Assessing current and future risks of invasion by the “green cancer” Miconia calvescens

Miconia calvescens D.C. appears in the list “100 of the world’s worst invasive alien species”, devised by the IUCN. It is considered the worst plant pest in Hawaii and French Polynesia. This species has also invaded the rain forest of Australia, New Caledonia and Sri Lanka, where it is extremely difficult to eradicate. To assess the susceptibility to invasion by M. calvescens in new areas, we investigated the current and future suitable areas for this aggressive invader worldwide. We also assessed the protected areas currently at risk of invasion by considering botanic gardens as a proxy for likelihood of introduction, since most successful invasions by M. calvescens originated from private or public garden escapees. Our results predict that about 7.2 % of total landmass is currently suitable for M. calvescens , with 54.8 % outside the native range including 44.5 % within tropical forests in the southern hemisphere. We identified 91 countries, 400 islands, and up to 364 protected areas with suitable environments outside of M. calvescens native range. By the 2080s, worldwide land suitable for M. calvescens is predicted to be reduced by up to half due to climate change. This decrease is mainly predicted to occur in M. calvescens native ranges as well as in countries where the presence of the species has not yet been reported. In contrast, the invaded range is predicted to slightly decrease, showing an interesting example of a double negative effect of climate change on the distribution of an invader. Our work provides information for land managers and stakeholders that can help to avert the introduction and spread of M. calvescens in their territories. We also emphasize the importance of risk assessments on the living collections of botanic gardens, as a common source of escapees of invasive plants.