What are we measuring? A review of metrics used to describe biodiversity in offsets exchanges

Marshall, Erica; Wintle, Brendan A.; Southwell, Darren; Kujala, Heini

doi:10.1016/j.biocon.2019.108250

Cited by 72 publications

(55 citation statements)

References 60 publications

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“…The ineffectiveness of biodiversity offsets has been attributed to inconsistent and unclear biodiversity metrics (Gibbons et al 2018) and inadequate postimplementation monitoring and compliance at offset sites (Theis et al 2019). Accurately measuring biodiversity is challenging, and popular offsetting metrics assign habitat condition or area scores to a site by assessing, scoring, and weighting several vegetation attributes (Oliver et al 2014;Marshall et al 2020;zu Ermgassen et al 2019). With habitat condition scores varying across an area of impact, it is common to simply sum scores such that, for example, 25 ha of perfect-condition vegetation would receive the same overall offset score as 50 ha of vegetation that scores 50% less (Marshall et al 2020).…”

Section: Introductionmentioning

confidence: 99%

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Quantifying the impact of vegetation‐based metrics on species persistence when choosing offsets for habitat destruction

Marshall

Valavi

O’Connor³

et al. 2020

Conservation Biology

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Developers are often required by law to offset environmental impacts through targeted conservation actions. Most offset policies specify metrics for calculating offset requirements, usually by assessing vegetation condition. Despite widespread use, there is little evidence to support the effectiveness of vegetation-based metrics for ensuring biodiversity persistence. We compared long-term impacts of biodiversity offsetting based on area only; vegetation condition only; area × habitat suitability; and condition × habitat suitability in development and restoration simulations for the Hunter Region of New South Wales, Australia. We simulated development and subsequent offsetting through restoration within a virtual landscape, linking simulations to population viability models for 3 species. Habitat gains did not ensure species persistence. No net loss was achieved when performance of offsetting was assessed in terms of amount of habitat restored, but not when outcomes were assessed in terms of persistence. Maintenance of persistence occurred more often when impacts were avoided, giving further support to better enforce the avoidance stage of the mitigation hierarchy. When development affected areas of high habitat quality for species, persistence could not be guaranteed. Therefore, species must be more explicitly accounted for in offsets, rather than just vegetation or habitat alone. Declines due to a failure to account directly for species population dynamics and connectivity overshadowed the benefits delivered by producing large areas of high-quality habitat. Our modeling framework showed that the benefits delivered by offsets are species specific and that simple vegetation-based metrics can give misguided impressions on how well biodiversity offsets achieve no net loss.

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Section: Introductionmentioning

confidence: 99%

“…With habitat condition scores varying across an area of impact, it is common to simply sum scores such that, for example, 25 ha of perfect‐condition vegetation would receive the same overall offset score as 50 ha of vegetation that scores 50% less (Marshall et al. 2020).…”

Section: Introductionmentioning

confidence: 99%

Quantifying the impact of vegetation‐based metrics on species persistence when choosing offsets for habitat destruction

Marshall

Valavi

O’Connor³

et al. 2020

Conservation Biology

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“…Another key topic is the ecological equivalence methods used to size offsets. These methods address the critical question of determining 'how much is enough' to achieve NNL [17,[28][29][30][31][32]. Initial area-based approaches aimed at securing the same amount of land for offsetting because the area impacted has been widely used, sometimes with multipliers to reflect the conservation status of the impacted land or other criteria of interest [2].…”

Section: Introductionmentioning

confidence: 99%

“…Initial area-based approaches aimed at securing the same amount of land for offsetting because the area impacted has been widely used, sometimes with multipliers to reflect the conservation status of the impacted land or other criteria of interest [2]. Growing criticism of the limitations of such approaches has led to more explicit considerations of ecological losses and gains using suitable metrics and exchange rules (see [32] for a review). In the case of wetlands, these metrics are generally based on proxies of ecosystem functions.…”

Section: Introductionmentioning

confidence: 99%

Modeling Alternative Approaches to the Biodiversity Offsetting of Urban Expansion in the Grenoble Area (France): What Is the Role of Spatial Scales in ‘No Net Loss’ of Wetland Area and Function?

Vaissière

Quétier²,

Bierry

et al. 2021

Sustainability

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It is increasingly common for developers to be asked to manage the impacts of their projects on biodiversity by restoring other degraded habitats that are ecologically equivalent to those that are impacted. These measures, called biodiversity offsets, generally aim to achieve ‘no net loss’ (NNL) of biodiversity. Using spatially-explicit modeling, different options were compared in terms of their performance in offsetting the impacts on wetlands of the planned urban expansion around Grenoble (France). Two implementation models for offsetting were tested: (a) the widespread bespoke permittee-led restoration project model, resulting in a patchwork of restored wetlands, and (b) recently-established aggregated and anticipated “banking” approaches whereby larger sets of adjacent parcels offset the impacts of several projects. Two ecological equivalence methods for sizing offsets were simulated: (a) the historically-prevalent area-based approach and (b) recently introduced approaches whereby offsets are sized to ensure NNL of wetland functions. Simulations showed that a mix of functional methods with minimum area requirements was more likely to achieve NNL of wetland area and function across the study area and within each subwatershed. Our methodology can be used to test the carrying capacity of a landscape to support urban expansion and its associated offsetting in order to formulate more sustainable development plans.

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“…For example, what cannot be measured, cannot be offset (Moreno-Mateos et al 2015), and biodiversity is a complex entity to measure. To try to account for this complexity, multiple or compound metrics that measure multiple elements of biodiversity are often used to quantify biodiversity losses and gains (Gonçalves et al 2015, Marshall et al 2020, Viehman et al 2009. However, biodiversity offset policies usually only account for certain biodiversity values; for example, threatened species and threatened ecosystems.…”

Section: Current Issues In Biodiversity Offsettingmentioning

confidence: 99%

Impact mitigation in marine and coastal environments: policy challenges and shortfalls

Shumway¹

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What are we measuring? A review of metrics used to describe biodiversity in offsets exchanges

Cited by 72 publications

References 60 publications

Quantifying the impact of vegetation‐based metrics on species persistence when choosing offsets for habitat destruction

Quantifying the impact of vegetation‐based metrics on species persistence when choosing offsets for habitat destruction

Modeling Alternative Approaches to the Biodiversity Offsetting of Urban Expansion in the Grenoble Area (France): What Is the Role of Spatial Scales in ‘No Net Loss’ of Wetland Area and Function?

Impact mitigation in marine and coastal environments: policy challenges and shortfalls

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