Mauritius: Forest Habitat Restoration in the Ile Aux Aigrettes Nature Reserve

Project Stage:
Implementation

Start Date:
1984-03-26

End Date:
2009-03-26

Primary Causes of Degradation

Degradation Description

Degradation of the islet began with the arrival of Europeans in the seventeenth century and has been driven by two primary causes: deforestation to meet the demand for its valuable hardwoods and enable the cultivation of sugar cane, and the introduction of a large number of exotic plant and animal species. By the time restoration activities began in 1984, the island had become a threatened ecosystem, and native species were under intense pressure from non-native competitors.

There are 97 known introduced plant species on the island, 28 of which are considered major weeds, including: false acacia (Leucaena leucocephala), prune malgache (Flacourtia indica) and tecoma (Tabebuia pallida). Others such as Asparagus setaceous and Kalanchoe pinnata are not currently present at high densities but represent a potential threat.

Rats, cats, mongooses, goats and chickens were previously present on the island, and although they have been successfully eradicated (mostly through trapping), there are still a number of alien animal species present. These include: shrews, Giant African landsnails (Acatina spp.), the Indian wolfsnake (Lycodon aulicus) and the agamid lizard (Calotes versicolor). Several species of house geckos are also present on the island. These species impact native species in several ways: they affect native invertebrate and reptile species both as competitors and predators; they feed on native seedlings and fruit, inhibiting natural succession; and they eat birds’ eggs, posing a threat to important avifauna species.

Project Goals

MWF’s objective is to restore Ile aux Aigrettes to a condition much as it was before the arrival of Europeans in Mauritius, with all the flora and fauna necessary for it to be a self-sustaining indigenous ecosystem. This includes conserving and re-establishing native plant and animal species by first removing exotic invasive species and then reintroducing native vegetation and endemic birds and reptiles.

A secondary objective is to develop a model for ecological restoration that can be applied to other sites.

Monitoring

The project does not have a monitoring plan.

Stakeholders

The key stakeholders in the project are: a) the national government (in the body of the National Parks and Conservation Service), which has the national responsibility of ensuring that Mauritius’s native and endemic species and habitats are conserved under the NEAP, b) the project executing agency, the Mauritian Wildlife Foundation c) the national and local communities, and the tourism operators who will all gain economically from any increased volume of ecotourists, d) Global Environment Facility (GEF), the World Bank and other co-financing organisations, and e) The national and international tourists who visit Ile aux Aigrettes.

Throughout its 16-year existence, MWF has collaborated closely with the Government of Mauritius National Parks and Conservation Service. MWF’s links with the national media, its newsletter and its Wildlife Supporters Club have provided regular information about all of MWFs projects to the national public and conservation enthusiasts. More recently, MWF has been involved in public education through the activities of MWF’s Community Conservation Educator for nearby Rodrigues Island, and the ecotourism project in Mauritius. The Rodrigues community education project and Ile aux Aigrettes tourism projects have integrated public consultation and involvement in awareness-raising and planning. MWF’s forest restoration projects in Mauritius and Rodrigues have made opportunities available for community participation.

