There is increasing political interest in the use of voluntary agreements (VA) as a policy instrument. The attraction has grown also in environmental policy, VAs are expected to be less costly, more effective and more cost-efficient than regulation. Using a realist review methodology, our analysis focuses on the effect of contextual factors and mechanisms on private forest owners' willingness to enter into formal voluntary nature conservation agreements. The framework we use to analyse the effects includes: forest owner characteristics, forest attributes, institutional context and process, advisors and other forest owners, and contract design, for contextual factors – and economic attitudes, environmental attitudes, sense of autonomy, sense of justice and fairness, trust as well as knowledge, for mechanisms. The analysis allowed merging findings from different types of VAs in varying contexts in a systematized way, and consolidating evidence of how the mechanisms influence the programme implementation process, and its outcome. 43 reviewed articles, from an originally retrieved set of 2231 papers, provide evidence for environmental attitudes supporting willingness to enter into an agreement. Environmental attitudes are strengthened by forest owners' wishes to protect a heritage, suggesting considerable influence through personal, emotional attachment to the forest. This finding shows the central role played by sense of autonomy, with economic compensation also importantly affecting the willingness to enter a VA. Along with these results, the developed comprehensive analytical framework shows how VAs can become more effective if tailored for different contexts and types of forest owners.

使用自愿协议（VA）作为政策工具的政治兴趣日益浓厚。环境政策的吸引力也越来越大，VA预计将比法规成本更低，更有效且更具成本效益。使用现实主义的审查方法，我们的分析集中于环境因素和机制对私有森林所有者签署正式的自愿性自然保护协议的意愿的影响。我们用来分析影响的框架包括：森林所有者的特征，森林属性，机构环境和过程，顾问和其他森林所有者以及针对环境因素（以及经济态度，环境态度，自治感，正义感）的合同设计机制的公平，信任和知识。通过分析，可以以系统化的方式合并不同类型VA在不同情况下的发现，并合并有关机制如何影响计划实施过程及其结果的证据。从最初检索的2231篇论文集中，有43篇评论文章为支持支持愿意达成协议的环境态度提供了证据。森林所有者保护遗产的意愿加强了对环境的态度，表明对森林的个人情感依恋产生了巨大影响。这一发现表明了自主意识所起的核心作用，经济补偿也很重要地影响了加入自愿加入的意愿。连同这些结果，