Download fique scienti Actualité Retreating glaciers

Actualité scientifique
Scientific news
March 2012
Thawing is taking place the
world over as a result of
global warming, and the
diversity of mountain
ecosystems is thus under
threat. IRD researchers and
their partners1, writing in the
journal Nature Climate
Change, have just revealed
that the retreating glaciers
may lead to the extinction of
between 10 to 40% of
aquatic fauna depending on
the region - tropical,
temperate or arctic.
Ecologists have been
studying the biodiversity of
streams created by
meltwater in the páramos (a
typical landscape feature in
the Andes) situated at an
altitude of between 3,500
and 5,000m. The species
that make these streams
their home, mostly insects,
are endemic to these
extreme environments and
subjected to a combination
of ice and intense sunlight,
aggressive winds, etc. The
disappearance of such
exceptional fauna would
lead to a loss in the
conservation of such
ecosystems, which are
unique in the world.
However invertebrates also
have a role to play as
bio-indicators, particularly
regarding the quality of the
water that supplies
downstream towns and
cities such as Quito, the
capital of Ecuador.
Retreating glaciers
are a threat to biodiversity
© IRD / O. Dangles
N° 398
Actualidad cientifica
If the glaciers melt entirely, up to 40% of species living in streams formed by meltwater may become extinct (shown here at the Antisana glacier in Ecuador)
The projected disappearance of small glaciers*
worldwide threatens to eliminate the water supply
for numerous towns in valleys, such as the Ecuadorian capital Quito, fed by the rivers that flow down
from the surrounding mountains. But retreating ice
is also a threat to freshwater fauna. According to a
study published in Nature Climate Change, the local
and regional diversity of mountain aquatic fauna will
be reduced considerably if predictions are realised.
Until now, the impact of global thawing on biodiversity in watercourses had never been calculated.
macroinvertebrates - mainly insect larvae such as
Ephemeroptera, Trichoptera and Diptera. These
organisms that mostly live at the base of glacial
torrents belong to a group that has already been
studied extensively, whose environmental needs are
relatively well known, and as such can be considered as a model for scientists. For example,
following over a year of regular sampling, over 150
species of invertebrates have been identified living
in just one páramo in the Antisana volcano, the
‘water tower’ serving Quito.
Insects, a model group
Extinction between 10 and 40%
The research team has focused on the future for
populations in streams formed by meltwater in the
Alps, Alaska and the equatorial Andes, where the
IRD researchers have been working. The IRD team
has collected samples from around fifty different
sites in the páramos. These highly particular
herbaceous ecosystems are typical of Andean
summits, situated at over 3,500m in altitude between
the limits of the forest and the permanent snowline.
Ecologists have calculated the population of
In the three regions being studied - temperate, arctic
and tropical -, the research team has analysed the
reaction of three key elements to the changes in
glacial coverage: the local taxonomic diversity (the
number of different species present in a stream, for
example), or at a regional level (across a hydrographic network, for example), and the variation in this
diversity between watercourses. Thanks to this
sampling at varying distances from glaciers, the data
has revealed that the local diversity increases when
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moving further downstream. In addition, it seems that
the populations in different streams at the same altitude is highly consistent. Within a distance of around
one hundred metres, the populations found in two
streams that appear the same can be substantially
different according to which glacier they drain from.
Indeed, the Andean glaciers have diverse actions,
melting slower or faster according to their size, which
varies greatly, and their exposure to sunlight, for
example.
According to these tests, in addition to data from
aquatic population studies dating back over 20 years,
as soon as the glacial coverage is reduced to the point
where it only covers 30 to 50% of the drainage basin,
several species begin to disappear. And if the glaciers
melted completely, between 11 and 38% of the
regional diversity might become extinct, depending on
the area being studied, including endemic species.
Earth, but also inexorably threatened by extinction if
glaciers continue to recede.
