# Global distribution, quantification and valuation of the biological carbon pump

F. Berzaghi, Jérôme Pinti, Olivier Aumont, Olivier Maury, Thomas

Cosimano, Mary Wisz

► To cite this version:

F. Berzaghi, Jérôme Pinti, Olivier Aumont, Olivier Maury, Thomas Cosimano, et al. Global distribution, quantification and valuation of the biological carbon pump. Nature Climate Change, 2025, 15 (4), pp.385-392. 10.1038/s41558-025-02295-0. hal-05075645

HAL Id: hal-05075645

https://hal.science/hal-05075645v1

Submitted on 5 Sep 2025

HAL is a multi-disciplinary open access
archive for the deposit and dissemination of sci-
entific research documents, whether they are pub-
lished or not. The documents may come from
teaching and research institutions in France or
abroad, or from public or private research centers.

L'archive ouverte pluridisciplinaire HAL, est
destinée au dépôt et à la diffusion de documents
scientifiques de niveau recherche, publiés ou non,
émanant des établissements d'enseignement et de
recherche français ou étrangers, des laboratoires
publics ou privés.

<figure><img src="image_1.png" /></figure>

Distributed under a Creative Commons Attribution 4.0 International License
1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

# Title: Global distribution, quantification, and valuation of the biological carbon pump

**Authors list:** F. Berzaghi¹*, Jérôme Pinti²,³, Olivier Aumont⁴, Olivier Maury⁵, Thomas Cosimano⁶, M. S. Wisz¹,⁷,#

## Affiliations:

¹Ocean Sustainability, Governance and Management, World Maritime University, Malmö, Sweden

²College of Earth, Ocean, and Environment, University of Delaware, Lewes, DE 19958, USA

³Gulf of Maine Research Institute, Portland, ME 04101, USA

⁵MARBEC, IRD, Univ Montpellier, CNRS, Ifremer, INRAE, Sète, France
⁶Blue Green Future, LLC Falls Church, Virginia

⁷Section for Ecosystem Based Marine Management, Technical University of Denmark, Lyngby, Denmark.

*Corresponding author: fab@wmu.se

#Senior author
21

Abstract

22

23

24

25

26

27

28

29

30

31

The biological carbon pump (BCP) sequesters vast amounts of carbon in the ocean but its importance for conservation, climate finance, and international policy has not been properly assessed. Here, using spatial analysis and financial valuation of the BCP service, we estimate that, annually, the BCP adds 2.81 Gt of carbon (range 2.44 - 3.53) to the ocean with a storage time of at least 50 years (±25 years). This ecosystem service is worth US$545 billion/year (471 - 694) in areas beyond national jurisdiction and US$383 billion/year (336 - 471) within all Exclusive Economic Zones where the sum of its discounted values for 2023-2030 is US$2.2 trillion (range 1.9 - 2.7). These results quantify the climate and economic importance of the BCP and the important role of large ocean states in carbon sequestration. These findings can support discussions in climate finance and in the COP global stocktake for climate action.
32

**Main Text:**

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

The ocean's ecosystem services are globally important and include climate regulation, biodiversity, and food provisioning¹,², and sustain a global economy worth US$1.5 trillion¹.

Human activities, such as unsustainable fishing, resource extraction, and shipping threaten the ocean's key functions²⁻⁵. Other emerging activities include deep-sea mining and mesopelagic fishing, whose impacts are actively studied (e.g.⁶,⁷). The biological carbon pump (BCP), the transport of organic carbon from the surface to the depths, is particularly important: it was estimated that without it atmospheric CO₂ concentrations would be roughly 200 ppm higher⁸,⁹.

Phytoplankton aggregates, zooplankton, fish, marine mammals, and other marine organisms mediate this sequestration passively (e.g., sinking as aggregates, fecal pellets, and carcasses) and actively (e.g., vertical migrations and respiration) by transporting carbon to depths where it remains stored for years to centuries¹⁰⁻¹².

Protecting and restoring the BCP and its carbon service is essential to promote natural solutions to climate change¹³⁻¹⁵, reduce emissions from ocean-based human activities¹⁶,¹⁷, and increase resilience of fish stocks¹⁸. Ecosystem recovery and BCP enhancement have also been suggested as potential marine CO₂ removal strategies and integration in carbon offset markets¹⁹,²⁰. However, these strategies are in the early stages of discussion and require further research before deployment.

Mapping and quantifying BCP carbon services can help their protection through area-based management (e.g., marine protected areas, MPA) and environmental assessments (e.g., impact and strategic) for promoting benefits for climate, biodiversity, and people²¹,²². Yet, few management efforts are designed to protect the BCP nor include climate change adaptation goals²³.
Deploying large-scale conservation, management, and mitigation actions requires substantial financial investments and a more sustainable ocean economy¹,²⁴. Currently, there is no financial incentive to protect the BCP for its climate regulating function even though this would benefit humanity²⁵. Valuation of ecosystem services, including carbon sequestration, is useful to assess non-market value of species²⁶, economic damages inflicted by greenhouse gases emissions²⁷, and nature's contribution to welfare²⁸. Valuation is a key step to financing nature protection through payments for the carbon service benefits provided by species²⁴,²⁹, which have been shown to be of substantial value²⁹,³⁰. Valuation of carbon services can contribute to financing mitigation and adaptation initiatives and financial negotiations (debt relief and restructuring, and financial support)³¹,³² with important implications for developing countries²⁸,³³. However, the focus of the blue carbon/economy, climate benefits of MPA, and financial valuation has been on coastal ecosystems and the social cost of carbon²²,²⁸,³⁴. The new Biodiversity Beyond National Jurisdiction (BBNJ) Treaty opens new opportunities for conservation and research, and capacity building beyond coastal areas but needs to be supported by science³⁵. However, for attracting large-scale financial investments, the valuation needs to speak the language of financial and policy experts and be based on market prices. Despite its importance to climate regulation, a global geopolitical assessment and valuation of the BCP is missing (a regional estimation already exists³⁶).

72

73

## Accounting for sequestration time of BCP carbon-capture

Here, we fill these gaps by mapping the BCP carbon sequestration based on global estimates from an Earth System model¹⁰ and by valuing its carbon service using market-based prices. BCP service was analyzed in relation to different area-based management and political boundaries, including Exclusive Economic Zones (EEZ) and areas beyond national jurisdiction (ABNJ), and national economies. We estimated the amount of annually exported carbon (i.e., the carbon that is

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78
transferred from the atmosphere to the ocean and injected at specific depths) that will remain
sequestered in the ocean for at least 50 years (±25) (see Methods). We refer to this rate as the “50-
year carbon sequestration rate (GtC/year)” or “50-year sequestration” for short, which we used to
valuate the BCP sequestration service across geopolitical boundaries. Carbon residence time is a
critical parameter often neglected, or arbitrarily set³⁷, in estimations of carbon sequestration and
valuation of carbon services³⁶,³⁸. What is considered “long-term” residence (or permanence) time
in policy and sequestration schemes varies greatly from 25 to 100 years³⁹; regardless, temporary
carbon storage can help transition to “2050 net-zero” and reduce peak warming⁴⁰. We chose 50
years (±25) as a compromise between climate mitigation potential and human-timescale decision
making (e.g, policy and investment horizons). Our analysis of the BCP includes processes driven
only by phytoplankton, zooplankton, and fish (see Methods), which together are the biggest
contributors of sinking organic particles in the open ocean¹⁰,⁴¹. Our results include a sensitivity
analysis of: carbon residence time to capture some of the uncertainty of modelling biological
carbon export⁴¹; and carbon credit price and real discount rates to capture the global variability in
these parameters. We also identify hotspots of carbon sequestration for prioritizing conservation.
We provide a baseline to measure ecological and economic loss when natural assets are
mismanaged or damaged, that could incentivize countries to protect the BCP, and support
international climate finance negotiations. These results provide information to support the
development of international financial markets for carbon if the effects of management and
conservation actions can be measured in terms of avoided/reduced emissions and/or carbon
additionality, similarly to carbon offset initiatives in other ecosystems²⁵.

