Moderate heritability (30%–40%) for concern for nature, environmental movement activism, and personal conservation behavior and high genetic correlations between them (.6–.7), suggesting a partially shared genetic basis

Genetic Contribution to Concern for Nature and Proenvironmental Behavior. Chia-chen Chang, Thi Phuong Le Nghiem, Qiao Fan, Claudia L Y Tan, Rachel Rui Ying Oh, Brenda B Lin, Danielle F Shanahan, Richard A Fuller, Kevin J Gaston, L Roman Carrasco. BioScience, biab103, October 20 2021. https://doi.org/10.1093/biosci/biab103

Abstract: Earth is undergoing a devastating extinction crisis caused by human impacts on nature, but only a fraction of society is strongly concerned and acting on the crisis. Understanding what determines people's concern for nature, environmental movement activism, and personal conservation behavior is fundamental if sustainability is to be achieved. Despite its potential importance, the study of the genetic contribution to concern for nature and proenvironmental behaviors has been neglected. Using a twin data set (N = 2312), we show moderate heritability (30%–40%) for concern for nature, environmental movement activism, and personal conservation behavior and high genetic correlations between them (.6–.7), suggesting a partially shared genetic basis. Our results shed light on the individual variation in sustainable behaviors, highlighting the importance of understanding both the environmental and genetic components in the pursuit of sustainability.

Heritability of concern for nature and proenvironmental behavior

The heritability of concern for nature and proenvironmental behavior was similar to an average heritability of human personality traits (such as the big five personality traits, which have heritability of about 30%–40%; Vukasović and Bratko 2015). Concern for nature and proenvironmental behavior have also been found to be associated with several human behavioral and personality traits, such as altruism and agreeableness (Pavalache-Ilie and Cazan 2018, Gifford and Nilsson 2014, Lades et al. 2021). The genetic components of these traits (e.g., dopamine-related genes for altruism and agreeableness; Reuter et al. 2011, Kim et al. 2013) may be linked with concern for nature and proenvironmental behavior. In addition, we expect the genetic influences may be mediated through individual differences in emotional or cognitive processes, such as future discounting, social discounting, or risk aversion (Lorenzoni et al. 2007, Gifford 2011, Weber 2017), which may be also linked to personality.

The genetic influences we found might have roots in evolutionary history. Cooperation is fundamental to sustaining natural common-pool resources; all individuals must limit their short-term self-interest for the long-term collective interest, including that of future generations (Gordon 1954, Hardin 1968, Chermak and Krause 2002). Kin selection, direct reciprocity, and reputation mechanisms have been proposed to drive the evolution of cooperative behavior (Apicella and Silk 2019). For example, kin selection favors individuals with sustainable behavior because the short-term loss will benefit their offspring, provided that the offspring are likely to continue to use the resource (Lehmann 2007, Palomo-Vélez et al. 2020). It has also been shown that parents are more likely to donate for climate change mitigation when their decisions are observed by their children as a reminder of genetic relatedness with future generations (Fornwagner and Hauser 2020). The fitness consequences for cooperators may be dependent on the context. For example, proenvironmental behavior will be less beneficial or costly when many people share the same pool of resource (Suzuki and Akiyama 2005, Chang et al. 2021). Context-dependent fitness trade-offs may allow for the coexistence of different resource use behaviors.

Heritability captures how much individual variation in a phenotype can be explained by individual differences in genes and describes the existing variations in a specific study population with its environment. The heritability estimated in this study can therefore not be directly transferred to other study populations. In addition, heritability may change with age (Visscher et al. 2008). In our age moderation analyses (supplemental note 1), genetic influences for concern for nature and personal conservation behavior slightly increased with age. This could be because people may actively choose their environments on the basis of their genetic predisposition (e.g., actively learn about climate change or spend time with people with similar interests), reinforcing their concern for nature and personal conservation behavior as they age (Rutter and Silberg 2002, Plomin and Deary 2015). As unique environmental influences also increased with age, heritability was stable across age groups.

High heritability does not suggest the insignificance of environments. Suitable educational policies have been found to mitigate the health problems arising from genetic background (e.g., obesity; Barcellos et al. 2018). Environmental interventions, such as policies, may influence heritability. For instance, a high-quality teaching environment, which reduces the variance associated with environmental factors, improves students’ educational achievements and increases the heritability of educational achievement (Taylor et al. 2010). In countries with higher social class mobility, heritability of educational attainment is higher because of lower environmental variance (Engzell and Tropf 2019). Future studies with access to twin data sets from other populations could expand the understanding of genetic and environmental influences in other cultural or demographic contexts. We hypothesize that, all other things being equal, heritability of proenvironmental behavior will increase if the environmental barriers are lower for most people in a population.

Limitations and future research

There are several limitations in our study. First, twin analysis assumes that MZ twins do not have stronger environmental similarity than DZ twins for shared environmental factors (Horwitz et al. 2003). However, this assumption may be violated if, for example, MZ twins are more likely to have the same school activities or be treated more similarly by their parents than DZ twins. If this assumption is violated, heritability may be overestimated. Second, the scale used to measure one's concern for nature only shows a marginally acceptable level of internal consistency (DeVellis 2012). Future studies could use other scales with higher internal consistency. Similarly, unique environmental influences also include measurement error, and future studies could conduct repeated measures to address this issue (Ge et al. 2017). Third, our study population is biased toward females. Although we adjusted for this in our analyses, future studies using a more gender-balanced population would be beneficial and could test whether there is a sex difference in the genetic and environmental influences of these phenotypes. Fourth, our population is predominantly older individuals. How genetic and environmental influences change across age should be further investigated. With long-term repeated measurements (e.g., from child to adult stage) in the future, understanding of the development of a person's concern for nature and proenvironmental behavior could be improved.