2011 International Year of Forests – Invasive threats to our forests

This post is also available in: Dutch.

The Bellisima, a plant with beautiful flowers but with ugly consequences.

Danger from the outside, for our natural environment! No nature-related topic has appeared in the media more often than this during the past two years. Well, it actually did not really deal with nature in itself but rather with the fact that the invasive species from abroad started feasting on plants, which were also imported from abroad, hence did not belong to local nature. Another invasive species started devouring the fish we wanted to get out of the water ourselves in order to eat. That the situation could turn into an environmental problem, that was also brought to the attention, to be fair, but a lot less prominent than the economic risks the invaders were causing.

Malicious intruders

We are talking about the infamous Red Palm Weevils, also well known as the “Evil Weevils“, and the Lionfish. The first probably got to Curacao as stowaways within a collection of imported date palms that were not checked properly at the border. The evil ones probably came from Egypt. The bugs soon learned that it was lovely on the Island. Sun, heat and enough palm trees to feast on. The aggressive prosecution of these insects still continues because its favorite food (actually of their larvae) are expensive palm trees in the gardens of luxurious resorts and in the gardens of palm lover. Lots of those palm trees soon lost the battle and died. An important question remains. Will the animal in question only target the date palms, or will it also add other imported palm trees to its list of favorites? Or even worse: the indigenous sabalpalm, the only naturally occurring palm on the Island? Unfortunately, the question is still unanswered. In that respect, the Lionfish is a lot easier to monitor. A few years ago there were none, and now there are dozens per hectare. Reliable sources inform us that the animals do group together in schools at certain times of day as if they are having a meeting. We know what they eat: fish of all sizes, as long as it can enter their mouths. In the Caribbean they have no enemies, so they can multiply without any limitation. And so they currently wreak havoc to fish stocks and the ecological processes occurring on the coral reef.

The Evil Weevil is not the only one

For forests the Lionfish, contrary to the “Evil Weevil”, poses no danger. Ironically, before the “Evil Weevil” got here, dozens of other species of plants and animals were imported from abroad, by accident or not. These species were already causing damage to the local plants, trees and animals for quite some time. And little or nothing has been done to combat those species.

Invasive plants

A good example is the so-called Bellisima (Antigonon leptopus), or Coralita under which name the species is known in the windward Islands. This fast spreading plant is famous for its beautiful bright-pink or sometimes white flowers. The plant grows rapidly and covers the ‘mondi’ in no time. The overgrown plants will not get enough light, their growth slows down, and they might die if the overgrowth will stay in place for too long. A major problem, especially on more humid islands, like St. Maarten and St. Eustatius. The natural cycle on Curacao causes the plant to die off in the long dry season, so the original mondi plants have the opportunity to recover. It has become clear, though, that as a result of the more frequent rains and higher humidity of the last few years, parts of the mondi stay overgrown by Bellisima year around, and thus slowly die. It is pretty difficult to remove the plant permanently. On the Windward Islands it is even necessary to burn the plants in order to avoid regrowth. The flowers do not bloom all at the same time so on the same branch there are always a bunch of buds that still have to develop into flowers alongside already fertilized flowers and fruits. If you remove the plant from your garden and put it on a pile, chances are that after the next rain new plants will rapidly sprout. Moreover, Ala Blanka’s (Bare-eyed pigeon; Columba corensis) go crazy over the fruits of this plant and they swallow the whole green fruit. In the afternoon you might encounter big troops of these birds picking away at the Bellisima. The plant is therefore very effectively, but unfortunately, spread by these animals.

The Palu di lechi has lilac flowers in the shape of a chalice.

Suffocating vine

Another well-known exotic species is the Rubber Vine, or the Palu di Lechi (Cryptostegia grandiflora) as it is known locally. The plant was originally imported to the Island in order to produce rubber. It quickly became obvious, however, that it would be an unsuccessful endeavor and the plantation was abandoned. The reproductive strategy of this plant is making it one of the bigger problems terrestrial nature had to deal with to date. After the production of beautiful lilac flowers twin horn-shaped seed pods are produced that will literally burst open after drying out. The seeds, small and brown, are attached to white fluffy umbrellas that are transported over large distances by the wind. Like the Bellisima the Palu di lechi is not a parasite but it will overgrow its victims. The strong thick leaves and stems overgrow and will wrap themselves around other plants and choke them over time. In some places on the island you’ll encounter the stems of the Palu di lechi wrapped around the trunks of trees to such an extent that the growth of the tree slowed down. Sometimes the vine even cuts into the trunk. This plant is difficult to eradicate as well, not only because of the windblown seeds, but also because of the fact that the root system of the plant is very strong and branching. Even after burning the main root group, often a new shoot will come up some distance away, courtesy of one of the surviving root branches. There are no natural enemies to the Palu di lechi to balance and minimize the threat to local plants and trees.

Invasive species: something needs to be done!

And that’s precisely the problem with invasive species. They are introduced to an island which is completely new to them and on which the local nature is completely unprepared for the often adverse effects they will cause. Before you know it invasive species get the upper hand and will push the local flora and fauna into oblivion, resulting into impoverishment of the local biodiversity and sometimes even causing large economic impacts. It is therefore necessary that measures be taken not only to prevent new invasive species from entering the island, but also to eradicate the already established invasive species in order to prevent further damage. To name one dramatic example: it is still possible to import all kinds of plants. And therefore more potential ‘Evil intruders’…..

Michelle da Costa Gomez

About Michelle da Costa Gomez