100

101

Spatial patterns and magnitude of BCP carbon sequestration
We calculated 50-year sequestration rates by multiplying the annually-injected carbon, provided by a widely-used global biogeochemical ocean model¹⁰, by the fraction of injected carbon that remains stored in the ocean after accounting for ocean circulation and depth of injection³⁸. Carbon injection refers to carbon that is exported and transformed into dissolved inorganic carbon (i.e. respired, either by animals or bacteria degrading organic matter), so that it cannot be reused by marine animals. As organic matter sinks at various speeds, carbon export and injection do not occur at the same place in the water column.

Spatial patterns of 50-year carbon sequestration rates varied greatly (Fig. 1a) and globally totaled 2.81 GtC/year (range 2.44 - 3.53) (Fig. 1b). The highest 50-year sequestration rates were concentrated primarily in the tropics and secondarily in temperate areas (Fig. 1a). Fifty-year sequestration rates peaked in the eastern Pacific, western Indian Ocean, the Americas and Africa's western coasts. Sequestration was intermediate in subtropical areas and in the Southern Ocean. In coastal waters, sequestration rates varied considerably but were generally lower in eastern coasts, particularly in southern America, North America, and the East China Sea.

The majority of 50-year sequestration occurred in ABNJ, estimated at 1.65 GtC/year (range 1.43 - 2.10; 59% of global carbon sequestered per year), and the remaining sequestration in EEZ was 1.16 GtC/year (1.02 - 1.43; 41%). Roughly 27% (0.77 GtC/year, 0.67 - 0.95) of global 50-year sequestration was concentrated within Ecologically and Biologically Significant Areas, as defined by the Convention on Biological Diversity; these areas are predominantly (~80%) in international waters. On the contrary, MPA are 93% located within EEZ but only represent a 0.19 GtC/year sink (0.17 - 0.24; 7% of global 50-year sequestration) (Fig 1b). The bulk of the carbon exported (~80%) that remains sequestered for at least 50 years is the carbon reaching depths between 300 m and 2000 m (Extended Data Fig. 1). At these depths, the spatial patterns of carbon
sequestration are very consistent with the ones described previously (Extended Data Fig. 2 and Fig. 1a).

## BCP sequestration in countries – the important role of SIDS

In terms of 50-year carbon sequestration per area (tC/km²), the total sequestration by country was not always proportional to its EEZ extension (Complete list in Supplementary Table 1). The five countries with the largest EEZ, including their large overseas territories (Australia, France, Russia, UK, and USA), comprised 23% of the total 50-year sequestration rate at 246 Mt/C per year (Fig. 2). However, in countries with smaller EEZ (e.g., Chile, Ecuador, Oman, Peru and Namibia), the 50-year sequestration rate per area was higher than the global average and resulted in noteworthy rates of sequestration. On the contrary, countries such as United States, Canada, Brazil, and Australia had lower-than-average sequestration rates despite their large EEZ. A potential explanation for these differences is that the first group of countries have a narrower shelf where carbon is exported deeper compared to the second group. In Africa, the majority of the 50-year carbon sequestration rate was contained primarily within countries in the Indian and South Atlantic Oceans (Fig. 1a and 2). The EEZ of Small Island Developing States (SIDS, some of which are self-identifying as “large ocean states”) such as Kiribati, Micronesia, or Seychelles comprised 11% of the total 50-year sequestration rates (Fig. 1a and 2) and up to 13% if non-sovereign SIDS were also included. This is substantial considering that there are only 39 sovereign SIDS, and 20 non-sovereign SIDS. In more than 60% of countries, the surface covered by MPA accounted for less than 3% of their national 50-year sequestration; MPA covered at least 10% of total carbon sequestration in 20% of all countries (Fig. 2).

## Value of the BCP sequestration service
We estimated the global value (sum of ABNJ and all EEZ) of the BCP carbon sequestration to be roughly US$1 trillion/year (range 0.8 – 1.1) based on the 50-year sequestration rate at a price of US$90 per t/CO2. The BCP carbon service is worth $383 billion/year (336 - 471) within all EEZ combined and $545 billion/year (471 - 694) in ABNJ. Country-specific carbon service values vary considerably following the spatial distribution of sequestration rate (Fig. 1 and complete list in Supplementary Table 1). The top three countries in terms of value (USA, Chile, and Australia) surpassed $18 billion/year per country. For an additional 53 countries, the value was > US$1 billion/year. The remaining countries, representing ~40% of all countries, had a carbon service value of > US$100 million/year. The annual values are based on the current ecosystem service benefits without any discount rate. The sum of Present Value (i.e., future cash flow) of carbon services of all EEZs from present until 2030 amounted to US$0.9-2.7 trillion and US$2.4-7 trillion until 2050, depending on price of carbon, carbon residence time, and real discount rates (Table 1); this Present Value is the discounted sum of annual payments until 2030/2050 based on the 50-year sequestration rate. Discount rates affect primarily longer-term investments. By doubling the discount rate, the 2030 valuation declines by 10% (Table 1), while the 2050 valuation declines by 27% (Table 1). Instead, changes in carbon prices scale linearly with the Present Value (Table 1); for example, the 2030 valuation declines by 10% for a 10% decline in carbon prices. The per-country summed Present Value until 2050 ranges between US$544 billion and US$1 billion, at 2% real discount rate (Supplementary Table 1).

Large differences in the area of each country's EEZ overshadow the importance of the financial value of BCP carbon services for national economies. This aspect emerges clearly when the value is analyzed in relation to the gross domestic product (GDP). For many low, lower-middle, and upper-middle income countries, the market value of the BCP carbon service accounted for a major percentage of their GDP (Fig. 3a). In many cases, market value represented 10% or more of
the GDP. The countries with the highest market value:GDP ratio are Pacific SIDS, including Kiribati where market value is 38 times its GDP (US$ 8.5 billion/year, Fig. 3b). Even though these percentages are highly dependent on the price of carbon, which does not have a global price and is variable from country to country, the majority of countries with a high value were small countries that are either highly indebted or have limited lending power (Fig. 3a, lending group IDA). The list includes SIDS (Fig. 3a and 3b) that are already being affected by climate change and other countries needing funding to cope with climate change and energy transition<sup>42</sup>. If a viable market for ocean carbon existed, a number of “Highly-indebted Poor Countries”, as defined by the World Bank, could significantly reduce their debt and potentially turn from debtors to creditors by obtaining payments for their BCP carbon services.

182

183

## Hotspots of carbon sequestration

Following the 30x30 target set by the Global Biodiversity Framework (conserving 30% of the Earth by 2030), we highlighted “hotspots” that would maximize the coverage of BCP carbon services if 30% of the ocean area were to be protected (Fig. 4). These top 30% carbon hotspots would hold a combined 1.64 GtC/year of 50-year sequestration rate (58% of global sequestration). A more conservative target of conserving the top 10% areas of carbon sequestration would cover 0.86 GtC/year or 30% of this global service. The top 10% areas include the eastern and northern Pacific, the West coast of Africa and the Americas, the Indian Ocean, and the Mediterranean Sea (Fig. 4). Within the 10% hotspots, 4% of total carbon sequestration (0.03 GtC/year) was within MPA, 58% was within EEZ (0.48 GtC/year), of which 90% concentrated in 40 countries.

