Biodiversity offset schemes often fail to meet aims

Biodiversity offset schemes, similar to those implemented for desalination projects, do not always fully compensate for loss of habitat due to development, new research suggests.

Writing in the journal Conservation Biology*, a team from Muséum National d'Histoire Naturelle in Paris, France, looked at 66 development projects in France with offset schemes.

They found that numbers of species in offset sites was on average five times lower than in the land destined for development. Furthermore, even endangered species were not always protected by these offset sites.

Under environmental legislation in Europe, as well as in the USA and other parts of the world, any development must maintain or restore a favourable conservation status for protected species. To do this, developers often use 'offset' land, restoring or creating habitats that can compensate for the development's effects by protecting the same species that have been lost in the development site.

Few studies have assessed whether this is truly achieved. In this study, researchers reviewed the offset activities of 85 French development projects undertaken between 2009 and 2010, which affected 253 species in all. These included reversible developments, such as landfill sites, that can be restored in the future, and irreversible developments, such as roads.

The results show that 19 of the 85 developments provided no offset measures at all and, out of the 66 that did, only 30 considered all affected species. A greater proportion of endangered species (82%) were protected than more common species (26%). However, the researchers stress that this result indicates that even endangered species were not always protected.

On average, the offset sites had five times fewer species than the pre‑development sites. In fact, when species richness was high (more than eight species per site) in pre-development sites, the numbers of the species in offset sites were up to ten times lower. The area of the offset sites was smaller and all together only amounted to 37% of the area of development sites.

* B Regnery, D Couvet, and C Kerbiriou, (2013). Offsets and Conservation of the Species of the EU Habitats and Birds Directives. Conservation Biology. DOI: 10.1111/cobi.12123.

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