Does increasing urban biodiversity enhance stress recovery? New experimental evidence

Urban nature, in the form of parks, gardens and semi-natural areas, has been cited as an important provider of health and well-being. Decades of research have investigated the salutogenic potential of urban nature, however, most of the evidence has compared “green” (i.e. vegetated) spaces against “grey” (i.e. urbanised) spaces, often giving limited attention to their ecological components such as biodiversity.
This PhD project aimed to investigate the relationship between biodiversity and well-being more systematically. This thesis presents the results of four studies, in which actual (i.e. really present) and perceived (i.e. subjectively estimated) species richness have been linked to psychological and physiological indicators of well-being. In particular, this was achieved by manipulating the number of plant species within the same space, creating alternative versions of the area which differed only in the species number. These experimental settings were then used to relax the participants during a stress induction and recovery procedure.
Results consistently highlighted that an increase in the actual number of species was not associated with increased well-being. Instead, perceiving a high number of species was strongly associated with improved emotional well-being. However, the perceived number of species did not always match the actual number of species. Interestingly, those participants who were able to relate their perceptions to some elements of biodiversity showed the greatest improvement in well-being.
This evidence suggests that the relationship between urban biodiversity and well-being passes through the sieve of subjective perception, which, however, does not represent the actual variety of species. This could lead to reduced support for sustainable enhancement and management of urban biodiversity. However, the improved well-being shown by those who noticed biodiversity suggests there may be a solution to this dilemma. If designers and practitioners could find a way to make biodiversity more noticeable future green spaces could be even more effective providers of well-being.