Inventory of river flora in Poitou-Charentes

Abstract

From 2023 to 2025, Poitou-Charentes Nature conducted an inventory of river flora in the former Poitou-Charentes region. Botanists from five associations affiliated federated by Poitou-Charentes Nature surveyed the territory to characterize this set of species along several hundred kilometers of watercourses. The objectives were (1) to conduct an inventory of river flora following a simple and reproducible protocol; (2) to update the distribution of endangered species and invasive species; and (3) to raise awareness among water professionals about this component of biodiversity. Three hundred and thirty-six 50-meter-long sections were established, supplemented by 993 spot floristic readings. Across all of these surveys, 34 endangered species and 22 invasive species were observed. Based on an IBMR-type analysis with “nutrient” indicator values adjusted according to recent literature, the floristic readings across the section network show that watercourses are on average mesotrophic to eutrophic. 38% of these sections harbor at least one invasive species, among which a new invasive species in Poitou-Charentes: Vallisneria cf. australis. These surveys are intended to provide a basis for diachronic monitoring.