Unchanged since the first European settlers arrived more than 400 years ago, Ferney Valley is one the last remaining indigenous forests on the Indian Ocean island.

However, environmentalists say the forest is under threat as construction gets under way to build a highway through it, primarily to service the island's lucrative tourism industry.

"Given the tiny amount of good quality tropical forest remaining on Mauritius, this development can only be viewed as catastrophic to the native biodiversity," says Achim Steiner, director-general of the World Conservation Union.

The aim of the 25-km (16-mile) South Eastern Highway is primarily to promote tourism, by providing a shorter route from the airport to east coast resorts for the thousands of visitors who flock to palm-fringed Mauritian beaches every year.

Tourism is a key economic pillar for the tiny island of 1.2 million people, host to more than 700,000 tourists a year.

LONG AND WINDING ROAD

With sugar and textile exports threatened by liberalised trade laws, the island wants to fully exploit its tourism sector which generated 23,448 million rupees ($780.3 million) last year -- a 20.8 percent rise compared with the previous year.

"At the moment there is only one main road from the airport along the east coast, which is a long, winding and often congested and unsafe route," says Sadruddin Diljore, divisional manager of the Road Development Authority.

"The new highway will provide a better alternative route and will support productive sectors of the economy and promote tourism".

Opponents of the $19 million project, funded by the African Development Bank, argue that the government could upgrade the existing coastal route or investigate alternative routes which will save Ferney Valley and benefit poor local communities.

About 60,000 people live in fishing villages on the east coast, yet the area remains one of the island's most under-developed, with low incomes and high unemployment.

"If the existing road was upgraded or another route going through the villages was considered it could benefit local people who could set up cafes, shops and restaurants," said George Ah Yan, president of the Mahebourg Citizens Welfare Organisation, a local community group.

"No one stays in Ferney Valley, so it would not benefit anyone to put a road there," he adds.

However, the government says upgrading the existing road would mean a costly relocation of communities, adding that abandoning the Ferney Valley route would incur contractual penalties of $1 million -- a hefty sum for a country with a budget deficit of five percent of gross domestic product.

NOISE, LITTER, FUMES

Since the first Europeans arrived on the island in 1598, the natural habitat has gradually been devastated by human habitation, the introduction of alien plants and animals, sugar cane cultivation and tourism.

Only 1.6 percent of the original forests remain and the World Conservation Union has ranked Mauritius, off East Africa's coast, as having the third most endangered flora in the world.

Scientists estimate more than 100 endemic plant and animal species are now extinct, including the island's most famous symbol, the dodo, a large, flightless bird which became extinct in the late 17th century because of over-hunting and habitat destruction.

Other extinct species include bats, reptiles, and birds such as the solitaire and the Mauritius blue-pigeon. The island has more threatened species per unit of area than any other country.

Environmentalists say Ferney Valley is vital for the survival of threatened flora and fauna and is home to six species of critically endangered trees, including the Eugenia Bojeri, Pandanus Macrostigma, Pandanus Iceryi -- trees assumed extinct until their discovery a few months ago.

The forest is also home to half the world's population of Mauritius kestrels, once the world's rarest bird. From near extinction in the 1970s, its population has grown to almost 1,000 as a result of a captive breeding programme in Ferney Valley.

Authorities say less than one percent of the 700 hectares (1,730 acres) of forest will be removed by the road, adding they will mitigate any damage by replanting four times as many trees.

Opponents of the project say losing even a tiny fraction of the original forest will be detrimental in the long term.