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

where the participants hardly noticed the difference in species, compared with control sites; nonetheless, those exposed to highly diverse meadows expressed a stronger preference [40] and higher site satisfaction [30] compared to controls. Perceived biodiversity and affective response In contrast to data on real biodiversity, the perceived level of biodiversity was associated with increased Positive Affect scores. Those who perceived the environment as more biodiverse showed an increase in their Positive Affect after the video. These results align with previous research which hypothesised a predominant role for subjective perceptions of biodiversity over the actual species richness of the location [23, 32, 33]. In other words, what was visually perceived to be more diverse was more strongly associated with the Positive Affect scores than the actual diversity. However, only half of the commenters (108 out of 208) associated their high perceptions of biodiversity with elements related to species richness (i.e. trees, birds, flowers) when asked. Fewer could narrow down their perceptions to birds (18 comments) or flowers (35 comments) which were experimentally designed to be evident. Those participants who noticed flowers, trees or sounds showed improved Affect scores after watching the video (i.e. reduced Negative Affect and increased Positive Affect). These participants received something more from the experience by engaging with the local species richness (i.e. trees) and the species we had intro-

duced (i.e. flowers and birdsongs). This suggests that noticing biodiversity could be a necessary step to receive extra emotional recovery after a stressful event. Research shows that actively noticing nature is more beneficial than passive exposure. Ran- domised controlled trials such as the Noticing Nature Intervention [72] and its replications [73, 74] showed that participants who were tasked to notice nature for two weeks reported higher Positive Affect, compared with participants who did not receive instructions. This increase in Positive Affect was independent of other well-being-related variables, such as Nature Connectedness and engagement with beauty. Similarly, noticing nature with all senses during a forest bathing session [75] improved Positive Affect as much as a session of Compas- sionate Mind Training, which is a more established intervention to improve well-being. Among the natural elements that participants used to evaluate the video’s biodiversity, flow- ers deserve a special mention. Flowers were the only biodiversity element correctly noticed by participants (i.e. there were no comments about flowers in the control condition). Noticing flowers was associated with improved Positive Affect, even when the effect of the perceived biodiversity was statistically controlled. Flowering plants are known to elicit positive emotions [76–78], especially when the flower coverage exceeds a certain percentage (e.g. 27% [79]). Although in this case it is difficult to estimate the scene coverage, due to its three-dimensional

nature, if the participants spent most of the condition time looking at the planted flowers, this could have prompted the increase in Positive Affect. Limitations and recommendations for future research As the study was conducted online, there are limitations in estimating how much the partici- pants engaged with the experimental procedure. Although metadata provided a measure of control on some of the factors (e.g. individuality of the response, type of device used), it is chal- lenging to say whether the participants followed the recommendations provided. Using a 360-degree video increased the simulation of “being there” but at the cost of some control over the condition. Since the participants could point the camera in any direction, some could have chosen to look at the tree canopy for the entire video, without noticing the ground flowers. Furthermore, participants did not receive any instructions other than to “look around”. It is 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 14 / 20