184

185

186

187

188

189

190

191

192

193

194

## Policy, climate finance, and conservation implications
Quantification of carbon sequestration and valuation of its services are central in climate finance, policy, and conservation²⁴,²⁸,³²,³⁴. Our spatially explicit analyses of ocean carbon sequestration sheds light on the geo-political distribution of the BCP, its magnitude and financial value. We highlight locations and jurisdictions that can play important roles in protecting, restoring, or enhancing carbon services to address the climate and biodiversity emergencies. These results can help to inform the implementation of international agreements to manage ocean carbon services in both EEZ and ABNJ. Protection will imply managing human activities (through limitation or exclusion) to prevent harm to the BCP. These activities might include fishing, deep-sea mining, dredging, shipping, and pollution. For example, we note that many of the carbon hotspots overlap with areas of medium to high fishing pressure⁴³,⁴⁴ and deep-sea mining designated areas⁶ (e.g., Pacific ocean Clarion-Clipperton Zone). Enhancing the BCP might include ecosystem restoration and other marine CO₂ removal strategies that could increase the BCP efficiency at large scale¹⁹,²⁰, although these strategies will have to be thoroughly and scientifically tested before any large-scale deployment and their cost-effectiveness evaluated⁴⁵.

The recently-agreed Global Biodiversity Framework calls for protecting 30% of the Earth to support ecosystem services, including climate regulation, for biodiversity and for people. Ecosystem and area-based management tools and environmental impact assessments play a central role in the Framework. Consequently, all areas (i.e., the entire territory of each country) are to be under effective spatial planning by 2030 and ecosystem-based environmental impact assessments must be undertaken for new human activities. We show that more than 41% of global 50-year carbon sequestration takes place in EEZ; consequently, countries can independently manage and protect marine ecosystems for socio-economic and climate benefits²⁸ by restoring or enhancing the BCP¹⁹,²⁰ or reducing/avoiding emission of human activities (e.g., fishing)¹⁵. For highly-indebted countries or with limited lending power, and under a nature-based economy, BCP carbon
services could represent an important part of their natural capital that would provide funding to implement adaptation strategies. Adaptation actions and conservation could be financed through payments for the carbon service, in debt-for-nature swap schemes²⁴, or emerging alternative financing (discussed later). Climate financing should account for the significant global importance, in climate and economic terms, provided by the BCP carbon service of low-income countries and SIDS. Changes in monetary policy could be directed to benefit local communities and regions that invest in maintaining or restoring marine ecosystems that can keep sequestering carbon. Countries could include the BCP in their accounting⁴⁶ (e.g.; national balance sheets) of natural resources and invest payments for carbon credits to improve long-term conservation and research on the effects of human activities on marine ecosystems and marine CO₂ removal strategies¹⁹.

Furthermore, the recently agreed BBNJ treaty calls for the creation of open sea MPA and the advancement of scientific knowledge on marine ecosystems³⁵, and includes in its principles the ocean's role in sequestering carbon. Roughly 60% of the global ocean is in ABNJ. Thus, if effectively implemented, BBNJ treaty will protect large areas through an ecosystem-based approach that promotes climate services. We document locations in the high seas that, if protected, can play an important role in long-term carbon storage. In ABNJ, 50-year sequestration rates are significant but will require wide-scale cooperation for protection.

## Challenges and opportunities for developing a BCP market

Currently, there is no clear definition or consideration of acceptable sequestration (residence) time in the Paris Agreement global stocktake nor carbon offset projects³⁸. We overcome this limitation by accounting for carbon residence time. Our 50-year (± 25 years) residence time might be different compared to other carbon projects. Nonetheless, accounting for it increases the transparency of the global stocktake and provides investors in carbon projects with
an additional metric to evaluate investment risks and offset quality. Most importantly, carbon
credits generated by the BCP, and sold on the carbon market, would have to clearly show the
carbon additionality (or avoided emissions) produced by the action taken to protect or restore the
BCP, as it is also required in other land or blue carbon schemes³⁹. This also applies for any
contributions toward Nationally Determined Contributions as part of the COP Paris Agreement.
Several challenges will need to be overcome to develop a market for BCP credits, these include
scientific, financial, and technical ones. The values of the BCP service remain potential until offset
projects can meet accreditation criteria including baseline, additionality, risk of non-additionality,
permanence, leakage, post-credit monitoring, and co-benefits³⁹, which are necessary in valuation
and carbon accounting²⁷. Alternative financial instruments such as bonds and ecosystem service
insurance may be considered to fund restoration and conservation of the BCP that are not solely
based on carbon offsets but other co-benefits⁴⁷ (e.g, biodiversity, sustainability, social, etc.).
Complementary market-based mechanisms have been actively implemented in blue carbon
projects and include a mix of public and private funding, and could potentially include repurposing
harmful subsidies, taxing harmful activities, and debt-relief schemes to indebted countries⁴⁷,⁴⁸.
Here we provide data on baseline and permanence but the rest is still missing. In the near future,
there should be consideration on how future marine mismanagement or inaction may harm the
BCP and create climate change costs. This will require quantification of how various human
activities could affect 50-year carbon sequestration rates, where work is currently ongoing.

The price per t/CO₂ is a key parameter in the valuation and varies considerably across
countries, from less than US$20 in several countries up to US$160⁴⁹. The price is likely subject to
increase. In the European Union Emission Trading System, one of the largest in the world, the last
2-year average price was ~EUR 80 per t/CO₂ and the World Bank and IPCC suggests a price range
of US$60-120 t/CO₂ for building an effective carbon market and meeting the 2°C target ⁴⁹. CO₂
concentrations have global effects and should be handled with a global carbon price. Even at a
very conservative price of US$5 t/CO₂ the value of BCP annually-stored carbon would be of great
monetary value. This implies that each country has the potential to attract sizable public or private
investments that could finance climate change actions including national adaptation plans
designated by the UNFCCC. For purely comparative purposes, the global median social cost of
carbon was estimated at US$ 417 t/CO₂ (c.i. US $177-805)⁵⁰, ~4.5 times higher than the carbon
price we used. As the total value scales linearly with changes in the price of carbon (Table 1), it is
trivial to realize that even a small loss of the BCP would incur a huge cost for our society.

## Conclusions

Present and future human activities might diminish the capacity of the BCP to sequester
carbon but many uncertainties still remain³,⁶,⁵¹. The contribution of different organisms to carbon
sequestration is still actively investigated with increasing evidence showing important
contributions of fish (including commercial species, pelagic species, sharks, etc)¹⁵,⁵²⁻⁵⁵, whales⁵⁶,
copepods⁵⁷, and cephalopods⁵⁸; although direct carbon sinking and migrations of lower trophic
level animals remain the main drivers of the BCP. In our analysis, we could not account for the
contribution of particular groups of marine organisms to carbon sequestration. Consequently, we
cannot produce punctual estimates of how the removal or protection of particular species would
affect BCP carbon services. Our results are based on one BCP model projection and are sensitive
to different model estimates of present and future changes in carbon export including large spatial
uncertainties in terms of magnitude and direction of change⁴¹,⁵⁹. However, projected changes are
based primarily on export in shallow waters (e.g., 100 m) where most carbon is outgassed quickly
in the atmosphere. Consequently, projected changes in shallow carbon exports might not equate to
similar changes in the 50-year sequestration rate.
289

290

291

292

293

294

295

296

297

298

299

300

What we provide is a ready-available, high-level analysis of BCP geographical patterns that can be integrated with current research, guide modeling studies for the global stocktake, and develop efforts for Nationally Determined Contributions and carbon market policy. Because the main factors influencing the BCP relate to changes in ocean conditions brought by climate change, including acidification, changes in nutrient supplies or temperatures, human interventions might have limited effects on the BCP. Consequently, the potential and net contribution of ecosystem restoration to climate mitigation should be evaluated by accounting for the effects of climate change<sup>60,61</sup>. Ideally, the effects of human activities on the BCP need to be thoroughly quantified and compared to the effects of climate change. Until then, we suggest a precautionary approach to protect marine organisms to reduce cumulative impacts of humans and climate. In addition to carbon sequestration services, protection will also increase the resilience of marine ecosystems to cope with climate change<sup>18</sup>.

