Individual behaviour change is a crucial component of our response to current environmental challenges and over recent years, a growing body of literature has focussed on the drivers and levers of pro-environmental behaviours. However, scholars have noted there is a considerable shortage of behavioural science research that focuses on behaviours that directly impact nature and biodiversity. This is concerning, given the enormous value populations place on nature, the fundamental role nature plays in society and because nature is declining rapidly. In this thesis, we focus on understanding volunteering for nature restoration groups, which we show is an under-researched behaviour in the literature. It also has relatively high potential to deliver positive impacts for biodiversity and nature. We start by developing a simple generalisable theoretical model that suggests three main factors may be inhibiting the uptake of volunteering for nature – uncertainty, inaccuracy and high behavioural adjustment costs. We use this model to inform the design and hypotheses for a large field experiment in Aotearoa New Zealand where we aim to answer the following questions: How can we increase volunteering for nature restoration groups? What are the effects of volunteering for the first-time on future volunteering behaviour? How does volunteering affect other important outcomes of interest, like environmental identity, locus of control beliefs and wellbeing? Our field experiment has two stages. In stage one, we randomly assign first-time volunteers (those who are not already engaged in nature volunteering) to treatment groups to assess the impact of a nudge, a supermarket voucher incentive and a nudge and incentive combined on volunteering behaviour. We find that a $50 NZD supermarket incentive increases attendance rates at volunteering events and commitment rates to attend volunteering events. On the other hand, an environmentally and socially motivated nudge in isolation has no effect on volunteering behaviour. However, combining the nudge with the voucher incentive enhances the efficacy of either treatment alone, demonstrating that significant positive synergies exist between nudges and incentives in this context. In stage two, we show volunteering for the first-time is plausibly randomly assigned, conditional on availability and being offered an incentive. We use this feature to estimate the causal impact of volunteering for the first time on future volunteering behaviour and other outcomes of interest. We find that volunteering for the first time crowds in future volunteering behaviour, generates positive spillovers to other pro-environmental behaviours and strengthens environmental self-identity and locus of control beliefs, which are important pre-cursors to pro-environmental behaviour. Our results show two mechanisms are likely driving these effects. Firstly, volunteering for the first-time provides important information about the benefits of volunteering that are used in future decision-making. Secondly, it strengthens environmental attitudes and identity, which in-turn affect preferences for pro-environmental behaviour. Taken together, our results show that using a financial incentive to help people experiment with volunteering can lead to large positive spillovers and crowding-in effects for future pro-environmental behaviour.