The Classification of Natural and Anthropogenic Vegetation in Madagascar
A NEW APPROACH TO VEGETATION CLASSIFICATION AND MAPPING IN
MADAGASCAR
In Madagascar, the application of the kind of careful, systematic
analysis developed by White is critically needed. However, as
White (1983) and many others have pointed out, a physiognomic
classification for a given area must be developed and tested on
the basis of direct field experience (although modern remote
sensing techniques can serve as a powerful complement). More
importantly, careful chorological analysis is absolutely
dependent on a thorough understanding of the taxonomy of the
native flora, and also on reliable specimen based distributional
data (White 1993).
Much work remains to be done before such an approach can be
implemented in Madagascar, although the recent progress in
botanical inventory work (now mostly being conducted by local
collectors) and systematic studies by Malagasy and foreign
botanists, is certainly encouraging.
We can, however, already formulate a few ideas of what the
application of White's basic approach might tell us here in
Madagascar. Cornet (1974) developed a bioclimatic map that clearly shows the presence of highly localized climatic conditions in several parts of the country, including in the
transition zone around Vohemar located between the humid east
coast and the dry north of the island, an area that corresponds precisely to a restricted zone containing a number of locally endemic plant species. Similarly, the transition between the humid east coast forest and the dry south to the west of Fort Dauphin, as shown here at Parcel 3 of the Andohahela Strict Nature Reserve, harbors numerous endemic species including Dypsis decaryi.
Cornet's map also shows a specialized local climate around
Morafenobe, where a disjunct area of true evergreen forest occurs
at Ambohijanahary Special Reserve, with many species that are otherwise
restricted to the eastern part of the country.
The application of White's approach to Madagascar would also
result in treating all evergreen forests as a single broad
physiognomic category -- whose distribution, largely coincides
with the humid and subhumid stages indicated in blue and green on
Cornet's map. Reliable chorological information would then potentially allow us to differentiate floristically distinct zones within these
evergreen forests.
If the ultimate goal of classification and mapping is to reveal
biogeographic patterns in order to recognize and delimit areas
that are biologically distinct, then chorology clearly must play
a central role. This certainly appears to be the case in
Madagascar, where one of the most important applications of a
vegetation map is for conservation planning.