Abstract
To the Editor:
We thank Drs Lawson and Newman for their letter.
1
We recognize your passion for safety. In this response, we address your critique of our work number by number and provide further commentary. To establish a baseline from which to proceed, the main finding of our study
2
is that after instituting restricted access to the Half Dome (HD) cables with a permitting system, there does not appear to be a correlation between crowding on the HD cables (route) and safety in the area above Little Yosemite Valley (LYV) in Yosemite National Park. We understand the original logical intent of the HD cables permitting system. The emergency action
3
in January 2010 to restrict use of the cables specifically cites safety as an aim of the intervention: “As use has increased in recent years, so have the number of accidents, rescues, and fatalities. Although the exact safe level of use has not yet been determined, current data suggest that once use increases beyond a certain point, accidents become more common.” By your description, the aim was to reduce “crowding.” On that premise, the system might be effective; however, we did not seek to evaluate it on that premise. We sought to evaluate it for other, perhaps not intuitively obvious, effects. Our work was not “misaligned.” We knew what we were studying and why we were studying it. Someone could certainly study the cables permitting system for its success or failure related to the number of mass evacuations from the cables and summit during storm events. Our answer is the same answer as in number 1. If an investigator assesses the efficacy of the HD cables permitting system with respect to this premise, the findings might be useful for others to consider should they face the prospect of similar situations with respect to a permitting system on crowded routes. The fact that persons were directed to HD during a unique evacuation/rescue situation does not lessen our findings. That circumstance called for a calculated effort intended to benefit the greatest number of persons and does not relate to routine limitation of persons allowed access to the area by permit. Our study design, including the study area, was developed in collaboration with the Yosemite National Park Emergency Medical Services coordinator. According to that person, at the time of our study, hikers above LYV were almost exclusively persons en route to HD. Per advice we were given, nonpermit holders rarely day hiked beyond the end of the Mist Trail (the top of Nevada Falls) because access to both subdome and HD cables was off limits to persons without a permit. The LYV campground was not part of the study area because it is not “above LYV” and is easily distinguishable as a location in search and rescue reports. To reiterate, although mass evacuations were included in our study, our intent was not to study only these occurrences. The fact that the HD cables permitting system is scoped to manage people on the subdome, cables route, and summit does not mean that this system can only have effects at these locations. In any ecosystem, there are knock-on effects. The correspondents point out that there might be factors in other locations that could be studied to determine their influence on the outcomes we measured. We accept that and look forward to one day having more comprehensive data to explore deeply all possible influences and relationships. Emphatically, this was not an experiment; it was data analysis. It yields a starting place for further consideration and perhaps investigation. With regard to the original HD cables permitting process, we never stated or implied that it was “flawed” or of no benefit. We applaud the intent of the permitting process and what it (likely) has accomplished. Regarding statistics, we have what we have. Stating that nonstatistically significant trends are meaningful, especially on such a small dataset, is conjecture for anyone, including us. The data are presented for readers to draw sensible conclusions (more about that later). We agree that targeted education should affect the preparedness of hikers, but this remains a non–evidence-based recommendation. These are good points about how the media interprets and sensationalizes science. For example, all crowded routes are not the same. On Mount Everest, waiting in line for a summit bid poses the deadly risk of running out of supplemental oxygen and risking asphyxiation, hypothermia, and/or frostbite. Is this mountain still safer in the overall? Increased summits have counterintuitively corresponded with a lower fatality rate (Table 1).
4
Despite improvements in the aggregate numbers, the reality is different for the subset of persons waiting nose-to-hindquarters for a chance to achieve the summit.
5
One year in the future when the queue is engulfed in a storm, we will witness a catastrophe. Crowding on a cabled route on HD is not about running out of oxygen—it is about different problems, namely fatigue and poor footwear traction on the smooth, dry granite that poses a constant risk even to prepared hikers, in contrast to the intermittent lightning storms and wet rock that are often reported.
6
We stand with the correspondents in urging responsible, accurate journalism and do not support erroneous titling intended to attract readers.
7
Summits and fatalities on Mount Everest by year
Compiled by ExplorersWeb/AdventureStats. 4
We appreciate the dedication of the correspondents and how they dissected our study. We agree that baseline data are critical. Perhaps we can agree that a permitting system has not been proven a panacea for every aspect of risk reduction. We agree that crowding of climbers on a mountain or rock surface is likely in some way a risk factor for bad local outcomes. However, if there is a benefit to alleviating such crowding, it might not extend far beyond. We believe that it is legitimate and wise to study all aspects of an injury prevention ecosystem for the intended and unintended impacts of any particular intervention.