It is said that about one-third of the world’s mangrove forests were lost between 1952 and 2002, and mangrove degradation has come to be recognized as a global issue. Mangroves have major impacts on the global environment and on human economies and societies. They have been discussed in international arenas for decades, and conservation activities have continued. In this context, recent reports suggest that in some regions mangroves are expanding and the rate of decline of total area is slowing. However, there are still challenges in terms of what lies behind these numbers and in the conservation activities themselves. This article revisits the value of mangroves, looks at actual tree‑planting sites in conservation practice, and summarizes the challenges for mangrove conservation.

Mangrove seedlings, Cambodia (Photo: Yuka Chijimatsu)

What are mangroves?

 “Mangroves” is a collective term for woody plants that grow in brackish zones where seawater intrudes at high tide, in the ecotone between sea and land in tropical and subtropical regions. It is thought that there are 50–80 species of mangrove plants worldwide, all of which have adapted to environments with low oxygen and high salinity. Their arch‑shaped roots pierce deep into oxygen‑poor mud, stabilizing the trees in the soft sediments while the parts exposed above the ground take in oxygen. In some species, roots extend upward vertically from underground, enabling respiration in low‑oxygen environments. As for their ability to grow in highly saline environments, they possess salt‑tolerance mechanisms. For example, when roots absorb water they can filter out up to 90% of the salt; they can excrete excess salt from roots and leaves after absorption; and they can sequester salt in old leaves. This allows mangroves to form forests in harsh salt marshes where other trees cannot survive.

Mangroves are distributed roughly between 25–30 degrees north and south latitude along tropical and subtropical coasts in more than 120 countries, occupying about 15% of the world’s coastline. According to Global Mangrove Watch (GMW), a satellite‑based mangrove monitoring database, global mangrove area as of 2025 is about 14.73 million hectares. Regionally, Asia has the largest area in 2025, accounting for about 40% of the total, followed by the Americas, Africa, and Oceania. At the national level, Indonesia alone holds about 20% of the world’s mangroves. The top five countries—Indonesia, Brazil, Australia, Nigeria, and Mexico—account for roughly 47% of global mangrove area, and the top ten countries—adding Malaysia, Myanmar, Papua New Guinea, India, and Bangladesh—hold about 64%. This highly skewed distribution is a distinctive feature.

Giant mangroves, Costa Rica (Photo: edward stojakovic / Flickr [CC BY 2.0]

Ecosystem services of mangroves as resources

Mangrove forests serve not only as direct economic resources for people in the form of timber, tourism assets, and rich fishing grounds, but also provide less visible functions—such as climate regulation and disaster risk reduction, discussed in the next section. In this way, they deliver highly diverse “ecosystem services” to coastal communities.

In terms of timber use, mangrove wood is highly resistant to salt and termites, and has long been used as building material, traditional roofing, fuel, and as a source of tannins from the bark, as well as an ingredient for tea products. As tourism assets, mangrove forests are developing as sites for ecotourism such as boat tours, birdwatching, kayaking, and snorkeling, with tourism development particularly advanced in Southeast Asian countries like Indonesia, Malaysia, the Philippines, Thailand, and Vietnam.

Mangroves also greatly benefit fisheries. A 2020 study estimated that there are about 4.1 million small‑scale fishers worldwide whose livelihoods are linked to mangroves, and about 30% of commercial fish species globally are thought to depend on mangrove ecosystems.

Ecosystem services of mangroves as functions

The rich fishing grounds noted above are underpinned by the biodiversity fostered by mangrove forests. In addition, mangroves play less visible but far‑reaching roles in climate regulation and disaster risk reduction. Estimates suggest that mangroves worldwide nurture more than 70 billion juvenile fish and crustacean larvae annually. Underwater, mangrove roots are covered with fouling organisms such as ascidians, sponges, algae, and bivalves, and the spaces between roots, with low predation pressure and abundant food, offer ideal habitat that combines shelter and feeding grounds for shrimp, crabs, and fish. The canopy also serves as habitat for birds, insects, mammals, and reptiles, while detritus (fine particles of organic matter) from fallen leaves, together with plankton and algae, supports the distinctive mangrove food web. Root systems trap sediments and pollutants, helping maintain water quality in offshore coral reefs and seagrass beds.

