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CORALS, THE EXPOSED NERVES OF THE OCEAN | 9

A MIXED REVIEW THE EXCEPTION OF THE CORAL
TRIANGLE, SOUTHEAST ASIA
Four decades of data obtained from 12,000 sites
spread across 10 coral reef regions in the world
1
show the major role that increased sea surface tem- This coral region, at the intersection between the Pa-
perature plays in coral decline. Added to local envi- cific and Indian Oceans, which represents a third of
ronmental pressures, such as overfishing and water global coral reefs, remains mysteriously spared from
pollution, this major contributor has led to an alarming the trend towards erosion due to the warming of the
level of erosion of these ecosystems, which are home surface water. Despite a decline in their distribution
to one quarter of all marine species. However, the being recorded over the last decade, on average
report shows that many coral reefs have shown resi- these reefs have greater coral cover today (+4%)
lience and are able to recover if the conditions allow, than in 1983, when the first data were collected in
a conclusion which offers a note of hope for coral reef this area.
health in the long term.
Why have the corals of this region, despite being ex-
posed to high temperatures and various anthropoge-
REGIONAL VARIABILITIES nic stressors, experienced a different fate? Had they
already endured warming events in the past? “We
From the 10 regions studied, almost all have been lack data prior to 1978, but with 800 coral species
affected by a decline in their coral cover. The ROPME listed, the high biodiversity of the Coral Triangle could
sea area (around the Arabian Peninsula), South Asia, come into play in respect of the dynamic nature of
Australia and the Pacific exhibited the greatest loss its coral cover”, suggests French researcher Serge
and a parallel increase in algae cover. “The statistical Planes from CRIOBE, as one of the possible explana-
probabilities of decline have exceeded 75% in these tions. The Coral Triangle exception and its numerous
regions, as well as in East Asia and the West Pacific archipelagos could serve as an example to protect
Ocean – representing in total almost 50% of global coral regions.
coral reefs”, the authors anticipate.

In Southeast Asia, the pattern differs from other global
trends: no noticeable effect after the first mass blea-
ching event in 1998, pronounced resilience in 2019 IN
after the bleaching event in 2016. “With a population FIGURES
of 700 million inhabitants, this area suffers the most
anthropogenic pressure but, surprisingly, remains re-
latively stable”, explains Serge Planes, CNRS Director
of Research at CRIOBE. ■ 40 years of data
■ 73 countries involved
The report also highlighted the fact that, even if the ■ 12,000 sites
lapse of time between large scale coral bleaching ■ Over 300 scientific contributors
events was not sufficient for full coral reef recovery ■ 2 million individual observations
over the last ten years, partial recovery was observed ■ 3 years of data compilation and analysis
between 2002 and 2009, and again in 2019 (+0.7%), ■ 2 main indicators
proof of their capacity for resilience.

1. Australia, Brazil, Caribbean, East Asian Seas, Eastern Tropical
Pacific, Pacific, South Asia, Western Indian Ocean, Red Sea and
Gulf of Aden, ROPME sea area (around the Arabian Peninsula).