Caribbean Island Terrestrial Habitats
|Our look at Caribbean terrestrial habitats will focus on those common in
the islands of the Lesser Antilles or Eastern Caribbean. The larger islands of the Greater
Antilles have a more diverse range of habitats. While the animal and microbial components
of a habitat are very important, it is the plant community which is used to refer to that
habitat. You should also be aware that the Caribbean is viewed as biodiversity
hotspot on account of its species richness.
|It is important to emphasize that in the Caribbean we live in a seasonal tropical climate with major differences in rainfall. The dry season results in water deficits which limit plant growth and the kinds of plant communities that can develop. Some plants shed their leaves at this time.|
|Fiddlewood (Citharexylum spinosum)
preparing to shed its leaves in the dry season.
|Whitewood (Tabebuia pallida), another
deciduous species, leafless and in full bloom in the dry season.
|Our tour of Caribbean terrestrial habitats will begin at sea level and work our way up a hypothetical mountainous island. This diagram below is a useful reference point in this trek.|
|A transect across a Caribbean island from Beard's (1949) The natural
vegetation of the Windward & Leeward islands
We start in a dry zone (<100 m) with a marked dry season,
February-June, which limits the plant communities which can develop. In the
intermediate zone (100-300 m) there is still a dry season but the period of
drought is shorter. In mountainous islands one ascends to the wet zone where,
although there is still a period of reduced rainfall, there is always an excess of water
supply over demand. Finally, in the montane zone water is in abundance.
Mist results in lower light intensities and water constantly condenses on vegetation to
create sodden conditions.
|Succession is a fundamental concept in ecology where any available
bit of land is colonised by plants, animals and micro-organisms and over time the
structure of this developing community changes. A useful concept is that of the climax
(community) which is the hypothetical optimal community that would eventually develop
under ideal conditions and without human interference. If climate dictates the nature of
this community we describe this as a climactic climax whereas if the soil
conditions limit the type of climax that develops we speak of an edaphic climax .
Where there has been some interference that degrades the climax we say that secondary
succession has occurred and if we now view this secondary community as on its way back
to the climax we can refer to this as a sub-climax.
The islands of the Caribbean are highly impacted ecosystems and even the most pristine habitats are, to varying degrees, secondary. Even were we arriving in the Caribbean in 1492 we would have found disturbed habitats as the original Amerindian inhabitants were agriculturists and fishermen, albeit operating in a more sustainable manner than us today. Furthermore, the periodic visit of hurricanes and the eruption of volcanoes have from time to time wreaked havoc on primary vegetation. Check out the Montserrat Volcano Observatory site to see the power of an active Caribbean volcano.
Approaches to vegetation classification
There are many ways to classify the plant communities or vegetation types of the
Caribbean islands. One way is to identify the climax community in each geographical zone
of an island and then to describe the sub-climax communities. This approaches involves
interpretation and pre-supposes that we actually know what the climax would be. This was
the approach used by the forester JS Beard in his (1949) The natural vegetation of
the Windward & Leeward islands.
In this scheme some 104 formations are recognized (and many more alliances and associations!!!). For our purposes we will just single out important representative plant communities but you should appreciate the usefulness of such schemes in mapping vegetation and hence natural resources. A final point to bear in mind is that these communities form a broad continuum and merge one into the other and are less clear-cut than such a classification system might suggest.
To just give a practical example of the two approaches, consider a coastal woodland vs sand dune vegetation. In the Beard approach the presumed relationship of the two are taken into account. Coastal forest might be termed a dry evergreen formation and the dune vegetation is in this same formation but is a subclimax i.e. given enough time the dune vegetation will eventually become the climax community (coastal forest) for that zone. In contrast, the second approach would have these in two very different groupings (Classes, in this case) based on the fact that one is a type of forest and the other is a form of herbaceous vegetation.
Get on your boots and let's begin the tour...
|Coastal plant communities
|Some useful websites
A useful resource book with descriptions and pictures of vegetation types and plants
Lack, AJ, Whitefoord, C, Evans, PGH, James, A (1997) Dominica nature island:
Illustrated flora, Min. of Tourism, Dominica.
Some other useful references