Coral reefs of the Western Indian Ocean at high risk of collapse


This study points to specific policies to address climate and fishery threats to coral reefs of the Western Indian Ocean

After an 18-month analysis, researchers at CORDIO East Africa in collaboration with scientists from over 35 other organizations around the world have published their findings on the state of coral reefs of the Western Indian Ocean in the journal Nature Sustainability (link to article at bottom of page).

Applying the IUCN Red List of Ecosystems framework to the coral reefs stretching from Somalia to South Africa on the African continent and extending eastward to the island states of Seychelles and Mauritius, we found that all coral reefs across the region are at risk of collapse within decades.

Of the 11 sub-regions, coral reefs in four of the subregions are Critically Endangered, three are Endangered, and four are Vulnerable to collapse. Overall, WIO coral reefs are classified as Vulnerable.

“We already knew that coral reefs around the world are in decline, but now we know to what degree in the Western Indian Ocean, and the varied threats in each sub-region,” said Dr David Obura, Founding Director at CORDIO East Africa and lead author of the study. “This standardized assessment can help decision-makers to develop and execute policy to halt and reverse the damage.”

Rising sea temperatures due to climate change, and overfishing, are the dominant threats to all coral reefs of the Western Indian Ocean. The highest risk levels of ‘Critically Endangered’ (CR) and ‘Endangered’ (EN) in seven ecoregions are driven by increasing sea temperatures, assessed over the coming 50 years. The lower (though still significant!) risk level of Vulnerable (VU) is driven principally by overfishing and reef decline in some subregions.

Top left) a large Grouper – Groupers are an important top predator on reefs but were shown to be heavily overfished in this study. Top right) a bleached reef in La Reunion during the 2016 mass bleaching event – bleaching due to warming sea temperatures is the biggest threat to coral reefs (photo credit: Julien Wickel). Bottom left) a heavily degraded algae-dominated reef in Tanzania. Bottom right) a vibrant, healthy coral reef in Bazaruto, Mozambique with high cover of living coral.


Threat status of each eco-region in the map (left), and (right) threat status at the regional level for Criteria A-D (and sub-components of Criterion D). Colours represent threat status from Least Concern to Critically Endangered (key bottom left). The center circle represents the final threat status for WIO coral reefs – VU.

Effective Management and Policy in the Western Indian Ocean

As a result of the findings, the study makes the following recommendations for actions to protect coral reefs in the Western Indian Ocean region:

1. Support actions targeted at alleviating fishing pressure through co-management of small-scale fisheries, and the establishment of no-take areas for fishery replenishment.

2. Embed climate mitigation and adaptation as national priorities within development and planning frameworks, including specific actions for coastal and marine systems and people linked to coral reefs.

Useful. Reduce stressors to coral reefs from land-based sources adjacent to coral reefs (e.g. pollution) to enhance resilience to warming temperatures.4.Increase area of coral reefs under effective protection to meet international targets in the Western Indian Ocean (likely to be 30% by 2030) in a way that’s compatible with sustainable use and equity at local levels.

4. Promote the application of the Red List of Ecosystems to other critical coastal and marine ecosystems in the Western Indian Ocean, particularly mangroves and seagrasses.

5. Invest in higher resolution analyses at national levels to meet national policy requirements for managing and conserving coral reefs.

6. Increase support (funding and capacity building) for reef monitoring, linked to the national and regional Global Coral Reef Monitoring Network nodes

7. Promote the inclusion of the Red List of Ecosystems as an indicator in the Global Biodiversity Framework of the Convention on Biological Diversity [https://www.cbd.int/conferences/post2020], and through that, for Goals 14 and 15 of the Sustainable Development Goals [https://sdgs.un.org/goals/goal14]

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