Rapid assessment of plant invasions in natural and semi-naturalforest habitat in Grande Comore Island

Anziz AHMED ABDOU1, Mathieu ROUGET1, Olivier FLORES2, Vincent BOULLET3 and Dominique STRASBERG2

IntroductionComoros archipelago is a biodiversity hot spot characterized by a relatively dynamic land use change. Species introductions increased in the 1951s due to the massive development of agriculture by European settlers. These land use changes have direct consequences on the disturbance of natural habitats and indirectly on the proliferation of invasive alien species.

Aims and objectives

• Identify the most invasive plant species• Quantify the invasion levels of different habitat

types in natural and semi-natural forest of GrandeComore island

Classification of habitat

Most invasive species Canopy and understory invasion

Syzygium jambos

Studyarea

Vegetationsurvey

•Exotic woody species

•Vascular species whose height ≥ 1m

•44 transects = 250 sections (30 x 10m)

Habitat

•Elevation, slope and dominant species

•11 habitats vegetation and 5 land use types

Methodology

•Native vegetation

•Less anthropogenicsdisturbances

Natural

•Forest invaded

•Agriculture andtree logging

Semi-natural

•Exotic vegetationon canopy andunderstory

Plantation

1: UMR PVBMT - CIRAD, 7, Chemin de l’IRAT, 97410 St-Pierre, La Réunion

2: UMR PVBMT - University of La Réunion, 15 avenue René Cassin CS92003, 97744 Saint-Denis, La Réunion

3: Retired person, self-employed, France - France

•Grande Comore Island

•La Grille (1087m) and Karthala (2361m)Land uses• Fo : Forest• B : Banana plantation• C : Cropland• D : Deforestation• Of : Old fieldsHabitats• LSDF : Leeward Submountain Dry Forest• LSHF : Lowland Sub-Humid Forest• WSNF : Windward Submountain Nuxia Forest• WSOF : Windward Submountain Ocotea Forest• WSTF : Windward Submountain Tambourissa Forest• WSWF : Windward submountain Weinmannia Forest• MVPC : Mosaic of vegetation at Psidium cattleianum• TkAN : Thicket at Nuxia pseudodentata• WSRF : Windward Submontain Rain Forest• LLRF : Lowland Rain Forest• WSEF : Windward Submontane Eucalyptus Forest

Eucalyptus camaldulensis

Conclusion and perspectivesThere are still relatively well-preserved forest remnants despite the different levels of invasions observed in Grande Comore Island.Results obtained in this study represent the first assessment of forest invasions in Comoros. In order to define management priorities, it isnecessary to expand these surveys. The alternative approach to dealing with this fragmentation of habitats would be to orient a restoration planin the natural and semi-natural habitat of Grande Comore. This results will contribute to improve decision-marking for Comoros national Park.

Clidemia hirtaPsidium cattleianum

Major plant invaders

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