By Ellen Rubin
Edited by Nina Purton

As explored in the last article, mangroves are a unique and unparalleled habitat for nursery sea life, land animals, and commercial fishing. They also have the potential to save the economy on climate-related expenses and damages.

Coastal ecosystems like mangrove forests are among the most effective at sequestering carbon and saving lives and property damage from tsunamis, storm surges, and high winds. These ecosystems provide the means for nearby communities to make a living while effectively securing a safer environment in comparison to other human-made climate-mitigation techniques.

Here are some of the main environmental and economic benefits to give you an idea:

Environmental Benefits of Mangrove Forests

Mangroves store, or sequester, more carbon than any other ecosystem – up to 1,000 tonnes of carbon per hectare. This is 4-5 times more carbon than land-based forests, including rainforests.

If left undisturbed, the mangrove ecosystem will store carbon for thousands of years – a huge boon toward mitigating climate change.

Here’s a little digest on the major environmental benefits:

Carbon Capture or Blue Carbon Sink

As mentioned above, one of the most important benefits of mangrove forests and attached salt marshes is their ability to store carbon, mitigating greenhouse gas emissions (CHG). They sequester more than 28 million tons of carbon every year.

As mangrove trees grow, they absorb and store carbon dioxide (CO2) in the tree’s leaves, branches, and roots. As the parts age and fall into the water, they decompose and release stored carbon on the seafloor, which is buried beneath the sediment and soil. The carbon can remain trapped there for centuries, and will not reenter the atmosphere as long as it remains undisturbed.

Mangrove ecosystems are categorised as Blue Carbon Sinks (coastal or marine ecosystems absorbing and storing CO2). Mangrove forests’s annual capacity to absorb carbon (15-18.3 million metric tonnes) matches the removal of four million cars from the road, according to the Emission Index.

Water Filtration

Mangroves filter and purify incoming and outbound water, protecting both saltwater and freshwater ecosystems.

The root systems slow the flow of the water, allowing sediments to settle. This helps to create nutrient-rich mud and filter nitrates, phosphates and other pollutants like heavy metals that are carried from rivers and streams before they hit the open sea. This alleviates or prevents dangerous conditions like red tide, sargassum, and algal blooms that thrive on excess water nutrients.

Mangrove filtering systems counter some of the 80% of sewage that is discharged directly into the sea without treatment, and the 8 million tonnes (according to a 2017 conference) of plastic waste that enters our oceans every year. The mangrove forests also keep seawater from encroaching on inland waterways where plant and animal life are not able to flourish in salt water.

Shore Stabilization & Weather Mitigator

Water is an efficient eroder. Over time it carved out the Grand Canyon and has shaped our continental outlines.

Mangrove forests help prevent erosion by protecting coastal areas from waves and storms. Forests help reduce the risk to nearby communities from weather events and rising seas.

Mangrove roots stabilize existing soil and add to it through decomposing leaves, silt, and sediment carried downstream from rivers. The evolution of sandbar to small island relies on mangroves to slow the flow of water so nutrient-rich sediment can accumulate allowing new seedlings to take root.

Mangroves also act as a buffer zone between wind and wave damage from storms, cyclones, hurricanes, tidal waves, and tsunamis, and the coastline ecosystem and local communities. Communities that exist within 328 feet of sea level and within three square miles of the coast benefit from mangroves having the natural protection from rising sea waters and global warming events.

This theory has been proven time and again in recent history. Research and experience have shown that:

• Strong roots and tree trunks break up wave energy and decrease storm surge. As a first line of defense for flooding and storm events, 100 meters (330 feet) of mangrove forest can reduce wave height and dissipate wave energy by up to 66% – 200 meters reduces it by 75%.
• In a tsunami, mangrove forests reduce wave heights between five and 35%.
• Where mangroves have been cut down to provide space for shrimp farms, the inland areas have been more vulnerable to destruction.

Here’s a little case study to give you an idea:

With the aim to get in the Guinness Book of World Records, the villagers in Naluvedapathy in Tamil Nadu planted 80,244 saplings of various trees to create a kilometer wide belt. When a tsunami struck the village in 2004, it suffered minimal damage while neighboring villages were flooded. During the same tsunami, a community in Sri Lanka that sat behind a dense mangrove and scrub forest suffered 2 deaths, while a nearby village without the mangrove buffer suffered up to 6,000 deaths.

Balancing Land and Water Ecosystems

There is a delicate balance between land and water systems that hinges on mangrove forests.

Mangrove buffers protect terrestrial plants from salt water, protecting marsh meadows, seagrass, and coral reefs from toxic pollutants such as heavy metals, pesticides, and agricultural runoff. They also provide the perfect habitat for thousands of species. They are natural breeding and nursery grounds for sea life, upon which many communities depend.

Types of ocean life that thrive among the mangroves are crustaceans such as shrimp, crabs, oysters, and other shellfish. For instance, oysters need a habit with a slow water flow, which is why they are often harvested from mangrove roots. There are even some communities, such as those in Gambia, that have created oyster farms that make it easier to harvest them without damaging trees and surrounding ecosystem.

