WESTERN INDIAN OCEAN CORAL REEFS
RED LIST OF ECOSYSTEMS ASSESSMENT 2020
Reefs in jeopardy!!
A new study of the coral reefs of the Western Indian Ocean shows that they are all at high risk of collapse within the next five decades. The study brought together researchers from more than 35 organizations to study the vulnerability of coral of the WIO based on the IUCN Red List of Ecosystems framework.
RLE inception workshop March 2019
RLE contributors validation workshop Jan 2020
How was the assement done?
Coral reefs in ten countries in and along the Western Indian Ocean were split into (i.e., , , , , , , , , , , and and assessed using the criteria of the IUCN Red List of Ecosystems , a framework developed by the International Union for Conservation of Nature (IUCN) to assess how close ecosystems are to collapse.
Reefs in were found to be at high risk of complete ecosystem collapse and irreversible damage.
We already knew that coral reefs around the world are in decline, but now we know more precisely to what degree,” said David Obura, Founding Director at CORDIO East Africa and lead author of the study. “This standardized assessment can provide the evidence required by decision-makers to develop and execute policies to halt and reverse the damage
Assessments & Ecoregion Results for each RLE criterion (A, B, C and, D) assessed
Reefs in island nations in the Western Indian Ocean were found to be under particularly high threat. In four of the sub-regions (East and South Madagascar, Comoros, and the Mascarene Islands), reefs were assessed as ‘Critically Endangered’ according to IUCN Red List of Ecosystems criteria, while they were found to be ‘Endangered’ in West and North Madagascar and Outer Seychelles. Rising seawater temperatures as a result of climate change were identified as the greatest threat to coral reefs in these island nations.
To explore the dashboard, use the selector tool on the upper left corner of the overall criterion map to select a region(s) of interest.
In the remaining four sub-regions, in North Seychelles, and along the entire mainland East African coast from South Africa to Kenya, reefs were classified as ‘Vulnerable’ to collapse. Overfishing, by altering the ecology of reefs and promoting algal takeover, was found to pose the greatest overall threat in continental African countries.
What's the situation like in the WIO?
The Western Indian Ocean (WIO) region spans across a large latitudinal range, from the Somalia region, influenced by the strong monsoon regime of the northern Indian Ocean, to the southern temperate regime of the tip of South Africa, where the Agulhas current diverges from the northward moving Atlantic Benguela current
The WIO encompasses tropical and subtropical regions of diverse nature, rich stretches of coast along the mainland countries of Somalia, Kenya, Tanzania, Mozambique and South Africa, and vast oceanic areas surrounding the island states of Madagascar, Seychelles, Comoros, Mauritius and French Territories.
Geomorphological and oceanographic features define the character of the WIO which is home to 16% of the world's coral reefs.
Unfortunately, Coral reefs in the WIO are Vulnerable!
Bazaruto Mozambique Lutjanus kasmira w Acropora. Photo credit Melita Samoilys
But why are the reefs in the WIO classified as Vulnerable?
Western Indian Ocean coral reefs experienced widespread coral bleaching during the first global coral bleaching event in 1998, in which 30-50% of corals were estimated to have died. It was also affected by what has been dubbed the “3rd global coral bleaching event” in 2016.
Bleached corals-Mayotte. Photo credit: David Obura
La Reunion 2016 bleached reef: Credits Julien Wickel
Increasing human population and demand for non-renewable source of energy (oil and gas exploration) as well as fishing pressure have all had an implication on environmental and biotic degradation now manifested by critically endangered Groupers near-threatened Parrotfish, and Coral. This coupled with the fact that the
Currently, the region is experiencing and increased threat from all drivers of reef decline which are also projected to increase in the coming days. Owing to this, Coral reefs of the WIO have been classified as vulnerable.
But how is the situation like in each ecoregion?
Find out more as we delve into each of the 11 ecoregions below:
#1/11-Northern Tanzania-Kenya
The ecoregion is the third-smallest with an area of approx 295,000 km2 but with the second highest reef extent approximately 3,240 km2 of which less than 30% are protected.
But why are the reefs in this ecoregion considered Vulnerable?
