Exploring the convergence of natural flows for the generation of natural capital stocks in marine ecosystems
Introduction
Marine ecosystems are open, complex, adaptive, and hierarchical systems highly integrated through matter and energy flow exchanges. Matter and energy flow exchanges allow ecological systems to operate at different scales acting as dissipative structures, building natural capital stocks capable of generating several ecosystem services vital for human well-being (Vihervaara et al., 2019).
Humans interact with marine ecosystems in different ways. They derive a wide range of vital goods and services from marine ecosystems including the provision of fish and raw materials, recreational opportunities for local communities and tourists, the regulation and sequestration of nutrients and toxic substances, and climate regulation (Blythe et al., 2020; Buonocore et al., 2020a; Chakraborty et al., 2020). At the same time, human activities cause several impacts on marine ecosystems, among which overexploitation of fish stocks, introduction of invasive species, climate change, eutrophication, and waste release (Cattaneo-Vietti et al., 2016; Halpern et al., 2019; Hughes et al., 2017; Renzi et al., 2018). The cumulative anthropogenic pressures on marine ecosystems cause biodiversity loss, seriously affecting their capacity to provide benefits to humans (Halpern et al., 2008; Haines-Young and Potschin, 2010).
Anthropogenic impact on marine ecosystems is a growing concern especially in coastal areas where multiple human activities occur, generating considerable inflows of pollutants and hazardous wastes (Filipkowska et al., 2018). In fact, although the coastal zones represent only about 4% of the Earth’s total land area, they contain more than one third of the world’s population and account for about 90% of the catches from marine fisheries (Barbier, 2017).
In view of the current human pressures on coastal areas, effective management strategies are crucial to conserve healthy and diverse marine ecosystems, maintain the valuable functions and services they provide, and allow for sustainable human activities.
In recent years, Marine Protected Areas (MPAs) have been increasingly acknowledged worldwide as important tools to achieve local and global marine conservation targets (Börger et al., 2014; Coleman et al., 2013; Rasheed, 2020). MPAs are recognized also across multiple international policy processes, including the 2030 Agenda for Sustainable Development, the Convention on Biological Diversity (CBD) and the Ramsar Convention, as tools to conserve biodiversity and achieve human well-being and sustainable development goals (UNEP-WCMC, IUCN and NGS, 2018; Terraube et al., 2017).
In 2010, the CBD’s Parties adopted the Strategic Plan for Biological Diversity 2011-2020 that includes the Aichi target 11 calling for protecting at least 10% of the oceans through coastal and marine protected areas by 2020. In line with the Aichi target 11, there has been a remarkable growth of the number of MPAs in the last decades (Maestro et al., 2019). At global level, MPAs have increased more than 15-fold since 1993 when the CBD entered into force. Since 2016, more than 8 million km2 of new protected areas have been added to the already existing MPAs (UNEP-WCMC, IUCN and NGS, 2018). Nowadays, the number of MPAs at global level is 16,916, covering about 7.5% of the global ocean. MPAs are more concentrated within national waters than in international ones. In fact, national waters represent about 39% of the global ocean of which about 17% are designated as protected areas (UNEP-WCMC and IUCN, 2020).
Assessing the stocks of natural capital and the flows of ecosystem services is crucial to ensure the sustainable management of marine ecosystems (Buonocore et al., 2018; Caro et al., 2018; Pauna et al., 2018). It is particularly useful in those areas where a protection regime is established to support conservation strategies and, eventually, assess their efficacy over the long term.
Environmental accounting represents a useful tool to assess the biophysical and economic value of ecosystem goods and services. In particular, environmental accounting allows the assessment of multiple aspects dealing with marine resources exploitation, among which sustained environmental costs, received benefits, and generated impacts (Häyhä and Franzese, 2014).
Several authors performed a monetary evaluation of natural capital and ecosystem services in marine and terrestrial ecosystems (Cavalletti et al., 2020; Costanza et al., 2014; Nikodinoska et al., 2018; Teoh et al., 2019), while others adopted a biophysical perspective (Berrios et al., 2017; Buonocore et al., 2019; Mancini et al., 2018; Monfreda et al., 2004; Yang et al., 2019). Nonetheless, the integration of economic valuations with biophysical accountings is much needed to capture the complex relationships between human and nature economy (Franzese et al., 2019; Myers, 2002).
