Le journal de l'IRD
n° 39 March-April-May 2007
Translator: Nicholas Flay
Abstracts for the international issue
Megaliths and rock art,
little-known heritage
of Cameroon
A
p. 8-9 Research
tion about the average and seasonal biogeochemical conditions.
At the core
of the Humboldt current
A new examination of the nutrition of
the anchovy, the dominantly important
species, seriously calls into question the
ecosystem function models.
●
Scientists are beginning to understand
and quantify the processes connecting
large-scale (i.e. regional) oceanography,
productivity of the system and interactions between compartments and fishing
activity.
© IRD/L. Ortlieb
© IRD/A. Bertrand
Researchers can now give a precise
description to the “life cycle” of El Niño
events, even though the fact that each
such event has its own characteristics was
already understood.
They can also compare them and examine
in greater detail the underlying mechanisms which cause them and those they
induce themselves.
© IRD/Y. Arnaud
Satellites view
glacier melting
In palaeoceanography, the first studies
on sedimentary drill cores from the continental shelf showed that a substantial
change in the climate regime took place
during the first half of the 19th Century.
It was a time of emergence from the
“Little Ice Age” and of a global warming.
In the 1820s, a strong increase in primary
production and of pelagic fish stocks
occurred, along with a change in the
regional impacts of the El Niño system.
●
● Although the bodies in charge of
resources management are adopting
more and more cautious approaches,
fishing overcapacity is at such a level that
overfishing of some species is inevitable.
This is particularly the case for the hake
stock, which is seriously affected. This
species is under intense fishing pressure
which has resulted in a decrease in its
reproductive capacity and has lowered
the proportion of large males to a point
where females find difficulty in finding
partners.
© IRD/L. Ortlieb
he Humboldt current system, which
runs alongside the coasts of Peru and
Chile, is the world’s most productive
oceanic region for fish.
Although it covers less than 1% of the
global ocean surface, it produces on average more than 10% of the world’s landings.
This high level of fishing productivity is
linked to a strong primary production
(phytoplankton),
characteristic
of
upwelling ecosystems.
However, the Humboldt current is subjected to the influence of El Niño events
which directly affect it by changing the
wind regime, the marine currents and the
thickness of the surface layer of warm
water.
Consequently, the dynamics of this current is closely tied with the ocean-atmosphere couple.
New in situ observation capabilities, satellite observation, historical series analyses
and digital modelling tools have enabled
scientists to apply their efforts to the
paradoxes of the Humboldt current system and to obtain an overall picture of
the processes involved.
This multidisciplinary approach to the
characteristics of the Humboldt current
system has already yielded some significant results, in particular:
Models are now employed by modelling and field ecologists to place the biological data gathered in situ (acoustics
data, fisheries data) in the three-dimensional context of the physical characteristics of the environment.
●
The shared development and use of the
Peruvian Marine Institute (Imarpe) database has yielded significant new informa-
●
© IRD/A. Bertrand
●
Such shrinkage is still 4 to 7 m between
4 400 and 5 000 m, and becomes 2 m
above 5 000 m. Estimates made from
satellite images yield an average balance
of – 0.7 to – 0.85 m per year on the
915 km2 of glaciers studied, which represents a total loss of water of 3.9 km3 in
5 years.
Satellite tracking of ships can now show
the positioning along fishing routes, postcampaign, of the whole fleet; this helps
the practice of spatially based management of resources, based on exhaustive
data of catches and the fishing effort.
Study of the paths taken by fishing vessels
also provides operational tools useful for
real-time monitoring of pelagic fish
stocks. This method, developed in Peru by
the IRD, is starting to be applied to
European fisheries in the Ceder project
(http://ceder.jrc.cec.eu.int/).
●
© IRD/A. Bertrand
p. 1 News
S
study on the archaeological vestiges
of Cameroon has revealed the
country’s impressive and largely unknown
heritage. This field investigation is part of
an ambitious operation devoted to megalith culture and rock art. The aim is to
identify the symbolic content then to link
it to past and present Cameroon societies.
A great number and variety of structures
have been found.
T
Moreover, in the field of health, the usual
role of women concerning “reproductive
health” and that of their children gives
them knowledge of how the health-care
system works.
Men, who have not acquired this experience and have more difficulty in fitting
visits to health facilities in with their work
timetable, rarely develop the social skills
and practices that help deal with the
health system.
