Imagine yourself travelling along the coasts of the Western Indian Ocean… From the Cape of Good Hope to Zanzibar, via the long beaches of Mozambique and the Reunion Island idyllic lagoons, to the mangroves of Madagascar, Tanzania and Kenya. These shores do not only inspire tourists forced into lockdown. They also host exceptional ecosystems, shelter surprising resources and help millions of people to live.

These coasts are precious and it is our duty to protect them and to keep the right balance between using their resources and conserving their environments. IRD scientists and their partners in Southern Africa, East Africa and the Indian Ocean work every day to deepen the knowledge of the region’s coasts and to outline sustainable solutions to protect them and their inhabitants.

Let us meet them through several stopovers.

Coral reefs are a haven for fish.

© IRD - Jean-Michel Boré

Coral reefs are a haven for fish.

Valuable and exceptional ecosystems

Warm waters of the western Indian Ocean envelop many countries and islands. These long coasts are home to rich ecosystems, adapted to local climate conditions. Deltas, mangroves and coral reefs are just a few examples of these unique and very sensitive environments on which the livelihoods of thousands of inhabitants depend.


Precious resources for nature...

Mangrove tree are a natural barrier against extreme events.

© IRD - Cécile Bégard

Coastal ecosystems of the Indian Ocean provide numerous services to the environment. Fish and crustaceans, for example, choose protected environments such as deltas, mangroves and coral reefs to breed in peace. They are real aquatic nurseries

Mangroves and coral reefs, along with the crustaceans and planktons that inhabit them, also store large amounts of carbon pumped from the atmosphere. Experts estimate that mangroves store on average five times and up to ten times more carbon per km² than tropical terrestrial forests?Mangrove Ecosystem Management Plan (2017-2027) – Government of Kenya.

Lastly, these ecosystems act as a natural barrier against extreme climatic events. They mitigate the devastating effects of tsunamis or cyclones on the coasts and protect them against the relentless erosion of waves.



...and for local communities


Thanks to specific environmental and climatic conditions, these ecosystems play a crucial role in protecting the local environment and constitute essential sources of income for coastal populations.

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© Richard Bremond

The Mikoko project team meeting inhabitants of Lamu.

"It is estimated that a billion human beings live on biological resources from coral reefs," said Pascale Chabanet, senior researcher and IRD representative in Reunion.

Coral reefs are indeed crucial for artisanal and commercial fishermen in the region, 1 km² of coral being able to produce up to 15 tonnes of fish yearly?Warren-Rhodes et al., 2004 : Mangrove forests are also an important fishing reserve, providing large quantities of fish, crustaceans and molluscs?More than 85% of fishing activities along the coast are carried out by artisanal fishermen in the shallow inshore areas within and adjacent to the mangroves directly employing more than 20,000 fishers (Mangrove Ecosystem Management Plan – Government of Kenya)..

Well-managed mangrove forests can sustainably provide fuel and construction wood to coastal populations?It is estimated that 70% of the wood requirement by the local communities adjacent to the forest is met by mangroves (Mangrove Ecosystem Management Plan – Government of Kenya).. Many species living in coral reefs also produce complex chemical compounds that allow them to survive in these highly competitive habitats. Some of these compounds could be used in the production of essential drugs.

Touristic tour in the Kenyan mangrove.

© IRD - Cécile Bégard

Last but not least, communities depend on coastal ecosystems for their tourism potential. Boat trips in mangroves or around coral reefs, bird and marine mammal observation, scuba diving or snorkelling are some of the ways to foster the local environment conservation and to generate significant tourism income.


Harnessing the potential of mangrove forests


A first stop in the province of Lamu, in Kenya, shows that IRD researchers appreciate the great potential of the region's coastlines. The Institute is leading an ambitious mangrove protection and conservation project around Lamu, in partnership with the Kenya Forest Service and CIRAD. In the area, communities directly depend on mangrove forests for their livelihood.

Mangrove forests provide important quantities of wood.

© IRD - Cécile Bégard

David Williamson, IRD researcher and co-leader of the project said: “The local populations, which mainly use mangrove wood for construction and heating, are the first to be affected by forest loss. We work together, and in particular with associations and local leaders, to preserve this precious ecosystem.” This participatory project allows them to make their voices and constraints heard and to participate in the development of solutions to protect the mangroves.

Capacity building is at the heart of the project, in particular for the Kenya Forest Service officers, who manage these forests on a daily basis. A collaborative platform will also allow anyone to engage in the project. It will include a set of information such as the flora and fauna sheltered by the mangroves, fishing techniques and the plant use possibilities. Contributors will be able to participate in monitoring the state of mangrove forests along the coast, by posting pictures and comments.

All coastal environments such as mangrove forests must be closely monitored in order to understand their evolution under human and natural pressures and to develop sustainable solutions to preserve them.

Cyclone in French Polynesia

© IRD - Bruno Marty

Cyclone in French Polynesia

Coastlines under strict scrutiny

The coastal ecosystems of the southwest Indian Ocean play a crucial role in the protection of the coastline and must in turn be protected, in particular through careful year-round monitoring. Let us make another stop in Reunion, where IRD researchers and their partners have set up several projects to closely follow the evolution of the region's coastlines.