Description of Project Activities:
Upon assuming responsibility for the management of Ile aux Aigrettes, one of the first steps taken by the MWF was to contract a resident watchman in order to stop illegal entry into the island reserve and protect the forest from massive firewood harvesting. Invasive plant eradication programmes on Ile aux Aigrettes began in 1985 and have been carried out by off-season sugar cane workers, contract labourers and a handful of volunteers, with the main target species being Leucaena leucocephala, Flacourtia indica and Tabebuia pallida. Weeding is done mechanically by uprooting (pulling by hand or removing mechanically for larger plants) and, where this is not possible, by simply cutting the tree stems and brushing a ten percent solution of herbicide (usually Tordon 101 (picloram) or Roundup (glyphosate)) on the cut stem. Labour costs for initial weeding have been estimated at approximately US$3,000 per hectare. Once these areas are cleared of invasive plants, it is necessary to replant immediately with native species in order to slow down secondary invasions and regrowth of non-natives from the seed bank. The island is divided into 12.5 x 12.5m grids for management purposes, and each grid is surveyed and given a planting prescription ranging from no planting to full planting. Seedlings are replanted at a density of up to four plants per square metre, and the main species planted include: Dodonaea viscosa, Gastonia mauritiana, Pandanus vandermeeschii, Tarenna borbonica and Dracaena concinna. Seedlings are produced in a nursery established on the island in 1997 from seeds collected on Ile aux Aigrettes and from some well defined areas on the mainland (although where possible, efforts are made not to mix mainland populations, as they may have separate genotypes). Planting occurs during the rainy season (February to April) in square plugs 4 - 5 cm deep, and the seedlings are usually about 20 cm high when planted. After initial weeding and replanting, regrowth and reinvasion of exotic species must be regularly monitored and controlled. Continuity is absolutely crucial to deplete the soil seed bank and to assure successful re-establishment of native vegetation. On Ile aux Aigrettes, the first maintenance weeding of the newly planted areas is carried out between one and six months after the initial weeding and replanting, with a second several months later (depending on the state of weed regrowth). All species except grasses are removed by hand. Weeding is subsequently carried out once a year with an estimated long-term cost of approximately US$140 per hectare per year (Mauremootoo and Towner-Mauremootoo in press). Although it is expected that once the native canopy is restored, regrowth of exotic species will sharply decline, low-intensity weeding will almost certainly have to be continued indefinitely. In 1991 rats, cats and mongooses previously present on the island were successfully eradicated. Based on advice from experts in New Zealand, anti-coagulant poisons were used to kill rats without affecting native species. Cats and mongooses were removed by trapping. No efforts have yet been made to eradicate the Giant African landsnails (Acatina spp.) or the Indian wolfsnake (Lycodon aulicus), although the populations have been surveyed. Once these predatory species had been eradicated from the island, the process of restoring native fauna began. Over 30 Mauritius Kestrels (Falco punctatus), formerly regarded as the world's rarest bird, were reintroduced between 1990 and 1994. In 1994, an aviary was set up on the island, and 35 Pink Pigeons were reintroduced. The critically endangered Mauritius Fody (Foudia rubra) was reintroduced in November 2003 and is now successfully breeding. Finally, in December 2006, 4 Olive White-eyes (Zosterops chloronothos) and 39 Telfair's skinks (Leiolopisma telairii), a native repile once widespread throughout Mauritius, were reintroduced to celebrate 20 years of conservation work on Ile aux Aigrettes. Mauritius once had two endemic giant tortoise species (Geochelone inepta and Geochelone triserrata), but these became extinct about 200 years ago as a result of excessive exploitation by man and predation by introduced animals. In 2000, 18 adult and sub-adult Giant Aldabran Tortoises (Geochelone gigantean) were released on Ile aux Aigrettes to simulate the impact of browsers on the island's vegetation and help control the regeneration of exotic species. The release of G. gigantea on a larger scale will only be carried out after it has been proven that native species do not suffer from grazing. Moreover, before the giant tortoises could be released island-wide, herbivore-dispersed weeds such as Leucaena leucocephala would have to be eradicated.

Ecological Outcomes Achieved

Eliminate existing threats to the ecosystem:
At the time of writing, nearly 90% of the island (all but 5 ha) had been weeded at least once and replanted with native plants. Some 30 endangered endemic/native plant species had been reintroduced to the island, including the critically endangered Round Island Bottle Palm and the Round Island Hurricane Palm, of which only one adult tree remains in the wild. Intense weeding efforts will be maintained until 2010 and will gradually be reduced as the forest canopy is restored. Under a good canopy, an area will require weeding about once every five years. The reintroduction of native fauna has been largely successful and has contributed significantly to stabilizing waning populations of important and critically endangered species. The island's population of Pink Pigeons has grown from 35 to approximately 70 and currently represents 20% of the world's remaining population, being 1 of only 5 sub-populations of this vulnerable species. The number of Fodies on Ile aux Aigrettes has increased every year since their release, and in December 2008, there were 152 individuals counted, the largest number on record. In fact, the Fodies have done so well that they will be used as the source population for a new sub-population to be reintroduced on Round Island (north of Mauritius) in 2009. The 4 Olive White-eyes released in 2006 have grown to 6 nesting pairs, and in December 2008, 35 nesting attempts were recorded, of which 13 produced eggs. The Mauritius Kestrel, reintroduced on Ile aux Aigrettes in the early 1990s, now visits the island only on rare occasions, preferring instead the nearby Bambous Mountains on the mainland. In spite of the fact that a population has not become established on Ile aux Aigrettes, Mauritius Kestrels now number between 800 and 1000 and are considered one of the MWF's greatest success stories after standing on the brink of extinction with only 4 individuals left in the wild in 1974. The release of reptiles on Ile aux Aigrettes has also been successful. The Aldabran tortoises show a grazing preference for exotic plant species and are thus helping to control weeds. The Telfair's skink, reintroduced in 2006, is also aiding in the restoration of the island, as it is reducing the number of problematic introduced animals that can't be removed by the MWF (e.g. Indian House shrew, Indian wolf snake) and dispersing the seeds of such endemic plants as Ebony.