Furthermore, a proportion of the failures
or obstacles that beset HIV prevention programmes stems from an omission to take
sufficient account of men, as sexual partners and as fathers, in prevention programmes.
1. The CNRS, Inserm, Cirad, Institut
Pasteur, the Conférence des Présidents
d’Universités and the IRD.
cientists from research units Great Ice
and Legos have used satellite imagery
for making comparisons of Himalayan
glacier topographies determined between
2000 and 2004, on an area of 915 km2
located in the Spiti/Lahaul region
(Himachal Pradesh, India).
Their thickness appears to have decreased
by an average of 0.85 m per year over this
period. The largest glaciers whose terminal tongues reach the lowest altitudes
(about 4 000 m) showed a distinct regression, with a loss of 8 to 10 m of their
thickness below 4 400 m.
A
●
© IRD/M. Dukhan
fter a
year of
preparation,
the agency
that the IRD
has
been
commissioned to set up
to enhance
French research effort for development is now in operation in 2007.
French organizations and universities1 have adopted a collective
approach in order to build this
agency geared to objectives, programming and funding.
There can be no research without
partners from the South, and no
Agency either.
Consequently the Steering Committee the Agency has set up to
guide it has an equally distributed
composition, with eight members
designated by the French research
establishments and eight figures
from abroad, seven of whom are
from the three continents of the
South and four put forward by
international research bodies. This
strict parity is a strong sign of the
Agency’s aims and ambitions.
The first discussions, on priority
research themes or on calls for tender, bear the strong imprint of this
collective initiative involving North
and South.
Financial resources are provided in
part by a contribution from the
establishments which signal in this
way their commitment to the initiative.
The Agency will make a decisive
contribution to placing French
research as a whole in the service of
development, thanks to its very role
as a mutualizing force.
© R. Oslisly
W
the 16th Century although this
does not mean that others
might not be more ancient.
All aspects of study remain
to be done in this domain;
inventories, probes, excavations, dating to try and
find out when these stone
cultures began and to
understand better the
Cameroon populations
that built them.
It appears in certain cases
that an undeniable appropriation of these megaliths has taken place. At
Bamali and Bambalang, the
local people use the power of
the megalith for ritualistic purposes in
order to gain protection. In the Nkambé
region, when the chief dies, a basalt
monolith is erected in the courtyard of
the chief’s residence. These two remarkable examples reveal how a megalithic
tradition can be perpetuated.
Megalithic culture has been widely studied in neighbouring Nigeria, in the
Central African Republic, Senegal and
Gambia. However, in Cameroon little
documentation has been made, even
though the country possesses such a
wealth of sites that previously undescribed examples are still being discovered. The study areas are three broad
geographical regions of Cameroon, characterized by open landscapes: the West,
the North and the East.
The megaliths are the
first forms of stone architecture and in the three
regions their configurations are varied: there are
isolated monoliths, monoliths set in groups;
sculptured, aligned, arrangements of standing
stones in squares and circles and tumuli. Two
megalith structures in
the West were dated to
Oslis
ly
Gender and Aids
omen and men are not equal
with regard to the risk of exposure to Aids. In Africa, the only continent
where more women than men are affected by the disease, their vulnerability is
linked to biological and social factors.
From a biological point of view, the risk
of Aids transmission from men to
women during heterosexual intercourse
is about twice as high as that from
women to men.
This universal biological risk is compounded by the many culturally and socially
related problems women are confronted
with when they try to protect themselves.
It is still the man who decides about prevention and women have little room for
negotiation when they wish to protect
themselves against HIV or sexually transmitted diseases.
Nevertheless, most programmes to provide increased access to subsidized antiretroviral drugs developed with the backing of international initiatives, now
available in practically all African countries, take charge of women more than
men. Some women gain access to treatment because they have taken part in a
programme of prevention of MotherChild transmission and women are more
likely than men to seek assistance from
associations, which help them in the
health measures they take.
by Jean-François Girard
Chairman of the IRD
© IRD/A. Debray
p. 10 Research
© R.
The Agency:
Year 1
p. 7 Research
© R. Oslisly
p. 1 Editorial
The hake population is now more vulnerable to environmental stress and especially to El Niño events. The population’s
resilience has fallen so dramatically that a
complete collapse of the population is
possible even if all fishing pressure were
to cease.
Consult the articles in full on the IRD Internet site: http://www.ird.fr