Counting crowds: New visitor estimation tools for parks and protected areas

Managers of parks and protected areas estimate the number of people who visit the lands and waters they steward to protect natural resources, improve visitor experiences, and communicate the value of public lands. However, the practice of visitor estimation is complex, challenging, and the methods are highly varied. While researchers and practitioners have spent decades improving and testing visitor estimation methods, determining the best approach for a specific situation remains difficult. As new methods have emerged in recent years, the need to evaluate them in the context of existing methods has become apparent. However, there has been little synthesis of this knowledge. Beginning with a systematic literature review and concluding with a Delphi approach, we review trends and themes in the research to develop a synthesized decision tool to aid in the practice of estimating visitors. We find that the volume of publications and variety of methods present in the literature has increased in recent years. Additionally, some methods are more prevalent in peer-reviewed journals than agency manuals, suggesting the connection between research and practice could be improved. We also identify three themes in the literature: all methods have benefits and shortcomings; emerging technologies create viable data; and these novel data require calibration. We synthesize our findings in table that we call the comparability matrix, which distills 30 attributes about 18 visitor estimation methods into one decision tool. This tool is hosted in an interactive online format for practitioners and researchers. Overall, we found that this two-phase approach, a systematic literature review followed by a Delphi method, is effective for subjects such as visitor estimation that are vast in scope and diverse in application.