Contacts
Olivier DANGLES,
IRD researcher
Tél. : (+593) 95651883
[email protected]
UR 072, Biodiversité et évolution des
complexes plantes-insectes ravageursantagonistes – BEI)
Address
Pontificia Universidad Católica
del Ecuador
Laboratorio de Entomología
oficina 207, Edificio de Ciencias
Av. 12 de Octubre
Quito - Equateur
A loss in services rendered
This study has demonstrated the crucial role played
by glaciers in the creation and dynamism of biodiversity, and thus the impact of their reduction for the
preservation of this diversity. But this is not the only
blow for the planet. The insects play a major role in
the functioning of mountain ecosystems, particularly through decomposition of organic matter that
enables soil to be formed. They can also be useful
downstream, for the 2 million inhabitants of Quito,
for example. For these organisms also function as
bio-indicators for the quality of the water that
supplies the city and can be used as a tool by those
who manage this resource. The threat of extinction
of several species has led to fears for the loss of
these crucial services provided by the ecosystem.
Dean Jacobsen,
associate professor
at the University of Copenhagen
Tél. : (+45) 35321913
[email protected]
Freshwater Biological Laboratory
Address
Department of Biology,
University of Copenhagen
Helsingørsgade 51, DK-3400 Hillerød
Denmark
References
Jacobsen D., Milner A.M., Brown L.E.,
Dangles Olivier. Biodiversity under threat
in glacier-fed river systems. Nature Climate
Change, 2012, doi:10.1038/nclimate1435.
Jacobsen D., Dangles Olivier.
Environmental harshness and global
richness patterns in glacier-fed streams.
2011. Global Ecology and Biogeography,
doi:10.1111/j.1466-8238.2011.00699.x
Dangles Olivier, Crespo-Pérez Verónica,
Aandino P., Espinosa R, Calvez Roger,
Jacobsen D. Predicting richness effects
on ecosystem function in natural
communities: insights from high elevation
streams. Ecology, 2011, 92(3), 733–743.
Fauna unique to these areas
High mountain regions are like isolated islets - migration by new species is restricted and they are favourable to speciation2. Low temperatures and atmospheric pressure, intense solar rays, irregular rainfall,
searing winds, ice... all of these extreme conditions
have driven the native species to adapt in singular
ways, particularly in the tropical Andes. Glacial
torrents also impose difficult living conditions on their
inhabitants, due to their low mineral content3 and
daily floods4 that produce major disturbances. A high
level of endemism thus characterises the páramos,
containing species not found anywhere else on
The ecological role played by the majority of invertebrates under threat in glacial rivers is still not well
known. The consequences at higher trophic levels,
such as for fish, amphibians, birds and mammals,
are difficult to predict. But these exceptional ecosystems seem to be condemned to disappear, before
they have even had the offer up all of their secrets to
researchers.
*See news sheet no.127 - Small glaciers in the tropical Andes:
a forewarning of disappearance
Keywords
Biodiversity, glaciers, climate change,
extinction
by Gaëlle Courcoux
On the same subject:
Video Canal IRD
Brochure Fauna acuática de la Reserva
Ecológica Antisana
Blog from the Antisana expedition
1. These studies have been led by the IRD and the University of Copenhagen, Denmark, in collaboration with the universities of Birmingham and Leeds in the UK, Alaska in the US and Paris-Sud 11, as well as the Pontificia Universidad Católica del Ecuador in Quito,
and the CNRS.
2. An ongoing process leading to the emergence of new species.
3. Environments less rich in minerals are generally unfavourable for aquatic fauna that draw crucial elements for survival from the water,
such as chlorides or sodium.
Coordination
Gaëlle Courcoux
Information and Culture Department
Tel: +33 (0)4 91 99 94 90
Fax: +33 (0)4 91 99 92 28
[email protected]
www.ird.fr/la-mediatheque
4. During the day, the glacier melts and increases the flow in streams, whereas the flows diminish at night.
Indigo, IRD Photo Library
Daina Rechner
Tel: +33 (0)4 91 99 94 81
[email protected]
IRD photographs on this topic, free for media
reproduction without additional permission:
www.indigo.ird.fr
Researchers have taken samples of invertebrate larvae, such as Trichoptera (right), from glacial streams (left, at the foot of the Crespo glacier in Antisana, Ecuador).
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© IRD / O. Dangles
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