Marine Spatial Planning in the Aegean Sea

Marine Spatial Planning (MSP) needs to answer a fundamental question: where should protection and restoration happen so that biodiversity goals are met while coastal communities remain economically viable? A recent case study conducted under the INSPIRE integrated planning framework highlights how a spatially explicit cost–benefit approach can support this decision-making in Greece-Aegean Sea Case Study. The framework links ecological value, ecosystem service benefits, and management and socioeconomic costs directly to specific places, so that marine conservation targets become operational rather than aspirational. This work is directly aligned with current Europe an policy objectives. The EU Biodiversity Strategy calls for 30% of marine waters to be protected by 2030, including 10% under strict no-take status. In parallel, the proposed EU Nature Restoration Law aims to restore at least 20% of degraded marine habitats by 2030. Our case study in the Aegean Sea translates these high-level goals into spatial planning actions: (i) expanding strictly protected (no-take) areas in shallow waters (0–50 m depth) and (ii) identifying priority areas for passive habitat recovery within existing marine protected areas.

Methodologically, the framework proceeds in three main steps.

1. Defining policy-relevant objectives

We formulated a clear S.M.A.R.T. objective for MSP in Greece — specific, measurable, achievable, relevant, and time-bound — so that protection and restoration targets can be communicated, assessed, and negotiated with stakeholders such as small-scale fishers. This step is essential for moving from “we need more protection” to “we need X% protection in these depth ranges, for these habitats, by 2030”.

2. Quantifying benefits and costs 

We estimated the economic value of ecosystem services provided by key shallow-water habitats in Greece, including seagrass meadows, hard substrate (rocky bottoms), and soft substrate (sedimentary bottoms). Seagrass meadows, for example, were valued on the order of 800,800 USD/km²/year through services such as coastal protection, carbon storage, and support to fisheries. Hard substrates and soft substrates provided lower but still measurable value.

In parallel, we mapped two categories of cost at the same spatial resolution:

• management / operational cost (enforcement, monitoring, governance), ranging from roughly 747 to 17,892 USD/km²/year

• opportunity cost, primarily the expected loss of income in small-scale fisheries, averaging around 2,824 USD/km²/year

  
  

By combining these layers, we produced a Benefit–Cost Ratio (BCR) for each planning unit. Areas with BCR > 1 were identified as “green zones”, meaning that the societal benefits of stricter protection outweigh the combined management and socioeconomic costs. These zones emerge as strong candidates for new or stricter no-take designation. Areas with BCR < 1 (“red zones”), where high cost is paired with relatively limited net benefit, were considered lower priority. 

3. Exploring alternative planning scenarios

We then tested different spatial planning scenarios. A biodiversity focused scenario prioritizes ecological value and restoration potential. A socio-economic scenario prioritizes minimizing expected conflict and economic disruption. Between these, a balanced scenario integrates both conservation impact and social feasibility and proves especially efficient. This scenario-based approach is important for governance: instead of delivering a single “solution map”, we provide transparent options and their trade-offs. Overall, our results show that integrating spatially explicit ecosystem service valuation and cost analysis can make marine planning both more defensible and more acceptable. Rather than treating conservation as a constraint on human activity, this framework treats it as an investment decision with quantifiable returns — ecological, social, and economic.

These results were presented at the ‘The International Society for Ecological Modelling Global Conference’ in Kashiwa, Japan (October 2025) as an oral presentation by the Aegean Sea case study team from Valentini Stamatiadou

You can find the presentation in the following link: https://www.researchgate.net/publication/396983870_A_Spatially_Explicit_Cost-Benefit_Framework_for_Marine_Spatial_Planning_Supporting_Decision-Making_with_the_Economic_Valuation_of_Ecosystem_Services