Mangrove roots seen from underwater (Photo: Phil’s 1stPix / Flickr [CC BY-NC-SA 2.0]

It is not only their contribution to fisheries that deserves attention. Mangroves account for only about 0.4% of the world’s total forest area, yet their “carbon storage capacity” is extremely high: they can store up to 10 times as much carbon per unit area in soils as terrestrial tropical forests. The Global Mangrove Alliance (GMA) estimates that mangroves existing as of 2022 store more than 21 billion tonnes of CO₂‑equivalent carbon in total. On land, when plants drop their leaves, the carbon‑laden leaves decompose relatively quickly and most of their carbon returns to the atmosphere as CO₂. In mangroves, by contrast, fallen leaves rich in carbon sink into the mud and decompose slowly over centuries, which underpins their high carbon storage capacity (※1).

Their coastal‑protection role in disaster risk reduction has attracted particular attention in recent years. Mangroves function as natural breakwaters that attenuate the energy of tsunamis and storm surges. Dense roots, branches, and leaves slow incoming water flows through friction, while trunks act as physical barriers that absorb impacts and trap floating debris. It is estimated that for every 100 meters of mangrove forest width, wave height is reduced by 13–66%.

Globally, mangroves are estimated to avert more than 6.5 billion US dollars of flood damage each year, and if they were lost, an additional 15 million people per year would be exposed to flooding worldwide. According to a 2024 World Bank report, the present value in 2020 of mangroves’ flood‑reduction benefits is US$855 billion in total (assuming a 4% discount rate and a 100‑year asset life). The value of mangrove forests derived from this disaster‑risk‑reduction function has been increasing in recent years amid growing populations and asset values in mangrove‑protected regions.

Mangroves also help curb coastal erosion, a cause of shoreline retreat; maintain freshwater supplies from rivers; and prevent salt damage to farmland. Thus, the loss of mangrove forests affects multiple dimensions—fisheries, disaster risk reduction, and livelihoods.

Loss of mangrove forests

As noted at the outset, it is said that about one‑third of mangrove forest area was lost between 1952 and 2002. Mangroves have continued to decline since then. According to GMW, when compared with 1996—the year with the largest mangrove area since 1985—about 3.21 million hectares of “existing” mangrove habitat had shrunk by 2025. Southeast Asia accounts for 47% of global net mangrove loss between 1996 and 2020, and Indonesia and Myanmar alone lost about 350,000 hectares of net area from 1985 to 2025. According to the global Red List of mangrove ecosystems (※2) published by the International Union for Conservation of Nature (IUCN) in 2024, 50% of mangrove ecosystem types fall into “threatened” categories, and the risk of further loss cannot be ruled out.

One cause of loss is sea‑level rise driven by climate change. When roots are submerged due to rising sea levels, mangroves cannot respire sufficiently and growth is hindered, with severe impacts especially on shorter seedlings. IUCN predicts that 25% of global mangrove area will be submerged over the 50 years following 2024 due to sea‑level rise. Mangroves are also sensitive to intensifying cyclones, typhoons, and hurricanes, drought, and El Niño events. For example, in 2017 a massive die‑off occurred in mangroves stretching 1,000 km across northern Australia when El Niño caused temporary sea‑level drops and a marked decrease in rainfall. It is estimated that 26% of the total reduction in mangrove area from 2000 to 2020 is due to such natural retreat.

