A court injunction to block development in western Pierrefonds was filed against the city of Montreal Wednesday.

In June, Montreal Mayor Denis Coderre announced up to 6,000 homes would be built on 185 hectares of forest and wetlands in the borough.

Coderre said it will help keep families on the island and 10 per cent of the land would remain as green space, but many say that won't be enough to protect the unique ecosystem.

“Coming out here, it's a nice escape really. One of the last nature spots I feel like is left on the island,” said mountain biker Andrew Sullivan, who rides through the nature reserve as often as he can.

The L'Anse-a-L'Orme nature park is 185 hectares of forest, meadows and wetlands.

“Together they form an ecosystem we have nowhere else. There's nothing else like that on the island,” said Sue Stacho, from the group Sauvons L’Anse-a-L'Orme.

The plaintiffs have filed an injunction to stop the residential project, saying five years ago the agricultural commission ruled any zoning change to a 20-hectare part of the park would have to be submitted before 2012.

The city of Montreal failed to meet this requirement, said Ricardo Hrtschan, the lawyer handling the injunction.

“The injunction that is added on is so that the developers, and that the city and that the (Communaute

metropolitaine de Montreal) respect the agricultural designation of the land,” he said, adding that any zoning change falls under the jurisdiction of the agricultural commission, not the city.

Mayor Coderre said the group is entitled to the legal process but the planned development will be sustainable and improve public transportation to the West Island.

“You know everybody's talking about housing, everybody's talking about retention and transport. We have a project to do so but even so, there will be some public consultation,” said Coderre.

Environmentalists say that this is a self-sustaining ecosystem, but a fragile one, and any potential development could upset the balance.

“If it's lost to development it means that we'll be under a threshold that provides for a great biodiversity of species, including plant and animal species and there'll be a collapse,” said David Fletcher of the Green Coalition.

Public consultations on the development are set for the fall, but those behind the injunction say they plan to use the courts to delay any development for as long as possible.