1.1 Climate change

The United Nations Framework Convention on Climate Change (UNFCCC) defines climate change as being, “attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods” [13] [p.7]. Despite ongoing debates in the media regarding the anthropogenic nature of climate change, the Intergovernmental Panel on Climate Change (IPCC) reported with 95% certainty that human activity is the primary cause [14], leading to a consensus that it is “marked by human influence” [15] [p.119]. Human activities, notably the burning of fossil fuels, have led to a significant increase in greenhouse gas (GHG) emissions, and consequently, the global surface temperature is currently averaging 1.2°C warmer compared to pre-industrial times (1850–1900) [3, 16]. With this alarming rise, climate change has been inextricably tied to the intensification and increased frequency of climatic hazards worldwide such as heatwaves, storms, drought, and flooding. Together with indirect effects including food and water insecurity and increased air pollution, climate change is having a detrimental impact on the social and environmental determinants of human health [17].

1.2 Climate change and mental health

Climate change has been expedited to one of the top priorities on the international political agenda over the last few decades following scientific evidence connecting it with adverse health outcomes [18]. These health effects are continuing to unfold across the globe with reported rises in premature deaths, infectious diseases, non-communicable diseases, and mental illnesses all attributed to climate change [2]. Whilst causality cannot be easily inferred as drivers of poor health are often complex and intertwined, the empirical evidence undoubtedly shows that climate change is a contributory exacerbating factor.

Whilst impacts to physical health have historically been the focus of academic inquiry, climate change also impacts mental health both directly, from exposure to climatic hazards, and via numerous indirect pathways including loss of livelihood, displacement and forced migration, and armed conflict and interpersonal violence [19, 20]. These risk factors can lead to the onset of mental health conditions and adverse psychosocial outcomes such as depression, anxiety, substance use, and suicidal actions, or have a compounding effect for those already living with these conditions [21]. Moreover, these effects are experienced disproportionately by the most disadvantaged members of society including people with pre-existing chronic disease(s) and/or disability as well as minority groups, people with low-incomes, and women and children. Adopting an intersectionality lens, which considers the systems of privilege and oppression resulting from the intersection of an individual’s multiple social identities [22], serves as a reminder that many people occupy a combination of these marginalised identities which may work in tandem to further increase their vulnerability to climate change [23].

Mental health is broadly defined as “a state of mental well-being that enables people to cope with the stresses of life, realize their abilities, learn well and work well, and contribute to their community” [24] [para.1]. Under this comprehensive definition, contemporary climate change research is also beginning to take heed of less pathological responses arising from an awareness of the slow and gradual changes to environmental conditions [25]. This phenomenon is now commonly referred to as ‘eco-anxiety’, which encompasses a range of negative emotional responses including fear, anger, guilt, dread, and anxiety itself towards the climate crisis and ensuing environmental deterioration [25]. One international study on climate anxiety surveyed 10,000 16-25-year-olds in ten countries (Australia, Brazil, France, Finland, India, Nigeria, Philippines, Portugal, the UK, and the USA). They found that over 50% of respondents felt one or more of the following negative emotional responses towards climate change: feeling afraid, sad, anxious, angry, powerless, helpless, and/or guilty [26]. Alternative terminology has also emerged to describe this affective dimension of climate change including solastalgia, which describes “the distress that is produced by environmental change impacting on people while they are directly connected to their home environment” [8] [p.S95], and ecological trauma which is the “experience of witnessing–consciously or not–the pervasive abuse and destruction of the natural world” [27] [para.2]. Whilst these new concepts are gaining traction within public discourse, there is still limited empirical evidence that can verify the true extent or prevalence of these psychological effects, particularly within Global South settings.

Attempting to quantify and measure emotional responses to climate change is not a simple feat considering the diverse array of mental health outcomes. However, one framework is prominent in the literature–the New Ecological Paradigm (NEP). The NEP is a widely adopted measure of an ‘ecological worldview’ that uses a Likert-type scale containing fifteen questions related to environmental concern [28]. This framework has been used to investigate the relationship between climate change concern and shifts in individual and collective behaviour as whilst some individuals may become paralysed by their feelings, others are galvanised into action, and modify their behaviour accordingly [29]. These may include changes to ‘everyday’ behaviours such as recycling, diet, or consumption patterns, but potentially could influence behaviours of even greater magnitude, such as reproductive decisions.

