Key issues and solutions for designing and sizing biodiversity offsets

Habitat loss through development is one of the major causes of biodiversity loss. The increasingly common legal requirement to first avoid, then reduce and, if necessary, offset impacts of plans and projects on biodiversity has however not always been appropriately enforced. The blame lies mainly in bad governance such as patchy monitoring or poorly defined liabilities. Biodiversity offsets also suffer from the lack of formal methods for designing and sizing offset requirements.

In a paper recently published in Biological Conservation, Fabien Qu├ętier (who is involved in this blog) and Sandra Lavorel address this gap by reviewing the different tools, methods and guidelines that have been developed in different regulatory contexts to design and size biodiversity offsets.

They formulated a typology of approaches that variously combine the methods and guidelines reviewed and then discuss how these relate to the objectives of offset policies, the components of biodiversity and ecosystems to which they apply, and the key issues for ecological equivalence.

One of the key messages from the paper might be that when gains are not realistic, e.g. because we do not know how to enhance or restore a habitat or ecosystem function (i.e. they are non renewable), then protection of as-yet unprotected habitats or ecosystems is the only realistic offset option.

This has several consequences, the most notable being that, in effect, using protection as offset means we assign a ratio of acceptable loss to the remaining unprotected habitat or ecosystem. For example, protecting 3 hectares for every unprotected hectare lost actually means that we accept to loose a quarter of the unprotected area. This then means we must think strategically about what we want to do with that quarter… which is then a non renewable resource too!

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