Testing the Savanna Hypothesis: Effect of Desert Landscape on Physiological Stress Recovery

Abstract

Background: Evidence suggests that green environments are protective of health and wellbeing. Many of these studies evoke prospect-refuge theory that poses that savanna-like landscapes offer opportunities for restorative experiences. However, evidence is still limited on how environments that do not match these criteria, and that instead may offer cues of danger (e.g., desert landscapes) affect health. In this study we quantified the effects of a desert landscape on physiological stress recovery and compared those with the effects of a green environment. Methods: Between-subjects experiments were conducted in El Paso, TX with 95 healthy adult men using virtual reality. Participants experienced an acute stressor (The Trier Social Stress Test) followed by one of three randomly assigned immersive virtual environments (IVEs: desert, green or control [office]) for 10-min. After the IVE, they then rested for 40-min. Physiological indicators of stress including systolic and diastolic blood pressure (SBP & DBP), pulse, mean arterial pressure (MAP) and salivary cortisol, were repeatedly measured throughout the experiment. Results: After the IVE, participants exposed to desert and green environments showed larger decreases in pulse rate than participants in the control group. Effects were similar between desert and green conditions. Additionally, participants in the desert condition experienced greater decreases in SBP, DBP and MAP than participants in the green condition. After the first 20 min of rest, participants in both the desert and green conditions showed greater decreases in SBP, DBP, MAP and cortisol than those in the control group. Conclusions: A desert landscape promoted similar or even greater physiological recovery from an acute stressor than a green landscape. These novel findings suggest that prospect-refuge theory does not adequately explain the protective effects of natural environments, and that exposure to environments such as savannas are by no means the only natural landscapes that may lead to stress recovery.