301

302

303

304

305

306

307

308

309

310

Marine organisms account for roughly 1% of all the dissolved inorganic carbon stored in the ocean but atmospheric CO₂ levels would be ~50% higher without the BCP⁸. Marine organisms should be part of climate mitigation strategies to broaden the portfolio of natural climate solutions¹³,⁶²,⁶³. The BCP carbon services are neither protected nor yet included in the global stocktake or carbon offset market despite their substantial economic value and climate importance. Area-based management tools can be used with financial instruments to support the protection of the BCP by generating additionality, avoiding emissions, and promoting co-benefits⁶⁴; for example through sustainable fisheries management. The climate benefits arising from the BCP are not necessarily experienced or measurable at a given local or regional scale, but do influence global concentrations of CO₂ and should be protected for the benefit of humanity.
**Acknowledgments:** We would like to thank Ralph Chami and Dinah Nieburg for the useful discussions on the valuation of the open sea. Tracy Sutton and Matthias Haeckel for the useful discussion on deep-sea mining, Jack Sutton of UNEP for assistance with the MPA data, and Emmanuel Blondel of FAO for assistance with EEZ shape files. We thank Richard Sanders and Murray Rudd for the feedback on the paper.

FB and MW work was funded by the European Union under grant agreement no. 101083922 (OceanICU) and UK Research and Innovation (UKRI) under the UK government's Horizon Europe funding guarantee [grant number 10054454, 10063673, 10064020, 10059241, 10079684, 10059012, 10048179]. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or European Research Executive Agency.
Neither the European Union nor the granting authority can be held responsible for them. FB and MSW recognize the support from the MEESO project funded by the European Union's Horizon 2020 research and innovation programme under grant agreement No. 817669.

**Author Contributions Statement:** FB and MSW conceived and designed the project. MSW obtained the funding. FB wrote the first draft with input from MSW. FB designed and developed the methodology with input from all other authors. FB performed the analysis and prepared the figures. FB led the writing and all other authors contributed with editing and feedback.

**Competing Interests Statement:** Authors declare that they have no competing interests.

330
331
<table><caption>**Table 1. Effects of price of carbon and discount rates on valuation of the BCP service in all EEZs combined.** Present Value is expressed in trillions of US$ summed from 2023 through 2030 or 2050. The lower and upper bounds of the Present Value is indicated in parenthesis and was calculated by using a residence time of carbon of respectively 25 and 75 years (see methods for more details).</caption><thead><tr><th>PV in trillions of US$ summed through year @ price of carbon</th><th>2% discount rate</th><th>4% discount rate</th></tr></thead><tbody><tr><td>2030 @ US$ 90 t/CO<sub>2</sub></td><td>2.2 (1.9 - 2.7)</td><td>2 (1.8 - 2.5)</td></tr><tr><td>2050 @ US$ 90 t/CO<sub>2</sub></td><td>7.0 (6.1 - 8.7)</td><td>5.5 (4.8 - 6.9)</td></tr><tr><td>2030 @ US$ 45 t/CO<sub>2</sub></td><td>1.1 (1.0 - 1.4)</td><td>1.0 (0.9 - 1.3)</td></tr><tr><td>2050 @ US$ 45 t/CO<sub>2</sub></td><td>3.5 (3.1 - 4.4)</td><td>2.7 (2.4 - 3.4)</td></tr></tbody></table>
343 **Fig. 1. Spatial and geopolitical distribution of BCP carbon sequestration.** Fifty-year carbon sequestration rate (a) spatial distribution and (b) within management and political boundaries. Fifty-year sequestration rate is the fraction of annually exported carbon that remains in the ocean for at least 50 years through passive and active processes driven by phytoplankton, zooplankton, and fish. In (a): azure lines indicate EEZ boundaries; areas with sequestration rates <1 ktC/year were grouped for facilitating visualization; contour lines indicate areas between 1, 10, 25, 50, and above 100 ktC/year. Margin bar plots (top & right) show average seq. rate across latitude/longitude bands. In (b): bars indicate the sum of 50-year sequestration rate globally and in ABJN, EEZ, ecologically and biologically significant areas (EBSA), and MPA. Whiskers indicate the total 25-year (lower) and 75-year (upper) sequestration rates for each group.
352

353 **Fig. 2. 50-year carbon sequestration rate within countries’ EEZ and MPA, grouped by continent.** Detached (overseas) territories were grouped with their sovereign state EEZ. The “Rest of ...” includes the sum of all countries that had less than 3% of their continent's 50-year sequestration; “transboundary” is the sum of all areas managed or claimed by more than one country. The UK has overseas territories where MPAs extend beyond EEZ, resulting in more carbon sequestered within its MPA than its EEZ. The Chagos Archipelago is a particular case as the UK is handing over sovereignty to Mauritius.
354
355
356
357
358
359

360 **Fig. 3. BCP carbon service value in relation to Gross Domestic Product.** Value of annual carbon sequestration was calculated based on $90 per t/CO2 and divided by nominal GDP. (a) Carbon service value by countries' income levels, only countries with % of GDP > 1 are shown (complete list in Supplementary Table 1). Lending groups (classification by the World Bank) relate to countries' creditworthiness and gross national income: IDA includes the poorest countries receiving low-interest loans, IBRD are credit-worthy poor countries, “Blend” are countries in both IDA and IBRD, and “None” are countries with no particular borrowing constraints. The hatched bars indicate Heavily Indebted Poor Countries (HIPC). (b) EEZ of the top-8 countries with the highest BCP carbon service value to GDP ratio and classified according to their income group. All these countries are SIDS in the South Pacific.
361
362
363
364
365
366
367
368
369
370
371

372 **Fig. 4. BCP 50-year sequestration hotspots covering 10% and 30% of the ocean surface and relative global coverage.** EEZ are indicated with azure lines. The EEZ of certain countries are fully covered by the carbon hotspots; countries might not be able to fully protect their EEZ just for carbon services.
373
374
375
376
377 References

378

379 1. Sumaila, U. R. et al. Financing a sustainable ocean economy. Nat. Commun. 12, 3259 (2021).

380 2. Cavanagh, R. D. et al. Future Risk for Southern Ocean Ecosystem Services Under Climate Change. Front. Mar. Sci. 7, (2021) ; doi:10.3389/fmars.2020.615214.

382 3. Cavan, E. L. & Hill, S. L. Commercial fishery disturbance of the global ocean biological carbon sink. *Glob. Change Biol.* **28**, 1212–1221 (2022).

384 4. Epstein, G., Middelburg, J. J., Hawkins, J. P., Norris, C. R. & Roberts, C. M. The impact of mobile demersal fishing on carbon storage in seabed sediments. *Glob. Change Biol.* **28**, 2875–2894 (2022).

