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The Western Indian Ocean lost 4% of its mangroves in 24 years, report finds

Mangrove forest on Nosy Lonjo, Antsiranana, Madagascar. Image by Kenguinaud via Wikimedia Commons (CC BY-SA 4.0).

Mangrove forest on Nosy Lonjo, Antsiranana, Madagascar. Image by Kenguinaud via Wikimedia Commons (CC BY-SA 4.0).

  • Analysis presented in a new report finds the Western Indian Ocean (WIO) region lost around 4% its mangrove forests between 1996 and 2020.
  • The WIO region includes the coastal areas of Kenya, Tanzania, Madagascar and Mozambique, which together account for 5% of the world’s mangroves.
  • The report finds the majority of WIO mangrove loss was driven by unsustainable wood extraction, land clearance for agriculture and the impacts of storms and flooding.
  • Mangroves provide vital ecosystem services to coastal communities and habitats, and sequester large amounts of carbon.

A new analysis of satellite data finds the Western Indian Ocean region lost around 4% its mangrove forests over the past quarter-century. In a report that discusses the state of these mangroves, the authors write that their findings provide decision-makers with the high-quality, reliable data they need to protect these threatened coastal forests.

Published July 2022 by Wetlands International, the International Union for the Conservation of Nature (IUCN) and the World Wildlife Fund (WWF), the report focuses on mangrove coverage in Kenya, Tanzania, Madagascar and Mozambique, which together account for 5% of the world’s mangroves.

The mangroves of the Western Indian Ocean are spread along the coasts of four countries: Kenya, Tanzania, Mozambique and Madagascar.

The report is based on analysis of satellite data collected by online monitoring platform Global Mangrove Watch (GMW) and builds on a 2020 global report. It is the first of several studies that will look more closely at what can be done to restore mangroves in specific regions, says Paul Erftemeijer, an independent marine scientist and one of the report’s authors.

The analysts used an algorithm to extract information from satellite imagery, turning this data into a map that showed the extent of existing mangroves forests. By focussing on a particular region, researchers can extract much more detailed information which, along with traditional fieldwork, offers: “a systematic approach that gets us as close as we can to the reality,” Erftemeijer says.

The report covers 1996-2020 and reveals that the region lost 30,156 hectares (3.9%) of its mangroves during the 24-year period. This was caused by a mixture of unsustainable wood extraction, land clearance for agriculture and the impacts of storms and flooding. But it also shows that, with the exception of Mozambique, losses have stabilized since 2007.

“There definitely seems to be a general standstill, which is good news indeed and quite different from the rather steep trends of decline during earlier decades,” Erftemeijer says.

Mangroves provide habitat for innumerable species, such as this mangrove kingfisher (Halcyon senegaloides). Image by Steve Garvie via Wikimedia Commons (CC BY-SA 2.0).

In the past, Erftemeijer explains, data was patchy at best, and rarely reliable, with the success of restoration programs often inflated and failures under-reported. According to Lilian Nyaega, a regional program officer at Wetlands International, only about 8% of the marine environment in the Indian Ocean has official protection. She said regional governments “simply don’t know where to start,” adding that they have lacked sufficient, consistent data.

But the datasets collated by Global Mangrove Watch are under the custodianship of some of the world’s most major conservation organizations, including WWF, Wetlands International and the IUCN, and is scrutinized by independent experts. This, Erftemeijer says, “brings consistency and greater certainty about what actually exists,” and makes it a powerful and relevant tool for regional decision makers.

The report also highlights the importance of mangroves as a carbon sink. Pound for pound, mangroves store five times more carbon than tropical rainforest, both in their aboveground biomass and also under the surface. Because they grow in waterlogged wetland ecosystems, organic material breaks down more slowly, creating marine peat, while their tangled root systems retain debris such as leaf litter.

“They are the absolute world champion when it comes to carbon storage,” Erftemeijer says.

According to Global Mangrove Watch data, the mangroves of the Western Indian Ocean store 838 million tons of CO2 and other greenhouse gases — the equivalent of more than 1.9 billion barrels of oil. The report finds a further 327,000 tons of CO2 could be sequestered annually if mangroves are restored on the more than 40,000 hectares of available land.

By putting blue carbon on the map for the first time, Nyaega hopes this will encourage more countries to include mangroves in their Nationally Determined Contributions (NDCs) — national plans to stay within the 1.5-degree target to mitigate the worst effects of climate change ­— and elevate these coastal forests to a much higher profile when COP27 convenes in Egypt in November.

Mangrove restoration is not without criticism. One issue conservationists point to is that well-meaning groups and organizations often focus on planting seedlings rather than recreating the conditions mangroves need to recover naturally. Projects can also fail if the wrong species is planted in the wrong place, wasting money and time.

Nyaega said that instead, projects should follow the principles of Community-Based Ecological Mangrove Restoration (CBEMR) because local people have historical knowledge and “know what species of mangrove works, and those that will wither and die.”

“Whatever we are doing will fail,” if mangrove conservationists don’t consult local communities, she says.

