Forest Policy and Economics 128 (2021) 102457 Available online 10 April 2021 1389-9341/© 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Voluntary agreements to protect private forests – A realist review Matilda Miljand a, * , Therese Bj¨ arstig a , Katarina Eckerberg a , Eeva Primmer b , Camilla Sandstr¨ om a a Department of Political Science, Umeå University, Sweden b Finnish Environment Institute, Finland A R T I C L E INFO Keywords: Realist review Voluntary conservation agreements Private forest owners ABSTRACT 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-effcient 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 fndings from different types of VAs in varying contexts in a systematized way, and consolidating evidence of how the mechanisms infuence 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 infuence through personal, emotional attachment to the forest. This fnding 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. 1. Introduction There is growing political interest in using voluntary agreements (VA) and compensation for nature conservation in privately owned forests and on private land (M¨ antymaa et al., 2009; Wunder et al., 2018). In this article, we investigate VAs as formalised agreements be- tween a non-industrial private forest owner and the state (or local government) to protect nature conservation, social or cultural values in the forest. The introduction of voluntary policy instruments has been triggered by a dissatisfaction with the incapability to protect biodiver- sity with regulatory instruments (Salomaa et al., 2016). Despite global commitment to halting the loss of biodiversity (CBD, 1992), the decline of biodiversity and loss of ecosystem services continue at an alarming rate (Brondizio et al., 2019). The European Union’s (EU) Biodiversity Strategy (EC, 2012) and accompanying policies in EU member states reiterate the need for increased conservation efforts, calling for forest owners to protect and enhance forest biodiversity through voluntary contract and payment arrangements. Indeed, engaging private land- owners in conservation activities for endangered species is considered critical for protecting and enhancing biodiversity (Sorice et al., 2013). Numerous conservation strategies exist, with various implications for different species (e.g., M¨ onkk¨ onen et al., 2014). Yet, in practice, the conservation activity for which a VA is made is often strictly defned, so that it would be institutionally feasible (Primmer et al., 2013). The VA might consist of retaining single trees or border zones with high biodi- versity value in forest management and/or setting aside specifc forest areas for protection of biodiversity. In nature conservation, VAs are presented as potentially more fex- ible and cost-effcient compared to regulatory measures, which place all information-sourcing responsibility onto the regulator, and may result in costly and cumbersome expropriation of private land (B¨ orner et al., 2017; Ferraro and Kiss, 2002; Lindfors, 2007). Information asymmetry might, however, result in limited effciency improvements (Juutinen et al., 2013). * Corresponding author. E-mail address: matilda.miljand@umu.se (M. Miljand). Contents lists available at ScienceDirect Forest Policy and Economics journal homepage: www.elsevier.com/locate/forpol https://doi.org/10.1016/j.forpol.2021.102457 Received 21 April 2020; Received in revised form 23 March 2021; Accepted 25 March 2021