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

layers), audio (birdsong from more or fewer species) and olfactory stimuli (1 to 3 smells from grasses species). Results showed that the low biodiversity scenario (2 vegetation layers, 1 bird, 1 smell) lowered anxiety and heart rate, compared against an urban control (i.e. little biodiver- sity) but also the treatments representing greater biodiversity. Another strand of studies has found that improved psychological well-being was more asso- ciated with people’s perceptions of biodiversity, rather than with the actual species richness [32]. Using measures of both the actual and perceived richness of trees, butterflies and birds in twelve urban parks in Lisbon, Gonc¸alves et al. [33] found that perceived species richness explained more of the variance of well-being (Attention Restoration) than actual species rich- ness. Similarly, students perceiving higher animal species richness in the parks of Singapore reported higher attention restoration and Positive Affect [23]. Perceptions of biodiversity are experienced through the senses [26] and several factors may influence these perceptions. These include visual clues such as planting height [30], diversity of flower colours [34] and broadleaf shapes [33]; auditory clues such as birdsong and sounds from water [35, 36]; and olfactory clues such as smells of understory plants and fungi [37]. Per- ceptions of biodiversity, however, have at times been reported to be closely aligned with recorded data sets [30, 31, 38], at other times overestimated [39] or poorly correlated with

actual biodiversity [32, 40]. This may be due to difficulties in conceptualising biodiversity out- side the expertise of ecologists [41]. Overall, these studies provide evidence of a positive link between species richness (actual or perceived) and some health indicators. Although limited by the number of studies, the experi- mental evidence suggested this relationship could be non-linear (i.e. a moderate level of diver- sity is more beneficial than too high or too low). However, since many studies have compared the effects of species richness present in different locations (e.g. different parks), the specific contribution of species richness to health and well-being remains unclear. Although different locations or settings allow for an easier (possibly more realistic) comparison of species rich- ness, it has been argued that as the location changes, so do other characteristics, such as land- scape size, heterogeneity, naturalness, management and other factors that influence landscape quality, e.g. the presence of water [19, 31]. The present study The study presented here aimed to provide further understanding of the role of biological diversity on human well-being by manipulating species richness and stress while controlling for the effect of the location. Similarly to Lindemann-Matthies and Matthies [22] one single locational setting (a woodland) was manipulated to increase the level of plant species richness by incorporating additional plants. Digital video recordings (360˚) of each scenario (condi- tion) were then taken for participants to view at a later date.

Videos were used because exposure to the natural environment can be simulated through visual and audio media and elicit positive health responses [42–46]. Interactive, 360-degree videos are emerging as a novel method to expose participants to green spaces [47, 48] and allow viewers to rotate the camera in any direction and explore the location. Such videos can mimic in-situ interactions, with participants who watched 360-degree videos of monuments [49] or scenic lakes [50] reporting similar spatial presence and emotional reactions to those who actually visited these sites. Understandably, however, direct exposure to the natural envi- ronment generates a stronger affective response, compared to any video-mediated exposure [51, 52]. The use of videos to record the location, but with and without additional plants or bird songs, meant that all other landscape factors were consistent across all video treatments, i.e. 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 3 / 20