More worrisome than crime, Ms. Cowles says, is the sheer volume of visitors who are unfamiliar with being in a wilderness area and don't know proper behavior. The visitor who is reckless on the trail or dives into a river for a swim above a waterfall makes the park even more hazardous for himself. At least once a year someone jumps into an inviting pool, gets caught in the current and goes plummeting over the falls. Most problems are minor. Park rangers' most common rescues involve dehydrated hikers who did not carry water, or those who sprained ankles.
Tourism increases as the season warms, and the valley can quickly turn to gridlock.
Ms. Cowles suggests. In the past two decades, annual visitation has doubled. In the early '70s, Yosemite management established one-way traffic patterns and began offering free shuttle bus rides to sites around the valley. The system runs efficiently and has helped protect the park's natural habitat. Overnight visitors have a range of choices for accommodations, depending on how much they want to rough it.