Wetlands, the forgotten carbon sink that can help mitigate impact of climate change

The climate crisis is intensifying and one of the measures that is attracting attention is to mitigate its impact is nature-based solutions (NbS), which involve increasing the ability of nature, such as forests, to absorb carbon dioxide.

According to the International Union for Conservation of Nature (IUCN), NbS are actions to protect, sustainably manage, and restore natural and modified ecosystems that address societal challenges effectively and adaptively, simultaneously benefitting people and nature.

The importance of NbS as a response to the climate crisis was also addressed in the Kunming-Montreal Global Biodiversity Framework, a new international biodiversity conservation framework for the period up to 2030 that was finalized at the UN Biodiversity Conference COP15 in December 2022.

Its target 11 states: "Restore, maintain and enhance nature's contributions to people, including ecosystem functions and services, such as the restore, maintain and enhance nature's contributions to people, including ecosystem functions and services, such as the regulation of air, water and climate, soil health, pollination and reduction of disease risk, as well as protection from natural hazards and disasters, through nature-based solutions and/or ecosystem-based approaches.”

In the context of climate change, the importance of forest conservation and large-scale afforestation is often discussed as a means of increasing nature's ability to absorb greenhouse gases. However, there is one ecosystem on earth receiving very little attention that is extremely important when considering NbS and that’s wetlands.

According to a 2022 paper published in Science, wetlands such as peatlands, mangrove forests, salt marshes and seagrass beds store 20% of the organic ecosystem carbon on the planet, even though they cover only 1% of the Earth's surface.

This is due to their high carbon sequestration rate and effective sequestration per unit area, far exceeding those of marine and forest ecosystems.

On the other hand, according to the 2021 Global Wetland Outlook by the Ramsar Convention Secretariat, which aims to conserve internationally important wetlands and promote their conservation and wise use, the area of wetlands in the world for which data are available has decreased by 35% since 1970 alone.

Natural wetlands are declining at a rate of 0.78% per year, well above the rate of natural deforestation. Outlook notes that the quality of remaining wetlands is also suffering due to drainage, pollution, invasive species, unsustainable use, disrupted flow regimes and climate change.

Quality of remaining wetlands is also suffering due to drainage, pollution, invasive species, unsustainable use, disrupted flow regimes and climate change, the report warns.

Protecting remaining important wetlands and promoting wetland restoration is not only an important mitigation measure for climate change, but also contributes to preventing flood damage, which tends to increase in scale, by utilizing and expanding natural water absorption and retention capacity.

Wetland conservation and restoration can be an important adaptation measure as well as a climate change mitigation measure. This is exactly the "wise use" of wetlands that the Ramsar Convention calls for.

Proactively utilizing international frameworks such as the Ramsar Convention and expanding NbS with wetlands as a major player has the potential to be an extremely effective countermeasure to the climate crisis.

Wetlands in Japan are also in decline, with more than 60% lost since the 1850s. On the other hand, more than 50 wetlands have been registered under the Ramsar Convention.

In Japan, a law to promote nature restoration was enacted in 2002, and unique nature restoration projects are under way in various regions. Wetland conservation and restoration is one of the important themes of this law.

Kushiro Marsh in Hokkaido is the largest wetland in Japan, but it is also the most rapidly declining wetland.

Here, a wetland restoration project is under way through the creation of a consultative organization involving many stakeholders, including environmental protection groups, development authorities, the Ministry of the Environment, local governments, and local companies. Efforts are being made to make rivers that were straightened by past construction projects meander like natural streams that existed in the past.

In the Kabukurinuma pond area of northern Miyagi Prefecture, a project seeks to restore disused rice paddies into wetlands. In Toyooka City, Hyogo Prefecture, where oriental storks, once extinct in Japan, were successfully reintroduced and released into the wild, a project is under way to restore a man-made river to its former natural flow, and the surrounding area has become a lush wetland where storks are now frequently seen.

Since its adoption in 1971, the Ramsar Convention has made various contributions to the conservation and wise use of wetlands around the world. It is expected to remain an important tool for international cooperation in the future restoration of wetlands.

The Convention’s Outlook states that wetlands are in a difficult situation, yet, wetland ecosystem services, ranging from food security to climate change mitigation, remain enormous, far outweighing those of terrestrial ecosystems.

Since the adoption of the new framework of the Convention on Biological Diversity, understanding of the importance of NbS has deepened. The importance of "nature positive" has also been pointed out, and some countries, such as the G7 nations, have set this as a national goal.

Coincidentally, the United Nations has designated the decade from 2021 to 2030 as the UN Decade for Ecosystem Restoration, calling on governments to actively restore and regenerate the various ecosystems on Earth. Now is the time to revisit the role of wetlands as a countermeasure against the climate crisis, which has often been forgotten, and to promote NbS through wetlands in international cooperation.