386 5. Leaper, R. The Role of Slower Vessel Speeds in Reducing Greenhouse Gas Emissions, Underwater Noise and Collision Risk to Whales. *Front. Mar. Sci.* **6**, (2019) ; doi:10.3389/fmars.2019.00505.

388 6. Drazen, J. C. et al. Midwater ecosystems must be considered when evaluating environmental risks of deep-sea mining. *Proc. Natl. Acad. Sci.* **117**, 17455–17460 (2020).

390 7. Dişa, D., Akoglu, E. & Salihoglu, B. Exploitation of mesopelagic fish stocks can impair the biological pump and food web dynamics in the ocean. *Front. Mar. Sci.* **11**, (2024) ; doi:10.3389/fmars.2024.1389941.

392 8. Maier-Reimer, E., Mikolajewicz, U. & Winguth, A. Future ocean uptake of CO2: interaction between ocean circulation and biology. *Clim. Dyn.* **12**, 711–722 (1996).

394 9. Nowicki, M., DeVries, T. & Siegel, D. A. Quantifying the Carbon Export and Sequestration Pathways of the Ocean's Biological Carbon Pump. *Glob. Biogeochem. Cycles* **36**, e2021GB007083 (2022).

396 10. Aumont, O., Maury, O., Lefort, S. & Bopp, L. Evaluating the Potential Impacts of the Diurnal Vertical Migration by Marine Organisms on Marine Biogeochemistry. *Glob. Biogeochem. Cycles* **32**, 1622–1643 (2018).

399 11. Pinti, J. et al. Model estimates of metazoans' contributions to the biological carbon pump. *Biogeosciences* **20**, 997–1009 (2023).

401 12. Saba, G. K. et al. Toward a better understanding of fish-based contribution to ocean carbon flux. *Limnol. Oceanogr.* **66**, 1639–1664 (2021).

403 13. Schmitz, O. J. et al. Trophic rewilding can expand natural climate solutions. *Nat. Clim. Change* **1–10** (2023).
404

405

14. Free, C. M. *et al.* Realistic fisheries management reforms could mitigate the impacts of climate change in most countries. *PLOS ONE* **15**, e0224347 (2020).

406

407

15. Andersen, N. F. *et al.* Good fisheries management is good carbon management. *Npj Ocean Sustain.* **3**, Article number: 17, 1–6 (2024).

408

409

410

16. Heinrich, L., Koschinsky, A., Markus, T. & Singh, P. Quantifying the fuel consumption, greenhouse gas emissions and air pollution of a potential commercial manganese nodule mining operation. *Mar. Policy* **114**, 103678 (2020).

411

412

17. Greer, K. *et al.* Global trends in carbon dioxide (CO2) emissions from fuel combustion in marine fisheries from 1950 to 2016. *Mar. Policy* **107**, 103382 (2019).

413

414

18. Sumaila, U. R., de Fontaubert, C. & Palomares, M. L. D. Editorial: How overfishing handicaps resilience of marine resources under climate change. *Front. Mar. Sci.* **10**, (2023) ; doi:10.3389/fmars.2023.1250449.

415

416

19. National Academies of Sciences, E. *A Research Strategy for Ocean-Based Carbon Dioxide Removal and Sequestration*. (2021); doi:10.17226/26278.

417

418

20. Hernández-León, S. The biological carbon pump, diel vertical migration, and carbon dioxide removal. *iScience* **26**, (2023) ; doi:10.1016/j.isci.2023.107835.

419

420

21. Roberts, C. M., O’Leary, B. C. & Hawkins, J. P. Climate change mitigation and nature conservation both require higher protected area targets. *Philos. Trans. R. Soc. B Biol. Sci.* **375**, 20190121 (2020).

421

422

22. Jacquemont, J., Blasiak, R., Cam, C. L., Gouellec, M. L. & Claudet, J. Ocean conservation boosts climate change mitigation and adaptation. *One Earth* **5**, 1126–1138 (2022).

423

424

23. Roberts, C. M. *et al.* Marine reserves can mitigate and promote adaptation to climate change. *Proc. Natl. Acad. Sci.* **114**, 6167–6175 (2017).

425

426

24. Berzaghi, F. *et al.* Value wild animals’ carbon services to fill the biodiversity financing gap. *Nat. Clim. Change* 1–4 (2022).

427

428

25. Chami, R., Cosimano, T., Fullenkamp, C. & Nieburg, D. Toward a Nature-Based Economy. *Front. Clim.* **4**, (2022) ; doi:10.3389/fclim.2022.855803.

429

430

26. Lew, D. K. Willingness to pay for threatened and endangered marine species: a review of the literature and prospects for policy use. *Front. Mar. Sci.* **2**, (2015) ; doi:10.3389/fmars.2015.00096.

431

432

27. Balmford, A. *et al.* Realizing the social value of impermanent carbon credits. *Nat. Clim. Change* **13**, 1172–1178 (2023).
28. Bertram, C. et al. The blue carbon wealth of nations. Nat. Clim. Change 1–6 (2021).

29. Chami, R. et al. The Value of Nature to Our Health and Economic Well-Being: A Framework with Application to Elephants and Whales. in *Economic Challenges for Europe After the Pandemic* (ed. Paganetto, L.) 117–162 (Springer International Publishing, Cham, 2022); .

30. Berzaghi, F., Chami, R., Cosimano, T. & Fullenkamp, C. Financing conservation by valuing carbon services produced by wild animals. *Proc. Natl. Acad. Sci.* **119**, e2120426119 (2022).

31. Chamon, M. d, Klok, E., Thakoor, V. V. & Zettelmeyer, J. Debt-for-Climate Swaps: Analysis, Design, and Implementation. *IMF Work. Pap.* **2022**, (2022) ; doi:10.5089/9798400215872.001.A001.

32. Druckenmiller, H. Accounting for ecosystem service values in climate policy. *Nat. Clim. Change* **12**, 596–598 (2022).

33. Johnson, C. M. et al. *Protecting Blue Corridors - Challenges and Solutions for Migratory Whales Navigating National and International Seas*. https://zenodo.org/record/6196131 (2022) ; doi:10.5281/zenodo.6196131.

34. Jankowska, E., Pelc, R., Alvarez, J., Mehra, M. & Frischmann, C. J. Climate benefits from establishing marine protected areas targeted at blue carbon solutions. *Proc. Natl. Acad. Sci.* **119**, e2121705119 (2022).

35. Gjerde, K. M. et al. Getting beyond yes: fast-tracking implementation of the United Nations agreement for marine biodiversity beyond national jurisdiction. *Npj Ocean Sustain.* **1**, Article number: **6**, 1–8 (2022).

36. Barange, M. et al. The Cost of Reducing the North Atlantic Ocean Biological Carbon Pump. *Front. Mar. Sci.* **3**, (2017) ; doi:10.3389/fmars.2016.00290.

37. Thamo, T. & Pannell, D. J. Challenges in developing effective policy for soil carbon sequestration: perspectives on additionality, leakage, and permanence. *Clim. Policy* **16**, 973–992 (2016).

38. Siegel, D. A., DeVries, T., Doney, S. C. & Bell, T. Assessing the sequestration time scales of some ocean-based carbon dioxide reduction strategies. *Environ. Res. Lett.* **16**, 104003 (2021).

39. Sheehy, J., Porter, J., Bell, M. & Kerr, S. Redefining blue carbon with adaptive valuation for global policy. *Sci. Total Environ.* **908**, 168253 (2024).

40. Matthews, H. D. et al. Temporary nature-based carbon removal can lower peak warming in a well-below 2 °C scenario. *Commun. Earth Environ.* **3**, Article number: **65**, 1–8 (2022).

