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Biodiversity offset credits in New South Wales are transacted within a regulatory environment defined by detailed trading rules and many different types of biodiversity credits that can lead to thin markets and high transaction costs. This paper describes a market designed to facilitate efficient and effective transactions. The market includes a search algorithm to identify who can exchange with whom, according to the regulatory constraints, and an online exchange tool to facilitate efficient price discovery and allocation of offset contracts.

No net loss (NNL) biodiversity policies mandating the application of a mitigation hierarchy (avoid, minimize, remediate, offset) to the ecological impacts of built infrastructure are proliferating globally. However, little is known about their effectiveness at achieving NNL outcomes. We reviewed the English‐language peer‐reviewed literature (capturing 15,715 articles), and identified 32 reports that observed ecological outcomes from NNL policies, including >300,000 ha of biodiversity offsets. Approximately one‐third of NNL policies and individual biodiversity offsets reported achieving NNL, primarily in wetlands, although most studies used widely criticized area‐based outcome measures. The most commonly cited reason for success was applying high offset multipliers (large offset area relative to the impacted area). We identified large gaps between the global implementation of offsets and the evidence for their effectiveness: despite two‐thirds of the world's biodiversity offsets being applied in forested ecosystems, we found none of four studies demonstrated successful NNL outcomes for forested habitats or species. We also found no evidence for NNL achievement using avoided loss offsets (impacts offset by protecting existing habitat elsewhere). Additionally, we summarized regional variability in compliance rates with NNL policies. As global infrastructural expansion accelerates, we must urgently improve the evidence‐base around efforts to mitigate development impacts on biodiversity.