In addition, environmental accounting can be usefully complemented by the use of spatial analysis. Assessing the value of natural capital and ecosystem services and mapping their spatial distribution enable identifying priority areas and related optimal management strategies, also facilitating the communication in policy contexts (Maes et al., 2012; Sannigrahi et al., 2019).
In 2014, the Italian Ministry of the Environment and Protection of Land and Sea funded a research programme for the implementation of an environmental accounting system for the network of Italian MPAs. The main goal of this research programme was the assessment of the biophysical and economic value of natural capital stocks and ecosystem services flows in the Italian MPAs (Franzese et al., 2015). Such environmental accounting system is meant to support the management and monitoring of the MPAs, supporting both local managers and policy makers committed to implement strategies for nature conservation and sustainable development.
Several recent studies assessed the biophysical and economic value of natural capital in marine ecosystems and MPAs. In particular, Franzese et al. (2017) applied an environmental accounting model to value natural capital stocks in the MPA “The Islands of Ventotene and S. Stefano” (Central Italy). Picone et al. (2017) calculated the biophysical value of natural capital stocks in the Egadi Islands MPA, also assessing the trade-offs between conservation measures and human activities. Paoli et al. (2018) calculated the emergy value of natural capital stocks in two MPAs located in Liguria Region (Northern Italy). Berrios et al. (2017) performed an emergy evaluation of marine benthic ecosystems in northern Chile assessing their contribution to the regional economy. Buonocore et al. (2020a) calculated emergy and eco-exergy indicators to assess the value of natural capital stocks in two MPAs located in Campania Region (Southern Italy) while Buonocore et al. (2020b) assessed natural capital value in the Gulf of Naples and Campania region (Southern Italy).
The present study aimed at calculating biomass and emergy-based indicators to assess the value of natural capital stocks in the MPA “Regno di Nettuno” (Southern Italy). The assessment was performed through a biophysical and trophodynamic environmental accounting model fed with field biomass data collected through ad hoc sampling campaigns performed in the MPA. In particular, the assessment focused on four main macro-habitats: sciaphilic hard bottom (coralligenous bioconstructions), photophilic hard bottom, soft bottom, and Posidonia oceanica seagrass beds. Finally, to complement the biophysical assessment with an economic perspective, the emergy-based indicators were converted into monetary units to better convey the results of the assessment into policy and socio-economic contexts.
Section snippets
The study area
The MPA “Regno di Nettuno” is located in the Gulf of Naples of Campania Region, Southern Italy (Fig. 1). The MPA was established in 2007 and it includes coastal waters of the three Islands of Ischia, Procida and Vivara, west of the Gulf of Naples.
According to the Italian law on protected areas, it includes three zones named A, B, and C characterized by different levels of protection and allowed human activities and covering a total surface of about 6300 ha (Fig. 1).
In particular, the A zone,
Results
The average biomass density values of the main autotrophic and heterotrophic groups identified in the four macro-habitats of the MPA are summarized in Table 6. This matrix represents the basic dataset for the trophodynamic analysis and the calculation of the mass and energy flows needed to generate natural capital stocks.
The emergy value of the main inputs (natural and nutrient flows) that supported the generation of autotrophic natural capital stocks in the four macro-habitats of the MPA are
Discussion
In this study, the biophysical value of natural capital in marine ecosystems was assessed in terms of work performed by nature for generating and concentrating autotrophic and heterotrophic biomass stocks. The assessment focused on benthic communities that, being more persistent over time than the pelagic ones, are effective indicators of long-term changes of both natural and anthropogenic origins (Ehrnsten et al., 2019).
The value of autotrophic natural capital of the PSB macro-habitat was
Concluding remarks
This study provided an ecological assessment of natural capital value in a Mediterranean MPA. The assessment was performed through an environmental accounting model fed with field data collected through ad hoc sampling campaigns in the investigated MPA.
The value of natural capital stocks was calculated in both biophysical and economic terms. The biophysical values are based on a deeper understanding of the complex ecological dynamics in marine ecosystems while the economic values, still based
CRediT authorship contribution statement
Elvira Buonocore: Conceptualization, Methodology, Software, Writing – review & editing. Maria Cristina Buia: Investigation, Data curation. Giovanni F. Russo: Conceptualization, Methodology, Supervision. Pier Paolo Franzese: Conceptualization, Methodology, Writing – review & editing, Supervision.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
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