**1. Introduction**

The recent geological nature of the Archipelago of the Comoros, their geographical position, the smallness of the territory and their multi-insularity give them a great originality that reflects the diversity of the landscapes and the richness of the vegetation, the fauna and the flora [1–3]. The flora of the Comoros has a great similarity with that of Madagascar. The archipelago is under a small

influence of the African continent, while some elements of the flora could come from Asia [4]. The vegetation of the Comoros Islands is known for its richness in endemic plant species; however, it remains little studied. It is characterized by two types of vegetation: medium-high and high-altitude moist forests, and low-lying, deciduous, lowland forests [2, 5–7]. The proportion of land covered by forests would decrease from 6.6% in 1990 to 1.7% in 2012, with nearly 500 ha of forest being lost each year [8]. In Ngazidja, forest cover is estimated at 8658 ha of natural forest [9]. The dry forest and thicket are found along the South-East and North slopes as well as the West Coast. Remnants of poorly disturbed dry forests are reduced to small areas of a few hectares regularly grazed by livestock [7]. In addition to these threats, climate change does not spare them. Forest species in arid and semi-arid areas have reached their limit of adaptation to aridity and, therefore, are more vulnerable to increased drought than wetland forest species [10]. In 2006, Labat already said is urgent to identify these remnants of dry forests and thickets, because these types of vegetation are the most threatened. To our

**Figure 1.** *Location of Ngazidja island, Comoros archipelago.*

*Phytoecological Study, Ethnobotanical and Dynamic of Dry Vegetation in the Ngazidja Island… DOI: http://dx.doi.org/10.5772/intechopen.107330*

knowledge, no study has been undertaken on the ecological characteristics of the dry plant formations on Ngazidja, Comoros Archipelago (**Figure 1**). The present study aim at providing ecological information on the dry vegetation formations of Ngazidja Island and propose solutions for their conservation. The hypotheses are: (i) the dry plant formations are still very rich in endemic and indigenous species and are still threatened; (ii) These knowledge should facilitate the definition of ways of managing and conserving the natural and semi-natural habitats of dryland species, especially forests and thickets in a context of insularity but also to demographic and urban expansion socioeconomic dynamics. Our approach is based on the survey of the floristic and structural description, and the determination of threats and pressures.
