What role can cemeteries play in conserving plant biodiversity in different urbanisation contexts?

The aim of this work is to assess the importance and the originality of plant vascular biodiversity of cemeteries at a regional scale, compare it with other urbanised habitats and assessing their conservation issues according to an urban-rural gradient. The study was carried out in the Île-de-France region (France) with a dataset containing 66,973 records of vascular plants collected in 817 cemeteries between 2000 and 2021. We analysed the preference of species for cemeteries or other anthropogenic habitats using indicator value analysis. To describe species-specific responses to the urban-rural gradient, we employed a niche model analysis coupled with a randomization procedure. We then compared naturalness and habitat preferences between the different species lists obtained by these two methods. Among the 731 spontaneous species were inventoried, 84% of which are native. Of these, 69 can be considered as species of conservation interest; species of anthropogenic communities were well represented but the majority were linked to semi-natural habitats: heathlands, dry grasslands on acidic or calcareous soils and meadows in particular. Species linked to cemeteries are associated with semi-natural habitats, while the species linked to other urban habitats are forest or wetland species. Finally, species specifically linked to cemeteries in an urban context are mainly non-native species. Species of semi-natural herbaceous habitats are much more represented among the species linked to rural cemeteries. When they exist in cemeteries, the conservation of remnant semi-natural habitats should be a priority.