The new report highlights Tanzania’s Rufiji Delta as an area where community involvement has helped revitalize restoration, with channels dug to reconnect abandoned rice fields to the sea and invasive plants removed. This creates the conditions that mangroves need to re-colonize an area, the authors write.

Erftemeijer agrees that tapping into this wealth of Indigenous knowledge is vital.

“The way that mangroves are being sustainably managed and conserved and restored is all about community, it’s all about engaging and transferring responsibility to local communities,” he says.

Mangrove forest in Zanzibar, Tanzania.Image by Fanny Schertzer via Wikimedia Commons (CC BY-SA 2.0).

In many countries, resources are scarce and mangroves grow in remote places, with governments simply lacking the money or the staff to properly monitor them, according to Erftemeijer. He says that to fill this gap, governments need to mobilize the communities that live amongst them and give them the tools they need to manage mangroves themselves. Then governments can start to operate as “facilitators not policeman,” he says.

Erftemeijer says that since mangroves provide livelihoods and resources for some 40 million people across the region, emphasis should be placed “on a more sustainable use of a resource rather than putting a fence around it.”

Such an approach is supported by national management plans like that introduced to the Rufiji Delta, which operates on a zonal system and offers a way of avoiding conflict between different interests.

In the Rufiji Delta, mangrove areas are divided into four main zones: Total Protection, Rehabilitation, Production and Development. In the Total Protection Zone, mangroves are completely protected and cutting them is prohibited, whereas permit-controlled wood harvesting is allowed in the Production Zone. In the Rehabilitation Zone, mangroves are left to regenerate themselves, while in the Development Zone, where restoration potential is low, it’s accepted that some conversion and development will take place.

The role of women in mangrove restoration is also critical, Nyaega says. She recommends that initiatives encourage women to take active roles because it is often women who are involved in mangrove-destroying practices such as rice farming. She cautions that due to patriarchal societal structuring, women “often don’t take part in decision making processes as much as men, so therefore they may not be in tune with what is happening in the legal framework.”

It’s important to give young people a voice too, she adds, and show them that mangrove conservation can generate sustainable livelihood opportunities, such as eco-tourism.

Mozambique boasts the largest mangrove coverage in the WIO region but it is also among the most degraded, the report finds, with coastal areas ­— which are home to two thirds of the population — often buffeted by storms, which can uproot trees and cause severe erosion and flooding. Research indicates mangroves play an important role in shoreline protection and their removal often leaves coastal communities less protected from storm surges. The loss of mangroves is also a problem for the country’s fishing industry, their labyrinthine roots forming a protective and important spawning ground for both crustaceans and key fish species.

Barred mudskippers (Periophthalmus argentilineatus) is one of the many species that can be found in WIO mangroves. Image by Heinonlein via Wikimedia Commons (CC BY-SA 4.0).

However, the report also highlights huge restoration potential in the country, with 25,899 hectares of land available for restoration, nearly twice as much as the other three countries combined.

The report zooms in on Mozambique’s vast Zambezi Delta as a particularly important blue carbon hotspot. The government is about to embark on Africa’s largest mangrove restoration project, working with restoration specialist organization Blue Forest to plant 100 million new seedlings that, if most survive to maturity, will be capable of sequestering an additional 200,000 tons of C02 annually.

The report finds Madagascar suffered some of the worst mangrove loss in the WIO region between 1996 and 2020 due to uncontrolled wood collection for charcoal production, firewood and timber. Satellite data from the University of Maryland visualized on Global Forest Watch show widespread deforestation continued in Madagascar in 2021 and into 2022 — particularly in the northern Diana region, which hosts some of the country’s most extensive tracts of mangrove forest.

Satellite imagery from Planet Labs Inc. captured July 2022 shows widespread deforestation in an area of Madagascar’s Diana region where mangroves are found.

To combat mangrove destruction, the Madagascar government has given communities the opportunity to become directly involved in their protection, with villagers patrolling local reserves and helping to enforce new restrictions on cutting.

The next steps, according to the report, include reducing the reliance of community conservation groups on support from NGOs by encouraging them to network and share data with other communities, while the government is aiming to increase Madagascar’s overall mangrove protection via a new national strategy for sustainable management.

In Kenya, conservationists are focussing on the peri-urban mangroves that grow along the creeks and inlets around the coastal city of Mombasa, which are often deforested for building materials and firewood for local communities. Erftemeijer says the overlying threat to Mombasa’s mangroves is that no-one really owns them.

He says that as a result, the mangroves have suffered from uncontrolled clearing, while pressure on the city’s sanitation system has seen effluent and sewage flood through them. They have also been hit by oil spills from nearby ports.

These urban mangroves play a crucial role in maintaining water quality, which is a growing problem in and around Mombasa, Erftemeijer says. He describes them as “a kind of kidney that filters all the dirty water from the city. It’s a free filter system for the city … if people realised that they would value mangroves more.”

Banner image: Mangrove forest of Nosy Lonjo, Antsiranana, Madagascar. Image by Kenguinaud via Wikimedia Commons (CC BY-SA 4.0).

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