41. Henson, S. A. et al. Uncertain response of ocean biological carbon export in a changing world. *Nat. Geosci.* **15**, 248–254 (2022).
461

42. UNFCCC Standing Committee on Finance. *Fourth (2020) Biennial Assessment and Overview of Climate Finance Flows*. (2021).

462

463

43. Kroodsma, D. A. et al. Tracking the global footprint of fisheries. *Science* **359**, 904–908 (2018).

464

44. Li, M.-L. et al. Tracking industrial fishing activities in African waters from space. *Fish Fish. 22*, 851–864 (2021).

465

466

45. Williamson, P. & Gattuso, J.-P. Carbon Removal Using Coastal Blue Carbon Ecosystems Is Uncertain and Unreliable, With Questionable Climatic Cost-Effectiveness. *Front. Clim. 4*, (2022).

467

468

46. Fenichel, E. P. et al. Modifying national accounts for sustainable ocean development. *Nat. Sustain.* **3**, 889–895 (2020).

469

470

47. Friess, D. A., Howard, J., Huxham, M., Macreadie, P. I. & Ross, F. Capitalizing on the global financial interest in blue carbon. *PLOS Clim. 1*, e0000061 (2022).

471

472

48. Chausson, A. et al. Going beyond market-based mechanisms to finance nature-based solutions and foster sustainable futures. *PLOS Clim. 2*, e0000169 (2023).

473

474

49. World Bank. *State and Trends of Carbon Pricing 2023*. (2023); doi:10.1596/39796.

475

50. Ricke, K., Drouet, L., Caldeira, K. & Tavoni, M. Country-level social cost of carbon. *Nat. Clim. Change 8*, 895–900 (2018).

476

477

51. McMonagle, H., Llopiz, J. K., Hilborn, R. & Essington, T. E. High uncertainty in fish bioenergetics impedes precision of fish-mediated carbon transport estimates into the ocean’s twilight zone. *Prog. Oceanogr.* **217**, 1030–1028 (2023).

478

479

480

52. Bianchi, D., Carozza, D. A., Galbraith, E. D., Guiet, J. & DeVries, T. Estimating global biomass and biogeochemical cycling of marine fish with and without fishing. *Sci. Adv.* **7**, eabd7554 (2021).

481

482

53. Mouillot, D. et al. Industrial fisheries have reversed the carbon sequestration by tuna carcasses into emissions. *Glob. Change Biol.* **29**, 5062–5074 (2023).

483

484

54. Stafford, R., Boakes, Z., Hall, A. E. & Jones, G. C. A. The Role of Predator Removal by Fishing on Ocean Carbon Dynamics. *Anthr. Sci.* **1**, 204–210 (2022).

485

486

55. Mariani, G. et al. Let more big fish sink: Fisheries prevent blue carbon sequestration—half in unprofitable areas. *Sci. Adv.* **6**, eabb4848 (2020).

487

488

56. Durfort, A. et al. Recovery of carbon benefits by overharvested baleen whale populations is threatened by climate change. *Proc. R. Soc. B Biol. Sci.* **289**, 20220375 (2022).

489
490

491

57. Pinti, J., Jónasdóttir, S. H., Record, N. R. & Visser, A. W. The global contribution of seasonally migrating
copepods to the biological carbon pump. *Limnol. Oceanogr.* **68**, 1147–1160 (2023).

492

493

58. Ottmann, D., Denderen, P. D. van, Visser, A. & Andersen, K. H. Impact of increased fishing on long-term sequestration of carbon by cephalopods. *Curr. Biol.* **34**, R526–R527 (2024).

494

495

59. Wilson, J. D. et al. The biological carbon pump in CMIP6 models: 21st century trends and uncertainties. *Proc. Natl. Acad. Sci.* **119**, e2204369119 (2022).

496

497

60. Littleton, E. W. et al. Dynamic modelling shows substantial contribution of ecosystem restoration to climate change mitigation. *Environ. Res. Lett.* **16**, 124061 (2021).

498

499

61. Gao, G. et al. A review of existing and potential blue carbon contributions to climate change mitigation in the Anthropocene. *J. Appl. Ecol.* **59**, 1686–1699 (2022).

500

501

62. Hilmi, N. et al. Deep sea nature-based solutions to climate change. *Front. Clim.* **5**, (2023) ; doi:10.3389/fclim.2023.1169665.

502

503

63. Hilmi, N. et al. The Role of Blue Carbon in Climate Change Mitigation and Carbon Stock Conservation. *Front. Clim.* **3**, (2021) ; doi:10.3389/fclim.2021.710546.

504

505

64. Reimer, J. M., Devillers, R. & Claudet, J. Benefits and gaps in area-based management tools for the ocean Sustainable Development Goal. *Nat. Sustain.* **4**, 349–357 (2021).

506

507

## Materials and Methods

508

509

### *Overview*

510

511

512

513

514

515

516

We gathered estimations of carbon exported annually by the BCP simulated by the state-of-the-art global ocean dynamics model NEMO-PISCES-APECOSM¹⁰. From NEMO-PISCES-APECOSM output, we then calculated the fraction of the exported carbon that remains sequestered in the ocean for at least 25, 50, and 75 years based on OCIM, an ocean circulation model³⁸. We chose 50 years as the average carbon residence time as this will allow the carbon to remain stored well past 2050, when humanity should be close to its net-zero goal. Fifty years is also more relevant for near-term climate change policy and understandable on a human time-scale than longer residence time. The
25 and 75 years of residence time were used to calculate the lower and upper bounds of our calculations. This annually-sequestered carbon was then valued according to current carbon-offset market prices for an investment horizon until 2030 and 2050. Valuation is highly dependent on the BCP model results given the large variability among models ⁴¹, in addition to discount rate, and price of carbon, which currently differs from country to country until local carbon markets are coordinated in a single global market. The investment horizon is the length of the contract signed by the buyer of carbon offsets. Carbon offsets generated by nature, in this case the ocean, are issued to the buyer that receives carbon credits for a specific duration (based on the yearly sequestered carbon). Part of the funding will need to be earmarked for the conservation of the ocean so that it can keep generating the carbon service ²⁴ or can be used to restore the ecosystem to increase the provision of the service. The service is provided because nature remains in the public domain and under national or international jurisdiction; this helps managing the ecosystem to maintain its resilience and functioning so that the service is continuously provided. As discussed later, the provision of the service is also dependent on the effect of major drivers such as climate change that cannot be directly controlled. The 50-year sequestration time and the 2030/2050 years investment horizon time are conservative thresholds chosen so that carbon offsets sold remain sequestered for a time period much greater than the investment horizon.

