Restoring whole island ecosystems
Between colonization in the 1770s and the 1980s the staple of the Seychelles economy was plantation agriculture; spices such as cinnamon, coconut as well as tobacco, and food crops were grown. By the early 20th Century the plantations extended over most of the land mass of the Seychelles, the native forests had largely been obliterated. .The problems were compounded by the introduction of alien predators, collection of animals for food, mining of guano and in the latter 20th Century the applications of pesticides. Under these multiple assaults many native species populations became rare, fragmented or extinct.
Economic changes over the last three decades have coincided with more enlightened views: over the 1970s and 1980s the plantations became unprofitable and have mostly been abandoned; this coincided with the start of tourism, which has provided
sustainable funding for islands managing their biodiversity sensitively. The result has been that the Seychelles, despite being one of the smallest countries is a world leader in environmental restoration. Restoration or rehabilitation has been conducted on a number of the islands, and typically involves several stages:
- The removal of alien predators such as rats
- The control or removal of alien plants and replacement with native species
- The reintroduction of native animals
The island restoration programme initiated in 1999, initially under a GEF MSP-Management of Avian Ecosystems- in the Seychelles points the way to sustainable mechanisms of island restoration. A collaborative effort between Nature Seychelles, private island owners and the Seychelles Government, the program is ongoing. Components include biological assessment of islands, cost analysis of restoration and maintenance, education and awareness, island management plans, removal of alien predators and other invasive alien species, establishment or rehabilitation of native coastal habitats, translocation of globally threatened endemic species and socio-economic valuation of restored ecosystems and ecotourism,. Islands in the programme include Frégate, Cousine, North and Denis Islands, private 5 -star hotel resorts. Establishment of new populations of endangered species will not only lead to down grading of the threat status of these species on the IUCN Red List but also to enhancing ecotourism potential thus inducing hotel owners to contribute to conservation efforts. The program has been financed by the GEF, the Seychelles government and island owners and has involved international partners such as BirdLife International.
Biodiversity management has developed immensely in the last 30 years, now standard procedures have been developed to remove alien species, rehabilitate native forest and re-introduce native species. Nature Seychelles has published biological assessments of many Seychelles islands as well developing a manual of assessment methods. The organisation has also published several papers on the subject including methods of eradicating Mynah birds.
The removal of rats is a prerequisite for restoration, and the methods first developed in New Zealand have been refined for the Seychelles climate and conditions. The process involves the application of a poison in a cereal based carrier pellet to all parts of the island. This can be done on foot, by placing bait on a 25 metre grid across an island on flat islands or by spreading the bait from a helicopter on large or rocky islands. To date three islands have been successfully cleared of rats: Frégate Island Private, Bird Island and Denis Island. Several others have been cleared of cats.
Forest restoration has also been carried out on several islands since Cousin was restored, Cousine and Aride have both had successful forest recovery programmes, removing alien species, constructing and stocking a nursery and replanting with native trees.
The final element is the re-introduction of native species, to date mainly birds. Several species have been reintroduced to restored islands in planned programmes in recent years: the Seychelles magpie robin has been reintroduced to three islands, the Seychelles warbler to three and the Seychelles fody to two. Re-introduction should not be taken lightly, a thorough understanding of the species ecology and hence suitability of the islands is needed. Birds are the best studied taxon, and hence have been reintroduced first, but as research and interest in restoration increase, reintroduction of other groups such as reptiles and insects seems likely in the near future.
Cousin, the first restored ecosystem
Cousin was acquired for conservation in 1969; at the time it was managed as a coconut plantation. The primary motive for the purchase of Cousin was that it held the last population of the Seychelles warbler, numbering about thirty birds that were largely restricted to the mangrove woodland, the last fragment of native forest. Early management was low key; the most important action was to collect coconuts that had fallen to the ground. This prevented the growth of a dense under-story of young palms that would prevent native plants from growing.
With the coconut under control the native trees began to regenerate, one of the most abundant being Pisonia grandis (Mapou in kreol), the sticky seeds being spread on the plumage of seabirds. Other trees that prevailed in small numbers have also recovered. In the early 1990s most of the remaining coconuts palms were removed and now the vast majority of the vegetation is native.
Cousin was one of the few islands that remained free of rats and mice, and hence cats were never introduced to control them. With the recovering forest and absence of alien predators native animals flourished. The Seychelles warbler population increased 10 fold, colonies of seabirds expanded greatly, and the endemic skinks and Bronze eyed gecko occur at high densities. A small number of Seychelles Magpie robins were introduced in the mid 1990s; there is now a thriving population of 30 birds.
Restoring whole island ecosystems on Denis Island: A private sector and NGO collaboration
Denis island has seen extensive environmental disturbance in the past, with removal of guano and creation of a coconut plantation over most of the island. Pesticides have been used in the past and the island was infested with mice and rats. Like many islands in the Seychelles its flora and fauna consisted mostly of alien species. The island owners have been desirous for some time to restore Denis to its natural state.
In 1999 the island management agreed on a joint program with Nature Seychelles which has proven expertise in species rehabilitation and island restoration. Denis Island management funded the eradication of rats and mice in 2000 and 2002. Nature Seychelles through a World Bank GEF project has undertaken a complete biological assessment of the island, cost analysis of restoration and maintenance, an island management plan and planting of native trees. It has undertaken the translocation of globally threatened endemic species.
The aim of the habitat management was to promote a more extensive high-canopy forest of native tree species which provide plenty of invertebrate food for birds and other endemic wildlife. The first stage of the habitat management by Nature Seychelles’ island assessment and restoration teams involved the removal of hundreds of coconut palms, most of which were self-sown plants from the original plantation palms, from around thirty hectares of woodland. In places these palms grew so thickly as to exclude all other vegetation.
A nursery was established by Nature Seychelles to provide about 2000 young trees of various native species for planting out. The second phase of work by the team was the planting of these saplings in the areas cleared of coconut growth. With additional natural regeneration, all the woodland areas should begin to fill with native trees in a few years time.
Denis Island now has no introduced predators: during this project, two cats (apparently the last individuals on the island) were killed, and the population of Mynah birds was considerably reduced. Unfortunately, despite an eradication attempt by the island management in 2000 black rats were once again on the island. However, in 2002 another eradication was successful.
Two rare species of Seychelles birds the Seychelles Warbler and the Seychelles Fody were transferred by Nature Seychelles to Denis in 2004 and these are successfully breeding.
Since 2002, Denis island management pays for a permanent conservation officer. The officer undertakes measures to guarantee that rodents do not re-invade the island and has ensured that dangerous pesticides have been phased out and practices on the island are compatible with conservation. It is hoped the full potential of the island will be realised when the native habitats fill most of the island and other endemic wildlife is established.