Does increasing biodiversity in an urban woodland setting promote positive emotional responses in humans? A stress recovery experiment using 360-degree videos of an urban woodland

positive emotions (uplift–Positive Affect) per se. Scores for Negative Affect were lower after the video than at the start of the procedure or immediately after an annoying noise (stressor). This confirms previous findings that viewing green space reduces psychological stress [4, 5], including situations where the exposure is through video alone [47, 67, 68]. Previous studies with video have indicated no difference based on the type of green space being viewed [44], but Tyrva¨inen et al. [69] working with real in vivo urban spaces, suggested that typology mat- tered (urban woodlands being marginally more restorative than urban parks, with both typolo- gies being better than a city centre location). It is possible that real locations stimulate stronger emotional responses than virtual ones [51], but real locations expose people to additional vari- ables, other than those solely linked to the green infrastructure–not least different experiences whilst travelling to experimental locations. This study attempted to limit such variables, by focussing on one location and systematically altering the natural elements within. Whilst all our ‘green’ scenarios were equally restorative (lowering Negative Affect), none actually strongly stimulated joy (Positive Affect scores being lower after both the stressor and the video, compared to the baseline). This suggests our landscapes were providing a calming influ- ence, but not necessarily stimulating strong feelings of excitement or joy. Biodiversity levels and emotions

Increasing the levels of plant biodiversity and inferring greater avian biodiversity through bird- song, had no additional significant effect on the affective response. In essence, there was no additional benefit from increasing these aspects of biodiversity to the green space. These results do not support our initial hypotheses that increased biodiversity improves the emo- tional (and potentially health) outcomes. Despite artificially altering distinct visual levels in plant (+21 species vs +4 species vs base) and sound levels of avian diversity (6 species vs none), we observed similar changes in the Affect scores as observed with the control treatment. Thus, for the sample population as a whole, the data does not support the notion that increased plant diversity corresponds to enhanced Positive Affect, and reduced Negative Affect, after a stress- ful event. Similarly, introducing background natural sounds (bird song and water) did not enhance Positive, or reduce Negative, Affect. Our findings are in line with those previous stud- ies where either an increase in biodiversity [32, 70]–or optimal biodiversity [71]–did not increase the health outcomes. This contrasts with the relationships between Positive Affect and biodiversity that have been found in other studies though. For instance, Wolf et al. [18] exposed their participants to videos with high vs low tree diversity and high vs low bird diversity. In both cases, they found a statistically significant effect for biodiversity and a higher post-video Positive Affect was asso-

ciated with the high biodiversity conditions. Cameron et al. [19] also found significant positive correlations for both avian diversity and habitat diversity and the positive emotions reported by park visitors in Sheffield. The absence of a direct biodiversity effect in this study could be due to non-exposure to the condition, rather than a non-response. It could be argued that the introduced species were not noticeable enough. However, the addition of brightly coloured, flowering plants was far from subtle. Comparing the Control condition with the High plant increase condition (Fig 1) it is evident that the plants stand out from the background. The same can be said for the avian diversity, where a rich soundscape was compared with the sound of the wind. It is possible, however, that the participants may not have paid much attention to the planting around them, focusing instead on the rest of the woodland. This would explain why, despite their actual dif- ferences in species, all videos received similar ratings of perceived biodiversity (S1 Appendix). This “nature myopia” has already been noted in previous experiments with flower meadows, PLOS ONE Does increasing biodiversity in an urban woodland setting, promote positive emotional responses in humans? PLOS ONE | https://doi.org/10.1371/journal.pone.0297179 February 7, 2024 13 / 20