisons using Holm's correction. Significant correlation coefficients (p-value < 0.05) are coloured in blue or red (representing positive and negative correlations, respectively).
This study presents a comprehensive and spatially-explicit assessment of the ecological potential underpinning the ES (ES capacity) and their actual use (ES flow) in the VL. The assessment of both these aspects of ES delivery represents a crucial advancement of this assessment with respect to previous ones (
Considering the aggregated ES indicators, we can first of all observe that the overall capacity and flow appear to be positively related. This is consistent with expectations given the definition of the ES concept (
This rich assessment dataset allows us to capture the different nuances of the relationship between ES and ecological status. In particular, our results highlight three main findings: there is a general lack of relationship between the BQE and ES, both in terms of single ES and aggregated indicators, when they are evaluated at the water body level according to the WFD; the same occurs if we change indicators of ecological status, but not the spatial level of assessment; a series of relationships emerge if we do not consider the water bodies as spatial units of the assessment and they are rather different amongst the different ES (in terms of capacity/flow indicators and ES categories) and ecological status indicators. This underlines the complexity of this relationship, in agreement with previous studies (
When considering different ecological status indicators, we can recognise that they belong to three different “categories” of indicators, according to
Our results highlight a scarcity of significant correlations when considering the average values per water body, if compared with the outcomes obtained disregarding these spatial units, both in terms of capacity-flow and ES-ecological status relationships. It seems that using the water bodies as spatial units of analysis hinders the detection of the relationships found using other spatial settings. This could suggest that this zonation could represent a limitation when it comes to the analysis of ES, not being able to fully capture the functional characteristics of the Lagoon ecosystem and, thus, the spatial patterns of ES. This becomes an issue if, in agreement with previous literature (
The assessment of ES capacity and flow brings a relevant advancement with respect to the previous knowledge on ES in the VL. In particular, on an aggregated level, the flow of multiple ES in the Lagoon is shown to be positively related to the overall ecological potential and, on average, about half of this aggregated potential is expressed as a flow. This suggests that the ES capacity is acting as a sort of carrying capacity for the ES flow: where this carrying capacity is degraded, we observe an overall loss of ES uses. Furthermore, the relationship with ecological status reveals a picture of great complexity. In terms of indicators, the relationship changes depending on the ES and on the ecological status indicators considered. In particular, the number of positive links increases as we move from more sectoral indicators (M-AMBI and MAQI) to a more integrated structural indicator (Kempton Q-90 diversity), to a more functional indicator (Secondary Production). This suggests that ES are more closely linked with indicators that reflect functional characteristics of the ecosystem as a whole rather than to indicators that represent the structural characteristics of isolated compartments of the ecosystem. From a spatial perspective, our results suggest some possible limitations of the WFD water bodies, as most of the relationships fail to emerge when we consider these spatial units of analysis. This zonation seems not to be able to capture the patterns of ES in the Lagoon, hindering the analysis from an ES perspective. We argue that ES, thanks to their capacity to “bridge” ecosystem properties and human uses, could play a role on the management of the Lagoon, possibly also with regards to the definition of spatial units to be used for management purposes.
We sincerely thank the reviewers for their detailed comments, which helped to improve the manuscript. Scientific activity performed in the Research Programme Venezia2021, coordinated by CORILA, with the contribution of the Provveditorato for the Public Works of Veneto, Trentino Alto Adige and Friuli Venezia Giulia.
Information about the surveys conducted to assess the tourism, recreational navigation and recreational fishing ES.