1.3 Reproductive decision-making

Reproductive decision-making “involves decisions about parenthood (whether and when to be a parent, and the number and spacing of children one wishes to have), including decisions around contraceptive usage and fertility” [30] [p.2]. These decisions are often multi-factorial, in flux, and consequently made over time [31]. The T-D-I-B model is a theoretical framework of reproductive decision-making, breaking down the process into a five-step psychological sequence [32, 33] (Fig 2). These discrete steps are, however, often incorrectly used interchangeably in analyses of environmental concern and reproductive decision-making, particularly with ‘desire’ and ‘intention’. Whilst both terms describe psychological states, desires represent what someone hopes or wishes for, whilst intentions represent desires evaluated with respect to what is achievable in reality [32].

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Fig 2. A model of reproductive decision-making combining the T-D-I-B model with climate change concerns.

Note. Adapted from: Miller [32, 33]. The dashed line represents the possibility of climate change-related concern acting as an intervening variable, mediating the transition between traits and desires, and desires and intentions respectively.

https://doi.org/10.1371/journal.pclm.0000236.g002

Over the last half-century, changes in childbearing patterns, most noticeably observed in the Global North, have seen a greater proportion of adults now choosing to abstain from parenthood and remain voluntarily childfree [34]. These demographic shifts have been linked to macro-level social changes such as the 1970s feminist movement that expanded women’s reproductive rights, as well as individual-level decision-making, with many citing freedom from childcare responsibility, and maintaining close relationships with their partner as determinants of their decision to remain childfree [35]. These decisions are inherently shaped by normative pressures and structural constraints that are culturally dependent, and variation both within and between Global North and Global South contexts is therefore likely.

The term ‘childfree’ is isolated as a distinct concept from ‘childless’, where the former refers to the ability to have children but choosing not to as a result of sociocultural shifts in societal norms, whilst the latter simply refers to an inability to reproduce despite wishing to have children [31]. This dichotomy is problematised as many describe feeling forced into the decision due to their climate change concerns which does not resonate with the typically voluntary nature of choosing to remain childfree [36]. This subset of individuals will therefore be referred to using more specific nomenclature, ‘environmentally childfree’, defined as “not hav[ing] children or restrict[ing] reproduction… partly or fully out of environmental concerns” [37] [p.201].

1.4 The current study

2.1 Ethics statement

Ethics approval and informed consent were not required for this systematic review as it uses published literature and data already available in the public domain.

2.2 Databases

The literature search was conducted on the 11^th of July 2022 and the following databases/platforms were searched to provide comprehensive coverage of the relevant literature: Web of Science Core Collection (WOS) (1990 –present), ProQuest Central (1806 –present), OvidSP Global Health (1973 –present), OvidSP PsycINFO (1967 –present), OvidSP MEDLINE (1946 –present), and EBSCO GreenFILE (1913 –present). WOS and ProQuest Central are multidisciplinary and include literature encompassing the cross-disciplinary themes of climate change, mental health, and reproductive decision-making within the research question. Global Health is a public health database which also includes articles discussing these three themes. The final three databases were selected as they each specialise in one of these disciplines: PsycINFO provides an index of literature from psychology and was relevant to the mental health branch; MEDLINE is a biomedical database exploring medicine and the healthcare system and provided insight into reproduction; and finally, GreenFILE covers publications focussing on human impact on the environment.

Additional relevant papers were found by handsearching the reference lists of included papers (backward snowballing) and reviewing publications that have cited them (forward snowballing) [42]. Google Scholar was also used to ensure a fully comprehensive search for all relevant literature.

2.3 Search strategy

The initial search strategy was formulated on WOS and then adapted to fit the formatting guidelines of the other databases. The search strategy consisted of three separate strands that were combined together to identify studies that focussed on (1) climate change, (2) mental health and wellbeing concerns, and (3) reproductive decision-making. On an initial exploratory search, the search terms included neutral ‘mental health’ terms and broader ‘climate’ and ‘environment’ synonyms. However, upon finding a large quantity of unrelated articles, these were refined to ensure the search had a narrower focus, specific to the research question. As well as synonyms, the search also incorporated Boolean terms, wildcards, truncations, and medical subject headings (MeSH) to ensure that all appropriate terminology was captured (S1 and S2 Tables).