### Biological carbon pump carbon long-term sequestration rate

We used carbon export estimates from a global dynamic model of ocean biogeochemistry and biology called the NEMO-PISCES-APECOSM ¹⁰. The NEMO-PISCES-APECOSM is a widely-used biogeochemical model and is part of the Earth System Models that contribute to the Intergovernmental Panel on Climate Change reports and the Inter-Sectoral Impact Model
Intercomparison Project (https://www.isimip.org/impactmodels/)⁵⁹. NEMO-PISCES-APECOSM combines an ocean circulation model (Nemo), a biogeochemical model of lower trophic levels of marine ecosystems (PISCES), and an upper trophic levels model of epipelagic communities (APECOSM). Note that various fully-coupled Earth System models produce estimates of biological carbon pump export but NEMO-PISCES-APECOSM is the only one with an explicit representation of fish and zooplankton vertical migration⁴¹, which are important processes in the BCP¹⁰. Briefly, the model was run offline and forced by the output of the IPSL Earth System model for 300 years. Note that running the NEMO-PISCES-APECOSM model fully coupled (i.e., online) with an Earth System model does not have any noticeable effects on carbon export by the BCP⁶⁵. In the first phase, a spin-up simulation was used to reach APECOSM open pelagic community steady-state. During a second phase the APECOSM was used fully-coupled with NEMO-PISCES and run for 1,000 years so that biology and biogeochemistry reached steady state. The lower trophic levels include two phytoplankton groups (nano phytoplankton and diatoms) and two zooplankton size classes (micro and meso-zooplankton). Upper trophic levels include visual predators and filter feeders ranging from 1 mm to 2m divided in 20 size classes. Upper trophic levels communities are of three types: epipelagic (first 200m), mesopelagic and bathypelagic (200-1000 m), and migratory, which perform daily vertical migration. The NEMO-PISCES-APECOSM model carbon export was previously validated against observation data of marine organisms' biomass ¹⁰. Carbon export is the result of the marine community biological processes including predation, respiration, egestion, excretion. The model estimates the exported carbon at 29 depth levels from 10 m to 5000 m. The model does not include other modest contributors to the BCP such as marine mammals, cephalopods, or jellyfish. As such, these are not included in our analyses. Further, we do not consider carbon fluxes from coastal shallow-water processes driven by kelp or seaweed, which are not usually considered to be part of the BCP.
Carbon exported in the ocean has different residence times, from a few days to centuries depending on depth and location of injection because ocean dynamics might transport carbon molecules close to the surface where it can go back to the atmosphere ³⁸. It is thus critical to consider ocean circulation when estimating what fraction of exported carbon remains sequestrated and for how long. The output of an inverse ocean circulation model provided the fraction of exported carbon that remains in the ocean as a function of depth and location of export/injection ³⁸. Specifically, the Siegel et al. data provide at each depth horizon from 15 m to ~4500 m (29 depth levels in total) the percentage of carbon export that remains stored for a certain number of years, namely from 1 to 1000 years. We matched the level depths of NEMO-PISCES-APECOSM with the ones in the ocean circulation model and calculated the amount of yearly exported carbon at each of the 29 level depths that will remain stored for at least 50 years by multiplying carbon export from NEMO-PISCES-APECOSM by the fraction of remaining carbon after 50 years according to the ocean circulation model. We call this the “50-year carbon sequestration rate”, in GtC/yr (shortened “50-year sequestration rate”), which is the sum of sequestered carbon at each depth layer following the formula:

$$C50 = \sum_{i=1}^{n} Cexport_{i} \times \%C50_{i}$$

Where C50 is the total 50-year carbon sequestration rate, i is the depth level going from 10 m to 4500 m, Cexport is the export rate from NEMO-PISCES-APECOSM, and %C50 is the percentage of exported carbon that will remain in the ocean for at least 50 years.

Both NEMO-PISCES-APECOSM and the ocean circulation model provide 3-D outputs, consequently we matched their output horizontally and vertically to the closest possible depth. This “50-year sequestration rate” was used to compute the total carbon exported from now until
2030 (and 2050) that will remain sequestered for more than 50 years. The total exported carbon was analyzed in relation to area-based management and political boundaries. Finally, a valuation of the BCP carbon service was performed for each of the different boundaries.

591

## Political and management boundaries

593

We analyzed global patterns of BCP carbon storage according to several boundaries that are relevant to national and international policies, fishing, conservation, and natural resources management. These boundaries included Exclusive Economic Zones, areas beyond national jurisdiction, Marine Protected Areas, and Ecologically or Biologically Significant Marine Areas.

Shapefiles of these boundaries were obtained from the sources specified in Extended Data Table 1. Marine protected areas and EEZs were assigned to countries according to their sovereign State.

Certain EEZs are joint or disputed between multiple countries and were marked as “transboundary” in our analysis.

## Carbon hotspots

The international conservation initiative called “30x30” was signed at the COP15 meeting of the Convention on Biological Diversity and has now been signed by more than 150 countries. This initiative has a target of designating 30% of the Earth as protected areas⁶⁶. We used this target to highlight the areas of the ocean that would maximize carbon sequestration if 30% of its surface would be protected. As a more conservative target we performed the same calculation with a 10% threshold.

609

## Gross domestic product and economic data
GDP data and countries income and lending classification were obtained from the World Bank website and are relative to the year 2022. The GDP of 33 countries was not reported for the year 2022. In such case, we used the first GDP reported from the year closest to 2022.

614

615
Financial valuation

We used an investment horizon until 2050 (27 years from 2023) and 2030 (7 years from 2023) and a 2% real discount rate to calculate the present value of the annuities along this investment horizon based on each country's estimated annual carbon sequestration (within EEZ). The real discount (or interest) rate is approximated by the difference between the actual discount rate and the expected inflation rate. The financial markets estimate of the real interest rate for long term investments can be measured by the difference between the 10-year US government bond rate and the 10-year inflation protected US government bond rate⁶⁷. This measure is 2.12% with standard deviation of 0.43 over the five years from 2019-2024 (Data from the Federal Reserve Bank of St. Louis database “Federal Reserve Economic Data” https://fred.stlouisfed.org/). Because of no-arbitrage between high-income countries’ investors, similar real rates of return are on the order of 2% in high-income countries⁶⁷. A 2% real discount rate was also recommended by 197 experts⁶⁸. This real rate of return is higher when there is additional risk, so it might be adjusted in particular cases of high-risk investments. In addition, the Department for Business, Energy and Industrial Strategy of the UK uses a policy discount rate of 3.8% in their Carbon Price Model. Thus, we also calculated the effect of a 4% discount rate for the global calculation of Present Value. Annuities were calculated using the “pv.annuity” function from the R package “FinCal”⁶⁹. Carbon was multiplied by 11/3 to convert carbon to CO₂ and by the average price of US$ 90 per metric ton of CO₂. This price is the average price of a future contract per t/CO₂ within the US$ 61-122 2030 Carbon Price Corridor estimated by the World Bank High-Level Commission on Carbon Prices adjusted for

617

618
based on each country's estimated annual carbon sequestration (within EEZ). The real discount (or

619
interest) rate is approximated by the difference between the actual discount rate and the expected

620
inflation rate. The financial markets estimate of the real interest rate for long term investments can

621
be measured by the difference between the 10-year US government bond rate and the 10-year

622
inflation protected US government bond rate⁶⁷. This measure is 2.12% with standard deviation of

623
0.43 over the five years from 2019-2024 (Data from the Federal Reserve Bank of St. Louis

624
database “Federal Reserve Economic Data” https://fred.stlouisfed.org/). Because of no-arbitrage

625
between high-income countries’ investors, similar real rates of return are on the order of 2% in

626
high-income countries⁶⁷. A 2% real discount rate was also recommended by 197 experts⁶⁸. This

627
real rate of return is higher when there is additional risk, so it might be adjusted in particular cases

628
of high-risk investments. In addition, the Department for Business, Energy and Industrial Strategy

629
of the UK uses a policy discount rate of 3.8% in their Carbon Price Model. Thus, we also calculated

630
the effect of a 4% discount rate for the global calculation of Present Value. Annuities were

631
calculated using the “pv.annuity” function from the R package “FinCal”⁶⁹. Carbon was multiplied

632
by 11/3 to convert carbon to CO₂ and by the average price of US$ 90 per metric ton of CO₂. This

633
price is the average price of a future contract per t/CO₂ within the US$ 61-122 2030 Carbon Price

