Mangroves: Coastal Ecosystems that Protect People, Climate, and Sharks

Did you know that mangroves are among the most productive ecosystems on the planet? They serve as natural shields for coastlines against storms, store vast amounts of carbon, and act as nurseries of the ocean where young sharks, rays, and fish grow. Yet, despite their importance, they are also among the most threatened habitats on Earth, and protecting them is essential for the future of both our oceans and ourselves.

Mangroves are unique coastal ecosystems made up of trees and shrubs that thrive where freshwater from rivers meets the salty water of the sea. Unlike most plants, they can withstand extreme conditions: high salinity, constant tidal changes, unstable muddy soils, and low oxygen levels. To survive, they have developed remarkable adaptations: pneumatophores (aerial roots sticking out above the surface that allow them to breathe), prop roots that anchor the trees in the mud, and even the ability to expel salt through their leaves.

These adaptations enable mangroves to create a complex root network that provides shelter and habitat for countless species - from tiny crustaceans to fish, birds, and mammals. In fact, mangroves are considered one of the most productive ecosystems on the planet.

Where Mangroves Are Found

Mangroves cover approximately 152,000 km² of coastlines across more than 120 countries and territories worldwide (Spalding et al., 2010; Bunting et al., 2022). The largest expanses are found in Indonesia, Brazil, Nigeria, Australia, and Mexico, with particularly high concentrations in tropical and subtropical regions - between 30° north and 30° south latitude.

• Southeast Asia - home to more than one-third of the world’s mangroves (especially Indonesia, Malaysia, and Myanmar).

• Africa - extensive areas in Nigeria, Mozambique, and Madagascar.

• Latin America and the Caribbean - Brazil, Mexico, Colombia, and Cuba.

• Pacific - Australia, Papua New Guinea, and the islands of Oceania.

Although mangroves account for just 0.1% of Earth’s land surface, their importance for climate regulation, biodiversity, and human communities is disproportionately immense.

Loss of Mangroves

Despite their importance, it is estimated that over 35% of the world’s mangroves have disappeared since the mid-20th century. More recent analyses suggest that while the rate of loss has slowed in the past few decades, it is still ongoing. The main drivers are urbanization, aquaculture (especially shrimp farming), logging, agriculture, and tourism development. The pace of destruction is alarming: according to FAO data, mangroves are vanishing faster than tropical rainforests.

Why Mangroves Matter

Mangroves are not only unique ecosystems but also invaluable natural allies for both people and the planet. Although they cover only a fraction of the world’s coastlines, their benefits are vast. They act as natural barriers against storms, serve as carbon reservoirs critical for climate stability, function as water filters, and form the foundation of food security for millions of people.

Coastal Protection Against Storms and Erosion

Mangroves are nature’s “first line of defense” against storms. Their dense root networks reduce wave energy and buffer the impact of tides and tsunamis. Research has shown that mangroves can reduce wave height by up to 66% over a distance of just 100 meters. During the devastating 2004 Indian Ocean tsunami, villages shielded by mangrove belts experienced significantly less damage and fewer casualties.

Beyond storm surges, mangrove root systems also protect coastlines from erosion by stabilizing sediments and preventing them from being washed away. In many regions, mangroves are now considered a cheaper and more effective alternative to concrete seawalls and breakwaters. That’s the hidden power they hold!

Major CO₂ Reservoirs (Blue Carbon)

And that’s not all. Mangroves are part of the so-called blue carbon ecosystems. Along with seagrass meadows and kelp forests, they store vast amounts of carbon. On average, mangroves hold about 1,000 tons of carbon per hectare - more than three times the amount stored in tropical rainforests.

Up to 80% of this carbon is locked in soils and sediments, which act as long-term reservoirs. When mangroves are destroyed, this carbon is rapidly released back into the atmosphere, becoming a major source of emissions. Estimates suggest that the loss of all mangroves could release more than 10 billion tons of CO₂.

Water Filtration and Pollution Control

Mangroves act as natural filters. Their root systems trap sediments, nutrients, and even heavy metals and microplastics. In doing so, they significantly improve water quality and protect nearby ecosystems - especially coral reefs, which are highly sensitive to turbidity and nutrient overload.

Beyond sediment capture, mangroves also play a role in the biogeochemical cycles of nitrogen and phosphorus, helping reduce the risk of eutrophication in coastal waters.

Supporting Healthy Fish Populations for Local Fishers

Mangroves are also critical habitats for the life cycles of many fish and crustacean species. They provide shelter from predators and an abundant source of food. Studies show that fish living near mangroves have higher population densities and faster growth rates than those in areas without mangroves.

