1. Ostrea edulis populations have declined by more than 95% since the mid‐1800s due to historical over‐harvesting, disease, competition from invasive species, and predators. Once the basis of a thriving fishery, it is now one of the most threatened habitats in Europe and restoration is high on the conservation agenda.
2. Impact investing is a novel financing model that attracts investors who put creating positive, measurable social outcomes at the heart of their decision‐making process, while also seeking a financial return. Impact bonds, more specifically, are instruments designed to link these investors with beneficial projects and financial returns. Payoff is derived from the success or failure of a service provider in delivering pre‐agreed outcomes. The Rhino Impact Investment is such a project, which aims to increase black rhino numbers by using an impact bond structure, where capital is directed to fund evidence‐based management interventions, and financial gain or loss to the investors depends on the scale to which rhino numbers increase or decrease across a portfolio of project sites.
3. The authors present a hypothetical impact bond model that could be used to address the decline in O. edulis. Investors provide capital that is dispersed among a portfolio of restoration sites to implement interventions designed to increase oyster habitat and numbers. At maturity, outcome payers reimburse investors with their capital plus or minus a rate of return based on independent verification of the outcomes achieved or not achieved.
4. The Rhino Impact Investment project is the only current impact bond model aimed at species recovery and, as such, there is very little evidence to go on with regards to the legal and regulatory framework surrounding such instruments and the restoration of ecological systems and biodiversity. More work is needed on a regulatory and project level to take feasibility testing to the next stage.

中文翻译：

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影响性投资能否促进原生牡蛎和原生牡蛎床的生态系统范围恢复？伦敦动物园协会犀牛影响投资债券的经验教训可能会影响牡蛎恢复的未来

1. 自从1800年代中期以来，由于历史上的过度收获，疾病，入侵物种的竞争以及掠食性动物，可食的Ostrea edulis种群减少了95％以上。曾经是蓬勃发展的渔业的基础，现在它已成为欧洲最受威胁的栖息地之一，恢复工作已成为保护工作的重中之重。
2. 影响力投资是一种新颖的融资模式，吸引了那些将创造积极，可衡量的社会成果作为其决策过程的核心，同时又寻求财务回报的投资者。影响债券，更具体地说，是旨在将这些投资者与有益项目和财务回报联系起来的工具。收益来自服务提供商在交付预定结果方面的成功或失败。Rhino Impact Investment是一个这样的项目，其目的是通过使用影响债券结构来增加黑犀牛数量，在这种结构中，资本用于资助基于证据的管理干预措施，而投资者的财务收益或损失取决于犀牛的规模项目站点组合中的数量增加或减少。
3. 作者们提出了一种假设的影响债券模型，该模型可以用于解决食用番茄的下降问题。投资者提供的资金分散在各个修复地点之间，以实施旨在增加牡蛎栖息地和数量的干预措施。到期时，结果付款人根据对已实现或未实现结果的独立验证，向投资者偿还其资本的正负收益率。
4. 犀牛影响投资项目是目前唯一针对物种恢复的影响债券模型，因此，围绕此类工具的法律和法规框架以及生态系统和生物多样性的恢复，证据很少。要在下一阶段进行可行性测试，需要在监管和项目层面进行更多工作。