The escalating climate crisis necessitates identifying individuals willing to take action. This study investigates the role of longtermism—an ethical philosophy prioritizing equal moral consideration for present and future generations—in predicting climate-protective attitudes and behaviors. Longtermism rests on three core principles: equal moral consideration for present and future generations; prioritizing future well-being due to a larger future population; and the significant impact of present actions on the long-term future. While longtermism has faced criticism regarding resource allocation, a substantial portion of the population (approximately 25%) strongly endorses its principles. This research explores whether longtermists exhibit greater environmental concern and if longtermism can promote pro-environmental actions. Existing research suggests a link between longtermism, reduced temporal and intergenerational discounting, increased prosociality, and a heightened sense of responsibility for addressing intergenerational challenges. While transcending psychological distance may play a role, a stronger sense of intergenerational responsibility appears to be a more robust predictor of pro-environmental behaviors. This study aims to determine if longtermists demonstrate stronger commitment to pro-climate policies, heightened climate change concerns, and greater willingness to take action, exploring the underlying mechanisms and developing targeted interventions to promote environmentalism.

The literature review draws upon existing research on the psychology of intergenerational concern and environmental psychology. Studies show that longtermists exhibit a reduced tendency to discount the welfare of future generations compared to the general population. This reduced discounting behavior, along with increased prosociality and empathy across social distance, suggests a broader circle of moral concern among longtermists. The literature also highlights the importance of bridging the psychological distance individuals feel from the negative impacts of climate change to encourage pro-climate action. However, more recent analysis suggests that this mechanism may be overestimated. The most consistent predictor of pro-environmental attitudes and behaviors seems to be an increased sense of responsibility for addressing collective, intergenerational challenges. Studies reliably demonstrate that feeling responsible for future generations predicts pro-environmental intentions, beliefs, charitable donations, support for policies, and willingness to engage in conservation efforts. This sense of responsibility transcends immediate concerns, emphasizing a moral duty to ensure a habitable world for future generations.

The study comprises four pre-registered studies and two supplementary pilots, employing various methodologies. **Study 1:** Conducted on Prolific, this study (N=790) used the Longtermism Beliefs Scale (LBS) to identify longtermists and assessed attitudes towards climate change using the Yale Program for Climate Change Communication (YPCCC) measures. Independent samples t-tests and chi-square tests were employed to compare longtermists and non-longtermists. **Study 2:** Also conducted on Prolific (N=768), this study used the LBS, a measure of responsibility to future generations, and measures of pro-environmental behaviors and pro-climate collective action participation. Independent samples t-tests and mediation analysis (PROCESS Macro) were used. **Study 3:** This Prolific study (N=769) used the LBS, a measure of responsibility to future generations, and measures of support for climate justice (for both minoritized and future generations). Independent samples t-tests and mediation analysis were used. **Study 4:** This large-scale Prolific study (N=2135) tested four interventions aimed at increasing responsibility to protect future generations. Participants were randomly assigned to one of five conditions: future generation harm reduction, letter to the past, future challenges, future generations committee, and a control group. The interventions manipulated the salience of present actions' impact on future generations. Independent samples t-tests, linear regression, and mediation analysis were conducted to analyze the effects of the interventions on responsibility and donations to an environmental charity. All studies controlled for demographic variables (gender, age, SES, political orientation). All aspects of the studies were preregistered, enhancing transparency and replicability. The data are available on the Open Science Framework.

The findings consistently demonstrate a robust link between longtermism and pro-environmental attitudes and actions. **Study 1:** Longtermists were significantly more likely to believe in human-caused global warming, the scientific consensus on climate change, and the current occurrence of global warming. They expressed greater worry, perceived sooner impacts, and believed more entities (themselves, other Americans, developing countries, animals, future generations) would be harmed by climate change. They also strongly believed that insufficient action was being taken, that addressing climate change should be prioritized and expressed increased support for related policies. Effect sizes ranged from d=0.34 to d=0.73. **Study 2:** Longtermists reported significantly higher levels of moral responsibility to protect future generations (d=0.91), greater engagement in pro-environmental behaviors (d=0.34), and higher pro-climate collective action participation (d=0.17). **Study 3:** Longtermists exhibited stronger beliefs in climate justice, greater awareness of climate justice issues, and higher support for relevant policies and political candidates. They also indicated greater intentions to participate in related campaigns, with effect sizes ranging from d=0.20 to d=0.62. **Study 4:** All four interventions significantly increased responsibility to protect distant future generations compared to the control group, with effect sizes ranging from d=0.30 to d=0.63. The 'future generation harm reduction' intervention significantly increased donations to an environmental charity (d=0.14), an effect fully mediated by increased responsibility. This intervention involved a thought experiment focused on mitigating harm in a relatable short-term future scenario.

The findings strongly support the hypothesis that longtermism beliefs predict a wide range of pro-environmental attitudes and actions. The heightened sense of moral responsibility towards future generations, a key characteristic of longtermists, appears to be the primary mechanism driving these associations. The interventions successfully demonstrated the malleability of intergenerational responsibility, highlighting the potential for targeted interventions to foster pro-environmental behaviors in the broader population. The effectiveness of the 'future generation harm reduction' intervention underscores the importance of framing environmental action in terms of preventing harm in relatable scenarios. This approach may enhance engagement by tapping into individuals' capacities for empathy, ethical reasoning, and imagination. The consistent findings across multiple studies enhance the reliability and generalizability of the results. The study's insights have significant implications for climate advocacy and the development of effective interventions to promote climate action.

This research demonstrates a robust link between longtermism beliefs and pro-environmental attitudes and behaviors, primarily driven by a heightened sense of responsibility for future generations. The successful interventions show that this sense of responsibility can be cultivated through low-cost, scalable methods. Future research should explore the long-term effects of these interventions, investigate cross-cultural variations, and examine potential moderators of intervention effectiveness based on pre-existing levels of intergenerational concern. These findings provide valuable insights for fostering broader societal engagement in addressing climate change.

The study primarily relied on online samples of Americans, limiting the generalizability of findings to other cultures. Future research should replicate the study in diverse cultural contexts to explore the role of cultural values in shaping intergenerational concern. The study measured the mediator (responsibility) without directly measuring longtermism beliefs in Study 4. While the strong correlation between responsibility and longtermism from prior research suggests confidence in the interventions' effectiveness, future studies could incorporate direct measures of longtermism beliefs to strengthen this aspect. Furthermore, future research should investigate whether pre-existing levels of longtermism beliefs moderate the effectiveness of the interventions.