Improving averted loss estimates for better biodiversity outcomes from offset exchanges


F LEUR J. F. MAS EY K,MARTINE MARON,ASC E L I N GORDON J O S EPH W. B ULL and MEGAN C. E VA N S


Abstract Biodiversity offsetting aims to achieve at least no net loss of biodiversity by fully compensating for residual development-induced biodiversity losses after the mitigation hierarchy (avoid, minimize, remediate) has been applied. Actions used to generate offsets can include securing site protection, or maintaining or enhancing the condition of targeted biodiversity at an offset site. Protection and main- tenance actions aim to prevent future biodiversity loss, so such offsets are referred to as averted loss offsets. How- ever, the benefits of such approaches can be highly uncer- tain and opaque, because assumptions about the change in likelihood of loss as a result of the offset action are often implicit. As a result, the gain generated by averting losses can be intentionally or inadvertently overestimated, leading to offset outcomes that are insufficient for achieving no net loss of biodiversity. We present a method and decision tree to guide consistent and credible estimation of the likeli- hood of biodiversity loss for a proposed offset site with and without protection, for use when calculating the amount of benefit associated with the protection component of averted loss offsets. In circumstances such as when a jurisdictional offset policy applies to most impacts, plausible estimates of averted loss can be very low. Averting further loss of bio- diversity is desirable, and averted loss offsets can be a valid approach for generating tangible gains. However, overestimation of averted loss benefits poses a major risk to biodiversity.


Keywords Averted loss offsets, biodiversity offset, counter- factual scenario, habitat protection, mitigation, restoration


FLEUR J. F.MASEYK* (Corresponding author, orcid.org/0000-0002-2712-0438)


The Catalyst Group, PO Box 1048, Wellington 6140, New Zealand E-mail fleur@thecatalystgroup.co.nz


MARTINEMARON* School of Earth and Environmental Science, The University of Queensland, Brisbane, Australia


ASCELIN GORDON School of Global Urban and Social Studies, RMIT University, Melbourne, Australia


JOSEPH W. BULL Durrell Institute of Conservation and Ecology, School of Anthropology and Conservation, University of Kent, Canterbury, UK


MEGAN C. EVANS*§ School of Earth and Environmental Science, The University of Queensland, Brisbane, Australia


*Also at: Centre for Biodiversity and Conservation Science, Faculty of Science, The University of Queensland, Brisbane, Australia §Also at: Centre for Policy Futures, The University of Queensland, Brisbane, Australia


Received 4 September 2018. Revision requested 19 November 2018. Accepted 1 May 2019. First published online 10 February 2020.


Introduction


iodiversity offset actions aim to generate biodiver- sity gains of adequate magnitude to counterbalance development-induced biodiversity losses. The goal is to achieve no net loss of biodiversity (IUCN, 2016). Best prac- tice dictates that the use of offsets should only occur once all attempts to avoid, minimize or remediate biodiversity losses have been exhausted, in line with the mitigation hierarchy (Arlidge et al., 2018). Nevertheless, the use of biodiversity offsets has become increasingly common globally (Maron et al., 2016) and it is therefore critical that anticipated gains generated from offset actions are estimated as accu- rately as possible. Many offset policies and projects rely wholly or partly on


B


generating a gain by protecting existing biodiversity which, in the absence of the offset, is anticipated to be lost in the future. These are known as averted loss or avoided loss off- sets. Processes resulting in the loss of biodiversity manifest in two general ways: (1) complete loss of area, such as that caused by deforestation or permanent draining of wetland habitat, and (2) loss of habitat condition (quality), as caused by impacts from factors such as surrounding land use, inva- sive species, climatic events and development-induced shifts in ecological processes that result in degradation. Thus, biodiversity area, biodiversity condition, or both, can be affected by threatening processes, and the loss of both can be averted to generate biodiversity gains within an offset exchange. The loss of an area valuable for biodiversity is typically


averted through actions that increase legal protection at a site (protection actions; Table 1), whereas averting loss of condition typically involves implementingmanagement ac- tions (maintenance actions; Table 1). Enhancement actions are often similar to maintenance actions, but rather than simply maintaining condition, they aim to improve the bio- diversity at a site above its current value, or to shift an an- ticipated upward trajectory onto a steeper positive curve (Table 1). Relying solely on a single action (e.g. protection) is unlikely to generate gains sufficient to offset losses, either at the project or policy level (Maron et al., 2018). In practice, offset proposals often rely on a combination of offset actions aiming to preserve both the area (via protection actions) and the condition (via maintenance or enhancement actions) of a site to generate biodiversity benefits adequate to counter- balance losses. However, the anticipated gains from all pro- posed actions need to be estimated accurately, or the total


This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited. Oryx, 2021, 55(3), 393–403 © The Author(s), 2020. Published by Cambridge University Press on behalf of Fauna & Flora International doi:10.1017/S0030605319000528


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