Factors limiting recovery of the ecosystem:
In spite of the efforts made by the MWF, there are still a number of introduced or alien animal species present on the island. This includes the Indian House shrew (Suncus murinus), Indian wolfsnake (Lycodon aulicum), and Giant African land snail (Achatina fulica), all of which affect native biodiversity as competitors and predators. In 1999, an attempt to eradicate the House Shrew proved unsuccessful, as managers of the island have yet to find a completely effective bait that attracts House Shrews to live traps or for poisoning. Furthermore, poisoning has proven problematic because an effective poison has not been found yet either. Managers are currently investigating new baits, possibly using micro-encapsulated shrew scent, and considering the use of dogs that can find "˜trap-shy' individuals. Once shrews have been successfully eradicated, a number of indigenous reptile species will be reintroduced. Other problematic species include the agamid lizard (Calotes versicolor) and house geckos. Researchers on the island feel that, given current technology, there is little hope of eradicating either of these two species. Nic Cole, the project's herpetologist, is currently investigating the interactions between the native and introduced geckos on the island. Fortunately, he has found that there are relatively more native geckos in restored vegetation than in invaded communities. Agamid lizards have been found to be much more common in open areas that are newly weeded and appear to decrease once the vegetation cover increases.

Socio-Economic & Community Outcomes Achieved

Economic vitality and local livelihoods:
This project is working to save a number of endemic and critically endangered species that would otherwise be lost to future generations. The coastal ebony forest on Ile aux Aigrettes is the last such remnant in Mauritius, and the restoration and protection of this unique resource is of paramount importance not only for the local population but also for the entire world. It provides habitat for rare and endemic species and represents a symbolic and invaluable hotspot of Earth's remaining biodiversity. Besides helping to conserve irreplaceable resources and safeguard Mauritius's natural heritage, MWF's work on Ile aux Aigrettes has made significant contributions to local livelihoods. Activities directly associated with the restoration effort have afforded employment and training opportunities, and the development and promotion of ecotourism on the newly restored island has generated additional income for local communities.

Key Lessons Learned

The lessons learned from this project have helped guide the development of restoration work on nearby Rodrigues Island and Round Island. In a couple of notable cases (e.g. Mauritius Fody), species reintroduced to Ile aux Aigrettes have even been used as a source population for the reintroduction of species in these other locations.

Long-Term Management

MWF has long-term leases to manage Ile aux Aigrettes and is expected to continue to raise funds internationally and domestically for its conservation activities (e.g. monitoring and maintenance of project sites). As the project is executed, diminishing maintenance is expected since the restored ecosystems should grow toward a stable climax state. Steps to promote ecotourism on Ile aux Aigrettes began in 1995 as a means of raising public awareness, generating income and employment, and contributing to the sustainable development of Mauritius. In the unlikely event MWF does not renew its lease, the Government of Mauritius may consider visitor fees for Ile aux Aigrettes in order to raise funds to support conservation activities. The project emphasizes strengthening local technical and administrative capacities to identify and respond to similar biodiversity threats in the future, and takes full advantage of the cooperative spirit between government, NGOs and the private sector to establish long-term relationships.

Sources and Amounts of Funding

Funding for the Ile Aux Aigrettes program has been provided mainly by the Government of Mauritius and the Global Environment Fund (through the World Bank), with additional support from the IUCN SSC Sir Peter Scott Fund for conservation actions, Rufford Maurice Laing Foundation, and St. Mary’s Charity. The local sugar estates have provided invaluable assistance by supplying labor for weeding and planting free of charge during the off-season.

Other Resources

Global Environment Facility. 1995. Mauritius Biodiversity Restoration Project. Report No. 14527-MAS.

Kueffer, C. and Mauremootoo, J. 2004. Case Studies on the Status of invasive Woody Plant Species in the Western Indian Ocean. 3. Mauritius (Islands of Mauritius and Rodrigues). Forest Health & Biosecurity Working Papers FBS/4-3E. Forestry Department, Food and Agriculture Organization of the United Nations, Rome, Italy.

Mauritian Wildlife Foundation
http://www.mauritian-wildlife.org/

Parnell, John A. N., Q. Cronk, P. Wyse Jackson, and W. Strahm. 1989. A Study of the Ecological History, Vegetation and Conservation Management of Ile aux Aigrettes, Mauritius. Journal of Tropical Ecology 5(4):355-374.

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