Loss driven by human activities is also pronounced. A study using satellite imagery from 2000 to 2016 estimates that 62% of global mangrove loss during this period https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7540710/ was caused by land‑use change (primarily aquaculture and agriculture), with up to 80% of that concentrated in six Southeast Asian countries. Coastal development associated with urbanization directly removes mangroves, but it also prevents mangroves from migrating landward to higher elevations as sea level rises; alters water and sediment supply from rivers; and leads to pollution. Over‑harvesting mangroves for fuelwood and construction material exerts strong pressure in fringe areas near settlements, causing shifts in species composition and fragmentation of forests. In some cases, extensive freshwater use for agriculture has reduced freshwater and sediment supply to mangrove areas, hindering their growth.

Ongoing mangrove logging in Bangladesh (Photo: Ayman Nakib Badhan / Wikimedia Commons [CC BY-SA 4.0])

Recovery of mangrove forests?

While existing mangrove forests continue to be lost, net loss of mangrove area from 1996 to 2025 has been limited to about 1.2%. “Net area” refers to the result of offsetting decreases in existing habitat by gains in new areas. This net loss has slowed in recent years. In other words, mangrove forests are expanding in some regions. After 2015, compared with 2014—the year when area had shrunk the most—mangroves have gradually expanded, especially around large rivers, estuaries, and deltas, resulting in a net gain of about 210,000 hectares by 2025 relative to 2014. The two countries that led this net gain are Australia and India, which together have gained about 260,000 hectares of mangroves since 1985.

This is partly because there are regions where mangroves can occupy higher coastal zones even under rising sea levels, or where sediment accumulation keeps pace with sea‑level rise so that mangroves are less affected by it, and partly because the distribution of mangroves—which grow in tropical and subtropical regions—is expanding into higher‑latitude temperate zones. This expansion is thought to be caused by global warming, which is raising temperatures on both land and sea. There are also cases where mangroves have regenerated naturally in abandoned aquaculture ponds. It is estimated that 82% of expansion from 2000 to 2020 is due to such natural processes, with the remainder due to human‑driven restoration activities such as planting.

Although expansion into new areas has slowed the pace of net area decline, this does not mean that the gross area of loss before offsetting is decreasing. As long as shrinkage of existing habitat continues, the ecosystems and livelihoods that depended on them will keep being lost. For example, in coastal Kampot Province, Cambodia, extensive mangrove forests were destroyed by illegal logging and large‑scale port development led by the government. As a result, fishery resources plummeted, residents who had lost their primary industry faced harsh economic hardship, and many were forced to migrate to neighboring countries for work, with children no longer able to attend school.

It should also be noted that young mangrove forests have a lower capacity to deliver ecological benefits than mature ecosystems. In terms of carbon storage, a study of 1996–2016 found that while logging released 232.6 million tonnes of carbon into the atmosphere, mangrove expansion absorbed only 74.2 million tonnes, meaning emissions were about three times greater than sequestration. Considering the expansion in mangrove area since 2014, it is possible that this net decline in carbon stocks has been moderated in recent years. However, newly expanding forests still have lower carbon density than mature forests, so carbon recovery is unlikely to keep pace with the rate of area recovery; this remains only the author’s conjecture.

Mangrove seedlings, Cuba (Photo: UNDP Climate / Flickr [CC BY-NC 4.0]）

International initiatives on mangrove forests

Broadly speaking, there are three types of international initiatives to protect mangroves: (1) treaties that register and protect wetlands as “sites to be conserved”; (2) mechanisms that provide financial rewards proportional to the amount of destruction avoided; and (3) mechanisms that directly fund conservation activities.

The first—registering and protecting wetlands as sites to be conserved—is exemplified by the Ramsar Convention. The 1971 “Convention on Wetlands of International Importance Especially as Waterfowl Habitat,” adopted in Ramsar, Iran, is an international framework for registering and conserving important wetlands, and coastal wetlands such as mangroves fall under its scope. At the 2018 Conference of the Parties, a resolution was adopted that explicitly recognizes mangroves’ carbon storage value within this framework. There are also arrangements from a biodiversity perspective. The Kunming‑Montreal Global Biodiversity Framework, adopted in 2022, sets the “30×30 target” of designating 30% of land and sea as protected areas by 2030, and coastal zones including mangroves are part of this target.   