Governments, businesses, and lenders worldwide are adopting an objective of no net loss (NNL) of biodiversity that is often partly achieved through biodiversity offsetting within a hierarchy of mitigation actions. Offsets aim to balance residual losses of biodiversity caused by development in one location with commensurate gains at another. Although ecological challenges to achieve NNL are debated, the associated gains and losses for local stakeholders have received less attention. International best practice calls for offsets to make people no worse off than before implementation of the project, but there is a lack of clarity concerning how to achieve this with regard to people’s use and nonuse values for biodiversity, especially given the inevitable trade-offs when compensating biodiversity losses with gains elsewhere. This is particularly challenging for countries where poor people depend on natural resources. Badly planned offsets can exacerbate poverty, and development and offset impacts can vary across spatial-temporal scales and by location, gender, and livelihood. We conceptualize the no-worse-off principle in the context of NNL of biodiversity, by exploring for whom and how the principle can be achieved. Changes in the spatial and temporal distribution of biodiversity-related social impacts of a development and its associated offset can lead to social inequity and negatively impact people’s well-being. The level of aggregation (regional, village, interest group, household, and individual) at which these social impacts are measured and balanced can again exacerbate inequity in a system. We propose that a determination that people are no worse off, and preferably better off, after a development and biodiversity offset project than they were before the project should be based on the perceptions of project-affected people (assessed at an appropriate level of aggregation); that their well-being associated with biodiversity losses and gains should be at least as good as it was before the project; and that this level of well-being should be maintained throughout the project life cycle. Employing this principle could help ensure people are no worse off as a result of interventions to achieve biodiversity NNL. Los gobiernos, negocios y financiadores están adoptando el objetivo de biodiversidad sin pérdida neta (NNL, en inglés), el cual comúnmente se logra parcialmente por medio de compensaciones por biodiversidad dentro de una jerarquía de acciones de mitigación. Las compensaciones buscan balancear las pérdidas residuales de la biodiversidad causadas por el desarrollo en una localidad con ganancias conmensuradas en otra localidad. Aunque los obstáculos ecológicos para alcanzar la NNL se debaten hoy en día, las ganancias y pérdidas para los accionistas locales han recibido menos atención. La mejor práctica internacional requiere compensaciones para que las personas no estén peor que antes de la implementación del proyecto, pero existe una falta de claridad con respecto a cómo lograr esto considerando el valor de uso o no de la biodiversidad por parte de las personas, especialmente dadas las compensaciones inevitables cuando se resarcen las pérdidas de biodiversidad con ganancias en otros lugares. Esto es un reto particularmente para los países en donde la gente pobre depende de los recursos naturales. Las compensaciones mal planeadas pueden exacerbar la pobreza, y los impactos del desarrollo y las compensaciones puede variar a lo largo de la escala espacio-temporal y por localidad, género, y sustento. Conceptualizamos el principio de no-peor-que en el contexto de la NNL de biodiversidad explorando para quién y cómo se puede lograr este principio. Los cambios en la distribución especial y temporal de los impactos sociales de un proyecto relacionados con la biodiversidad y sus compensaciones asociadas pueden resultar en una inequidad social e impactar negativamente el bienestar de las personas. El nivel de agregación (regional, aldea, grupo de interés. hogar, individual) en el que se miden y balancean estos impactos sociales también puede exacerbar la inequidad en un sistema. Proponemos que la determinación de que las personas no estén peor que antes, y de preferencia mejor que, después de un proyecto de desarrollo y de compensación por la biodiversidad debería basarse en las percepciones de las personas afectadas por el proyecto (evaluadas en un nivel apropiado de agregación); que su bienestar asociado con las pérdidas y ganancias de biodiversidad debería por lo menos ser tan bueno como era antes del proyecto; y que este nivel de bienestar debería mantenerse durante todo el ciclo de vida del proyecto. Si se emplea este principio, se podría ayudar a asegurarle a las personas que no estén peor que antes como resultado de las intervenciones para alcanzar la NNL de biodiversidad. 世界各国的政府、企业和贷款机构都在努力实现生物多样性无净损失(no net loss, NNL)的巨标，这一目 标一定程度上是通过分级减控行动中的生物多样性补偿实现的。补偿旨在平衡一千地区发展导致的生物多祥性 剩余损失与另ー个地区的同等收益。虽然实现无净损失面临的生态挑战仍受到争议，但当地的利益相关者的相 应收益和损失受到的关注甚至更少。目前，国际上的最优做法要求对人们的补偿应能够保i正其生活水平不会比 项目实施前更低，但就人们对生物多祥性的利用及菲利用价值来说如何达到这一要求还不明确，特別是考虑到 用其它地方的收益来补偿生物多祥性损失时所不可避免地产生的利弊权衡。而这ー问题在贫困人ロ依赖自然资 源生活的国家格外具有挑战性。计划不当的补偿可能会加剧贫困，发展和ネト偿的影响还会随时空尺度、地点、 性别和谋生方式而变化。我们在生物多祥性无净损失的背景下，通过分析无恶化原则将为谁实现、如何实现，构 建了该原则的概念。发展及其补偿所引起的生物多祥性相关的社会影响在时间和空间分布上的变化会导致社 会不平等，并对人们的福祉产生负面影响。在何种聚合程度上（地区、村庄、利益集团、家庭、十人）衡量和平 衡这些社会影响，可能会再次加剧系统中的不平等性。我们认为，发展及生物多祥性补偿项目对人们生活水平影 响(不应比项目开展前更差，最好有所改善)的测定应建立在对受项目影响人群的理解和认识上即在ー个合适 的綜合的水平上进行评估;另外，人们与生物多样性收益及损失相关的福祉也至少要与项目实施前一祥好，且项 目全程都保持这ー水平。采用这个原则有助于确保实现生物多祥性无净损失的干预不会导致人们生活水平下 降。

