Dr Dimitrios Kaloudis, Manager of the Centre for Environmental Solutions at PML Applications, co-authored new research that details how we value blue ecosystems in a paper titled ‘Co-benefits reveal the true value of blue ecosystems’. The project, led by Plymouth Marine Laboratory’s Dr Olivia Rendón and co-authored by Professor Nicola Beaumont and Dr Dimitrios Kaloudis, demonstrates the true worth of habitats like saltmarshes, seagrass meadows, kelp forests and oyster beds beyond carbon sequestration alone, increasing their economic value by 10 to 100 times. These habitats are already recognised for their ability to capture and store carbon, but this study provides a broader view of the natural capital value.

To reveal the more accurate value of blue ecosystems, the research team carried out the first comprehensive review of all available monetary valuations of ecosystem services across saltmarsh, seagrass, kelp, maerl, and oyster habitats for the UK.

Dr Dimitrios Kaloudis said:

“At PML Applications, my role supports the development of natural capital, nature-based solutions and nature restoration projects, among others. This work highlights the benefits of assessing nature conservation and restoration in a multi-dimensional, holistic manner. Gaps remain and we must address them to better understand the benefits of nature conservation and restoration. However, this work clearly makes the case for more ambitious and better-funded restoration projects – ensuring these ecosystems can continue protecting coastlines, supporting biodiversity, productive fisheries, and storing carbon long into the future.”  

These co-benefits include flood protection, improved water quality, biodiversity support, nursery habitat for marine life, recreation and food provision. The results show that standard carbon-focused valuations only tell part of the story, as demonstrated in this case study.

Case study: The Solent

To test real-world implications, the team applied their co-benefit valuations to The Solent, one of the UK’s largest estuarine systems. The results showed:

  • Saltmarsh restoration potential increases from £841k (carbon only) to £96.9m (with co-benefits)
  • Seagrass increases from £524k to £189.8m
  • Kelp increases from £27k to over £15m
  • Oyster beds increase from £62k to £36.6m

One of the strongest contributors was pollutant breakdown, which plays a major role in water quality, but there are discrepancies between the different valuation methodologies.

Lead author, PML’s Dr Olivia Rendón, said:

“Our study shows that when we look beyond the carbon sink benefits of blue ecosystems, the values increase by several orders of magnitude. If we want to unlock meaningful finance for restoration, we need to reflect the full suite of benefits these habitats provide – from flood protection to cleaner water and recreation.” 

This holistic value has important implications for investors, policymakers and project developers working on nature-based solutions and coastal restoration. It means that restoration and conservation efforts could be far more cost-effective when the full suite of benefits is accounted for, supporting stronger business cases and alignment with environmental goals.

Not all benefits can be quantified in financial terms. This, among other large evidence and methodological gaps, was highlighted in this study. Despite the enormous value of blue ecosystems, the study reveals:

  • Nearly half of all ecosystem services have no monetary valuation (especially true for cultural benefits like recreation, aesthetic value or heritage) meaning their overall economic contribution is significantly underestimated.
  • Existing valuations vary widely in quality, with some methods, such as replacement cost used for pollutant breakdown, producing very high, variable values.
  • Ecosystem condition is rarely accounted for. The majority of studies do not adjust values when blue ecosystems are degraded, even though poorer ecosystem condition means fewer benefits.
  • Value transfers between regions can be unreliable. Different species, environmental contexts and social settings can make transferred valuations inaccurate.

Dr Rendón added: 

“While valuation gaps persist, it is clear that as more ecosystem services are incorporated, the estimated value of these ecosystems rises – strengthening their case for investment and improving their ability to compete with alternative uses of coastal and marine spaces.” 

Professor Nicola Beaumont, of the National Oceanography Centre, commented:

“To restore blue ecosystems at scale, policymakers and investors need robust, decision-grade data. This work takes an essential step toward standardising valuation and making these ecosystems central to climate and biodiversity finance.”

There is further work to be done but this paper highlights the importance of looking at overall impact and value rather than focusing on just one area. The study highlights evidence gaps and variations in valuation methods that need addressing to improve valuation robustness further, with six clear recommendations included in the paper for improving valuation, including standardisation, more primary economic studies, and clearer methods for bundling/stacking co-benefits to avoid double-counting.

The goal is to support clearer, more comprehensive decision making for environmental investment and policy frameworks that recognise the full value of marine and coastal ecosystems.

If you would like PML Applications and Plymouth Marine Laboratory (PML) to carry out work in natural capital value, please contact Dr Dimitrios Kaloudis at dka@pml.ac.uk
 
Read the ‘Co-benefits reveal the true value of blue ecosystems’ paper
 

Related information

This study was funded by Blue Marine Foundation (BLUE) and supported by the EU Horizon project C-BLUES (grant no. 101137844) and UK Research Councils under Natural Environment Research Council award NE/X002357/ 1-Sea the Value.

Citation:

Rendon, O.R., D. Kaloudis, N. J. Beaumont. 2025.

Co-benefits reveal the true value of blue ecosystems.

Cell Reports Sustainability 100582,

https://doi.org/10.1016/j.crsus.2025.100582.

(https://www.sciencedirect.com/science/article/pii/S2949790625002782)