Biotic disruption of fish communities has driven this Ecoregion into Vulnerable status under RLE criterion D. Groupers are classified as Critically endangered while Parrotfish and Algae are near-threatened.
Algal reef - Tanzania: Credits David Obura
Pemba Island Nov 2020: Credit Melita Samoilys
This ecoregion is also under immense threat from both direct and indirect pressure through resource exploitation and human-induced habitat degradation.
Does this situation change as we move further south?
#2/11-Southern Tanzania-Northern Mozambique
The ecoregion is located in the Northern Mozambique Channel (NMC) a region now recognized as a second peak for coral reef biodiversity globally.
Photo credit: Nick Riley
The region comprises the marine and coastal areas of southern Tanzania and Northern Mozambique and stretches from Mafia Is. in Southern Tanzania to the South of Nampula province in Mozambique.
Northern Mozambique channel locator
It is a unique ecoregion with a smaller size (fifth smallest area of 295,000 km sq ) that hosts approximately 25% of all the reefs in the WIO. Unfortunately, all the reefs in this ecoregion are listed as Vulnerable.
But why are reefs in this ecoregion Vulnerable?
The ecoregion is located in one of the hottest parts of the Western Indian Ocean and parts of it have experienced 4 major bleaching events – in 1984, 1998, 2010, and 2016.
Although the reefs in this region have demonstrated high resilience, biotic disruption of fish communities manifested by Endangered Groupers and near-threatened Parrotfish has pushed this Ecoregion into Vulnerable status under RLE criterion D.
#3/11-Comoros
This ecoregion is at the heart of the Northern Mozambique Channel a coral biodiversity hot spot.
Humpback Whales in Moheli Comoros. Photo Credit Philipp Oppermann.
The ecoregion is relatively large and encompasses the Comoros archipelago and all the reefs around Mayotte and Glorieuses.
More than 85% of reefs in this ecoregion are within Marine Protected Areas of Moheli, Shisiwani, and Parc National Coelacanthe in Grande Comoros and other large MPA in Mayotte and Glorieuses.
Despite a high level of protection, reefs in the Comoros ecoregion are critically endangered! Why?
The ecoregion is at the center of one of the hottest parts of the Western Indian Ocean an area that has experienced four bleaching events since 1998.
Susceptibility to thermal stress, with darker colors indicating higher susceptibility and risk of coral bleaching © Maina et al. 2008
The region is susceptible to thermal stress and this coupled with high rates of pollution and sedimentation are contributing to environmental degradation now assessed as Critically Edangered under criterion C
Overexploitation of marine resources, coastal development, and tourism are among the main anthropogenic pressures causing biotic disruption already manifested by dwindling Parrotfish and Groupers which were assessed as Near Threatened and Critically Endangered respectively. The overall implication is a Critically Endangered Ecoregion
#4/11-West Madagascar
This is the third-largest coral ecoregion in terms of size and proportion of reef it hosts 12% in the WIO.
The ecoregion is located on the west coast of Madagascar extending from the northern border of Boeny region in the north to the southern boundary of Atsimo-Andrefana region.
This ecoregion is located in one of the most dynamic parts of the WIO characterised by hotter temperatures (SST) and variable eddies.
But why are coral reefs in this ecoregion endangered?
Environmental degradation and Biotic disruption of the ecosystem in this ecoregion have an implication in the Near Threatened and Vulnerable status of; coral, Algae, and keystone fish species i.e., Parrotfish and Groupers respectively. The overall outcome is thus an Endangered ecoregion.
#5/11-North Madagascar
This is the smallest coral reef ecoregion and is home to 10% of the coral reef extent in the WIO.
The ecoregion sits at the heart of the Northern Mozambique channel which is one of the hottest parts of the WIO.
Coral reefs in this ecoregion are classified as Endangered. But why?
This ecoregion is located in one of the hottest parts of the Western Indian Ocean. SST dynamics coupled with other local stressors are key drivers of environmental degradation in this ecoregion. The overall implication is that this ecoregion is categorized as Endangered
#6/11-Seychelles Outer
The ecoregion extends from the central Indian ocean through to the Mascarene plateau.
It is the largest and most isolated of all ecoregions and home to the largest giant tortoise population in the world.
