Nature-based interventions, often abbreviated as NBIs, have proliferated in recent years as policymakers and communities grapple with the twin crises of mental ill-health and environmental degradation. These programmes range from structured green prescriptions issued by health services to participatory science initiatives and community gardening schemes. Despite their wildly different formats, most share two common ambitions: promoting psychological wellbeing and strengthening what researchers call nature connectedness, the subjective sense of closeness to the natural world. Yet the sector has been repeatedly criticised for lacking a consistent evidence base, because countless projects evaluate themselves with different methods shaped by individual funder requirements, producing scattered datasets that cannot be compared, combined, or analysed with any statistical power.

The new study, led by Michael L. Lengieza of Durham University together with Elizabeth Richardson of Natural England and Miles Richardson of the University of Derby, tackles this fragmentation head-on. The team presents a centralised evaluation tool, developed by Natural England, that allows individual projects to administer a standardised survey, enter key features of their programme, and feed participant data into a shared dashboard. Larger organisations gain the ability to combine data across many initiatives, while smaller organisations, which often lack the expertise to design their own evaluations, receive a ready-made solution that removes the burden of survey design, ethics applications, and basic analysis.

As a proof of concept, the researchers pooled data from 75 members of the public who participated in one of eight real-world nature projects and completed both baseline and follow-up surveys. Nature connectedness was measured using an adapted version of the inclusion of nature in self scale alongside the statement-based item measuring how much people feel part of nature, while wellbeing was captured with the Office for National Statistics personal wellbeing questions. Project coordinators also completed a survey describing their programme’s features, including whether they used a recognised delivery framework such as the pathways to nature connectedness.

The results were striking. Using multi-level statistical models with random intercepts for both participants and projects, the team found that nature connectedness increased significantly between the start and end of the programmes across all eight initiatives. But the more revealing discovery emerged when the researchers tested whether the size of that increase depended on programme characteristics. Projects that explicitly employed the pathways to nature connectedness framework, which identifies five routes to connection through sensory contact, emotion, beauty, meaning, and compassion, showed a robust and statistically significant rise in participants’ nature connectedness. Projects that did not use the framework showed only a small, non-significant change, suggesting they might not have been effective at all.

Crucially, the analysis showed that pathways-based and non-pathways-based projects attracted participants with similar baseline levels of nature connectedness, meaning the difference in outcomes could not be explained by one type of programme simply recruiting more devoted nature lovers. The type of engagement, not the type of audience, appeared to make the difference. This pattern aligns closely with the existing academic literature, which has repeatedly shown that actively noticing nature, attending to its beauty, and engaging the senses produce stronger gains than mere time spent outdoors. Analysing any single one of the eight projects in isolation would have been statistically impossible; only the pooled data made the comparison feasible.

The authors are careful to stress what the data cannot show. Because the study lacked experimental control, causality cannot be established. People who seek out nature-connection programmes might be making other lifestyle changes that drive the effect, and programmes using the pathways framework might simply be more enthusiastic or rigorous in ways that matter more than the framework itself. Nevertheless, the researchers note that pre-post time-series designs have a long and respected history in public health evaluation, and that the absence of a change would have more definitively ruled out a causal link. The observed increase, combined with the moderation by framework type, signals exactly where the sector should direct its next wave of controlled experiments and its resources.

The study also offers practical guidance for scaling the approach. Data must include at least one baseline and one follow-up measurement, ideally collected at similar intervals relative to each project’s start and end. Because crowdsourced data will inevitably be noisier than laboratory data, larger samples are essential, and null effects should be interpreted with caution since they may reflect insufficient statistical power rather than a true absence of effect. The tool’s live dashboard, built on Power BI, already gives project managers simple benchmarked summaries of their own performance against the sector, while allowing policymakers and funders to view aggregated results and export datasets for formal analysis.

