scientists advocate “a less interventionist vision”

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The island of Herblay extends over 16 hectares, between the banks of the town of Herblay-sur-Seine (Val-d'Oise) and those of the Seine-Aval station opposite.

This uninhabited place bought by the Department is home to around a hundred plant species and 41 bird species which come here to feed, rest and reproduce.

Scientific verdict

Supported by the Val-d'Oise Departmental Council, the project to create a “ biodiversity sanctuary unprecedented in Île-de-France”, consisting of reconstituting a “mosaic of habitats” – meadows, wooded areas and wetlands -, in order to be the subject of observations by scientists, is criticized by certain environmental associations, including the Gnsa, estimating that this 2.7 million euro program would go “against nature”.

“The island suffers from its anthropic past”

A project defended by the Departmental Council. “Despite its green appearance, the island of Herblay suffers from its anthropic past. In fact, it was used for cereal cultivation until the post-war period, then left abandoned, which led to the development of vegetation (…) which was banal and not very interesting from a point of view. ecological. In addition, the island is invaded by exotic or other unregulated species. This is why, before it can be left to evolve freely, it is necessary to carry out renaturation actions.”

The developments aim in particular to lower the altimetry of the island in order to “promote the expansion of floods”.

The wetlands thus created and connected by a network of ponds and channels would thus be, according to the Departmental Council, “richer in biodiversity”. A grassy area would be created on almost half a hectare and a wharf built so that scientists would have access to the site to monitor the evolution of the island.

The project had been criticized by the French Biodiversity Office which, in a letter addressed to state services, had estimated that the planned work program “raises questions about the destruction of species and habitats. Furthermore, the ecological added value presented by the development appears poorly substantiated.”

Questions from the scientific council

Associations are now relying on another element to question the project, that of the opinion of the Regional Scientific Council for Natural Heritage (Csrpn).

This body of experts, placed under the authority of the Regional Prefect and the President of the Regional Council, took a position last March after the presentation of the project to the Departmental Council.

If “the ambition and the means committed by the Department for this project are to be underlined (…) the question which is finally asked to the Csrpn by the Department, at this stage of the project, could be formulated as follows: is it preferable to leave the site in free evolution as it is today or to undertake ecological engineering work now and then leave all or part of the island to evolve freely?

The first scenario would constitute a rare opportunity and experiment to study the resilience of such an ecosystem. The second scenario, more interventionist, would suggest a more rapid improvement of the existing biodiversity of the island”, but it raises “questions”.

“Carrying out ecological developments and then letting the island evolve freely to see its biodiversity improve is not encouraged by the Csrpn [qui] is therefore favorable to (…) a scenario in favor of a less interventionist vision, with the main recommendation of directing financial resources towards the establishment and long-term implementation of scientific monitoring of the site in the face of global changes, through the evolution of its biodiversity and its naturalness”.

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