INTRODUCTION: THE GLOBAL SIGNIFICANCE OF ISLAND BIODIVERSITY 47Box 3.1 Islands as hotspots and their place in Conservation International’s hotspots scheme
There are at least three separate hotspot concepts
employed within this book (and there are others
around in the literature). First, is a geological
usage, whereby hotspots are localized but long-
lived areas of volcanism overlying plumes in the
mantle (Chapter 2). Second, in the introduction to
this chapter we have applied the term
biodiversity hotspotto signify the concentration
of endemic species on isolated islands. This usage
is exemplified in BirdLife International’s Endemic
Bird Area (EBA) scheme, which delimits areas
supporting two or more species of birds with
breeding ranges of <50 000 km^2. Of the 218 EBAs
designated in the 1996 version of the scheme, 113
are island EBAs (21 continental islands, 21 large
oceanic islands, 55 small oceanic islands) (Long
et al. 1996). It is beyond doubt that the world’s
islands, and especially the tropical islands, hold a
disproportionately high degree of global diversity.
The third usage stems from an approach to
conservation prioritization put forward by the
British environmentalist Norman Myers in the late
1980s and recently promoted by the international
environmental NGO Conservation International
(Myerset al. 2000). Myers’ approach was to
combine a measure of the concentration of
biodiversity, with a simple index of threat, i.e. it is
really a hotspot–threatspot scheme. The version of
the CI hotspot scheme published in 2000
identified as ‘hotspots’ 25 areas of the world that
met two criteria: (1) the area should possess at
least 0.5% (1500) of the world’s plant species as
endemics, and (2) the area should have lost 70%
or more of its primary vegetation. Islands featured
prominently among the 25 CI 2000 hotspots,
which is appropriate given the high proportion of
global species losses over recent centuries that
have been island species. The CI hotspot
approach attracted unprecedented levels of
funding following the 2000 paper, and has
become extremely influential in strategic
conservation planning.
Partly as a result of the phenomenal fund-
raising success of the organization (aided by
the publication of the 2000 scheme in Nature
magazine), partly in response to new data on
diversity and habitat loss, and partly in an effort
to improve the fit of their scheme with another
major conservation planning effort (the WWF
ecoregions approach), CI revisited the boundaries
of their hotspots in a review carried out in 2004,
which resulted in a new map published on their
web site (CI 2005). We term this version the
CI 2005 hotspots. It depicts 34 hotspots, and
increases the coverage of the world’s islands,
particularly in the Pacific.
Although the stated reason for the addition of
the East Melanesian islands as one of the new
hotspots is recent habitat loss, to a large degree
the increased attention to islands represents
merely a widening of their cast to include islands
of high biodiversity value (e.g. the Galápagos and
Juan Fernández islands) that, as they put it, might
otherwise have slipped through the net of
conservation priorities. The approach is
acknowledged on their web site (CI 2005) to be
pragmatic, ‘with full recognition that the floristic
affiliations of these islands with their associated
land masses are often tenuous at best.’
Within the 34 CI 2005 hotspots, 9 areas (see
map) are composed exclusively of islands.
Organized by geographical region these are:
(1) the Caribbean islands (American ‘region’); (2)
Madagascar and adjacent islands (the Comoros,
Mascarenes, and Seychelles) (African region); (3)
East Melanesia, (4) Japan, (5) New Caledonia, (6)
New Zealand, (7) Philippines, (8) Polynesia-
Micronesia, and (9) Wallacea (all Asia-Pacific
region). Three more have a substantial proportion
of their diversity within islands: (10) the
Mediterranean basin (including the Atlantic
islands of Macaronesia) (Europe and Central Asia
region); (11) the Western Ghats and Sri Lanka,
and (12) Sundaland (both Asia-Pacific region). In
this expanded version of the scheme, almost all
tropical and subtropical islands of high biodiversity
value have been included, although it is evident
that were many of the individual archipelagos
considered as separate biogeographical entities
they would not have reached the qualifying
diversity-plus-threat criteria. Examples of newly
included islands in the 2005 scheme include the
Galápagos and Malpelo islands, lumped into a
Tumbes–Chocó-–Magdalena hotspot; the Juan