Looking ahead, the authors envision a modular future for the tool, with optional modules capturing additional outcomes such as physical activity and loneliness, demographic variables, and psychological factors like mindfulness and emotion. They also argue that national and regional bodies, including environmental funders, should move beyond publishing evaluation frameworks and instead provide practical tools that support reporting and data combination. By reducing the evaluation burden on small organisations, the approach frees resources for delivery while building the scalable, policy-relevant evidence base that nature-based interventions need to influence decision-makers at national and international levels, from the Dasgupta Review to the Kunming-Montreal global biodiversity framework.

For a sector long dismissed as fragmented and under-evidenced, the message of this proof of concept is quietly transformative: the collective data of many small initiatives, pooled intelligently, can illuminate what works, guide investment, and ultimately amplify the social and ecological benefits of humanity’s reconnection with nature.

Subject of Research: Crowdsourced evaluation of nature-based interventions using pooled nature connectedness and wellbeing data

Article Title: Amplifying social benefits from multiple nature-based initiatives by crowdsourcing nature connectedness and wellbeing data: A proof of concept

Article References: Lengieza, M. L., Richardson, E., & Richardson, M. (2026). Amplifying social benefits from multiple nature-based initiatives by crowdsourcing nature connectedness and wellbeing data: A proof of concept. Ambio. https://doi.org/10.1007/s13280-026-02472-1

Image Credits: AI Generated

DOI: 10.1007/s13280-026-02472-1

Keywords: nature connectedness, nature-based interventions, crowdsourcing, programme evaluation, wellbeing, pathways to nature connectedness, Natural England, green prescriptions, environmental psychology, evidence-based practice, biodiversity policy, public health

The study, spearheaded by Saeedy Robat and colleagues, represents an unprecedented endeavor to synthesize extant evidence by evaluating 116 systematic reviews in the overview, and distilling them further through a second-order meta-analysis of 30 reviews selected for methodological rigor. These reviews collectively encompass an astonishing 3,870 primary studies, reflecting data from over ten million estimated participants — an unparalleled scale that endows the conclusions with remarkable statistical power and generalizability. Notably, the scope of evaluation spans both psychological and physiological dimensions of health, thereby recognizing the complex interplay between mind and body in the context of stress, anxiety, and depression.

Central to the study is the observation that nature-based interventions demonstrably reduce overall negative outcomes related to these mental health disorders when compared with control groups. The standardized mean difference (SMD) for overall negative outcomes was found to be -0.69, with a 95% confidence interval (CI) ranging from -1.05 to -0.33, which signals a moderate to strong effect size. Parsing these results further reveals that NBIs significantly diminish symptoms of anxiety, with an SMD of -0.83, as well as depressive symptoms, which show an SMD of -0.72. Physiological markers such as heart rate also exhibited improvements, marked by an SMD of -0.70. The reduction in negative affect further corroborates the therapeutic potential of engagement with nature, which was quantified with an SMD of -0.61.

Crucially, the study not only highlights reductions in negative symptomatology but also underscores the ability of NBIs to foster positive psychological states. The positive outcomes across interventions were even more pronounced, with an overall SMD of 0.90. Within this domain, increases in positive affect (SMD 0.52) and relaxation (SMD 2.85) stand out as particularly compelling evidence of nature’s restorative properties. These findings are significant because they suggest that NBIs do more than simply reduce distress—they actively promote enhanced well-being. By elevating positive affective experiences and inducing pronounced states of relaxation, NBIs appear to facilitate pathways to resilience and improved mental health recovery.

Delineating psychological versus physiological positive outcomes was another noteworthy element of this meta-analysis. The psychological dimensions of well-being featured a large effect size (SMD 1.18), signifying robust improvements in mental states such as mood and perceived relaxation. On the other hand, physiological outcomes exhibited a more modest and statistically nonsignificant improvement (SMD 0.24). This dichotomy suggests that while the psychological benefits of exposure to natural settings are profound and consistent, physiological changes might be influenced by additional variables or require longer durations for measurable impact. This nuanced insight calls for deeper explorations into the mechanisms through which NBIs exert their effects and the temporal dynamics involved.