Non-Aquatic Animals

Mangrove forests also create a unique habitat where insects, amphibians, birds, and land animals thrive. Over 1,500 non-aquatic animal species are associated with mangrove forests in some way in places such as Selangor, Malaysia; Queensland, Australia; the Philippines, Kenya, and Puerto Rico .

With the shrinking of mangrove acreage, encroaching human activity, pollution, and mismanagement of resources, the risk of extinction for all mangrove inhabitants is increasing: While almost 20% of assessed mangrove ecosystems are either endangered or critically endangered, 341 animal species that use mangroves are also considered endangered

A UNEP report estimated that 50% of the mammals, 22% of the fishes, 16% of the plants, 13% of amphibians, and 8% of the bird and reptile species that live or feed in mangrove forests could go extinct in the coming years. This includes species such as the Bengal tiger, which relies on the camouflage that trees and shrubs provide.

Mangroves also provide prime resting and nesting sites for shore and migratory birds like kingfishers, herons, and egrets. Other endangered species that thrive in mangroves include crab-eating macaque and proboscis monkeys, fishing cats, monitor lizards, tree-climbing fish, dugongs, manatees, olive Ridley turtles, white-breasted sea eagles, straight-billed woodcreepers, and scarlet ibis.

Economic Benefits of Mangrove Forests

Some people need economic reasons to justify saving habitats.

Luckily, there are some very valid and compelling reasons to restore and sustainably manage mangrove forests. Investments to restore mangroves are estimated to generate benefits that are four times greater than the cost.

Here are some of the main economic benefits of restoring and preserving mangroves:

Reduces Climate-related damages and expenses

In Florida, mangroves prevented $1.5 billion in direct flood damage and protected over ½ million people during Hurricane Irma in 2017. It’s estimated that they prevent more than $65 billion in damages and reduce the flood risk to 15 million people yearly worldwide.

Protecting, or even restoring or planting mangrove forests is far less expensive and more effective than building sea walls which tend to increase the amount of erosion on immediate and adjacent beaches, as well as nearby properties because of coastal currents. Instead, forested land is an effective buffer against erosion and water events and can help mitigate the 8-9 inche global sea level rise since 1880.

Income Generation

Mangroves support the livelihoods of hundreds of millions of coastal dwellers around the world. Overall, mangroves generate $40-50 billion from fisheries, forestry, and recreation while protecting thousands of indigenous species.

Mangrove ecosystems are worth an estimated $33,000-$57,000 per hectare per year. This is because of the services they provide, ranging from managed timber use, fuel wood, construction materials, natural fisheries for fish, shrimp, prawn, crabs, and lobsters, nursery habitats for commercially important species, medicinal compounds, water quality maintenance, coastal protection, ecotourism, and nutrient cycling.

Game and sport fish such as barracuda, tarpon, and snook find shelter among the roots of trees as juveniles, forage in the seagrass as they mature, and then venture out to the open ocean as adults. Around 75% of all commercially caught fish spend some part of their life cycle among the mangroves or coastal forests. In parts of the world, such as South Florida, this figure increases to 90% of all commercial species. Even coral reef species in the Caribbean rely on mangroves as nursery grounds.

By creating habitats that nourish fish and seafood populations, mangrove forests protect the communities and provide a way for people to earn a living. Low tides are a perfect time to collect seafood and fish move in to feed on juvenile fish during high tide so fishing is easier. They provide food security for neighbouring communities and even entire countries.

Fish are the most critical source of protein for 1.5 billion people worldwide; especially in low-income countries with food deficits. An estimated 4.1 million fisherman depend on mangrove areas for their jobs and nutrition.

Honeybees also thrive on the nectar of mangrove trees and provide a source of income for the community. This is a complete and sustainable ecosystem, as long as it isn’t abused.

Property Protection

Mangrove ecosystems reduce the risk of storm-related property damage for more than 18 million people and prevent more than $80 billion in property damage every year.

In the US alone, it’s estimated that mangroves have prevented $50 billion in annual damages from hurricanes, tropical storms, winds, and flooding (this is before the estimates from the 2024 hurricanes Helene and Milton were compiled).

Manufacturing solutions to weather events is far more expensive and less effective than restoring mangroves. For instance, engineering and building structures like the sea walls mentioned above are 2-5 times more expensive and lead to erosion of the ocean floor immediately around them. You also lose the carbon sequestering and wildlife habitat benefits that forests provide.

The Bigger Picture

Mangroves are essential for preserving healthy natural habits, encouraging biodiversity, and protecting local communities and endangered species.

While the primary driving factor for conserving should be saving natural habitats and lives, having a mangrove buffer also makes great economic sense. Every dollar spent protecting mangroves is worth upwards of $5 worth of climate adaptation benefits like maintaining access to food resources for nearby communities and protection from weather events.

In the next article of this series, we will cover the current state of mangroves, what is being done to preserve this precious ecosystem and what we can expect.