Destruction and reconstruction: is freshwater offsetting achieving No Net Loss?

ABSTRACT

‘Biodiversity offsetting’ aims to address the residual negative environmental impacts of human development. It’s goal is to achieve No Net Loss (NNL), and preferably a Net Gain of biodiversity attributes between development and offset sites. Biodiversity offsetting suffers from a lack of ‘proof of concept’, as little work has been done to critically test the ecological efficacy of offsetting practices. Offsetting of stream ecological functions was investigated in Aotearoa New Zealand, via review of regulatory documentation for 76 offsets and field assessments of 14 offset sites. Field results indicated some functions, including fish passage connectivity, respond rapidly post-offset enhancement whilst others exhibit recovery lags (such as fish spawning habitat provision). However, most offsets were considered unlikely to achieve NNL due to failures in practice and process. Factors included inadequate consideration for restoration uncertainty, inappropriate monitoring conditions, insufficient data and inequivalent trade-offs. Key linkages between aquatic and terrestrial ecosystems, particularly regarding floodplain connectivity, were poorly considered in offset implementation. Thus, development may be occurring based on inadequate regulatory processes, and poorly evaluated ecological outcomes. These findings join a growing body of evidence which indicates that, in the context of a global biodiversity crisis, offsetting is not achieving its purpose of NNL.

KEYWORDS:

• Biodiversity conservation
• biodiversity offsetting
• ecological restoration
• environmental management
• environmental policy
• freshwater ecology
• No Net Loss

Data availability statement

Fully anonymised data will be made publicly available via an appropriate public data archive at the time of publication.

Authors contributions

C.A.P. conceived and developed the research ideas and methodology in collaboration with K.S.S. and M.N.; C.A.P collected and analysed the data, and led the writing of the manuscript. All authors contributed critically to the drafts and gave final approval for publication.

Acknowledgements

We sincerely thank Dr Stephen Knight-Lenihan (University of Auckland) for his feedback, Finnbar Lee for your R assistance, and the Auckland Freshwater Ecosystems Lab of 2019 for your support.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the University of Auckland Research Masters Scholarship; and the Auckland Council RIMU Masters Scholarship.