2.4 Eligibility criteria

As research in this field is still incipient, exclusion criteria were not extensive (S3 Table). Firstly, no limits were placed on geographical location to allow for critical reflection on any discernible differences between countries or geographical gaps in current research. The search was also not limited by study design resulting in a review with methodologically triangulated data. Based on the population, exposure, outcome (PEO) framework, during initial abstract screening, articles on plant or animal reproduction were excluded. At full-text screening, literature exploring retrospective reproductive decision-making and/or the intersection of climate change and fertility outcomes, without also addressing mental health concerns, were also excluded. Primary studies, books, and book chapters were all eligible for inclusion as long as they included empirical methodology and findings. Newspaper, magazine articles, and blog posts were excluded but student theses were included to try and capture more empirical research. Peer-reviewed journals are less likely to publish studies with null results, whilst the opposite is true for statistically significant findings [43]; student theses were therefore also included to mitigate this publication bias to some extent. As the lead author of this review only speaks English, all papers that were published in a language other than English were excluded. Additionally, any study that was not available as open access or accessible through university library e-resources was excluded from analysis. Finally, no documents were excluded based on date of publication as this may have unnecessarily restricted the scope of included literature.

2.5 Data extraction and synthesis

Data from the included studies were identified and extracted into a detailed spreadsheet. This included information on the article (first author, publication year, and title), measurement tools, location, participant information (sample size and demographic characteristics), reproductive focus, and key findings. Given the variation in exposure and outcome measurement, a meta-analysis was not feasible, and findings were instead described narratively in accordance with Popay et al.’s [44] guidance. Findings were analysed using a parallel-results convergent synthesis design [45] in which the quantitative, qualitative, and mixed-methods data were initially analysed independently before being consolidated in the discussion and interpretation of the results.

2.6 Risk of bias assessment and quality appraisal

The quality of included studies was assessed using peer-reviewed checklists to inform the final analysis and interpretation of the data (no studies were excluded based on quality). Different checklists were used according to study design: the Joanna Briggs Institute (JBI) Critical Appraisal Checklist for Analytical Cross-Sectional Studies [46], the Critical Appraisal Skills Programme (CASP) Qualitative checklist [47], and the Mixed Methods Appraisal Tool (MMAT) [48] for the quantitative, qualitative, and mixed-methods studies respectively.

3.1 Quantitative results

3.1.1 Study characteristics.

Table 1 presents the study characteristics of five included quantitative studies. All studies were cross-sectional, used surveys, and were conducted in denominated Global North countries (Canada and 27 EU countries) (Fig 3). Measurement instruments were heterogeneous, with four different tools, and one single-item measure used to assess environmental concern. In total, 10,788 participants were included, none of whom identified as gender-diverse, defined as “people on the continuum between binary male and female” [61] [p.82] (although information on gender was unattainable for one study [50]).

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Fig 3. A map showing the geographical distribution of included studies.

Note. ¹The Brandt Line is “a way of visualising the world that highlights the disparities and inequalities between the wealthy North and the poorer Global South” [60] [p.85]. It is critiqued for being outdated; however, it is still regarded as a useful way to visualise economic inequities in world politics. Base layer of map available from: https://www.mapchart.net/.

https://doi.org/10.1371/journal.pclm.0000236.g003

3.2 Qualitative results

3.3 Mixed-methods results

4.1 Summary of evidence

Thirteen studies detailing how climate change-related concerns link to reproductive decision-making were narratively synthesised. The majority of studies (12/13) reported that stronger environmental concerns are associated with less favourable reproductive attitudes and a diminished desire and intention to have children. However, weaker evidence from four studies suggested climate change concerns may be associated with increased reproductive intention for some. Four key areas of concern were identified: uncertainty of an unborn child’s future, ecological impact of reproduction, meeting family subsistence needs, and contributing to environmental politics. The qualitative, quantitative, and mixed-methods findings are consolidated in this section, and contextualised in relation to other literature, to answer the research question and objectives of this review.

