Mort sans précédent des plus vieux baobabs d'Afrique

14 Juin, 2018, 07:41 | Auteur: Anatole Charbonneau
  • Les baobabs millénaires d'Afrique se comptent maintenant sur les doigts d'une main

Les baobabs d'Afrique se meurent.

Capables d'atteindre un âge proche de 2.000 ans, les baobabs sont l'un des principaux emblèmes des savanes où ils se dressent fièrement et sont visibles à une distance de plusieurs kilomètres.

Pourtant, ces arbres mythiques contribuent à donner un paysage exceptionnel à ces savanes arides, avec leur tronc imposant, ses branches et ses racines qui arpentent le sol, donnant au final un vrai chef-d'œuvre tel un tableau.

Cette disparition des baobabs monumentaux serait liée au changement climatique qui affecte particulièrement l'Afrique australe.

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Pour cela, entre 2005 et 2017, Adrian Patrut et ses collègues ont étudié tous les plus grands (et donc généralement les plus vieux) baobabs d'Afrique, plus de 60 en tout. Toutefois, même s'ils citent comme éventualité le dérèglement climatique, les chercheurs ont été incapables de se fixer définitivement sur les causes du phénomène. "Au cours des 12 dernières années, huit des treize plus vieux baobabs sont partiellement ou totalement morts". Des fragments dont ils ont ensuite défini l'âge à l'aide de la datation au carbone.

Parmi les victimes, trois monstres symboliques: Panke, au Zimbabwe, le plus vieux baobab avec 2 450 ans au compteur; l'arbre de Platland en Afrique du Sud, l'un des plus gros du monde, avec un tronc de plus de 10 mètres de diamètre; et le célèbre baobab Chapman du Botswana, sur lequel l'explorateur David Livingstone grava ses initiales, classé monument national. Une fois que les nouveaux apparaissent, les anciens tiges et troncs ne font qu'un avec, permettant ainsi à l'arbre de vivre très longtemps.

"Ces décès n'ont pas été causés par une épidémie", affirment les auteurs. "Avant de commencer nos recherches, nous avions été informés de l'effondrement du baobab Grootboom en Namibie mais nous pensions que c'était un événement isolé" , explique Adrian Patrut. La situation de ces arbres millénaires s'est aggravée au cours des 15 dernières années, probablement à cause du changement climatique. "La région dans laquelle les baobabs millénaires sont morts est l'une de celles où le réchauffement est le plus rapide en Afrique", remarque Adrian Patrut. C'est ce qui ressort d'une étude publiée dans la revue scientifique Nature Plants.

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