634
Corridor estimated by the World Bank High-Level Commission on Carbon Prices adjusted for
2023 terms from the US$ 50-100 range proposed in 2017⁴⁹. The Commission proposed the Price Corridor as functional for developing a potential global carbon market that to would limit global warming to below 2°C⁴⁹. The Intergovernmental Panel on Climate Change Working Group III also indicated in their Sixth Assessment Report a price of roughly US$ 90/tCO₂ by 2030 in 2015 terms or US$ 115 in 2023 terms would be needed to reach a mitigation pathway limiting warming to 2°C⁴⁹. The Network of Central Banks and Supervisors for Greening the Financial System recommends a price of $70/tCO₂ by 2030 and $276 by 2050 to achieve a 2°C scenario. For example, in the European Union Emission Trading System, one of the largest in the world in terms of volume, the average future price per tCO₂ for the last two years (7-2022 to 7-2024) was US$ 84. Finally, we preferred to use market-based prices of carbon offsets instead of the social cost of carbon which is represented by shadow prices, willingness to pay, or other implicit or indirect measurements. Social cost of carbon is more focused on evaluating potential economy damages and the cost to society (health, agriculture, and sea-level rise, etc.) expected from CO₂ emissions. In general, the market price of carbon is lower than the social cost, since the social cost includes both private and public costs. Our choice of using only carbon credit prices is motivated by the potential of market-based valuation to generate potential investments in emission avoidance or reduction activities, in ecosystem restoration that could generate carbon sequestration additionality ¹³,²⁵,³⁰, or investment through other financial instruments⁴⁷.

**Data availability:** Data used to perform the analysis are available from their respective sources indicated in Extended Data Table 1. The output from the NEMO model is available in a Zenodo repository⁷⁰ at https://doi.org/10.5281/zenodo.14773923.

**Code availability:** The code is available in a Zenodo repository⁷¹ at https://doi.org/10.5281/zenodo.14773923.
660 **Methods-only references**

661 65. Dupont, L. *et al*. High trophic level feedbacks on global ocean carbon uptake and marine ecosystem dynamics under climate change. *Glob. Change Biol.* **29**, 1545–1556 (2023).

663 66. Conventional on Biological Diversity. COP15: Final text of Kunming-Montreal Global Biodiversity Framework. (2022).

665 67. Diebold, F. X. & Rudebusch, G. D. *Yield Curve Modeling and Forecasting: The Dynamic Nelson-Siegel Approach*. Princeton University Press, 2013; doi:10.1515/9781400845415.

667 68. Drupp, M., Freeman, M., Groom, B. & Nesje, F. Discounting disentangled: an expert survey on the determinants of the long-term social discount rate. *Cent. Clim. Change Econ. Policy Work. Pap.* **195**, (2015); doi:https://www.lse.ac.uk/granthaminstitute/publication/discounting-disentangled/.

670 69. Felix. FinCal: package for time value of money calculation, time series analysis and computational finance. Zenodo https://doi.org/10.5281/zenodo.49954 (2016).

672 70. Olivier, A., Olivier, M., Laurent, B. & Stelly, L. Dataset and code of NEMO-PISCES-APECOSM. Zenodo https://doi.org/10.5281/zenodo.1460596 (2018).

674 71. Berzaghi, F. Global distribution, quantification, and valuation of the biological carbon pump. Zenodo https://doi.org/10.5281/zenodo.14781145 (2025).
a

<figure><img src="image_2.png" /></figure>

50-year carbon seq. rate (ktC/year)

<figure><img src="image_3.png" /></figure>

b

<figure><img src="image_4.png" /></figure>

Political and administrative boundaries
<figure><img src="image_5.png" /></figure>

Yearly sequestered carbon (MtC)

EEZ

MPA
Country

<figure><img src="image_6.png" /></figure>

<figure><img src="image_7.png" /></figure>

<figure><img src="image_8.png" /></figure>

<figure><img src="image_9.png" /></figure>

Lending

<figure><img src="image_10.png" /></figure>

Other

<figure><img src="image_11.png" /></figure>

HIPC

SIDS

Carbon service value (% of GDP)
<figure><img src="image_12.png" /></figure>

**Palau**
50-year seq. rate: 3 MtC/year
BCP value: 835M US$/year

**Nauru**
50-year seq. rate: 2 MtC/year
BCP value: 664M US$/year

**Tuvalu**
50-year seq. rate: 2 MtC/year
BCP value: 774M US$/year

**Niue**
50-year seq. rate: 1 MtC/year
BCP value: 170M US$/year

**Marshall Islands**
50-year seq. rate: 9 MtC/year
BCP value: 2,919M US$/year

**Kiribati**
50-year seq. rate: 26 MtC/year
BCP value: 8,525M US$/year

**Cook Islands**
50-year seq. rate: 5 MtC/year
BCP value: 1,570M US$/year

BCP value
to GDP ratio

<figure><img src="image_13.png" /></figure>

Income
group

<figure><img src="image_14.png" /></figure>

Low

<figure><img src="image_15.png" /></figure>

Lower middle

<figure><img src="image_16.png" /></figure>

Upper middle

<figure><img src="image_17.png" /></figure>

High
<figure><img src="image_18.png" /></figure>

30% surface coverage – 58% of global BCP seq.

10% surface coverage – 30% of global BCP seq.
<figure><img src="image_19.png" /></figure>
<figure><img src="image_20.png" /></figure>

50-year carbon seq. rate (tC/year)

<figure><img src="image_21.png" /></figure>
<table><caption>**Extended Data Table 1.** Sources, acronyms, and description of data used in the BCP spatial analysis of carbon sequestration and valuation of its service.</caption><thead><tr><td>Data type</td><td>Acronym</td><td>Description</td><td>Data source</td></tr></thead><tbody><tr><td>Marine protected areas</td><td>MPA</td><td>Developed by the United Nations UNEP and our analysis includes Other Effective Area-Based Conservation Measures (OECM)</td><td>UN-UNEP <a href="https://www.protecte dplanet.net/en">https://www.protecte dplanet.net/en</a></td></tr><tr><td>Areas beyond national jurisdiction</td><td>ABNJ</td><td>This area was calculated as the global ocean minus all EEZs.</td><td>Same as EEZ source</td></tr><tr><td>Exclusive economic zones</td><td>EEZ</td><td>Global EEZ boundaries are the layers gathered from gazetted datasets that the Pacific Community (SPC) has received from the project countries. In areas where there are no gazetted datasets provisional layers are being sourced from the Global Marine Regions database (https://www.marineregions.org/).</td><td>Forum Fisheries Agency <a href="https://pacificdata.org/data/dataset/global-exclusive-economic-zone-200-nautical-miles/resource/417d95b1-a25f-483c-a8cd-f8ba3301ccee">https://pacificdata.org/data/dataset/global-exclusive-economic-zone-200-nautical-miles/resource/417d95b1-a25f-483c-a8cd-f8ba3301ccee</a></td></tr><tr><td>Ecologically or Biologically Significant Marine Areas</td><td>EBSA</td><td>These areas were defined by the Convention of Biological Diversity Conference of Parties.</td><td>UN-UNEP <a href="https://www.protecte dplanet.net/en">https://www.protecte dplanet.net/en</a></td></tr><tr><td>Other effective area-based conservation measures</td><td>OECM</td><td>These areas were defined by the Convention of Biological Diversity Conference of Parties.</td><td>UN-UNEP <a href="https://www.protecte dplanet.net/en">https://www.protecte dplanet.net/en</a></td></tr><tr><td>Gross domestic product</td><td>GDP</td><td>Gross domestic product in USD dollars.</td><td><a href="https://data.worldbank.org/indicator/NY.GDP.MKTP.CD">https://data.worldbank.org/indicator/NY.GDP.MKTP.CD</a></td></tr></tbody></table>