The second category—mechanisms that provide financial returns for conservation—includes “REDD+” and “blue carbon credits.” REDD+ (※3), formally adopted under the UN Framework Convention on Climate Change (UNFCCC) in 2010, originally provided funding to countries and organizations that reduced deforestation in tropical forests. In recent years, its scope has expanded to include coastal wetlands such as mangroves. In parallel, “carbon credits” purchased voluntarily by companies and others to offset their greenhouse gas emissions now include “blue carbon credits” (※4) generated by mangrove conservation and restoration, which are traded on voluntary markets. However, the overall market is still small: blue carbon makes up only about 1% of the voluntary carbon market.

As noted in Section 3, mangroves’ flood‑protection effect alone is estimated to be worth US$855 billion per year. Yet the total volume of blue carbon credits issued over the 11 years from 2014 to 2025 is only about 7 million tonnes, traded at around US$27 per tonne, amounting to less than US$200 million (calculated from the source data)—a scale far below their true value. There are also concerns that labor‑intensive processes to verify carbon stocks are constraining supply, and criticisms that many credits are being transferred from projects in low‑ and middle‑income countries to buyers in Europe and North America at prices below their intrinsic value, resulting in unfair benefit‑sharing.

International REDD‑related conference, Norway (2016) (Photo: Norad / Flickr [CC BY-NC-ND 2.0])

The third category—mechanisms that directly fund conservation activities—includes project‑based funding from bilateral aid agencies and the “Mangrove Breakthrough,” a UN‑backed initiative. Launched on the occasion of the 2022 UN Climate Change Conference (COP27), the latter aims to conserve and restore 15 million hectares of mangroves by 2030 and to mobilize a total of US$4 billion from private, public, and philanthropic capital to achieve this goal (※5). As of November 2025, 44 national governments—together accounting for roughly 40% of global mangrove area—support the initiative, and several countries including Jamaica, Papua New Guinea, Brazil, and Pakistan have begun incorporating quantitative mangrove‑related targets into their nationally determined contributions (NDCs) under the Paris Agreement (※6).

Challenges in financial flows related to mangrove forests

Funds provided by governments move according to diplomatic commitments and policy decisions, and are not necessarily determined by “profitability.” Funds from private investors, however, are strongly influenced by expected returns. Mangrove restoration typically involves up‑front costs for planting and engineering works, while benefits and revenue from carbon credits may take more than 20 years to accrue, which makes such projects difficult to reconcile with conventional investment criteria that demand short‑term payback. Moreover, because planted forests face a “permanence risk”—the possibility that they may die off or disappear in the future—investors tend to be cautious, which helps explain the low price and small size of the blue‑carbon credit market.

While some aspects are underestimated by investors, others are conversely overestimated. Environmental, social, and governance (ESG) ratings—indicators of companies’ non‑financial soundness—have been criticized as having problems similar to those seen before the 2008 financial crisis. At that time, rating agencies gave AAA ratings to fundamentally unsound securities without sufficiently vetting the underlying loan data. A similar pattern is visible today in ESG ratings: even companies that profit while degrading marine ecosystems can obtain relatively high scores simply by stating that they “recognize the existence of risks,” without any concrete response plans. Existing accounting systems also do not treat oceans and mangroves as “assets whose value can depreciate.” There are emerging efforts to fill this gap in both evaluation and accounting. For example, the Taskforce on Nature‑related Financial Disclosures (TNFD) is developing a new framework that requires companies to disclose their dependencies and impacts on nature, seen as an important step. However, it still largely relies on voluntary self‑reporting by companies. 

Viewed in this light, there are two distinct distortions in financial flows related to mangroves. Forward‑looking efforts such as restoration projects are harshly judged by investors because of their long time horizons and high risks, making it difficult for them to attract funding. Meanwhile, companies that profit while damaging marine ecosystems remain untouched, because shortcomings in rating and accounting systems mean capital is not withdrawn from them. Fixing these distorted evaluation criteria is key to achieving the goals set by international frameworks.

