RM Journal

The use of modelling for terrestrial biodiversity offsets and compensation: a suggested way forward


Authors: Baber, Christensen, Quinn, Markham, Kessels, Ussher and Signal Ross  

In recognition of New Zealand’s indigenous biodiversity declineoffsetting and compensation principles are increasingly identified in statutory planning documents to address residual effects on terrestrial biodiversity.

The proposed National Policy Statement for Indigenous Biodiversity (NPSIB)when finalised (likely April 2021), is expected to require the use of these measures more generally 

A key challenge for consent decision-makers is determining the adequacy of offsets and compensation for residual adverse effects on terrestrial biodiversity values (i.e. those adverse effects remaining after all appropriate avoidance, minimisation and remediation measures have been sequentially applied). 

To our understanding no operative or proposed policy documents mandate a specific method for the calculation or assessment of the adequacy of offsets and compensation, and there is currently no consistent approach used.  

One of the key principles of an offset is achieving ‘no net loss’ (NNL) or preferably net gain (NG) of indigenous biodiversity. However, demonstrating that NNL/NG will occur at the consenting stage is difficult due to data deficiencies and uncertainty in the success of the measures proposed.

Correspondingly, efforts to address residual effects often default to compensation, which in many instances is based solely on professional opinion and may include the use of compensation ratios or ‘multipliers’ (i.e., wetland enhancement at a ratio of 1:3 to address wetland loss). 

These approaches have been challenged due to a lack of transparency and rigour, and their often ad-hoc application 

This article considers the merits of two different modelling approaches for providing guidance on the type and amount of habitat restoration and enhancement activities needed for a project to achieve NNL or NG at the consenting stageBiodiversity Offset Accounting Models (BOAMs) and Qualitative Biodiversity Models (QBMs).  

We conclude that QBMs are useful as the primary modelling approach at the consenting stage because, unlike BOAMs, QBMs can provide guidance on both offsetting and compensation requirements and can be readily applied across the full spectrum and scale of consent applications

That said, to provide greater assurance that NNL/NG outcomes are achieved if consent is granted, BOAMs based on ongoing biodiversity monitoring should be used to verify NNL/NG outcomes are achieved and/or guide adaptive management needs as required. 

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