4.2 Complex relationship between climate change concerns and reproductive decision-making

The findings revealed a complex relationship between climate change-related concerns and reproductive decision-making. In all but one study, stronger concerns were associated with a desire for a smaller number of children or simply none at all. This accords with a recent cross-country study [26] involving 10,000 16-25-year-olds reporting that four in ten participants were hesitant to have children as a result of climate change. Additionally, these concerns sparked the inception of political movements such as BirthStrike, with Blythe Pepino, the founder of this collective stating, “we feel too afraid to have kids because we feel that we’re heading toward civilization breakdown as a result of the environmental crisis” [36] [p.2].

However, results were mixed; two quantitative studies in EU countries [50, 52] suggested that climate change concern may be associated with an increased desire for children for some. These studies, however, used a single item measure of concern as opposed to the NEP, and dichotomised environmental concern on a binary scale from ‘strong concerns’ to ‘no strong concerns’. This ignores the continuous nature of mental health issues and meant a considerable amount of this variable’s information was lost, reducing its statistical power [65]. However, one qualitative study [55] found that some Zambian men desire more children during times of environmental degradation, and in one mixed-methods study [58] environmental concerns were justified as a reason to have children.

Additionally, participants’ narratives were not so clear-cut as they explained their process of decision-making was often fraught with competing tensions from societal norms and divergent individual attitudes towards reproduction. This idea is grounded in the Theory of Planned Behaviour (TPB), which proposes that behavioural intentions are determined by personal attitudes, subjective norms, and the degree of control over the behaviour [66]. In the context of reproductive decision-making, climate change concerns compete with pro-reproductive attitudes and normative expectations to bear children, as well as the ability or inability to control reproductive trajectories in many settings.

To explain these contradictory findings, it is important to discuss the various concerns that motivate these shifts in reproductive decision-making.

4.3 Explanations for factoring climate change concerns into reproductive decision-making

Participants’ climate change concerns factoring into their reproductive decisions are divided into four themes. Firstly, participants worried about the quality of their child(ren)’s life in a future affected by climate change. These are altruistic environmental concerns, according to Davis et al. [39], as they consider the impacts to others, in this case one’s children, and embody a “degree of nature-self overlap” [p.95] by placing them within an interdependent environment. This narrative is echoed in Dow’s [67] conceptualisation of an ecological ethic of reproduction which encourages prospective parents to look beyond their individual nuclear family to the broader environment, representing the conditions into which a child will be born.

Dow’s [67] theory also naturally intersects with the second theme, participants’ concerns of their ecological impact, as it proposes a reconsideration of “bring[ing] future generations into a world with stretched and unequally distributed resources” [p.653]. Participants feared that having children would contribute to overpopulation and overconsumption, which corresponds to recent calculations of the ecological cost of reproduction. Wynes et al. [68], for example, concluded that having one fewer child is the highest impact action one can take to reduce personal emissions. Interestingly however, these concerns were not expressed by participants in the Global South, which may reflect their relatively negligible involvement in overconsumption practices [1]. Whilst the fertility rate in many Global South countries has historically been higher than their Global North counterparts, focussing on overpopulation discourses has been critiqued as reductive and racist as consumption, aggravated by a capitalist way of living, is considered the primary anthropogenic driver of climate change [69].

The third and fourth themes were reported to a lesser extent, in two studies each. In Zambia and Ethiopia, participants desired fewer children to meet subsistence needs during periods of declining agricultural productivity. However, this competed with the lived reality of shortages in contraception provision which epitomises the distinction between ‘desire’ and ‘intention’ in Miller’s [32] T-D-I-B model. Given this finding was unique to the studies from the Global South, this may imply that the transition from desires to intentions is more challenging in these countries with generally weaker sexual and reproductive health (SRH) service provision, and where reproductive rights is, at times, still a taboo subject [70]. Contextualising this within broader discourses of reproductive freedom, it is important to remember that many people may not have the ability or privilege to choose whether, or how many children they have. Consequently, this highlights the highly situated nature of environmentally childfree behaviour as organised along social class hierarchies that are prevalent both within and between Global North and Global South settings [54].

