Bilan des connaissances sur la flore, la fonge et les habitats naturels de l’archipel de Saint-Pierre-et-Miquelon

The archipelago of Saint-Pierre-et-Miquelon, with an area of 240 km², consists of three main islands, Saint-Pierre, as well as Miquelon and Langlade, joined by an isthmus since the 18th century. Located at the latitude of Nantes, this archipelago benefits from subarctic climatic conditions due to the influence of the cold current of Labrador. The first botanical surveys in this territory date from the early 19th century. They have been regularly continued since and have made it possible to carry out fairly complete inventories of vascular flora, bryophytes, algae, fungi and lichens, the updated lists of which are presented on the naturespm website and included in the National Natural Heritage Inventory (INPN). However, the precise knowledge of the archipelago’s vegetation and natural habitats remains much more limited. These inventories clearly highlight the boreal and subarctic affinities of the flora and vegetation of this territory, resulting in the presence of boreal forest and arctic tundra ecosystems at very low latitudes and altitudes. However, it appears that some species mentioned in 19th and 20th century inventories have not been found in recent decades and may have disappeared. Other species are rare and threatened. But this territory has also been the subject of voluntary introductions of exotic plants, mainly of European origin, for agricultural (forage plants) or horticultural purposes. Some of these species have become invasive and have been monitored and harvested and eliminated in recent years to limit their expansion. Animal species have also been introduced voluntarily for hunting purposes: American hare (Lepus americanus Erxleben, 1777), white-tailed deer (Odocoileus virginianus (Zimmermann, 1780)), arctic hare (Lepus arcticus Ross, 1819); they have a very important impact on forest regeneration. More recently, the appearance of green crab (Carcinus maenas (Linnaeus, 1758)) in ponds and lagoons greatly disrupts the functioning of these lake environments. Actions to disseminate knowledge and promote plant heritage are developed in the archipelago, such as the digitization of herbaria preserved in Saint-Pierre-et-Miquelon, the inventory of key biodiversity areas (Znieff), the Compteur Biodiversité Outre-mer portal, the portal of natural heritage, etc. All these data constitute an appropriate framework to allow the network of National Botanical Conservatories to deepen knowledge with the aim of better valorization and protection of this plant heritage.