Conference on green investment, Rwanda (Photo: Ministry of Environment – Rwanda / Flickr [CC BY-ND 2.0]）

On‑the‑ground conservation efforts

While international frameworks and systems are evolving, the situations faced by those actually doing conservation on the ground are seldom highlighted in public forums. As of 2020, 8,183 km² of lost mangroves were considered restorable, and efforts to halt decline are underway in various locations. However, mangrove planting faces numerous challenges. For example, it is suggested that about 70% of restoration projects in parts of Southeast Asia and Latin America struggle to establish healthy forests. Specific issues include low seedling survival rates, failures in drainage management, lack of funding and technical guidance and long‑term support structures, weak incentives to continue conservation after planting, declining interest, insufficient ongoing monitoring, and continuous pressure from surrounding agricultural development and infrastructure projects. It is also pointed out that shrimp aquaculture is a vital source of foreign currency for many low‑income countries, making it difficult to reconcile conservation with local economies (※7).

To illustrate this more concretely, let me describe the physical burdens involved from my experience participating in a mangrove planting project carried out by an NGO (※8) in Cambodia. Mangrove planting is labor‑intensive and relies heavily on manual work at every stage: collecting seeds, raising seedlings, and planting them in tidal flats. In areas where mangroves are already established to some degree, natural expansion through seed drop can be expected. Elsewhere, however, seeds must be collected one by one from trees by hand, grown into seedlings in mud pots, and then planted individually in mudflats where, at high tide, the water can reach chest level. Your feet sink into deep mud, and each seedling must be planted with care so it is not washed away by waves or currents.

In addition to such physical burdens, on the ground there are also structural challenges such as “friction with other industries and limits of regulation.” Illegal logging for charcoal production and other uses still exists, while the areas that communities can manage are limited by jurisdiction, leaving them without authority to police logging outside their zones. Residents know that continued logging will harm their own fishery resources, yet they cannot intervene, revealing the limits of community‑based conservation. Even so, in Kampot Province, Cambodia, the cumulative effect of these steady efforts has helped ecosystems and fish catches recover, leading to the return of residents and the emergence of new income sources from ecotourism.

 Another point drawing attention in conservation is the significant role played by women. A 2017 IUCN report highlights a structural gap: in many coastal communities, women are the main users of resources such as shellfish collection and mangrove wood—activities that tend to be unpaid and informal—yet they are often excluded from decision‑making spaces concerning conservation planning and resource management.

In response, efforts are underway in various locations to involve women—who are directly engaged in resource use—in decision‑making, thereby improving the effectiveness of conservation. In Senegal, the “Natur’ELLES” project worked with women’s groups to design combinations of tree species to plant, tripling women’s representation on protected‑area management committees and achieving the restoration of more than 190 hectares of mangroves. In Kenya, the “Mikoko Pamoja” project channels revenue from women‑managed ecotourism into local schools and healthcare, which in turn serves as a community incentive to sustain conservation activities. 

Mangrove planting, Indonesia (Photo: Irwandi wancaleu / Wikimedia Commons [CC BY-SA 4.0]）

Conclusion

Mangroves deliver immense value in terms of fisheries, disaster risk reduction, and climate change mitigation, yet rich existing forests are still being lost to human‑driven coastal development and increasingly severe climate impacts. In recent years, “natural expansion” linked to poleward shifts under global warming, together with planting efforts, has slowed net loss, and area is increasing in some regions, offering some hope of recovery. Nonetheless, we cannot afford to be complacent just because “net mangrove area is expanding.” In shrinking regions, existing ecosystem services and the livelihoods built upon them are being “lost,” and in expanding regions, the functionality of young forests remains limited. The loss of primary forests that have formed over centuries—along with their biodiversity and huge carbon stocks—cannot be quickly offset by natural regeneration alone.

