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

the only factors that varied were the ones we artificially manipulated. This allowed us to test the following hypothesis: • Increased plant diversity corresponds to improved Positive Affect and reduced Negative Affect after a stressful event. • Increased bird diversity corresponds to improved Positive Affect and reduced Negative Affect after a stress event. Finally, given that perceptions of biodiversity could be more important than actual species richness in producing well-being, we measured perceived biodiversity to test if: • Higher perceived biodiversity corresponded to improved Positive Affect and reduced Nega- tive Affect after a stress event. Methodology Condition set up and video recording Plant biodiversity was manipulated by creating four different conditions for the one woodland location in Sheffield (UK). The site is managed as an urban conservation zone and is approxi- mately 200 x 150 m in size. Access to the site was granted by the Estates and Facilities Manage- ment of the University of Sheffield. A botanical survey in May 2021 found 36 vascular plant species in the woodland, including non-native species (S1 Appendix). A camera was set up on a southeast sloping site in the northwest sector of the woodland, and only recorded natural fea- tures (e.g. the presence of vehicles, houses etc. were excluded). The camera lenses were placed at 1.3 meters from the ground, simulating an average eye level for a sitting person. Condition 1 acted as a control and was filmed without introducing any additional plants.

For condition 2 (low plant diversity), 60 individual plants of 4 taxa were introduced to the woodland within view of the camera (Table 1). These plants were then removed and for condi- tions 3 and 4 (high plant diversity) replaced by 60 other individuals representing 23 taxa (Table 1). Small-flowered (i.e. non-flamboyant) varieties were used to represent typical wood- land plant types. The plants were placed alongside existing natural herbaceous vegetation, avoiding excessive shade, pathways or where there might be a strong contrast between the flowers’ colours (Fig 1) in an attempt to maintain an illusion of naturalness. In conditions 1–3, the audio from the footage was replaced with the sound of a gentle breeze (Table 2). This provided a credible background sound for a woodland while controlling for the effects of plant (visual) and bird (auditory) diversity. Condition 4 was produced with the footage of condition 3 and audio recorded in the same location but on a different day. This featured birdsong from 6 species (S1 Appendix) and water sounds from a nearby stream (Table 2). The sound was recorded with a Zoom H1 (Zoom Corporation, Tokyo, Japan), set to record at a sampling frequency of 48kHz at 16 bits. All footage was captured with the camera Insta360 OneX (Arashi Vision Inc., Shenzhen, China), at 5.6k resolution and 30 frames per second and leaving the rest of the settings on auto. Adding sounds to all videos was a necessary step to simulate the woodland on screen. Participants can experience “restlessness” and feel

“cut off” from the experience of nature when watching a slideshow of a woodland with no sounds [53]. Participants’ recruitment and ethics statement Participants were recruited through social networks (Facebook and Twitter), via a University of Sheffield Volunteer mailing list (including staff and students), and on two survey exchange 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 4 / 20