The current state of the flora of Madagascar must be judged from two perspectives.
1. It's uniqueness.
2. The gap in our knowledge of it.
The uniqueness of the Malagasy flora is renowned amongst botanists with 10,000+ species of plants approaching almost 96% endemism. Interestingly the coastal and freshwater areas have the least number of endemic species due to a number of factors such as the ability of seeds from further afield to float into these areas and colonise them or the fact that many foreign species are introduced by humans living near water and become naturalised. You can broadly divide the vegetation into two areas, each of which will have subdivisions.
1. Humid areas which comprise the East and centre of the island and the Sambirano region further West. These areas can have annual rainfall of between 2,000-6,000 mm.
2. Dry areas in the West, South and the North with very low seasonal rainfall. The South West and the extreme South is almost desert like in it's low rainfall (average 700mm annually) and is renowned for the Spiny Forest, a collection of indigenous plants totally adapted to the dry heat and found nowhere else on earth. Actually when I first visited this area in 2001 I thought I was on another planet such was the unusual diversity of plant shapes! The vegetation is dominated by species from the families Didiereaceae and Euphorbia.
Madagascar holds 20% of all of Africas mangroves, a particularly important coastal vegetation type. Recent events such as the Tsunami in Asia and the cyclone which affected Burma have shown that areas where the mangroves were still abundant suffered the least damage during these natural disasters. In effect the mangroves acted as a buffer zone.
Baobabs mainly occur in the western areas of the island and are in extreme danger due to habitat loss with A. Suarezansis and A. perrieri being in the most danger due to fact that the surviving populations are widely scattered and are not within any currently protected areas.
Uapaca. (One of the main survivors of the original forest species)
In the Central Highlands the original forest is greatly degraded and is still being utilised by humans. Many Uapaca bojeri trees have their lower branches removed for firewood and their leaves used to feed silkworms which are a big local business. Interestingly enough this removal of lower branches provides some protection against man made fires as the crowns of the trees remain above the fire and survive better. However, cover for mammals, birds,insects etc. is greatly reduced as a result.
Madagascar has a very varied collection of endemic palms which are unfortunately greatly threatened by habitat loss. Many areas of the island remain unexplored for palms and it was not until 1995 when the Palms of Madagascar by Dransfield and Beentje was published that interest in the plight of the palms was renewed. However collecting by private palm enthusiasts has failed to add to our knowledge because of the unscientific methods used in collecting. 176 species in 16 genera occur in Madagascar whereas the whole of Africa only has 60 species in 16 genera. So the survival of Madagascar's palms is obviously important . Some of these palms only occur in small unprotected areas. One example is Dypsis ambositrae which has only 10 specimens remaining in an area of high agricultural activity. Seed exporting for export is also a threat. Many of Madagascar's palms are tolerant of cold and there is a great interest in them from palm collectors in Europe where very few palms survive the winters intact.
Pandanus. (Screw pines)
There are 100 species of these distinctive shrubs and trees which are commonly mistaken for true palms by the uninitiated. Nearly all of them are found nowhere else on Earth.
When you walk through the remaining forest areas of the island you cannot but notice the great variety of ferns present with over 586 species so far named and most of these being endemic. Interestingly enough the highest proportion of endemic species inhabit the central areas of the island. Although 27 species of fern have adapted themselves to the dry Southern regions none of these species are endemic.
There are 43 species of Cyathea tree ferns alone in Madagascar with 39 of these being endemic.
Madagascar has some fantastic endemic bamboos with 32 species currently recognised. Work is ongoing on the identification and naming of Malagasy bamboos but that is not unusual as the bamboo family worldwide is constantly being reassessed.
The Gap in our Knowledge.
Although there appears to be a lot of information available on the Malagasy flora on the web, there are still enormous gaps present. For example you can purchase field guides to the flora of many countries around the world. Whenever I intend to travel somewhere I usually track down field guides on the flora, birds , mammals etc to bring along with me. They are invaluable reference sources for the local guides also as they may only know the species you want to see by its local name and at least a well illustrated book can be used to pinpoint what you want to see. Madagascar has an excellent field guide to the Palms but the rest of the flora is only covered by generic guides in some cases. For example the Pandanus mentioned above comprise a 100 species but only the genera itself is described in any of the current guides. This can lead to unscrupulous people trying to take plants out of the field to identify them later. I was always taught to "bring the field guide to the plant and not the plant to the field guide".
There are reasons for this paucity of field guides on the flora.
1. The diversity of habitat on the island and the resulting endemism associated with this. There is a lot of work still to be done.
2. The remoteness of many areas which often have little if any access by road and their sheer size leads to even more problems of coverage.
3. Prior to the 1990's there were very few native Malagasy botanists trained in modern taxonomic and field research techniques. Happily this has changed and continues to do so.
I understand that printed guides to Madagascar's flora are being prepared through the Vahinala Project led by the Missouri Botanical Gardens who have a particular interest in the flora of this amazing island.
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