Monitoring the ecosystems’ health status


Pascale Chabanet contributes to the GCRMN global project to monitor the health of coral reefs. She regularly dives around the island with her colleagues, equipped with underwater pads, black pencils and a 50-meter tape measure. After delicately putting the tape on the reef, the researcher-divers write down all the corals and algae types they can see around the tape, as well as their size. Others are responsible for listing the number and size of all the fish they can see in a 5-metre wide corridor along the measuring tape.


Pascale explains: “We have used this standardized method of observing reefs for years around the world. Thanks to the data collected, we are able to determine the health condition of reefs around the world and their evolution from one year to the next. We can also recommend, for example, management measures to regulate fishing". Other research projects complete the observations made by the GCRMN by studying the causes of these changes.


Assessing the damages of a cyclone by satellite

Map of flooded areas (in red) in North-Western Madagascar, after the Enawo cyclone.

© Sentinel 1

Let us stay in Réunion where several cyclones hit the coasts each year, like in many islands and countries bordered by the Indian Ocean. The IRD and its partners in Réunion and Madagascar use data collected through remote sensing to assess the natural and material damage they cause on the coasts. The Remote Sensing and Geomatics Competence Centre based in Saint-Pierre de la Réunion collects satellite images of the coasts of the area, updated every five days. By comparing images taken before and after a cyclone has passed, researchers are able to estimate the impacts on urban areas, forests, coastlines and agricultural areas. The scientists ultimately wish to design and deploy an automated chain for detecting changes in surface conditions following a natural disaster by remote sensing.

Once collected, this monitoring information is intended to support policy makers in the Indian Ocean in their decisions for better coastal protection.

Kenya coastal village, from above.

© IRD - Cécile Bégard

Kenya coastal village, from above.

A better management of coastal areas

Observations and monitoring of coastal ecosystems currently carried out by scientists show their gradual degradation, due to sometimes natural, but often human-induced threats.


The coasts of Reunion Island are for example subject to an unprecedented erosion. The coral reef, which surrounds them and protects them against this phenomenon, is degrading more rapidly than the normal rate, following chronic anthropogenic impacts accentuated by increasingly frequent extreme events (increased temperature of surface water, cyclones, etc.). In Kenya, scientists estimate mangroves have shrunk by around 20% from 1985 to 2009. The deltas plunging into the Indian Ocean are also changing rapidly due to significant alterations in the flow of fresh water from upstream rivers, such as deforestation of watersheds, large-scale freshwater debiting for agriculture and construction of dams.

Based on these observations and coastal monitoring systems, IRD researchers and their partners implement research projects that act directly for the preservation of the resources provided by the region's coastal ecosystems, and their fair distribution. Faced with the complexity of the common challenges to all countries, they provide the necessary information and data for large-scale conservation policies.

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© IRD - Cécile Bégard

Coastline near Watamu, Kenya.

For a fluid and constructive dialogue between scientists and policy-makers


Scientists have a great deal of data and knowledge about natural environments and their vulnerabilities. However, public policies only partially take them into account,” explains Stéphanie Duvail, an IRD geographer we met during our stopover in Mozambique. She is the co-leader of the DiDEM project, a regional initiative launched in July 2020 and dedicated the inclusion of scientific knowledge and user needs in decision-making in the management of coastal and marine areas of the western Indian Ocean. The idea is to support key stakeholders in making informed decisions, that are respectful of environmental dynamics and that would encourage a fair distribution of resources.

On the basis of research already carried out in the area, the project partners wish to develop innovative methodologies and tools to help decision-makers; train experts who can advise local decision-makers; and involve civil society through the education of young people and the support for multi-actor partnership dynamics. The project will take place in seven countries in the area and will focus on three study topics: islands and archipelagos, deltas and high seas.

This project is supported by the “young team associated with IRD” working on the governance of natural resources in Mozambique, ITANGO-MOZ. The team is working on defining tools and innovative approaches. Dinis Juizo, hydrological engineer from Eduardo Mondlane University, coordinates the project: "our interdisciplinary studies aim to reconcile environmental protection and the fight against poverty, through new approaches presented to decision-makers".


For aware and committed citizens

A young student from Maurice is planting mangrove.

© IRD - Lola Massé

The public also has a role to play concerning the threats faced by coastal ecosystems. Many research projects thus include actions to use scientific knowledge to inform citizens about the health status of the coastlines they inhabit and to raise awareness about the actions they can undertake to make a difference.

The PAREO project, carried out in Réunion, Mauritius and the Seychelles, is one of them. Thanks to new technologies and the MARECO educational kit, dozens of children from each of these countries follow a fun and interactive program that increase their knowledge of the importance of coral reefs. “Children are the citizens of tomorrow,” comments Lola Massé, project leader. “After this programme, they become the reefs ambassadors. They are part of the change and can then educate their families, who in turn influence public policies."

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The PAREO project aims at raising awareness of coral reef protection among children.

Jean-Pascal Torréton, IRD representative in Southern Africa, concludes: “Informing the public and decision-makers on the basis of scientific research is at the heart of our mission. This contributes to safeguarding the coasts of the region."