This article has been amended since it was first published.

It is the last bastion of the dodo – the only place on Earth where fossils of the iconic extinct bird are known to exist.

The 0.5-sq-km Mare aux Songes fossil site is a unique portal into the island of Mauritius's remote past before humans arrived. It has the potential to become one of the most famous fossil localities in the world.

And soon you might be able to view it from a hotel window.

Researchers and local campaigners are concerned that if planned building projects around the fossil site go ahead, their impact could irreversibly spoil the area and jeopardise any future bid to have the site's natural heritage recognised internationally.

However, the developers of one proposed hotel in the area say that their plans comply with all the relevant environmental regulations, and that the development will be "the first real sustainable project on the island".

Despite its fame, the dodo has suffered a shameful fate since its extinction 350 years ago. Several specimens were collected on Mauritius before the bird disappeared – but by the early 19th Century not a single complete skeleton survived.

In 2005, almost miraculously, the Mare aux Songes was rediscovered

This made the discovery of the Mare aux Songes in 1865 all the more important. In this unassuming swamp, researchers uncovered numerous fossilised dodo bones, enough to cobble together a complete dodo skeleton.

Although that skeleton contains bones from several individual birds, it still gave Victorian scientists their best opportunity to understand the anatomy of the lost species.

But by the mid-20th Century, the Mare aux Songes had itself been lost. The swamp is a breeding ground for mosquitoes, so it was filled with rubble during a malaria epidemic. No one thought to note its exact location beforehand.

"Many people thought it was [subsequently] paved over by the runways of the nearby Mauritian airport," says Leon Claessens at the College of the Holy Cross in Worcester, Massachusetts.

The Mare aux Songes was a beautiful oasis with a shallow lake back then

But in 2005, almost miraculously, the Mare aux Songes was rediscovered. The diligent work of dodo enthusiasts established the site's location, just beyond the airport's perimeter.

Kenneth Rijsdijk of the University of Amsterdam in the Netherlands and his colleagues have since begun studying the site again. Their work emphasises just how important the Mare aux Songes is.

Alongside the dodo bones, Rijsdijk and his colleagues found skeletal remains from a diverse array of animals. The famous flightless birds shared the landscape with at least two types of giant tortoise, fruit bats, flamingos, lizards, parrots and harriers, to name but a few species.

"The Mare aux Songes was a beautiful oasis with a shallow lake back then, where thousands of animals came to drink fresh and clean water," says Rijsdijk.

This means the fossil site is not simply a place to go looking for dead dodos. It is the only place on Earth where we can get a true sense of the dodo as a living and breathing animal, part of a thriving – and now lost – ecosystem.

With proper care and attention, the Mare aux Songes could become as famous as the dodo itself

The team's research also helped explain why the Mare aux Songes fossils are so rare and unusual.

Most of Mauritius is blanketed with acidic soils that rapidly eat away bones buried in the ground. The Mare aux Songes is different. It is near the coast, and the fossils lie on top of a bed of alkaline coral sand from an ancient beach.

It is the chemistry of the sand that has helped buffer the groundwater to create an environment suitable for bone preservation. Without these special conditions, it is unlikely that the fossils would have survived as long as they have – 4,200 years.

With proper care and attention, the Mare aux Songes could become as famous as the dodo itself, says Rijsdijk. He thinks it could be made the heart of a science park, constructed carefully to avoid damage to the fossil site.

Rijsdijk is concerned that construction works will inadvertently disturb the unique chemistry of the Mare aux Songes

This science park would be somewhere that locals and curious tourists alike could visit, to learn more about the dodo and the island habitat it occupied before humans arrived.

Similar sorts of tourist attractions already exist at other world-famous fossil sites that have been given UNESCO World Heritage status.

But Rijsdijk, and other members of a non-profit scientific organisation called Dodo Alive, say that this vision is under threat from proposed building developments in the area, including hotels and an urban complex.

One hotel is being developed by Currimjee Jeewanjee & Co Ltd. They say the project will be a boon to the local economy, and that it incorporates "a plan to restore a coastal forest with 16,000 endemic species as it existed centuries ago".

The Mare aux Songes fossil site is a unique portal into the island of Mauritius's remote past

A spokesperson for the company told BBC Earth that the planned hotel buildings will actually be constructed several hundred metres away from the Mare aux Songes.

An access road has already been built that passes 36m from the site. A spokesperson said that the road "has obtained clearances from all authorities".

However, Rijsdijk and Dodo Alive say other proposed buildings  in the area are not far enough away to guarantee the safety of the fossils.

In particular, Rijsdijk is concerned that construction works will inadvertently disturb the unique chemistry of the Mare aux Songes. These delicate natural balances have preserved the site for 4,200 years. Altering them could mean the fossils still buried at the site will waste away before they can be studied.

It has also been suggested that the Currimjee Jeewanjee & Co Ltd hotel project could damage a nearby dune system that has helped shelter the Mare aux Songes from the sea. However, the developers' spokesperson says this has been "dealt with by leading scientists in our Environment Impact Assessment clearance of 2013".

The Mauritian Government's National Heritage Fund did not respond to a request to comment.

The Ramsar Convention Secretariat is now aware that this ecological character is under threat

UNESCO refused to discuss the criteria it uses to determine whether a given site is worthy of World Heritage or Global Geopark status – although a spokesperson did confirm that the wider environment, beyond the site itself, is taken into consideration.

Technically, the Mare aux Songes already has international recognition. In 2008, the stretch of coast adjacent to the site was designated a wetland of international importance under the Ramsar Convention.

"The [Mare aux Songes] is part of the Blue Bay Marine Park Ramsar Site as a buffer zone," says Paul Ouedraogo, the Ramsar Convention Secretariat's Senior Regional Advisor for Africa.

As such, the Mauritian government has already made a commitment to conserve the ecological character of the region.

The spokesperson for Currimjee Jeewanjee & Co Ltd points out that the hotel project "obtained a National Ramsar clearance in June 2014".

It is the only place on Earth where we can get a true sense of the dodo

However, Ouedraogo says that the international Ramsar Convention Secretariat is now aware that the ecological character of the Blue Bay Marine Park is under threat.

He says there are plans to place the Blue Bay Marine Park on a list of "Ramsar Sites with reports of human-induced negative changes having occurred, occurring or likely to occur". This move is likely to be formalised next month.

Update 1 July 2016: This article has been amended to make it clear that the developers have taken a number of steps to make their projects sustainable.

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