Le journal de l'IRD
n° 40 June-July-August 2007
Translator: Nicholas Flay
Abstracts for the international issue
Special trapping devices led to the capture of some highly peculiar crabs and
shrimps. These are now being studied.
O
© Xavier Desmier/Gamma
ne team studied the “filling-up” of
shallow caves and shelters under
the rocks of Santo.
The 20 sites surveyed, spread between
Cape Cumberland (north-west of Santo),
Cape Queiros (south-west), the east coast
of Santo and the islet of Aoré, off its
south coast, were found to contain
archaeological
or
palaeontological
remains.
Save the
swamp forest
Underground life
T
he island of Santo has the largest surface of karst relief of all the islands in
the Pacific, except for Papua-New Guinea.
T
© Claude Rives/Gamma
I
efore this survey, 36 species of ant
were known on the island. During
the work, scientists isolated 50 or so,
including about 15 that are certainly
allochthonous.
Among these was the fearsome electric
ant, Wasmannia auropunctata, which not
only stings humans but also decimates
insect communities.
These small ants, originally from tropical
America, and travel easily. They are present in many parts of the Pacific where
they cause enormous damage. Fortunately, its distribution on Santo is
apparently limited to a hectare and its
eradication is therefore feasible.
In almost every site, ceramics estimated at
more than 1000 years old were found,
and traces of hearth sites, sometimes
along with tools and fossils of rats, birds,
bats and lizards, probably consumed by
Melanesians of the 1st Era. Human bones
were also discovered, sometimes accompanied by canines of Suidae, probably a
sign of the elevated social status of the
person buried.
T
he “Waste land and aliens” module
of the expedition was devoted to the
role of humans on the local evolution of
biodiversity on the island. Its main objectives were to record the allochthonous
species of the island of Santo, by focusing
A second type of ancient forest appears
from 1000 metres. It is characterized by
the abundance and diversity of liverworts
(plant forms close to mosses) and by the
presence of huge trees of the genus
Metrosideros.
The effect of altitude
on arthropod communities
B
Waste land
and alien species
he botanists of the expedition were
struck by the strong contrast existing
between the almost intact forest, which
still persists above 600 metres of altitude,
in the west part of the island in particular,
and the “secondarization” of vegetation,
which predominates at lower levels.
From 600 to 1100 metres, the vegetation
is marked by the presence of a species of
conifer with no needles, of the genus
Agathis, commonly called kaori.
On the scale of the archipelago, Santo
could therefore hold the last intact examples of this type of plant formation.
Ibisca
© Xavier Desmier/Gamma
© IRD/ S. Carrière
p. 4 Partners
Caribbean
pecialists
on invasive
rodents have
compiled
an
inventory
of
this group of
mammals on
Santo.
Their first results indicate that at least four introduced
species are currently live there: the Pacific
rat (Rattus exulans), the black rat (Rattus
rattus), the brown rat (Rattus norvegicus)
and the common house mouse (Mus
musculus).
Only the Pacific rat could have arrived on
the island with the first Melanesians, who
also introduced pigs. The other three
rodents present on Santo would have
arrived later, with the Europeans.
Electric ant alert!
© A. Alcover
he 97 participants of the marine part
of the survey conducted their investigations from the beginning of August to
the end of October, mainly in the south of
the island. They applied a range of methods in their survey embracing the intertidal zone (the parts uncovered at low
tide) and parts down to 1000 metres’
depth, for collecting flora and fauna, with
a special effort for sampling molluscs,
decapod crustaceans (crabs, shrimps, hermit crabs).
The first results of this module are impressive: 1103 species of decapod crustaceans, 3000 to 4000 species of molluscs
and 486 species of fish were collected, of
which about 100, 1000 and 15 species,
respectively, are new to science. In addition around 250 species of algae and 7
marine phanerogams were collected
T
S
© IRD/J.-M. Boré
T
Two major types of ancient
forest
Of rodents
and men
On the traces of the past
he IRD is giving its support to the creation of a documentation centre on
ethnicity, development and social change in
South-East Asia, by the university of Chang
Mai in Thailand. This tool should help
achieve a more realistic analysis of the ethnic composition of societies, in this region
which is undergoing some deep social
changes.
© Amadou Bâ
he underground waters of Santo
apparently harbour quite a large
number of stygobiont crustaceans (strictly
adapted to the aquatic subterranean
habitat), which are transparent and blind.
Do they originally come from the sea? If
so, how have they succeeded in colonizing these underground waters?
