Quite often, the ravages of nature are the forces of change, and such has been the case in these national parks. Recent rock slides and floods have reestablished nature's supremacy, and preservation efforts and long-term studies have been underway for more than a decade.

In Yosemite, the return of the peregrine falcon was heralded as a milestone. When bird-watchers counted three nesting pairs and five offspring in 1996, the news traveled across the nation.

Considerable attention is going toward restoring meadows, limiting trails, and bringing back native plants pushed out by the impact of humans. The valley has seen the reseeding of a black-oak forest along the bikeway between Yosemite Village and Yosemite Falls, while controversy regarding its future (as well as that of Hetch Hetchy) rages on.

Large boulders placed in the Merced River long ago by settlers and early park managers changed the course of the waterway and created unnatural swimming holes. These are being removed, and the river is being allowed to pursue its own direction. Volunteers are also working to repair damage done by hikers who step off the trails.

In Sequoia & Kings Canyon, fire management has been a major concern since the 1960s, when the park policies began to be questioned. Early on, tree preservation was the cornerstone of park policy, so natural wildfires were squelched whenever possible. But after a noticeable decline in tree germination, research determined that f ire is necessary -- it dries out the cones to release their seeds, burns underbrush, and clears openings in the canopy for sunlight to reach the seedlings. In 1968, an unprecedented fire-management program began that allows some natural wildfires to burn, sets prescribed burns, and suppresses unwanted blazes. Consequently, over the past 20 years, the increase in the regeneration rate of giant sequoias has been noticeable.

Other environmental concerns for the park include air quality and drought. Unfortunately, Sequoia & Kings Canyon is located near California's smoggy Central Valley, and thus has the most chronically polluted air of the parks in the American West, often obscuring what would otherwise be superlative views. In 2004, the Environmental Protection Agency designated Sequoia & Kings Canyon as an area in which ozone pollution was a risk to human health. Ozone pollution also weakens the trees so that, when natural drought comes along, these damaged trees often die.

Dealing with the issues facing Yosemite and Sequoia & Kings Canyon requires time, money, and commitment -- all high hurdles. Partnerships have been formed with foundations, nature conservancies, and even oil companies to provide funding for study and restoration. But the single biggest issue for both parks remains overcrowding -- they are too popular for their own good.

For most of the 20th century and into the 21st, the parks have walked a tenuous line between increasing visitation and consistent management of visitation. Research has changed some policies; experience is changing others; and educational efforts will, we hope, help preserve the parks for future generations of nature enthusiasts.

Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.