Skip to main content
Kent Academic Repository

Evaluating the impact of biodiversity offsetting on native vegetation

zu Ermgassen, Sophus O. S. E, Devenish, Katie, Simmons, B. Alexander, Gordon, Ascelin, Jones, Julia P. G., Maron, Martine, Schulte to Bühne, Henrike, Sharma, Roshan, Sonter, Laura J., Strange, Niels, and others. (2023) Evaluating the impact of biodiversity offsetting on native vegetation. Global Change Biology, 29 (15). pp. 4397-4411. ISSN 1354-1013. E-ISSN 1365-2486. (doi:10.1111/gcb.16801) (KAR id:101630)


Biodiversity offsetting is a globally influential policy mechanism for reconciling trade‐offs between development and biodiversity loss. However, there is little robust evidence of its effectiveness. We evaluated the outcomes of a jurisdictional offsetting policy (Victoria, Australia). Offsets under Victoria's Native Vegetation Framework (2002–2013) aimed to prevent loss and degradation of remnant vegetation, and generate gains in vegetation extent and quality. We categorised offsets into those with near‐complete baseline woody vegetation cover (“avoided loss”, 2702 ha) and with incomplete cover (“regeneration”, 501 ha), and evaluated impacts on woody vegetation extent from 2008 to 2018. We used two approaches to estimate the counterfactual. First, we used statistical matching on biophysical covariates: a common approach in conservation impact evaluation, but which risks ignoring potentially important psychosocial confounders. Second, we compared changes in offsets with changes in sites that were not offsets for the study duration but were later enrolled as offsets, to partially account for self‐selection bias (where landholders enrolling land may have shared characteristics affecting how they manage land). Matching on biophysical covariates, we estimated that regeneration offsets increased woody vegetation extent by 1.9%–3.6%/year more than non‐offset sites (138–180 ha from 2008 to 2018) but this effect weakened with the second approach (0.3%–1.9%/year more than non‐offset sites; 19–97 ha from 2008 to 2018) and disappeared when a single outlier land parcel was removed. Neither approach detected any impact of avoided loss offsets. We cannot conclusively demonstrate whether the policy goal of ‘net gain’ (NG) was achieved because of data limitations. However, given our evidence that the majority of increases in woody vegetation extent were not additional (would have happened without the scheme), a NG outcome seems unlikely. The results highlight the importance of considering self‐selection bias in the design and evaluation of regulatory biodiversity offsetting policy, and the challenges of conducting robust impact evaluations of jurisdictional biodiversity offsetting policies.

Item Type: Article
DOI/Identification number: 10.1111/gcb.16801
Additional information: For the purpose of open access, the author(s) has applied a Creative Commons Attribution (CC BY) licence to any Author Accepted Manuscript version arising
Uncontrolled keywords: Australian native vegetation; biodiversity offsets; counterfactual analysis; environmental policy; impact evaluation; net gain; no net loss; regulatory markets; statistical matching
Subjects: G Geography. Anthropology. Recreation
Divisions: Divisions > Division of Human and Social Sciences > School of Anthropology and Conservation
Divisions > Division of Human and Social Sciences > School of Anthropology and Conservation > DICE (Durrell Institute of Conservation and Ecology)
Funders: Natural Environment Research Council (
SWORD Depositor: JISC Publications Router
Depositing User: JISC Publications Router
Date Deposited: 12 Jun 2023 10:47 UTC
Last Modified: 27 Feb 2024 12:19 UTC
Resource URI: (The current URI for this page, for reference purposes)

University of Kent Author Information

zu Ermgassen, Sophus O. S. E.

Creator's ORCID:
CReDIT Contributor Roles:

Bull, Joseph W..

Creator's ORCID:
CReDIT Contributor Roles:
  • Depositors only (login required):

Total unique views for this document in KAR since July 2020. For more details click on the image.