The European Union aims for sustainable marine development, balancing ocean health and the blue economy. Effective policy requires country-level data on progress towards strong sustainable development (balanced socio-economic and environmental progress). This study comprehensively assesses sustainable marine development (focusing on blue growth) for 15 EU coastal countries (Baltic, North, and Atlantic Seas) from 2012 to 2022. The research differentiates between weak and strong sustainability to determine the extent of balanced progress. Existing datasets like the UN SDG indicator database, Eurostat reports, and the Sustainable Development Report offer limited country-level data and temporal coverage for a comprehensive assessment. The Ocean Health Index (OHI) and Baltic Health Index (BHI) provide insights into ocean health, but lack information on balanced development (the trade-off between economic progress and ecosystem health). This study addresses these gaps by developing new indicators using data from various sources, including the International Council for the Exploration of the Sea (ICES), to achieve better coverage of marine sustainable development, particularly focusing on fisheries and ocean governance.

The paper reviews existing assessments of SDG 14 progress, highlighting limitations in data availability and coverage across countries and time. The UN SDG indicator database, Eurostat reports, the Sustainable Development Report by Sachs et al., and OECD assessments all suffer from incomplete data, focusing on only a subset of SDG 14 targets. The Ocean Health Index (OHI) and Baltic Health Index (BHI) offer insights into ocean health but lack a focus on balanced socio-economic and ecological development. The authors note that many studies use the Eurostat indicator set, which is also limited in scope. The paper emphasizes the need for a more comprehensive approach that accounts for both economic and environmental dimensions of sustainable development, distinguishing between weak and strong sustainability.

The study uses an indicator framework derived from SDG 14, selecting and developing at least two indicators for each target (except 14.c). Data from various official sources (CMEMS, EEA, Eurostat, GI TOC, ICES, IMO, IUCN, OECD, and OHI) were gathered. The data were normalized using a difference-to-target method, creating ratio-scale, fully comparable indicators with a 0-100 range. Fisheries-related indicators were based on ICES data, using catch-weighted averages for country-level assessments. A generalized mean was employed to aggregate indicators, allowing for the assessment of both weak and strong sustainability. Weak sustainability assumes full substitutability of natural capital, while strong sustainability assumes complementarity but not interchangeability. The authors used a Monte Carlo simulation (N=10,000) with varying substitution elasticity values (σ) to calculate composite indicator values under both concepts. Target scores were calculated using σ = 10⁶ (weak sustainability) and σ = 0.5⁺ (strong sustainability). At the SDG level, σ was set to ∞ for weak and σ~U(0,1) for strong sustainability. The change in scores between 2012 and the most recent assessment year was determined to assess progress. To assess the direction of progress over time, the slope coefficient of a log-linear regression of each indicator against time was calculated, enabling the calculation of the average annual growth rate. The findings were then compared with the OHI and BHI scores for further validation.

The analysis shows varied performance across countries and indicators. Most countries performed well in targets related to ecosystem-based management, sustainable fishing, small-scale fishing, and marine agreements. Performance was weaker in pollution and economic targets. Figure 2a illustrates the varied indicator scores, with some targets showing homogeneous performance and others exhibiting heterogeneity. Figure 2b shows that only 13 of 22 indicators show positive development. Improvements were observed in spatial planning; however, the growth of established blue economy sectors declined. Analysis comparing weak and strong sustainability revealed differences in country rankings. Figure 3a illustrates that countries above the 45° line performed better under weak sustainability, indicating less balanced achievement of SDG 14. Figure 3b shows that seven countries improved under both sustainability concepts, seven improved only under weak sustainability, and one showed no improvement. Estonia, Lithuania, and Poland were top performers under both concepts. The Netherlands showed no improvement under either concept. A comparison with OHI values (Figure 4) showed general agreement in the overall picture of marine development, but with some notable differences highlighting nuances not captured in the SDG 14 indicators alone. Figure 5 compares SDG 14 status and progress across countries, grouping them into four categories (moving ahead, catching up, losing momentum, and falling further behind). Estonia, Lithuania, and Poland are identified as 'moving ahead,' while the Netherlands is 'falling behind'.

The study highlights the importance of choosing appropriate indicators for measuring sustainable development, emphasizing the challenges in balancing data availability and the comprehensiveness of indicator selection. The focus on blue growth and intergenerational equity, while neglecting intragenerational equity and social dimensions, represents a limitation. Data limitations, including uncertainties in data quality and the effectiveness of certain objectives like marine protected areas, are acknowledged. The 'country-first' approach prioritizing official country data over secondary sources is also noted as a potential source of bias. The study finds that while the EU achieves sustainable marine development, it's not comprehensive across all countries. The comparison with OHI and BHI reinforces the robustness of the findings, while highlighting the limitations of any single indicator framework. The authors emphasize the importance of multiple assessments using different methodologies to enhance the understanding of sustainable marine development.

This study provides a comprehensive assessment of sustainable marine development in 15 EU coastal countries using a framework that distinguishes between weak and strong sustainability. The findings highlight the uneven progress across countries and emphasize the need for a balanced approach that considers both economic and ecological dimensions. Future research should incorporate social equity considerations, address data limitations, and explore more nuanced indicators to capture the full complexity of sustainable marine development. The study's approach, differentiating weak and strong sustainability, provides a valuable tool for policymakers to assess progress towards sustainable blue economy goals.

The study acknowledges several limitations. The indicator selection, while guided by SDG 14, might not fully encompass all aspects of sustainable development due to data availability. The focus primarily on blue growth and intergenerational equity, neglecting intragenerational equity and social dimensions, limits the scope of the analysis. Data quality and the effectiveness of some indicators (e.g., marine protected areas) remain uncertain. The 'country-first' approach relying on official data might introduce biases. Finally, the normalization method introduces some level of arbitrariness into the assessment.