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Marine Heatwaves

Understanding the Threats They Pose to Overseas Territories in the Pacific; Co-developing Decision Support Tools and Adaptation Solutions

(Coordination: Sophie Cravatte (IRD), Catherine Sabinot (IRD), Guillaume Mitta (IFREMER))

About MaHeWa

Marine heatwaves are prolonged episodes of extreme ocean temperatures that can have devastating effects on marine ecosystems, such as massive coral bleaching, coastal species mortality, and toxic algal blooms. The intensity and frequency of marine heatwaves are expected to increase in the future, posing a growing threat to island societies that heavily rely on marine resources.

MaHeWa is an interdisciplinary project funded for four years (2024–2028) by the French National Research Agency (ANR) as part of the Priority Research Program “Ocean and Climate: An Ocean of Solutions.”

This project brings together a consortium of climatologists, oceanographers, biologists, anthropologists, and economists from France and overseas institutes and universities. These teams collaborate to make significant advances in understanding the characteristics and impacts of marine heatwaves on socio-ecological systems in Pacific Overseas Territories.

MaHeWa has 2 main objectives

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1Enhancing Knowledge: Assessing the Risks of Marine Heatwaves to Socio-ecosystems

MaHeWa will study:

  • The characteristics of past and future marine heatwaves around these territories and in lagoons with contrasting geomorphologies, as well as the physical processes driving them.
  • The sensitivity and adaptability of coral reefs, the vulnerability of mariculture species, and the impact of marine heatwaves on the risk of ciguatera poisoning.
  • The socio-economic resilience of these territories to marine heatwaves, exploring how “risk cultures” designed to address extreme events are constructed, transformed, and negotiated. The project will also produce biocultural risk indicators.
2Co-developing Solutions to Mitigate Risks

Throughout the project, MaHeWa will facilitate close collaboration between scientists and the project’s partner territorial managers responsible for health and marine resources.

  • Together, they will co-create decision support tools: short-term marine heatwave alert systems, health alert networks, and long-term vulnerability maps, along with crisis management action plans and public policies on environmental and health issues.
  • Together, they will test innovative, nature-based solutions to counter habitat degradation and ensure food security, focusing on thermotolerance markers and enhancing species resilience.
  • MaHeWa will engage the public through innovative activities in close collaboration with local associations.

News

Mahewa
In Bouraké, Australian researchers study reef fish resilience

International collaboration · April 2026

Australian researchers in Bouraké studying reef fish resilience to climate change

As part of a collaboration funded by the French Embassy in Australia (Australian-French Student Exchanges in the Pacific 2025) and the University of Adelaide,
two researchers joined the MaHeWa team to conduct studies on reef fish in the Bouraké lagoon — a naturally extreme environment characterized by high temperatures, low oxygen levels, and acidification, making it a natural analogue of future ocean conditions.

Continue reading In Bouraké, Australian researchers study reef fish resilience
Mahewa
a new Master’s student in the MaHeWa team

New intern · March 2026

Welcome to Axelle Saget-Lethias, MaHeWa intern studying microbial biodiversity in the southern lagoon

As part of her third and final year of the Bachelor of Technology in Biological Engineering, specialising in Environmental Sciences and Ecotechnologies, at the University of Clermont Auvergne, Axelle Saget-Lethias is currently undertaking a four-month internship at Ifremer, from 16 March to 6 July.

Continue reading a new Master’s student in the MaHeWa team
Mahewa
Ocean Fresco 2026

Awareness · March 2026

MaHeWa co-facilitates the Ocean Fresco in Koné alongside the Northern Province

On Thursday 5 March, the Ocean Fresco workshop was held in Koné. Inspired by the Climate Fresco, the Ocean Fresco consists of six themes and uses a set of 100 cards to build a systemic view of the ocean. It is rooted in an awareness-raising approach and allows participants to discover the issues related to the ocean and the actions that can be taken to preserve it.

Continue reading Ocean Fresco 2026