Offsetting policies have increased worldwide, utilizing a range of biodiversity metrics to compensate for development impacts. We conducted a global analysis of offset legislation by reviewing policies from 108 countries, which have voluntary offsets, or which require offsets by law. We sought to understand how well biodiversity metrics and offset currencies are documented in current policies. Where biodiversity metrics are documented we aimed to understand how metrics were scored, combined, and multiplied to create offset currencies. We found only 22 jurisdictions (from 14 countries) had guidelines documenting how biodiversity should be assessed during offsetting, representing a significant gap in the guidance available for offsets. Of the 22 guidelines, 14 (63%) documented use of aggregated currencies, eight (23%) did not aggregate biodiversity metrics into a single currency, and three (17%) did not specify either approach. Habitat type and condition, as well as area, were widely recommended across policies (>50%). Where species‐level metrics were considered, guidelines generally focused on habitat distributions rather than abundance or population metrics. The lack of consistent and clear guidance about how biodiversity should be measured in offsets reduces our ability to determine the effectiveness of offsets in compensating for development impacts long term.

The mitigation hierarchy is a decision-making framework designed to address impacts on biodiversity and ecosystem services through first seeking to avoid impacts wherever possible, then minimizing or restoring impacts, and finally by offsetting any unavoidable impacts. Avoiding impacts is seen by many as the most certain and effective way of managing harm to biodiversity, and its position as the first stage of the mitigation hierarchy indicates that it should be prioritized ahead of other stages. However, despite an abundance of legislative and voluntary requirements, there is often a failure to avoid impacts. We discuss reasons for this failure and outline some possible solutions. We highlight the key roles that can be played by conservation organizations in cultivating political will, holding decision makers accountable to the law, improving the processes of impact assessment and avoidance, building capacity, and providing technical knowledge. A renewed focus on impact avoidance as the foundation of the mitigation hierarchy could help to limit the impacts on biodiversity of large-scale developments in energy, infrastructure, agriculture and other sectors.

Offsetting is emerging as an important but controversial approach for managing environment–development conflicts. Biodiversity offsets are designed to compensate for damage to biodiversity from development by providing biodiversity gains elsewhere. Here, we suggest how biodiversity offset policies can generate behaviours that exacerbate biodiversity decline, and identify four perverse incentives that could arise even from soundly designed policies. These include incentives for (i) entrenching or exacerbating baseline biodiversity declines, (ii) winding back non‐offset conservation actions, (iii) crowding out of conservation volunteerism and (iv) false public confidence in environmental outcomes due to marketing offset actions as gains. Synthesis and applications. Despite its goal of improving biodiversity outcomes, there is potential for best‐practice offsetting to achieve the opposite result. Reducing this risk requires coupling offset crediting baselines to measured trajectories of biodiversity change and understanding the potential interaction between offsetting and other environmental policies.

Biodiversity offsets have become a widely accepted means of attempting to compensate for biodiversity loss from development, and are applied in planning and decision-making processes at many levels. Yet their use is contentious, and numerous problems with both the concept and the practice have been identified in the literature. Our starting point is the understanding that offsets are a kind of biodiversity compensation measure through which the goal of no net loss (or net gain) of biodiversity can be at least theoretically achieved. Based on a typology of compensation measures distinguishing between habitat protection, improvement (including restoration, habitat creation and improved management practices) and other compensation, we review the literature to develop a framework of conditions that must be met if habitat protection and improvement initiatives can be truly considered offsets and not merely a lesser form of compensation. It is important that such conceptual clarity is reflected in offset policy and guidance, if offsets are to be appropriately applied and to have any chance of fully compensating for biodiversity loss. Our framework can be used to support the review and ongoing development of biodiversity offset policy and guidance, with the aim of improving clarity, rigour and therefore the chances that good biodiversity outcomes can be achieved.

Biodiversity offsetting is a last-resort scheme to prevent biodiversity loss due to development. However, measuring biodiversity is a complex endeavour, even more so in hyperdiverse landscapes. With few South African scientists able to comprehensively measure biodiversity, assuming equivalence between sacrificial and offset areas would be problematic and potentially fatal. Caution is required as the erosion of our unique biodiversity is at stake. We advise that a panel of biome-specific experts and data modellers unite to provide tools for more accurate trade-offs, based on functional diversity. In the meantime, the value of focusing on landscape heterogeneity is highlighted.

