344
in the scientifi c community due to science progress. Acidifi cation is a
good example appearing less than two decades ago and presently the most
worrying factor, as well as adaptation of corals to temperature which was
unsuspected one decade ago. These facts lead us to consider that published
predictions will be modifi ed by new discoveries and incline us to be cautious. We comment on the catastrophic ambiance which characterises the
scientifi c production on the future of coral reefs amplifi ed by the media in
our society.
1
Introduction
Coral reefs are the richest marine ecosystem in
terms of biodiversity, equivalent to the rainforests
on land. According to the latest report of the
IPCC ( 2014 ), this is the most threatened ecosystem on the planet. Although its surface in tropical
coastal areas, reefs and lagoons, is of the order of
half a million square kilometres, the coral ecosystem brings humanity considerable services
(services rendus, voir plus haut) to over half a billion people in nearly 80 countries. Natural and
anthropogenic degradation has resulted in a
decline in health over the past century and especially for the past 50 years. A global health status
needs to be considered regionally. Predictions of
global change, demography, development and
climate change lead to pessimism for the near
future argued by many scientists. It should put
these items with a view on what scientists said
since half a century and in a broader temporal
context, over millions of years, where we have to
distinguish regarding humanity and the planet.
2
Coral Reefs
Coral reefs are the largest ever built construction
on the surface of the planet by living beings and
that persisted over time. Corals behind these
buildings are primitive colonial invertebrates
whose basic unit is the polyp, a kind of small
anemone. Due to their association with symbiotic
algae, zooxanthellae per billion in cells of polyps, corals have the ability to build a limestone
skeleton. But this association limits corals living
in shallow waters for photosynthesis which is
essential for their symbiotic algae. Corals also
require warm waters. All these constraints limit
their distribution to tropical and subtropical
coastlines.
This association is symbiotic and both partners have metabolic benefi ts. The ability of calcifi cation is prodigious; a square metre of corals
can produce up to 10 kg of calcium carbonate per
year, and dead coral skeletons accumulate on top
of each other meanwhile undergoing eustatic or
tectonic movements. There are some 650 species
of these symbiotic corals, hermatypic and reef
builders, while other species, ahermatypic and
without zooxanthellae, are living in the depths of
the ocean.
Coral reefs are distributed in two biogeographic provinces: the fi rst is the Indo-Pacifi c
from the African east coast to the Pacifi c without
really being drawn to west American shores and
the second is the Caribbean. Species of reef complexes of these two provinces are not the same.
The reefs cover about 280,000 km
2 as built construction (Spalding et al. 2001 ), but with sandy
lagoons and associated ecosystems such as seagrass beds and mangroves, the total area exceeds
600,000 km
2
. The Great Barrier Reef alone,
which stretches over 2,000 km along the eastern
coast of Australia, covers more than 350,000 km
2 .
After Australia and Indonesia, France has the
third largest area of coral reef ecosystem mainly
with New Caledonia (35,000 km
2 ) and French
B. Salvat
in the scientifi c community due to science progress. Acidifi cation is a
good example appearing less than two decades ago and presently the most
worrying factor, as well as adaptation of corals to temperature which was
unsuspected one decade ago. These facts lead us to consider that published
predictions will be modifi ed by new discoveries and incline us to be cautious. We comment on the catastrophic ambiance which characterises the
scientifi c production on the future of coral reefs amplifi ed by the media in
our society.
1
Introduction
Coral reefs are the richest marine ecosystem in
terms of biodiversity, equivalent to the rainforests
on land. According to the latest report of the
IPCC ( 2014 ), this is the most threatened ecosystem on the planet. Although its surface in tropical
coastal areas, reefs and lagoons, is of the order of
half a million square kilometres, the coral ecosystem brings humanity considerable services
(services rendus, voir plus haut) to over half a billion people in nearly 80 countries. Natural and
anthropogenic degradation has resulted in a
decline in health over the past century and especially for the past 50 years. A global health status
needs to be considered regionally. Predictions of
global change, demography, development and
climate change lead to pessimism for the near
future argued by many scientists. It should put
these items with a view on what scientists said
since half a century and in a broader temporal
context, over millions of years, where we have to
distinguish regarding humanity and the planet.
2
Coral Reefs
Coral reefs are the largest ever built construction
on the surface of the planet by living beings and
that persisted over time. Corals behind these
buildings are primitive colonial invertebrates
whose basic unit is the polyp, a kind of small
anemone. Due to their association with symbiotic
algae, zooxanthellae per billion in cells of polyps, corals have the ability to build a limestone
skeleton. But this association limits corals living
in shallow waters for photosynthesis which is
essential for their symbiotic algae. Corals also
require warm waters. All these constraints limit
their distribution to tropical and subtropical
coastlines.
This association is symbiotic and both partners have metabolic benefi ts. The ability of calcifi cation is prodigious; a square metre of corals
can produce up to 10 kg of calcium carbonate per
year, and dead coral skeletons accumulate on top
of each other meanwhile undergoing eustatic or
tectonic movements. There are some 650 species
of these symbiotic corals, hermatypic and reef
builders, while other species, ahermatypic and
without zooxanthellae, are living in the depths of
the ocean.
Coral reefs are distributed in two biogeographic provinces: the fi rst is the Indo-Pacifi c
from the African east coast to the Pacifi c without
really being drawn to west American shores and
the second is the Caribbean. Species of reef complexes of these two provinces are not the same.
The reefs cover about 280,000 km
2 as built construction (Spalding et al. 2001 ), but with sandy
lagoons and associated ecosystems such as seagrass beds and mangroves, the total area exceeds
600,000 km
2
. The Great Barrier Reef alone,
which stretches over 2,000 km along the eastern
coast of Australia, covers more than 350,000 km
2 .
After Australia and Indonesia, France has the
third largest area of coral reef ecosystem mainly
with New Caledonia (35,000 km
2 ) and French
B. Salvat