Amazon rainforest is home to 16,000 tree species, estimate suggests

Almost four hundred billion trees
belonging to 16,000 different species
grow in the Amazon, according to a
new estimate.
More than 100 experts analysed data
from 1,170 surveys to come up with
the figures, highlighting the
extraordinary scale and diversity of
the Amazon rain forest.
The vast size and difficult terrain of
the Amazon Basin has historically
restricted studies of tree communities
to a local or regional level, making it
difficult to see the "big picture". This
lack of information about
Amazonian flora on a basin-wide
scale has hindered science and
conservation efforts, according to
experts.
"In essence, this means that the
largest pool of tropical carbon on
Earth has been a black box for
ecologists, and conservationists don't
know which Amazonian tree species
face the most severe threats of
extinction," said research author Dr
Nigel Pitman, from the Field Museum
in Chicago, US.
The new findings, published in the
journal Science , provide the first
estimates of the abundance,
frequency and distribution of many
thousands of Amazonian trees.
Extrapolating the data, compiled over
10 years, suggests that greater
Amazonia harbours around 390
billion individual trees, including
Brazil nut, chocolate and acai berry.
The area covered encompasses the
Amazon Basin (including parts of
Brazil, Peru, Columbia) and the
Guiana Shield (Guyana, Suriname,
and French Guiana), spanning an
area roughly the size of the 48 North
American states. In total roughly
16,000 tree species are believed to
exist in the Amazon, but half the total
number of trees are thought to belong
to just 227 species.
"Thus, the most common species of
trees in the Amazon now not only
have a number, they also have a
name," said co-author Dr Hans ter
Steege, from the Naturalis
Biodiversity Centre in the
Netherlands. "This is very valuable
information for further research and
policymaking."
Almost none of the most dominant
species are widespread throughout the
Amazon. Instead, most are abundant
in a particular region or forest type,
such as swamps or uplands.
The study also offers insights into the
rarest tree species in the Amazon.
According to a mathematical model
used in the study, roughly 6,000
Amazonian tree species have
populations of fewer than 1,000
individuals. This would automatically
qualify them for inclusion in the
International Union for Conservation
of Nature (IUCN) Red List of
Threatened Species - if they could be
found and identified.
US ecologist and co-author Professor
Miles Silman, from Wake Forest
University, said: "Just like physicists'
models tell them that dark matter
accounts for much of the universe,
our models tell us that species too
rare to find account for much of the
planet's biodiversity. That's a real
problem for conservation, because
the species at the greatest risk of
extinction may disappear before we
ever find them."
Why some species are hyperdominant
and others are rare remains an
unanswered question. Large numbers
of hyperdominants, including Brazil
nut, chocolate, rubber and acai
berry, have been cultivated and used
for millennia by human populations,
the scientists note.
"There's a really interesting debate
shaping up between people who think
that hyperdominant trees are
common because pre-1492
indigenous groups farmed them, and
people who think those trees were
dominant long before humans ever
arrived in the Americas," said Dr
Pitman.