“Why are they letting Mirror Lake dry up?” she demanded. “Why, ten years ago it was so beautiful, you could see Half Dome mirrored in its surface. And now, it’s nothing more than a big sandbar!”

The ranger smiled, and replied, patiently.

“Well, ma’am, here we preserve the natural scene, so we’re letting Mirror Lake fill up with sediments. Eventually it will become Mirror Meadow.”

“But you’re not preserving Mirror Lake, you’re letting it fill up!”

“Yes ma’am, you’re right. We’re not preserving Mirror Lake, the place. We’re preserving Mirror Lake, the process.”

The point was well taken and, after a time, the woman left with a new and fascinating perspective. A common enough occurrence in Yosemite National Park, this scene demonstrates a shift in Park Service environmental policy — that of preserving processes instead of simply places.

For many years, the National Park Service interpreted its mandate to preserve the parks “unimpaired for future generations” as if it read “unchanged for future generations.” In recent years, there has been an impressive turnaround. On conducted walks, we now ask not only “what is the name of this plant?” but also “how do you suppose this plant interrelates with all the other organisms of its natural community?” The idea of the future has come into our walks on the geologic wonder of Yosemite, and we are watching the natural process of succession take place at Mirror Lake. Indeed, much has changed.

With these changes has come a great challenge. How do we understand and intepret this abstract concept of “processes” — how do we approach Yosemite from a process standpoint? Perhaps the first ingredient is simply to go out and walk among the mists and gardens of the park with a sense of wonder — a heightened perception. Visitors must “turn on” and “tune in” to the natural sights, sounds and smells of Yosemite’s wildlands. They must forget the overwhelming sights and sounds of modern civilization. This is easy. The next step is more difficult. The visitor must acquire what may be called “mindsight,” and that requires more than simple, perceptive observation. While opening the eye of the mind begins with a heightened perception, it comes to fruition with interpretation.

The California black oak provides a good example. When the importance of light to this tree is explained to the visitor, he can perceive how the oaks are reaching out towards the light, as if grasping for life. Mindsight comes into play as the oak’s futile struggle for survival against the towering, encroaching pines and cedars is explained. With the eyes of their minds, the visitor can see the pines and cedars creeping up on the oaks, forcing them to grow predominantly on the edges of the meadows. Concern may be expressed with the realization that the oak, through its acorns, is very important to park wildlife, yet probably will disappear entirely from Yosemite Valley over the next several hundred years.

“Do you think we should cut selected cedars and pines so that these magnificent oaks may survive and provide food for our wildlife?” asks a ranger-naturalist.

No, that wouldn’t be natural,” is the usual perceptive response. The disappearance of Yosemite’s oaks is a natural succession and has been going on for thousands of years. Indeed, there wouldn’t be a Yosemite Valley today if it weren’t for this process.

Slowly but surely, the visitors come to realize that a national park is more than a haven for animals, plants, and rocks; it is a sanctuary for the natural processes involving them all.

Fire is another good example of a natural process. For a hundred years, fire was thought a deadly, destructive force that could only damage a natural environment. Armed with the image of Smokey the Bear and with helitack crews, campaigns were launched to wipe out fire in our lifetime. It has been only within the past 15 years that this practice was found to be wrong. Through the remarkable discoveries of a new breed of scientist, the fire ecologist, fire is now recognized as an integral part of most natural communities.

In Yosemite, fire is vital to the meadows, mainly for fertilization and perpetuation. When a fire sweeps through a meadow, it spills the nutrients bound up in the meadow plants back into the soil, thereby clearing and fertilizing it. In addition, the heat generated by a fire kills the sapling oaks, pines, and cedars that are encroaching on the meadow and slowly choking it.

What happened when, for a hundred years, all meadow fires were extinguished? The results are plain in a series of photographs taken since the turn of the century from a point on the Valley rim. These show the meadows become smaller and smaller as the years go by, allowing the forest, unhindered by fire, to take over. Fortunately, within the past several years, fire ecologists have been trying to make up for lost time, and are deliberately burning the meadows. During the off season, usually the spring months, the meadow to be burned is carefully measured for soil moisture, air temperature, fuel load, etc. When all conditions are optimum, a prescribed burn is made employing new controlled burning techniques. Each meadow is burned on a rotating basis every 3 to 5 years. Thus, the natural process of fire and the meadow ecosystems are preserved to function unimpaired.

Thanks to the foresight (and the hindsight) of the National Park Service, the processes preserved within Yosemite National Park go on today essentially as they have for thousands of years. Here much more than meadows, lakes, trees, things and places are preserved; preserved too are natural processes and living, functioning systems - for the benefit and enjoyment of all the people.

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