Greenery hypothesis: An evolutionary explanation for why presence/absence of green affects humans

A growing body of empirical evidence shows that experiences of nature provide people with diverse psychological benefits, including improved cognitive function and mental health. While our understanding of the proximate causes of these positive psychological responses of humans to nature has advanced, the ultimate (evolutionary) drivers behind them remain poorly understood. In this study, we provide a summary of several widely accepted evolutionary hypotheses originating from Biophilia, reviewing their challenges and limitations. Subsequently, we propose a new evolutionary psychological hypothesis—the greenery hypothesis—that integrates recent findings in evolutionary psychiatry with many experimental results unexplained by existing hypotheses/theories. Our proposed hypothesis states that humans have adapted to periodic severe drought and re‐watering cycles by developing both negative and positive psychological responses to the absence or presence of greenery within the landscape as cues to optimise their own behavioural activity. The greenery hypothesis holds the potential to yield several insights into the fundamental understanding of human psychological responses to nature exposure with significant implications for various related fields, including psychiatry, urban planning, and biodiversity conservation and restoration. Read the free Plain Language Summary for this article on the Journal blog.