Friday, 17 October 2008

Motu (coral islands) born from a coconut palm !

Location of Tuamotu Archipelago
During 2009, the IFRECOR (French Initiative for Coral Reefs) and CRIOBE (Island Research Centre and Observatory of the Environment) funded a scientific survey on the atoll of Fakarava, Tuamotu Archipelago, French Polynesia.

You can click on photos and maps to enlarge them.



Location of Fakarava Atoll in the Tuamotu Archipelago

The objective of this survey  was to conduct an inventory of coconut varieties and assess the potential conservation of traditional varieties on the many small motu (coral islands) of the atoll.

Fakarava, Havaiki-te-araro, Havai'i or Farea is  is the second largest of the Tuamotu atolls.
Fakarava map and location of a small motu
The shape of Fakarava Atoll is roughly rectangular and its length is 60 km and its width 21 km.

Approximatively 700 inhabitants are living here. Fakarava  is among seven atolls that have been grouped together as part of the UNESCO Man and the Biosphere (MAB) global network until October 2008.

Precise location of a small motu
At the time, Mr. Cyril Tshonfo Ayee said Tehira was president of the Association of the Biosphere Reserve of the Municipality of Fakarava. He welcomed us with great hospitality and he gave us a great deal of valuable information. We also took a boat to visit the numerous motu of the attoll. One of the smallest of the motu was particularly interesting...

Coconuts germinating in very harsh conditions
Tehira indicates that for the Polynesian, a motu is defined as a small island on which vegetation grows. A rock or a sand without vegetation are not motu. According Tehira, in many cases, "it is the coconut tree which creates the motu." Tehira said and have seen over the years, some sandbanks become small motu.


bird on a coconut seedling strongly carenced
The photographs illustrate the various stages of this process.

Coconuts brought by sea germinate on a sandbar that has not yet stabilized.

Then the birds come to rest on the palms. Their feathers or their droppings, the birds carry seeds that are deposited on the sand around the coconut. Bird droppings enrich the soil.

Detailed view of the motu
In most cases, a single coconut tree manages to survive to adulthood. Gradually, vegetation grows at the foot of a coconut tree. The roots of the coconut palm and other plants help to establish and maintain the sandbank.

We observed this small motu with only one adult coconut palms. This motu is located at 750 m from another motu where 20 to 30 adult coconut palms are growing. According to the main direction of the  wind and to the 750 m distance, it is very improbable that the coconut pollen can reach this motu. Studies conducted in Africa have shown that a 300 m distance is sufficient to obtain a high reproductive isolation.

The unique coconut palm of the small motu was bearing 9 fruits bigger than a fist. On the ground at the basis of its stems, 15 coconuts were counted. 13 of these coconuts looks  the same shape, and we think that they originates from the unique adult palm of the motu. Some of theses coconuts, when they were shaken, made the usual sound of normal mature nuts containing a normal amount of coconut water.

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