Blue climate solutions: the role of marine natural capital in mitigating climate change

The natural resources that regulate all life on Earth, also known as natural capital, are central in the fight against climate change. Ocean-based natural assets, such as mangroves, seagrass—even whales—as well as land-based natural assets, such as soil, trees and elephants, function as carbon sinks and contribute significantly to biodiversity. 

However, nature’s contributions to stabilising our climate—and to regulating and supporting all life systems—have not been properly valued, leading to centuries of human-driven ecological damage and the climate crises we now find ourselves in. That is why the Valuing Natural Capital Conference focused on finding innovative governance and financial solutions to protect nature and its ecological services. The event was hosted by Geneva Macro Labs in collaboration with the International Labour Organisation, United Nations Institute for Training and Research (UNITAR), United Nations Capital Development Fund (UNCDF), Harvard University, FootPrint Coalition and ServiceNow.

As part of a panel on the “Economic and Ecological Significance of Natural Capital and Biodiversity”, my presentation highlighted the critical role of marine natural capital in mitigating climate change. The ocean absorbs 25-30% of global CO2 emissions, or 33bn tonnes of CO2. Coastal and marine ecosystems therefore have huge emissions-reduction potential. For example, restoring coastal wetlands could contribute 14% of the mitigation potential to keep global heating below 2°C. Moreover, the ocean’s natural carbon-storage capacities can be increased through technical solutions, such as storing carbon in liquid form, increasing alkalinity, and electrochemical removal. Meanwhile, there is significant climate-change adaptation potential via enhanced resiliency and biodiversity support.

Seagrass meadows are often overshadowed in the public discourse by other ocean ecosystems such as mangrove forests and coral reefs (see below). But they are vital for ocean health, biodiversity and carbon storage. Despite comprising only 0.2% of the sea floor, seagrass meadows account for around 10% of the ocean’s capacity to store carbon. Seagrass’s impressive capabilities include being able to capture carbon from the atmosphere up to 35 times faster than tropical rainforests. This contribution has been valued at $2.3trn by economists, including Ralph Chami, who provided a keynote address at the conference. Additional benefits of seagrass meadows include that they are an important nursery and food source for marine life, provide a home for many fish, protect coastlines, produce oxygen, and can clean the ocean by absorbing polluting nutrients produced by humans on land.

Despite these opportunities, annual rates of decline of seagrass meadows have averaged around 7% since 1990 (up from 0.9% before 1940). They are also at risk of marine heatwaves. Unfortunately, they have been largely neglected by policymakers: although 159 countries have seagrass, it is not included widely in the Nationally Determined Contributions (NDCs)—the plans that countries must submit to contribute to global climate targets.

Nevertheless, there is some recognition of the often underestimated value of seagrass, seen for example in restoration projects taking place in Sweden, the UK and the US.

Mangrove forests are effective carbon sinks too. They store around 20bn tonnes of carbon, 50 times more than tropical forests. In addition, they are protected from wildfires and provide nurseries for global fisheries. Another major co-benefit is that mangrove forests offer vital storm and flood defence services, preventing more than US$65bn in property damage each year and protecting more than 15 million people. This has major implications for insurance. Reinsurance companies such as Swiss Re and Munich Re are developing financing tools to evaluate habitat-restoration projects that factor in the risk-reduction value of mangroves.

Similar to seagrass, mangroves have been under pressure. Over the past 50 years, half of the world’s mangroves have been lost. Policymakers are only slowly waking up to the need to protect and restore them. A notable example is the Seychelles, which announced at the COP26 climate conference that it would protect 100% of its mangroves and seagrass by 2030. There are also restoration projects in Colombia and Vietnam. These can generate significant co-benefits, such as development opportunities in countries like Sri Lanka, where microloans are provided to communities in return for mangrove

Coral reefs provide a vital habitat for about 30% of fish species despite encompassing less than 0.5% of the ocean floor. They provide significant ecosystem services: they absorb 97% of coastal wave energy, provide food and well-being to more than 1bn people, create jobs from fishing, recreation and tourism, and hold huge potential for natural medicine.

Tragically, half of the world’s coral reefs have already been lost, and 90% could be lost by mid-century if current trends persist.

But there are promising conservation initiatives involving local communities, for example in Chile, Hawaii, Madagascar and Nicaragua. Projects include the Coral Reef Rescue Initiative and an innovative impact investment to support the Turneffe Atoll marine protected area (MPA) in Belize.

The carbon sequestration capacity of seaweed is enormous: 173m tonnes (that’s about the mass of 28 great pyramids of Giza) of carbon per year, worth US$1.2-3.5bn in nutrient bio-mitigation services. 

Seaweed has varied applications in areas such as food, feed, fertilisers, pharmaceuticals, cosmetics and bio-fuel. At the World Ocean Initiative we have highlighted the example of Indonesia, where the seaweed industry provides around 1m jobs, employing many former artisanal fishers. Globally, the seaweed market could see annual growth exceeding 12% to 2026 alone, from US$58.9bn to US$85.5bn.

An exciting opportunity also exists for kelp reforestation through marine permaculture in places like Indonesia, the Philippines and Tasmania.

However, major challenges persist, notably a lack of genetic diversity in many geographies, the risk of marine heatwaves, and access to finance.

At the World Ocean Initiative we are particularly excited about the emergence of so-called blue carbon markets. “Blue carbon” refers to the ocean ecosystems that help to sequester carbon, several of which I have discussed in this article. Projects that restore these ecosystems can generate “credits” based on the tonnes of carbon captured and stored, and these can then be sold to businesses seeking to offset some of the emissions they generate. Global demand for carbon credits is set to increase 15-fold from 2020 levels, to be worth around US$50bn by 2030.

We have already discussed some of the significant co-benefits of restoring these ecosystems and making their benefits tradeable as credits, including generating employment, skills and community well-being.

There are still too few suitable projects to meet the rising demand for high-quality blue carbon credits. However, this gap will narrow as blue carbon is increasingly integrated into climate-mitigation strategies via new trading platforms, the NDCs and the Natural Capital Protocol for the Ocean.

An exciting case study is the Mikoko Pamoja project in Kenya, one of the recent winners of the UpLink Blue Carbon Challenge. Certified by Plan Vivo, the proceeds are 65% reinvested in the community. For projects like this to work there need to be strong systems for designing, registering and validating blue-carbon projects.

Marine natural capital holds huge climate-change mitigation potential—not only mangrove forests but also seagrass meadows, coral reefs, seaweed and others not discussed here, such as tidal marshes.

These valuable ecosystems are under threat from climate change, development, and pollution. Their restoration is not only important for tackling climate change, but could also provide significant co-benefits, including climate-change adaptation, biodiversity and community resilience. 

Policymakers are starting to embrace the potential of blue carbon. That said, there is a need for blue carbon to be embedded within a holistic ecosystem management approach, including social and community dimensions.