Does activity context and its temporality matter in the stress-relieving effect of greenspace? Evidence based on individual mobile sensing

Existing discussion on the stress-relieving effects of greenspace tends to overemphasize the dynamics of travel trajectories while overlooking the rich activity contexts and temporality underlying individual behaviors. This oversight may lead to biases and inconsistent findings. Using GPS trajectories of 756 participants in Hong Kong, this study integrates street view data, geographic ecological momentary assessment (GEMA), and activity-travel diaries to derive individual-level activity contexts. We examine how these contexts moderate the relationship between eye-level greenspace exposure and momentary stress, including temporal dynamics. The results identify three distinct activity contexts with differential impacts on mental stress and the stress-relieving effects of greenspace: (1) Substitutional Activity Contexts (e.g., flexible-schedule activities, solitary or familiar social interactions). These contexts are defined by activities that inherently alleviate stress through intrinsic psychological benefits but diminish the stress-relieving efficiency of greenspace, thereby reducing the reliance on greenspace. (2) Stress-Priming Activity Contexts (e.g., rigid-schedule work/study). These involve activities that elevate baseline stress but amplify the stress relieving efficiency of greenspace, creating a “stress-resilient” dynamic. (3) Synergistic Activity Contexts. These unique contexts both reduce stress independently and enhance the efficiency of stress relieving effect of greenspace through combined mechanisms. Active travel (e.g., walking, cycling) embodies this synergy: its intrinsic stress-reducing effect requires long-term exposure (80–160 min), while it enhances the stress-relieving efficiency of greenspace after shorter exposure (10–50 min) through sensory-rich engagement with greenery. Policymakers should not only consider the quantity of greenspace in physical environments but also focus on their alignment with people's actual daily activity contexts.