World Mangrove Day: The Value of Mangroves for Marine Life, Coastal Communities and Climate Change

On the 27th of July BCSS celebrated #WorldMangroveDay. To highlight their importance and complexity, we ask the question:

How do land and marine animals as well as coastal communities and the planet in general, depend heavily on healthy mangrove forests? And why is this of relevance to Mozambique?

Studies have found that mangrove trees can sink four times more carbon than rainforests can.

What is a mangrove?
A mangrove is a tree or shrub which grows in tidal, mainly tropical, coastal swamps, having numerous tangled roots that grow above ground and form dense thickets. Mangroves are salt-tolerant trees, also called halophytes, and are adapted to life in harsh coastal conditions.

Providing safe habitats for thousands of species
Previously often overlooked by coastal communities and scientists, mangrove forests have gained well-deserved attention over the last few years. Environmentalists, NGO’s and scientists have studied forests all over the world thoroughly and conclude they are remarkably diverse and crucial for the oceans. Working together with seagrass beds and coral reefs, they safeguard the health of marine life and oceans as a whole.

As nursery grounds, mangrove forests provide the ideal shelter for numerous species, from fish and mollusks to megafauna like sea turtles. As a breeding ground, it ensures that these species are protected from predators and can grow to a mature size without being threatened.

The ecosystem of a mangrove forest is complex as it is home to thousands of species, not limited to marine animals. The trees are inhabited by insect species which attract a wide range of bird species that nest and live in the dense branches, using the habitat as a prime nesting and resting site. Other land animals like monitor lizards and crocodiles scavenge among the roots to find food, along with several endangered species such as dugongs (of which there is an estimated population of 200 in the BANP) and olive ridley turtles.

The leaves that fall from the trees form the base of a rich food web that accommodates all these different types of animals. They are packed with nutrients for algae and invertebrates, which feed different organisms like sponges, shrimp and juvenile fish. Nutrients brought in by the tides, coming from coral reefs and mudflats, form food for the species that live on the seabed, like oysters.

Protecting coastlines and livelihoods
Mangrove forests form a natural coastal defense, as their sturdy root systems help form a natural barrier against violent storm surges and floods. By collecting silt and sediments that the tides and rivers carry, they stabilize the soil and shorelines, avoiding erosion. The trees also form a buffer against strong winds, waves, cyclones and even tsunamis. Damage to the land and buildings that are located behind mangrove forests is significantly less than locations where mangroves have been cut down.

By forming important habitats for thousands of species, mangrove forests provide coastal communities with food and economic welfare. Fish populations are high when mangrove forests are sufficiently present, which brings locals the opportunity to not only a healthy diet but also a reliable stock for the fishing industry.

Fighting climate change
Mangrove forests act as efficient carbon sinks as they remove carbon dioxide from the atmosphere. Studies have found that mangrove trees can sink four times more carbon than rainforests can. The carbon is stored in the soil beneath the trees’ roots. Because of the incredible efficiency of the trees being able to store the carbon, researchers have estimated the monetary value of mangroves to be $194,000 per hectare, annually. Globally, this means that the Earth’s remaining mangroves provide approximately $2.7 trillion in services every year. It is estimated that in a period of fifteen years (2000-2015), around 20 million tons of carbon was released as a result of mangrove forests loss (source). These soil carbon emissions came mostly from mangrove deforestation in Indonesia, Myanmar and Malaysia, accounting for over 75 percent of the loss of carbon. The main reason of deforestation is shrimp farming and other forms of aquaculture, secondly for wood. 

BCSS facilitated fieldwork for data used in IUCN report ‘Coastal Blue Carbon Stocks in Tanzania and Mozambique’ in April 2019. The research station was used to conduct research on blue carbon, which refers to carbon dioxide removed from the atmosphere, buried and accumulated as organism matter in soils, mostly via plant growth.

“Mangroves host a variety of life and provide numerous ecosystem services. Now, more than ever, we should be protecting, preserving, and restoring ecosystems that do just that, for the survival of all species (including ourselves) on Earth.”
– Karen Bowles, Research Manager at BCSS

Mangrove forests in Mozambique
With mangrove forests covering an area of approximately 300,000 hectares, Mozambique has the second largest total mangrove cover in Africa (the first being Nigeria), taking the 13th place on the list of most mangrove-rich countries. However, of this area more than a thousand hectares disappear each year due to deforestation. Nine of the 80 different species of mangrove trees can be found in Mozambique.⁠ The most common found species in the Bazaruto Archipelago and surrounding area is the Pemphis acidula, often called bantigue or mentigi.

With more than 60 percent of the country’s population living along the coast, the mangrove forests constitute one of the main sources of income and building materials for houses and boats.

Despite their undeniable importance to the environment, wildlife and coastal economies, mangrove forests are under threat. Globally, over a third have already disappeared, and in regions such as South America they are being cleared at a faster rate than tropical rainforests.

The Mozambican government acknowledges the dependency of both animals and communities on mangroves and in 2017 committed to replanting 5,000 hectares by 2022, in during the United Nations conference.

BCSS visits the mangrove forests on Benguerra Island regularly to educate both volunteers and interns as well as team members and local community members about the mangrove ecosystem in a practical and tangible way. The team also regularly cleans the mangroves from debris, nets and plastic. Sustainable management, community management, continuous monitoring and research are crucial efforts to the mangroves’ survival.

Sustainable management, community management, continuous monitoring and research are crucial efforts to the mangroves’ survival.

For questions about this article, please contact:
Iris Uijttewaal, Bazaruto Center for Scientific Studies
+44 7 882 030 249

Host of the first permanent Ocean Observatory focused on multi-ecosystem time series research in Africa, the Bazaruto Center for Scientific Studies (BCSS) was established in 2017 as in independent, non-profit organisation with a mission to protect and support the fragile ecosystems of the Bazaruto Archipelago, Mozambique. The research station is located on Benguerra Island, off the coast of Mozambique.
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