Restoring glacis habitat to protect Seychelles’ plant biodiversity |30 January 2012

(An inselberg is an isolated rock or small mountain that rises abruptly from a gently sloping or virtually level surrounding plain which has survived erosion.)

Some locations contain almost entirely species that are native to the islands, including many which are endemic, occurring only in Seychelles.

From an aerial perspective, these glacis with their rich plant diversity resemble disconnected pockets of biologically important plant communities embedded in a matrix of habitat dominated by introduced species and forestry plantations.

While introduced species such as ‘albizya’, ‘bwazonn’, ‘santol’, cinnamon and mahogany are economically viable species, they directly compete with Seychelles’ native plants for nutrients and space, often destroying the preferred living environment of native plants. 

Given that the majority of native species are slow growing, they are replaced by fast growing introduced species and become restricted to small isolated patches.

The invasion of natural areas by introduced plants over the last decades has resulted in many glacis plants now being classified as endangered or critically endangered, including the iconic pitcher plant Nepenthes pervillei (Lalyannpotao), and the jellyfish tree Medusagyneoppositifolia (Bwamediz), which occur exclusively on glacis.

The National Parks Authority in collaboration with Dr Christopher Kaiser-Bunbury from Aarhus University, Denmark, have set out to put a halt to the further degradation of the most diverse glacis plant communities on Mahé.

In a project funded by the Environmental Trust Fund (Seychelles) and the Swiss National Science Foundation, a team of National Park and forestry staff removes all introduced plant species from four separate glacis, using carefully selected plant removal techniques, thus creating space to allow the native plants to spread and reproduce more prolifically.

The removal techniques were rigorously tested in a one-year scientific study prior to implementation on the large scale. The most dominant introduced species that are removed from the glacis are Chrysobalanusicaco (prindefrans), Alstoniamacrophylla (bwazonn), Cinnamamomverum (cinnamon) and Psidiumcattleianum (gouyavdesin).
 
Of the four glacis that are being restored, on two of them the removal of introduced plants has been completed. In a second phase starting imminently, about 2000 native seedlings will be planted across the most affected glacis to support the already established native plants in their efforts to re-create a dense vegetation of indigenous plants.

Once the glacis have been fully rehabilitated, two of them will be established as eco-tourism sites. These glacis, which are easily accessible to the public, will be equipped with an educational billboard, highlighting their outstanding conservation value and their importance for Seychelles’ plant biodiversity.

The rehabilitation work is part of a larger commitment of the National Park Authority to research the effects of humans on the health and robustness of ecosystems in Seychelles.

To safeguard Seychelles’ natural treasures, it is vital to understand the impact of humans on natural systems, and to mitigate these impacts before the threatened plant species and the native animals that are associated with them go extinct.

Interactions between native species breathe life into ecosystems and they provide the basis for the sustainability of Seychelles’ plants and animals. 

Contributed by Seychelles National Parks Authority