A herbarium of the Mer de Glace

A witness to the vegetation of the rocky islets of the famous glacier

102 sheets of herbarium collected during an expedition to the islets of the Mer de Glace were donated to the Grenoble Museum by botanist Cédric Dentant (Ecrins National Park) in 2022. A scientific publication on the results of this expedition comes to be published in 2023.

This expedition to the islets, emerged in the middle of the glaciers, of the Mer de Glace came after that of Venance Payot, guide, naturalist, and former mayor of Chamonix, who, at the end of the 19th century, carried out botanical surveys at these same locations, and collected specimens to form a herbarium which is currently in Turin.

The interest of this study and collection is, in the context of global warming and rapid evolution of the Mont-Blanc massif, to provide concrete elements, and verifiable thanks to the herbarium, of the evolution of the flora. Brad Carlson, researcher at CREA Mont-Blanc and mountain guide, Sébastien Lavergne, evolutionary biologist at LECA, Cédric Dentant, botanist at the Ecrins National Park, and Nicolas Bartalucci (mountain guide and M2 LECA/Parc national des Ecrins) revisited the sites that Payot had explored to observe how floral diversity had evolved over 150 years. Their results show a dramatic change on the largest and lowest islets.

Several hypotheses could explain these differences, in particular the greater isolation of islets at altitude, or even climatic differences: the warming of 2°C at altitudes and the less snow cover in the lowest islets could have caused them to evolve towards the limit thresholds. , which makes these environments more welcoming for new plant species. (sources: Altitude Ecosystems Research Center).

This herbarium is therefore a support for argumentation of the study and new research on these environments, and must therefore benefit from long-term conservation. Subsequent analyses, and new surveys in several decades, will certainly need these elements.

Access the scientific publication: Cédric Dentant, Bradley Z. Carlson, Nicolas Bartalucci, Arthur Bayle & Sébastien Lavergne (2023): Anthropocene trajectories of high alpine vegetation on Mont-Blanc nunataks, Botany Letters, DOI: 10.1080/23818107.2023.2231503

Access herbarium parts online: Herbarium Dentant - Payot Islands Expedition