Plants of Saint Lucia

Invasive Species

An invasive species is a naturalized species that causes or is likely to cause economic or ecological/environmental harm or harm to human health. (Some indigenous species also have the same effect in disturbed areas and under some definitions are considered invasive as well).

Because it is impossible to determine whether species arrived naturally or were introduced by Amerindians, I define an introduced alien as any species which has arrived in Saint Lucia from the colonial period onwards.

A naturalized species is an introduced alien (non-native) species that spreads into the wild and whose reproduction in the wild is sufficient to maintain or increase its population. Some naturalized species are very common but not invasive - they seem to cause no harm.

Most of our naturalized species are found in areas which have been altered by human activities such as cultivation, animal husbandry, charcoaling, clearing for settlements and modification of drainage pattern. The rain forest reserve and the Pitons remain relatively free of naturalized species but the Pitons are now under threat by the rapid spread of two Commelinaceae (Callisia fragrans and Tradesacant zebrina, both garden ornamentals).

Also important to note is that a naturalized species can become invasive many decades after its introduction.

Thus it is important to minimise the importation of exotic species.