The influence of plant species richness on stress recovery of humans

Natural sceneries or single plants may have positive influences on human health. Here we show that plant species richness can positively influence recovery from stress. Meadow-like arrays of different species richness (1, 16, 32, 64 species) were presented to visitors (n = 171) of a popular park in Zurich, Switzerland (one array per participant). Participants' systolic blood pressure was measured twice: directly after they had been stressed and once again after a 2 min post-stress relaxation period during which they looked at one of either the meadow-like arrangements of plants in pots or at bare ground, shielded on three sides by a tent-like structure. The decrease in blood pressure was larger when respondents could view an arrangement of plants instead of ground without vegetation. Relaxation was strongest at intermediate species richness (32 species). Age, gender, and a person's attachment to nature did not influence relaxation. Our results indicate that species-rich vegetation may contribute to recovery from stress which should be considered in landscape management and planning.