WORLD ATLAS OF CORAL REEFS
the way to the sea surface. The long offshore reef tracts of
Florida, Cuba and elsewhere rival many true barrier reefs
in length, but are frequently not regarded as true barrier
reefs because they are only separated from the mainland
by a very shallow lagoon, or because they are not located
on the edge of the continental shelf. Small physical
structures, often lying within the wider formation of a
barrier or atoll lagoon, are often referred to as patch reefs.
Perhaps more importantly, there are significant areas
around the world where there are coral communities
which perform the same ecological function as coral reefs,
but lack a clear physical structure. These include recent
formations where there may be a thin veneer of live coral,
or they may be physical reefs, but not yet mature or clearly
visible. For clarity such structures are frequently referred to
as coral communities, submerged reefs, or sub-surface reefs.
Global distribution
Charles Darwin was probably the first person to prepare
a global map of coral reefs. His and other efforts are
described in Chapter 3. Coral reefs are restricted to a
broad swathe, roughly confined to the tropics, and circling
most of the globe (Map I.I). Within this range they are
far from evenly distributed, with large areas confmed to
remote island regions and offshore areas far from major
land masses. Further investigation shows that coral reefs
are largely absent from the Central Atlantic and the shores
of West Africa, they are highly restricted along the western
(Pacific) shores of the Americas, and are also restricted
along the coastline of South Asia from Pakistan to
Bangladesh.
Using the maps shown in this publication it is
possible to estimate the total area of coral reefs in the
world. Although there are clear limitations to such
estimates, these figures are clearly valuable for getting an
overall perspective on the area of coral reefs in the world,
and in allowing for regional comparisons. There are an
estimated 284 300 square kilometers of coral reefs
worldwide'. This figure represents only 0.089 percent of
the world's oceans and less than 1.2 percent of the world's
continental shelf area. Thus, at the global scale, coral reefs
are a rare habitat. Further analysis clearly shows that the
great majority of coral reefs are found in the region known
as the Indo-Pacific, which stretches from the Red Sea to
the Central Pacific. Less than 8 percent of the world's
reefs are found in the Caribbean and Atlantic.
Zooming in to these maps, new patterns emerge at
finer resolutions. Reefs are often limited in their development in the nearshore waters of large continental land
masses, although barrier structures are widespread in such
places. They are poorly developed close to large river
mouths. In contrast, they are particularly well developed
around islands and along the coastlines of drier continental areas.
In order to understand these patterns of reef
distribution it is necessary to look at the organisms which
make up the coral reef ecosystem. The factors impinging
on their evolution, dispersion, and survival are the same
factors which have created the patterns in coral reef
distribution that we see today.
1, The reef area figures used tfiroughout this work are based on a new
calculation, and replace the early estimate provided by Spalding and Grenfell
119971 of 255 000 square kilometers. It is likely, as mapping work continues,
that such figures will continue to be refined and improved. This may lead to
further upwards adjustment of the global total, although in some areas
there is also likely to be some reduction of figures as maps are improved.
Thus It seems unlikely that a final" figure would exceed 300 000 square
kilometers.
Map 1.1: The coral reefs of the world
W:-^ ,."..-»?;;%
-^>^
r-l^i'
30
20
.
10
—
10
20
30
Distribution of scleractlnian corals
the way to the sea surface. The long offshore reef tracts of
Florida, Cuba and elsewhere rival many true barrier reefs
in length, but are frequently not regarded as true barrier
reefs because they are only separated from the mainland
by a very shallow lagoon, or because they are not located
on the edge of the continental shelf. Small physical
structures, often lying within the wider formation of a
barrier or atoll lagoon, are often referred to as patch reefs.
Perhaps more importantly, there are significant areas
around the world where there are coral communities
which perform the same ecological function as coral reefs,
but lack a clear physical structure. These include recent
formations where there may be a thin veneer of live coral,
or they may be physical reefs, but not yet mature or clearly
visible. For clarity such structures are frequently referred to
as coral communities, submerged reefs, or sub-surface reefs.
Global distribution
Charles Darwin was probably the first person to prepare
a global map of coral reefs. His and other efforts are
described in Chapter 3. Coral reefs are restricted to a
broad swathe, roughly confined to the tropics, and circling
most of the globe (Map I.I). Within this range they are
far from evenly distributed, with large areas confmed to
remote island regions and offshore areas far from major
land masses. Further investigation shows that coral reefs
are largely absent from the Central Atlantic and the shores
of West Africa, they are highly restricted along the western
(Pacific) shores of the Americas, and are also restricted
along the coastline of South Asia from Pakistan to
Bangladesh.
Using the maps shown in this publication it is
possible to estimate the total area of coral reefs in the
world. Although there are clear limitations to such
estimates, these figures are clearly valuable for getting an
overall perspective on the area of coral reefs in the world,
and in allowing for regional comparisons. There are an
estimated 284 300 square kilometers of coral reefs
worldwide'. This figure represents only 0.089 percent of
the world's oceans and less than 1.2 percent of the world's
continental shelf area. Thus, at the global scale, coral reefs
are a rare habitat. Further analysis clearly shows that the
great majority of coral reefs are found in the region known
as the Indo-Pacific, which stretches from the Red Sea to
the Central Pacific. Less than 8 percent of the world's
reefs are found in the Caribbean and Atlantic.
Zooming in to these maps, new patterns emerge at
finer resolutions. Reefs are often limited in their development in the nearshore waters of large continental land
masses, although barrier structures are widespread in such
places. They are poorly developed close to large river
mouths. In contrast, they are particularly well developed
around islands and along the coastlines of drier continental areas.
In order to understand these patterns of reef
distribution it is necessary to look at the organisms which
make up the coral reef ecosystem. The factors impinging
on their evolution, dispersion, and survival are the same
factors which have created the patterns in coral reef
distribution that we see today.
1, The reef area figures used tfiroughout this work are based on a new
calculation, and replace the early estimate provided by Spalding and Grenfell
119971 of 255 000 square kilometers. It is likely, as mapping work continues,
that such figures will continue to be refined and improved. This may lead to
further upwards adjustment of the global total, although in some areas
there is also likely to be some reduction of figures as maps are improved.
Thus It seems unlikely that a final" figure would exceed 300 000 square
kilometers.
Map 1.1: The coral reefs of the world
W:-^ ,."..-»?;;%
-^>^
r-l^i'
30
20
.
10
—
10
20
30
Distribution of scleractlnian corals