Moreover, by combining the results of BCD-
RICH, BCD-AREA, and BCD-POP, we identi-
fied three “core regions” of global biocultur-
al diversity that include countries of various
sizes and populations (Figure 3):
Q The Amazon Basin, consisting of Brazil,
Columbia, and Peru, which ranked highly
in BCD-RICH; Ecuador, which ranked
highly in BCD-AREA; and French Guiana,
Suriname, and Guyana, which ranked
highly in BCD-POP.
Q Central Africa, consisting of Nigeria,
Cameroon, and the Democratic Republic
of Congo (BCD-RICH), Tanzania (BCD-
AREA), and Gabon and Congo (BCD-
POP).
Q Indomalaysia/Melanesia, consisting of
Papua New Guinea and Indonesia (BCD-
RICH), Malaysia and Brunei (BCD-AREA),
and Solomon Islands (BCD-POP).Limitations of the IBCD
It should be remembered that the aim of
any index, including the IBCD, is to gauge
current conditions and trends; it is not
intended to substitute for in-depth analysis.
Two of the limitations of the IBCD relate to
its sensitivity to trends over time, and theavailability of data. The IBCD indices are
measures of richness based on the number
of languages, religions, ethnic groups or
species of bird or mammal in a country. The
underlying data record only the presence of
absence of a particular language, religion,
ethnic group or species of bird or mammal
within each country, but not its relative
abundance. Therefore the IBCD is sensitive
to changes in diversity only when there is
an increase or decrease in the number of
languages, religions, ethnic groups or
species in a country, but not when there is
a change in their relative abundance. This is
a limitation in the index, as the IBCD is sen-
sitive only to extinctions, or introductions,
but not to declines in population, or num-
bers of individuals, as long as that popula-
tion remains greater than one. Extinction,
however, is only the ultimate end point of a
terminal decline, which would not be picked
up by the IBCD.To be able to track
trends in biocul-
tural diversity in a
country where the
overall number of
languages, reli-
gions, ethnic
groups and
species remains
unchanged over
time, it would be
necessary to mon-
itor the numbers
of speakers of
each language,
practitioners of
each religion,
members of each ethnic group and the pop-
ulations of each species. Data availability
and quality are the ultimate limiting factors
for any index. All global environmental and
cultural indices are based on datasets that
are incomplete, possibly out of date, or of
uneven quality. Furthermore, these indices
rely on simple proxies to measure complexHistory, cculture aand cconservation
Figure 3. The three “core regions” of global biocultural diversity.