GCRMN_COI_2017-Western Indian Ocean Reef Status

Coral reef status report for the Western Indian Ocean (2017)
Global Coral Reef Monitoring Network
Recognising the importance of coral reefs socio-economic and ecological values and their
general degradation, countries in the Western Indian Ocean (WIO) through the Indian
Ocean Commission, and Nairobi Convention have aligned with the Global Coral Reef
Monitoring Network (GCRMN) of the International Coral Reef Initiative (ICRI) to contribute
to sustainable management of the vital ecosystems. A regional framework has been set up
for monitoring the status of coral reefs and its associated biodiversity.
This report presents the latest compilation and quantitative assessment of data on coral
reef health by the regional monitoring networks in the WIO, adding to the global GCRMN
reports published from 1999 to 2008.
The main objective of this report is to provide updated information on the status of coral
reefs in the region, up to and including the impact of the 2016 third global coral bleaching
event. Secondary objectives are to a) illustrate broad patterns that explain the differing
health status of various reefs, and the prospects for reef management in relation to this,
and b) present regional drivers of change and how they may evolve in coming years, to
help countries in planning for impacts and recovery of coral reefs.
Part I of the report provides a regional overview,
documenting quantitative trends for Western Indian
Ocean reef corals, fleshy algae and fishes based on
data from 822 reef locations from 1992 to 2016,
from 9 countries. It also documents coral bleaching
and mortality in early 2016, based on 699 reports of
bleaching from 54 organizations and over 80 observers
across all 9 countries. Part II of the report presents
country-level summaries of coral reef monitoring up to
2015/16 and observations of coral bleaching in 2016,
distilled from national reports prepared by the National
Coral Reef Task Forces (where applicable) from each of
the countries.
Overall reef health. The results indicate that hard coral
cover declined substantially across the region immediately
after the 1998 bleaching event, and in the years since,
average coral cover has remained at about 30% which
is 25% lower than pre-bleaching levels. The subsequent
increase in algae cover lagged by a year, rising rapidly from
1998 to 2000, then remaining at about 35% for the last
15 years, 2.5 times higher than before 1998. Aggregated
at the regional level, both coral and fleshy algal cover have
remained essentially the same in the post-1998 period,
however coral cover has differed greatly among countries.
The Seychelles and Kenya suffered the greatest mortality
of corals in 1998, but since then have shown good
recovery of corals. South Africa has shown slight increases
in coral cover since monitoring started. The other countries
(Comoros, France, Madagascar, Mauritius, Mozambique
and Tanzania) have all shown a progressive decline in
overall cover since monitoring began in each country.
In the past, coral cover was higher,
algae cover low, and fish diverse and
abundant (above). Now, coral cover is
lower, algal cover is equal to coral and
increasing, and fish populations are
low (below).
EXECUTIVE SUMMARY
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