The problem of invasion by exotics.
Réunion has about 500 indigenous plant species of which 160 are endemic, and 50 of these are very rare or threatened. Of about 1000 introduced species, 430 are naturalized, and among these are several which are considered problems as weeds: Ulex europaeus (which is more susceptible to forest fire than the indigenous vegetation), Rubus alceifolius, Psidium cattleianum, Ligustrum robustum (a very recent introduction), Syzygium jambos, Solanum mauritianum, Fuchsia magellanica and Heydichium [Hedychium] gardnerianum. Among the techniques being tested for controlling these weed species is the encouragement of indigenous species (such as Dombeya sp., Weinmannia tinctoria and Monimia sp.) as understorey components, through silvicultural tending and release felling.