This effect directly translates into economic value. The global fisheries yield directly tied to mangroves is estimated at up to USD 1.6 billion annually (UNEP, 2014). In countries like Mexico, the Philippines, and Mozambique, the links between healthy mangroves and strong fishery catches have been documented by dozens of studies.

Still, regulation and management of fisheries are essential. Why?

Mangroves as Safe Havens for Shark, Fish, and Ray Nurseries

One of the most important roles of mangroves is their function as nurseries for young marine animals. Thanks to shallow waters, intricate root systems, and abundant food, they provide ideal conditions for the growth and survival of vulnerable early life stages. They are especially critical for sharks and rays, which require time and safe environments to reproduce. Unlike most bony fish, sharks mature only after many years, have long pregnancies, and produce very few young. Many shark species reach sexual maturity only after 10 - 15 years, with females often giving birth to just a handful of pups after 9 - 12 months of gestation. This slow life strategy makes every safe nursery habitat vital for their survival.

What is a “Nursery Habitat”?

The scientific definition of a nursery habitat relies on three criteria:

1. Juveniles are found in these areas more frequently than elsewhere.

2. They remain there for extended periods of time.

3. The site is used repeatedly over multiple years.

Mangroves meet these conditions perfectly, combining shelter, food, and a relatively stable environment.

Mechanisms for Survival

• Protection from predators: Dense root systems act as natural barriers, reducing the chances of juveniles being caught by larger predators.

• Warmer waters: Shallow lagoons heat up more quickly, speeding up metabolism and supporting faster juvenile growth.

• Abundant food: Mangroves are extremely productive ecosystems, where small fish and crustaceans provide an ideal food source for growing sharks and rays.

  
  

Field Evidence:

• Bahamas - Lemon Shark (Negaprion brevirostris): Bimini is one of the most extensively studied shark nurseries in the world. Over 20 years of research have shown that juveniles consistently use mangroves, and the loss of these habitats has led to a significant decline in populations.

• Mexico - Scalloped Hammerhead Shark (Sphyrna lewini): Along Mexico’s Pacific coast, pregnant females return to the same estuaries and mangrove areas to give birth. Genetic studies confirmed strong female philopatry to these sites, meaning that protecting specific stretches of coastline is critical for population survival.

• Cape Verde - Multi-species Nurseries: In Sal Rei Bay, scientists documented mangroves being used by juveniles of several shark species, confirming their role as true “nurseries of the oceans.”

Every destroyed nursery habitat represents a dramatic weakening of future shark populations. Protecting mangroves as shark nurseries is therefore one of the most effective measures in safeguarding these endangered species.

The AMOARA Project in San Blas, Mexico

This very principle lies at the heart of AMOARA, an initiative developed by Blue Religion in the San Blas, Nayaritregion. Local mangroves and estuaries serve as key nurseries not only for scalloped hammerhead sharks (Sphyrna lewini), but also for various other species of sharks, rays, and fish. The region is also known for intense fishing of blue sharks (Prionace glauca) and other species. This makes protecting these habitats especially urgent: it is not just about preserving biodiversity, but also about halting the overexploitation of endangered species.

The project is built on three main pillars:

• Scientific research: In collaboration with Mexican scientists, monitoring focuses on how shark juveniles use mangroves and mapping critical areas.

• Collaboration with local fishers: Instead of conflict, the emphasis is on dialogue, since healthy shark and fish populations also mean more sustainable fisheries.

• Pursuit of protected status: The goal is for San Blas to become an officially protected area where mangroves remain safe havens for sharks, rays, and fish.

This approach combines scientific knowledge, community cooperation, and practical conservation - the most effective way to protect sharks as well as entire coastal ecosystems.

Protecting Mangroves = Protecting Oceans and Ourselves

Mangroves may be small in size, but their importance is immense. They shield coastlines from storms, store vast reserves of carbon, filter water, and provide livelihoods for millions of people. At the same time, they are the nurseries of the oceans - without them, young sharks, rays, and fish would have no safe place to grow and mature.

The loss of these ecosystems means the loss of protection for both people and marine biodiversity. Scientific evidence is clear: where mangroves disappear, so do shark nurseries, fish populations, and even safety for local communities.

Let’s keep mangroves alive - for the oceans, for us, and for generations to come.

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Photo: Unsplash | Kristin Hoel, Mohmed Nazeeh, Timothy K.

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