The answers may be found in the anchialine caves, where both fresh water and
sea water are present, and the survey
team therefore concentrated especially
on exploring them.
An impressive harvest
T
he Pterocarpus
officinalis swamp
forest, a remarkable ecosystem of the
Caribbean, is threatened by the strong
pressure of human activity on the island
environment. Scientists from the Université Antilles-Guyane, the IRD, Cirad and
Iinra are studying Pterocarpus officinalis
and the symbiotic microorganisms associated with it. This research work opens up
interesting prospects for the conservation
and regeneration of this specific environment.
T
Marine diversity
p. 4 Partners
Ethnology and
documentation
in Thailand
on certain “target groups”, study their
distribution according to a gradient of
anthropization of sites and habitats, and
define how local people perceive these
species.
A team of 11 scientists set out on field
studies during the whole of October in
the eastern half of the island, where
Man’s presence has been most intense.
© Xavier Desmier/Gamma
M
ichel Gauthier, oceanographer, member of the Club
des Argonautes, advocates the use
of thermal energy from the seas.
The temperature differences between the ocean surface waters and
the deep layers can be utilized for
producing energy.
These differences are particularly
marked in the tropics and could
become an abundant source of
renewable energy.
The environmental and economic
considerations now fully justify reinvestment in this field of research,
dominated in the past by French
teams.
In the tropical ocean a temperature
gradient exists between the warm
surface water and the cold water at
some hundreds of metres depth
that can exceed 20°C.
This gradient can be taken advantage of to generate mechanical
energy.
Two approaches emerge as to the
harnessing of this resource. One is
based on large production units
that could provide up to 100 MW
and meet the needs of urban
agglomerations.
The other uses smaller installations
and combines the use of energy,
freshwater and nutrient qualities of
deep waters for developing aquaculture; these are multi-product units,
capable of supplying a few MW electrical power adapted to the needs of
small-size island communities.
Weird
and wonderful fauna in
underground Santo
© Claude Rives/Gamma
© IRD/B. Osès
wo hundred
and three
participants
were involved,
including 153
scientists, of 25 different nationalities.
More than four months were spent in
the field. The Santo expedition 2006 will
mark History as one of the largest biodiversity inventory operations ever realized.
This unprecedented scientific mobilization was organized to fulfil a sizeable
ambition: compile a comprehensive picture of the biodiversity situation of the
isle of Espiritu Santo (more commonly
called “Santo”), part of Vanuatu, by
including highly diversified and relatively
unknown groups of organisms like
insects, in terrestrial environments, and
molluscs and crustaceans, in marine
habitats. This inventory will help to
obtain a reliable assessment of the magnitude of biodiversity, in its most diverse
compartments and in the richest environments, to assess the relative significance of rare species in the composition
of communities and gain a better grasp
of the spatial dimension of biodiversity.
In that way a better idea should emerge
of the extent to which a site is representative at the regional scale.
rom mid November to mid December,
the “FMR” module (about 90 participants) applied their attention to biodiversity of ancient forests and surface freshwater bodies.
The members of this team were divided
according to their working approach: several small groups travelled across Santo
collecting species of flowers or fruits on
their way, while a “sedentary” group was
based above the village of Pénaorou, in a
bush camp built with great craftsmanship
by people from the village.
n forests, and particularly in the tropical regions, the animal group with the
most species represented is the arthropods (insects, arachnids, collemboles). But
at what stage of vegetation are these
species the most numerous?
And how does the structure of their communities vary with parameters such as
altitude?
For one month, a dozen entomologists
conducted some highly precisely targeted
sampling.
This work should reveal which arthropods
depend the most strongly on altitude to
live in such habitats.
That would provide a
good model for
assessing and anticipating the consequences of climate
change.
The mission resulted
in the collection of
between 100 and
200 species of arachnid belonging to
25 different families
and also 47 species
of fish and 28 species of freshwater
crustaceans
from
Santo.
© Laurent Pyot/Gamma
T
F
© Xavier Desmier/Gamma
© IRD/J.-M. Boré
Santo 2006
Destination
biodiversity
Why not use
heat energy
from the seas ?
Forests, mountains,
rivers
© Xavier Desmier/Gamma
It is also one of the least known in terms
of subterranean fauna, which prompted
field research by about 20 specialists of
such habitats. They formed the “karst”
module of the expedition, which set itself
up on the island for the whole of
September.
Special feature p. 7-10
p. 1, 15 Tribune
Consult the articles in full on the IRD Internet site: http://www.ird.fr