Despite these encouraging findings, the study authors sound a note of caution about limitations inherent in the primary research landscape. A large proportion of the reviewed studies utilized passive control groups, such as waitlists or no-treatment comparators, rather than active controls engaging participants in alternative interventions. This raises the possibility that some effects might partially reflect placebo or expectancy biases rather than specific properties of nature exposure. Moreover, the inconsistent definitions and operationalizations of what constitutes an NBI across studies complicate the synthesis of results and cloud interpretations regarding which types of interventions are most effective. These methodological shortcomings underscore an urgent need to standardize intervention protocols and deploy active comparator groups in future trials to rigorously assess relative efficacy.

Another salient aspect of this meta-analytic work is the stringent quality assessment implemented through AMSTAR 2, a validated tool for appraising systematic review quality. Such a layered approach to evaluation enhances confidence in the robustness of the conclusions, separating high-quality evidence from lower-quality or potentially biased research. This is essential in a field that is rapidly expanding yet remains vulnerable to publication bias and variable study rigor. Addressing publication bias was another methodological forte of this study, reinforcing that the observed positive effects are unlikely to be artifacts of selective reporting.

From a clinical and public health perspective, these findings herald important implications. NBIs could represent a scalable, low-cost, and accessible complement to traditional pharmacological and psychotherapeutic treatments, particularly relevant in nonclinical populations or as preventive strategies. The magnitude of effect sizes observed—especially for anxiety, depression, and positive affective states—rivals or even surpasses those reported for some established interventions, bolstering the case for integrating natural settings into mental health promotion frameworks.

Furthermore, the physiological benefits, albeit modest, open intriguing possibilities for holistic health interventions that simultaneously engage both body and mind. The observed heart rate reductions align with theories of autonomic nervous system regulation facilitated by nature exposure, suggesting pathways through which psychological distress might be alleviated via somatic mechanisms. Future research utilizing biomarkers and neuroimaging tools could richly deepen understanding of these biopsychological processes.

Importantly, the study acknowledges that NBIs are not one-size-fits-all solutions. Variation in intervention type, intensity, duration, and participant characteristics likely moderates outcomes and warrants personalized approaches. For example, passive viewing of natural scenes might differ in effect from active engagement in gardening or forest bathing, yet current evidence synthesis struggles to disaggregate these nuances. This points toward a future research agenda emphasizing mechanistic studies, intervention standardization, and the identification of moderators and mediators.

In summary, this comprehensive systematic overview and second-order meta-analysis crystallizes a compelling narrative: nature-based interventions hold substantial promise as both preventive and therapeutic tools against the escalating burdens of stress, anxiety, and depression. The convergent evidence gathered from millions of individuals worldwide affirms the salutary power of nature not only to diminish negative emotions and physiological arousal but also to foster profoundly positive psychological states and relaxation. However, real-world translation hinges on bolstering the evidence base through high-quality trials with rigorous controls and standardized methodologies.

As mental health systems grapple with increasing demand and resource constraints, NBIs emerge as an attractive adjunctive strategy grounded in evolutionary affinity with natural environments. These findings revitalise the call for urban planners, healthcare providers, and policymakers to rethink and reintegrate nature access as a fundamental component of public health infrastructure. Further interdisciplinary collaborations involving psychology, environmental science, and clinical medicine will be essential to realizing the full potential of nature for nurturing mental health resilience in an increasingly urbanized and technology-driven world.

Ultimately, this landmark synthesis not only consolidates prior fragmented research but amplifies an urgent message: embedded in nature lies a powerful remedy against the pervasive mental health crises of our time. Leveraging this potential mandates a concerted scientific commitment to refining, standardizing, and scaling nature-based interventions so that their benefits can be reliably harnessed, equitably distributed, and enduringly sustained.

Subject of Research: Nature-based interventions for stress, anxiety, and depression

Article Title: A systematic overview and second-order meta-analysis of nature-based interventions for stress, anxiety and depression

Article References:
Saeedy Robat, E., Bayazi, M.H., Nayyeri, M. et al. A systematic overview and second-order meta-analysis of nature-based interventions for stress, anxiety and depression. Nat Hum Behav (2026). https://doi.org/10.1038/s41562-026-02433-4

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41562-026-02433-4