Visual attention as a complementary indicator of social carrying capacity in parks and protected areas

Assessing carrying capacity has been an essential and challenging issue for parks and protected areas. Traditional indicators such as people at one time (PAOT) and people per view (PPV) focus on density of use while providing limited insight into how encounters are perceptually experienced by visitors. This study addresses this gap by a two-stage approach: (1) a methodological scoping review of social carrying capacity research, and (2) an empirical investigation that introduces visual attention as a complementary indicator within the Indicators and Standards of Quality framework and tests it across different types of recreation settings using eye-tracking analytics. Results from the scoping review indicate that although visual and digital approaches have been widely adopted in social carrying capacity assessment, very few studies have incorporated visual or physiological response measures. The eye-tracking analysis results show that increasing encounter levels consistently disrupted visual engagement with environmental elements, manifested by longer fixation duration on people, shifts in first gaze toward social stimuli, fragmented scan paths, and reduced attentional coherence. These results indicate that visual attention thresholds can serve as complementary benchmarks for traditional standards of quality guided by normative theory. In addition, this study proposes an integrated physical-perceptual-prescriptive measurement framework in which visual attention indicators supplement PAOT and PPV to inform adaptive management. The findings enhance the transferability and transparency of the social carrying capacity framework and reveal how attention-based metrics can support impact-oriented and context-specific visitor use management across diverse recreation settings.