The final theme explored environmental political concerns in some individuals’ decisions to restrict their reproduction. Participants in Schneider-Mayerson [58] believed that the energy required for parenting would detract from their personal endeavours to mitigate climate change. This parallels Blackstone’s [35] research suggesting that childfree individuals wish to “leave a legacy” [p.76] by making a positive mark on the world through philanthropic work, civic engagement, and in this case, climate change activism. Reproduction was also seen as a socio-political tool in participants’ private lives, although interestingly only two participants across all studies reported their refusal to have children on a more public scale, as a method of ‘striking’ until systemic change was enacted. This is surprising given the prominence of BirthStrike, Conceivable Future, and No Future No Children that had this notion at the very core of their movements.

These final two themes were also articulated in participants’ intentions for a greater number of children within two studies. Firstly, participants in Zambia were concerned about their ability to support their family without the household labour provided by additional children. This idea supports demand theories of fertility previously mentioned and is observed in other Global South countries including Bangladesh and Nepal where children are seen as “helping hands during difficult times” [71] [p.105] to support with domestic work as well as water and fuel wood collection [72]. These concerns may also be reasonably linked to demographic theories of ‘insurance’ births, whereby women in unfavourable environmental conditions have more children to compensate for the risks to child mortality [73]. Consequently, this is another example in which the transition from reproductive desires to intentions may be more challenging in Global South countries with a dependency on children to provide support. Regarding environmental politics, participants responses were reflective of a political fertility gap in the US, with statistics from the 2006 General Social Survey highlighting a 41% increase in numbers of children had by ‘conservative’ adults than ‘liberal’ adults [74]. Participants feared that this gap would widen if they, as liberal and environmentally conscious individuals, chose to have fewer children which could further exacerbate the climate crisis.

These studies have therefore highlighted a complex and multidimensional relationship between climate change concerns and reproductive decision-making. This contrasts with an oversimplified depiction of this relationship within the media that has typically only highlighted people’s concerns of the quality of a child’s life in a climate-changed future as a factor in their reproductive decisions. Additionally, important distinctions were found between, as well as within, Global North and Global South counties, adding further complexity to the relationship as climate change concerns and their impact on reproductive decision-making were not generalisable on a global scale. Finally, the scope of this review limited a detailed analysis of competing reproductive tensions from social norms and conflicting individual beliefs that may obscure the relationship between participants’ climate change concerns and reproductive decisions.

4.4 Recommendations

4.5 Limitations

This review has identified a gap in the literature and provided key recommendations to be taken forward into the field, however, some limitations remain. Firstly, as the screening of databases was conducted in July 2022, potentially relevant studies published after this date were not included. This temporal limitation emphasises the evolving nature of research and serves to encourage future updates that incorporate the latest research findings. Other relevant studies may also have been omitted as only English language papers were eligible for inclusion. Additionally, the inclusion of different study designs resulted in inconsistencies in the quality appraisal as three separate tools had to be used. However, not limiting by study design was justified as it facilitated methodological pluralism which is useful, not only for neutralising the limitations inherent in a single method, but also for gaining a more holistic analysis that is not achievable through the use of just one study design [79]. The narrative synthesis approach is often critiqued for lacking transparency [80] and an in-depth description of the process was beyond the scope of this review. However, synthesis was conducted in line with Popay et al. [44] and we have provided detailed information on the review’s methods to ensure utmost transparency and reproducibility of findings. This detail was also provided to offset the risk of selection bias resulting from the single screening of articles as much as possible [81].

The included studies were all appraised as either high (n = 7) or medium quality (n = 6), enhancing the strengths of the conclusions drawn. However, there was significant variability in sample sizes with three qualitative studies recruiting only 7, 14, and 20 participants, resulting in low statistical power. All quantitative studies were cross-sectional, leading to an inability to infer a temporal relationship or to evaluate any changes prospectively. However, confounding factors were identified and adjusted for, and the qualitative and mixed-methods studies supported a directional relationship from climate change concern (exposure) to reproductive decision-making (outcome), making it unlikely that the inverse was true for the quantitative studies. Finally, there was significant geographical homogeneity in the data, with 85% (n = 11) of studies conducted in Global North countries, limiting the generalisability of these findings to the Global South.