Aim: Oceanic islands possess unique floras with high proportions of endemic species relative to their small land areas. Island floras are expected to be severely affected by changing climatic conditions as species on islands have limited distribution ranges, small population sizes and face the constraints of insularity to track their climatic niche. We aim to assess how ongoing climate change affects the range sizes of oceanic island plants to identify species of particular conservation concern.

Location: Canary Islands, Spain

Methods: We combined species occurrence data from single-island endemic, archipelago endemic, and non-endemic native plant species of the Canary Islands, representing ~71% (n = 503 species) of the certainly native Canary Island flora, with data on current and future climatic conditions. We used Bayesian Additive Regression Trees to assess the effect of climate change on species distributions. To further assess how climate change interacts with plant functional traits, we collected data on woodiness and succulence.

Results: Single-island endemic species were projected to lose a greater proportion of their climatically suitable area (x ̃= -0.36) than archipelago endemic (x ̃= -0.28) or non-endemic native species (x ̃= -0.26), especially on Lanzarote and Fuerteventura, which are expected to experience a reduction in annual precipitation in the future. Moreover, we found that herbaceous single-island endemics were projected to gain less and lose more climatically suitable areas than insular woody ones. In contrast, we found that succulent single-island endemics and non-endemic natives gain more and lose less climatically suitable areas.

Main conclusions: We emphasise the conservation importance of all native species, but especially single-island endemic species not characterised by traits associated with water use efficiency. Our results are particularly critical for other oceanic island floras not constituted by a vast diversity of insular woody species as on the Canary Islands.

We collected data on insular woodiness and succulence, plant traits necessary for a species’ response to changing climatic conditions. As insular woodiness can be challenging to distinguish from primary woodiness and herbaceousness, we mostly referred to literature sources from extensive studies on the woodiness of Canary Island plants (Hooft van Huysduynen et al., 2021; Lens, Davin, et al., 2013; Zizka et al., 2022). We defined plants as succulent if they display thickened or fleshy leaves or stems. The thickness or fleshiness of plant organs indicates the ability of those organs to store water in their tissue (including moderately succulent species such as Rumex lunaria). We retrieved information on woodiness and succulence from Muer et al. (2016) and taxonomic monographs which have been shown to be a reliable source for trait data (Cutts et al., 2021).