Biodiversity cannot always be conserved. Economic development activities can result in biodiversity losses, but also increase human well‐being, so trade‐offs must sometimes be made between conservation and development. An alternative strategy to avoidance of impacts through the strict protection of biodiversity (‘prevention’) is to permit certain biodiversity losses and fully compensate for them through offsets elsewhere (‘cure’). Here, we build a stochastic simulation model to explore trade‐offs between biodiversity loss prevention and cure, in the context of development under ‘no net loss’ (NNL) biodiversity policies. Our model implements a Management Strategy Evaluation framework, monitoring outcomes using four different performance metrics: total biodiversity, net biodiversity, total economic activity and development activity. We find that a ‘cure’ strategy can potentially perform just as well as a prevention strategy in terms of biodiversity objectives, while outperforming the latter from an economic perspective. However, this does not undermine the need for a mitigation hierarchy, and the best‐performing strategy depends strongly upon both the degree of compliance with the NNL policy and upon underlying ecological parameters. Perhaps counterintuitively, when evaluated as advised by the technical literature (i.e. against an appropriate counterfactual scenario), we find that net biodiversity outcomes are highest when natural ecosystem recovery rates are slow (so long as development rates are also slow). Finally, using the illustrative example of US wetlands, we suggest that real‐world NNL policies could already be driving landscape‐scale avoidance of development impacts under a ‘prevention’ approach. Policy implications. No net loss (NNL) biodiversity policy is currently being developed or implemented by over 100 countries world‐wide and incorporated into environmental safeguards by multinational lenders. The socioecological model presented here can be used to advise decision makers about the best structure for nascent NNL policy on the basis of region‐specific ecosystem recovery rates, development activity, legal compliance and monitoring uncertainty. Furthermore, the model presents a means for estimating the degree to which biodiversity impacts are avoided by developers under NNL—an important monitoring consideration given that ensuring high levels of avoidance is crucial to robust NNL policy, but which has to date evaded assessment through purely empirical means. View over the town of Jasper, in the heart of the Jasper National Park (and World Heritage Site), Canada. Recent infrastructure development in the region has sought to meet strict standards around mitigating biodiversity impacts. Credit: J. W. Bull.

There is an urgent need to improve the evaluation of conservation interventions. This requires specifying an objective and a frame of reference from which to measure performance. Reference frames can be baselines (i.e., known biodiversity at a fixed point in history) or counterfactuals (i.e., a scenario that would have occurred without the intervention). Biodiversity offsets are interventions with the objective of no net loss of biodiversity (NNL). We used biodiversity offsets to analyze the effects of the choice of reference frame on whether interventions met stated objectives. We developed 2 models to investigate the implications of setting different frames of reference in regions subject to various biodiversity trends and anthropogenic impacts. First, a general analytic model evaluated offsets against a range of baseline and counterfactual specifications. Second, a simulation model then replicated these results with a complex real world case study: native grassland offsets in Melbourne, Australia. Both models showed that achieving NNL depended upon the interaction between reference frame and background biodiversity trends. With a baseline, offsets were less likely to achieve NNL where biodiversity was decreasing than where biodiversity was stable or increasing. With a no‐development counterfactual, however, NNL was achievable only where biodiversity was declining. Otherwise, preventing development was better for biodiversity. Uncertainty about compliance was a stronger determinant of success than uncertainty in underlying biodiversity trends. When only development and offset locations were considered, offsets sometimes resulted in NNL, but not across an entire region. Choice of reference frame determined feasibility and effort required to attain objectives when designing and evaluating biodiversity offset schemes. We argue the choice is thus of fundamental importance for conservation policy. Our results shed light on situations in which biodiversity offsets may be an inappropriate policy instrument Importancia de la Especificación de Línea de Base en la Evaluación de Intervenciones de Conservación y la Obtención de Ninguna Pérdida Neta de la Biodiversidad