The money or the trees: What drives landholders’ participation in biodiverse carbon plantings?

• A BBN model was constructed based on a literature review, interviews and expert elicitation.
• Program characteristics are more influential at driving participation than financial incentives.
• Biodiversity co-benefits is another important factor.
• Combining biodiversity incentives with flexible permanence options increases program adoption.

Carbon farming programs typically aim to maximise landholder participation rates to achieve desired environmental outcomes. This is critical for programs aiming to tackle both climate change and biodiversity loss simultaneously, as landholder participation in those schemes directly determines the level of carbon sequestered and the potential biodiversity gains. Biodiverse carbon planting is a key private land conservation practice that needs active stakeholder involvement to deliver successful policy design and implementation. In this study we developed a Bayesian Belief Network (BBN) of landholder participation in biodiverse carbon planting schemes to determine factors most likely to influence program participation. An initial conceptual model was developed based on a review of the literature. The model was refined through interviews with participating landholders and other key stakeholders and, finally, parameterised using expert-elicited information. Our results indicate that participation rates are most influenced by program attractiveness and the identified values of co-benefits (such as biodiversity conservation) rather than financial incentives. Scenario evaluation revealed that providing a combination of biodiversity incentives with more flexible permanence options could increase the program adoption rate. Stacking or bundling credits combined with contract agreements is also likely to increase the participation rate. These findings can assist policy development by focusing on the aspects of policy design most likely to increase participation.