Sequoias are mighty trees that can live for more than 3,000 years and grow to a height of nearly 300 ft. But they’re not invincible. And the more than 1 million people who pour into Yosemite National Park’s Mariposa Grove each year to appreciate their splendor also potentially damage them—mostly with car pollution and water-blocking parking lots and asphalt roads. So in a rare move, the National Park Service closed the grove in July 2015, launching a three-year, $40 million effort to rework the park and protect its sequoias. Among the changes it made: ripping out the parking lot and roads and revegetating the land, building wooden boardwalks and bridges to improve water flow, and erecting a visitors’ center. In order to visit the new Mariposa Grove, which opened in June, visitors must take a shuttle from a more distant parking lot. But they can do so knowing their grandchildren may one day have the same awe-inspiring view of nature. —Kate Rockwood