What matters is halting human‑driven destruction and protecting and nurturing existing forests and ecosystems. To do so, we must properly value mangroves, correct the structural distortions in markets and finance that are lenient toward ecosystem destruction while overestimating conservation risks, realign international mechanisms and financial flows, and ensure that on‑the‑ground, long‑term conservation and planting efforts receive fair compensation, authority, and support that exceed the pressures undermining mangrove conservation.

※1 Anaerobic decomposition in wetlands generally produces methane, but in mangroves, seawater supplies abundant sulfate ions. Sulfate‑reducing bacteria therefore outcompete methanogens, so methane emissions are relatively suppressed compared with freshwater wetlands. This is another reason mangroves can be described as having excellent carbon storage potential.

※2 The IUCN (International Union for Conservation of Nature) “Red List of Ecosystems (RLE)” is a globally standardized framework for assessing risks to ecosystems. It makes it possible to identify common symptoms (in both spatial and functional terms) and to determine the degree of risk faced by any given ecosystem.

※3 “REDD” stands for Reducing Emissions from Deforestation and forest Degradation, while the “+” signifies additional activities such as sustainable forest management, conservation of forest carbon stocks, and enhancement of forest carbon stocks.

※4 The concept of “blue carbon”—carbon stored in marine and coastal ecosystems—was introduced in a 2009 report led by the UN Environment Programme (UNEP). Subsequent research syntheses have established mangroves, along with salt marshes and seagrass beds, as “practicable blue carbon ecosystems” that (1) meet the definitions of wetlands and forests, (2) can be incorporated into existing policy and financial mechanisms such as REDD+ and carbon markets, and (3) contribute to both climate change mitigation and adaptation. Credits issued by the verifier Verra dominate the market, and real‑world projects such as Pakistan’s “Delta Blue Carbon” and Kenya’s “Mikoko Pamoja” have raised funds through this mechanism.

※5 The Mangrove Breakthrough rests on four pillars: (1) halt further loss; (2) restore half of the area lost since 1996; (3) double the area under protection; and (4) secure sustainable finance for existing mangroves.

※6 The Paris Agreement is the first legally binding international treaty bringing together all countries to undertake climate change mitigation and adaptation. It was adopted on 12 December 2015 at the 21st Conference of the Parties (COP21) to the UNFCCC in Paris, France, by 195 Parties, and entered into force on 4 November 2016. (The United States withdrew in January 2026, and as of July that year there are 194 Parties to the Agreement.) Its paramount objectives are to “hold the increase in the global average temperature to well below 2°C above pre‑industrial levels” and to “pursue efforts to limit the temperature increase to 1.5°C above pre‑industrial levels.” Since the Intergovernmental Panel on Climate Change (IPCC) warned that exceeding the 1.5°C threshold would bring a much higher risk of more frequent and severe droughts, heatwaves, and heavy rainfall events, the world has increasingly stressed the need to limit warming to 1.5°C by the end of this century. To achieve this, global greenhouse gas emissions must peak no later than 2025 and then decline, and be reduced by 43% by 2030.

※7 In recent years, “silvofisheries” that combine aquaculture with mangrove conservation or restoration—without clearing mangroves—have gained attention, and there are examples in which mud crab and other aquaculture are pursued while maintaining mangrove forest area. However, mainstream shrimp farms operate in closed systems; while fallen mangrove leaves serve as fertilizer in open environments, in closed environments they are said to rot, and no broad solution has yet been found for aquaculture as a whole.

※8  In 2007, local fishers formed the “Trapaing Sangke Fishing Community (TFC)” and, in cooperation with the Ministry of Environment, began exploring conservation pathways. From 2012, they started working with external organizations such as the international volunteer NGO “Cambodia Youth Action (CYA)” and the Japanese organization “NICE.” To date, they have successfully restored about 28 hectares of mangrove forest.

Writers: Kanako Kinoshita / Yuka Chijimatsu