Introduction

Max Whittaker for The New York Times

It’s the 100th anniversary of the National Park Service this year, and record crowds are expected at many of the most popular sites this Memorial Day weekend. But the throngs of tourists are straining the parks the agency protects, increasing pollution and creating conflicts between humans and wildlife.

Should the Park Service more widely restrict access to protected areas, or does that contradict its mission to keep the lands open and accessible?