A viviparous lizard -

M.Berroneau

  • An imminent risk of local extinction of lizards exists in Nouvelle-Aquitaine.

    "They are much less abundant in the Landes massif", notes a study.

  • Field observations also show "a marked decrease in their activity" during the dry years, which are increasing in the region.

  • The drying up of the lagoons in recent decades is also contributing to the destruction of their habitat.

Is the viviparous lizard threatened with extinction in the Landes triangle?

This is what scientists say within the framework of the scientific program of the Cistude Nature association, Les sentinelles du climat.

Genetics, observations of populations in the field, morphology, physiology (the study of the functioning of the organism) indeed converge towards a great fragility of the species vis-à-vis global warming and an imminent risk. local extinction.

If we continue at the same pace, "there will be no more viviparous lizard in the Landes triangle in ten to fifteen years", says Andréaz Dupoué of the CNRS in Moulis (Ariège).

A group of CNRS researchers joined the Cistude Nature team to conduct a genetic study.

Using saliva samples, the genome of several populations was studied, ranging from wetlands in the plains to high-altitude meadows and peat bogs in the Pyrenees.

For Andréaz Dupoué, “the results are edifying, not only are viviparous lizards much less abundant in the Landes massif but they have a genetic heritage clearly different from other populations, a higher rate of consanguinity visibly concomitant with an interruption in the flow of genes. between populations.

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The wall lizard "touched but later"

The study focused on the viviparous lizard populations of the Landes triangle, that is to say in the Gironde and the Landes, "which are populations distinct from those found in the Pyrenees, or more to the north in Limousin, ”explains Maud Berroneau.

Note that within this same species, there are viviparous and oviparous forms.

In addition, the viviparous lizard is a species particularly adapted to the cold, able to spend winters in restrictive areas for other species, as far as Scandinavia.

“It is therefore at the forefront of species that will be impacted by climate change,” analyzes Andreaz Dupoué.

And we can expect that other species like the wall lizard, will be affected but later.

"

“Over the past four years,” explains Maud Berroneau, “during very hot and dry years, we have observed consequences on their surface activity.

Usually, we are used to observing them in activity, sunning themselves to fill up with energy, or feeding themselves, but in 2017 for example, which was a very dry year, we noticed a marked decrease in their activity.

They took shelter under the vegetation, and their traditional cycle of activity could no longer be carried out.

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65% of lagoons have dried up over the past thirty years

"It also impacts the growth of individuals, with young people who must mature faster," adds the scientist.

"These species burn themselves, living quickly and dying young," adds Andréaz Dupoué.

What is also happening in this Landes triangle is a disconnection of populations from one another: they find themselves completely isolated in the Landes lagoons which are favorable to them.

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The repetition of dry years is part of the explanation, but not only.

"The repeated drying out of wetlands due to drainage, the exploitation of maritime pine, urbanization, reduced rainfall" are also involved.

“In barely a century, the water levels of the lagoons in the Landes triangle have fallen by at least three meters, which is enormous, assures Maud Berroneau, and in the last 30 years, 65% of them have fallen. dried up.

It went very quickly.

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A so-called "umbrella" species

"The drainage of these areas is the most critical factor for this species", assures Andreaz Dupoué, who adds that "a whole procession of species that goes with [insects, birds, plants…]" is also threatened.

He continues: “The viviparous lizard is a so-called 'umbrella' species, meaning that if it goes extinct, others will probably go extinct.

"" What this implies, confirms Maud Berroneau, is that its habitat has changed, and all the other species that are linked to these habitats can also disappear, such as the Iberian pippin.

"

Our dossier on global warming

Supported by the Cistude Nature association, the Sentinelles du Climat scientific program assesses the effects of climate change on biodiversity in New Aquitaine.

Launched in 2016 for a period of six years, it is based on around twenty species or groups of species that are not very mobile and distributed in sensitive ecosystems in the region.

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