Evidence for the effectiveness of Green Prescriptions – doses of nature tailored to patients’ needs – comes from many disciplines, but this brief summary concentrates on the medical and public health literature. The research demonstrates numerous correlations between different indices of health and wellbeing and exposure to nature, and the most recent overview shows that the evidence regarding these benefits is strong (Hartig et al 2014). What is missing, largely because studies for such interventions are often hard to design, is knowledge about cause-and-effect relationships.