© UNESCO Aldabra Atoll (Seychelles) Photo credit: Ron Van Oers
It encompasses some of the region's iconic atolls including Aldabra the world's second-largest coral atoll and a marine heritage site. The ecoregion has a rich diversity of ocean and landscapes that contribute to the ecoregion's scenic and aesthetic appeal.
Aldabra Anse Var
Despite its large size, this ecoregion host only 9.2% of the WIO total reef extent all of which are classified as Endangered.
But why are the reefs in this isolated ecoregion classified as Endangered?
First, coral reefs in this region are geographically constrained and clustered in small patches making them susceptible to potential threats thus the vulnerability status under criterion A
Meanwhile, the ecoregion is located in one of the hottest part of the WIO where reefs are highly susceptible to bleaching a key ingridient for abiotic and biotic degradation under criterion C and D respectively.
The interplay between the geographical constraints coupled with degradation of both biotic and abiotic factors renders coral within this ecoregion as Vulnerable and an Endangered status for the entire ecoregion.
#7/11-Seychelles North
Seychelles North is home to numerous beaches, coral reefs, and nature reserves.
Mahe Seychelles Photo source: Got2Globe
With an area of approx.507,00 km2, this ecoregion is smaller than Seychelles Outer but hosts almost the same proportion of reefs i.e., approx. 8.1% of all the total reefs in the WIO all of which are classified as Vulnerable.
But why are coral reefs in this region classified as Vulnerable?
Geographical constriction and Abiotic disruptions manifested by Vulnerable groupers and near threatened Corals are the key drivers for the overall vulnerable status of this ecoregion.
#8/11-Mascarene Islands
This ecoregion is located east of Madagascar and encompasses the islands belonging to the Republic of Mauritius as well as the French department of Réunion.
It is the second largest of ecoregion but hosts a relatively smaller proportion of the total reefs (only 4.7%) in the WIO.
Unfortunately, the reefs in is ecoregion are Critically Endangered.
Why are the reefs in this ecoregion classified as Critically Endangered?
The ecoregion is faced with a myriad of environmental pressures including tropical cyclones that occur occasionally, bringing heavy rain and high winds, and causing erosion and landslides. The average temperatures are also high in this ecoregion during the summer season (Dec-April). Owing to these and more, the ecoregion is listed as Critically Endangered under criterion C.
The ecoregion is also facing biotic disruption as evidenced by Critically a near threatened ecoregion score under criterion D an implication from Critically Endangered Groupers
Meanwhile, reefs in this ecoregion are geographically constrained to a small extent of occurrence making them Vulnerable under criterion B.
#9/11-East Madagascar
This ecoregion s slightly larger than the Northern Tanzania -Kenya ecoregion and hosts a relatively smaller extent of coral reef i.e., only 4% of the total reef area in the WIO.
Reefs in this region are geographically constricted with a smaller extent of occurrence and thus Vulnerable under criterion B.
Reefs in this ecoregion are exposed to various environmental threats including tropical that occur occasionally, bringing heavy rain and high winds, and causing erosion and landslides. Consequently, the ecoregion is Critically Endangered under criterion C and for overall status.
#10/11-South Madagascar
Although relatively bigger, this ecoregion has the smallest proportion of Coral reefs in the WIO i.e., approx. 0.3%.
Reefs in this ecoregion are experiencing environmental degradation and the reefs are geographically constrained. As such, the ecoregion is endangered under criterion B and Critically Endangered under criterion C.
#11/11-Delagoa.
Delagoa ecoregion covers the entire coastline of Inhambane Mozambique and to the Northern parts of Kwazulu Nata province in South Africa.
ISimangaliso Wetland Park - Photo Credits: Triton Dive Lodge
The ecoregion is relatively large in terms of size 461,250 Kmsq and hosts the second smallest area of reefs in the WIO i.e., <1%.
Approximately 80% of the reefs in Delagoa enjoy some form of protection within a MPA.
But why are coral reefs in this ecoregion classified as vulnerable?
This ecoregion is facing a myriad of challenges including biotic disruption of the ecosystem components. This coupled with limited geographical space/distribution are pushing this ecoregion into the blink of near threatened groupers and vulnerable corals, algae, and, parrotfish.
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