Stand on the rim of Grand Canyon and you feel like you're looking into wilderness that has remained essentially unchanged since nomadic hunters hid split-twig figures there 4,000 years ago.
Unfortunately, your feelings don't square with the science, says Robert H. Webb, author of "Grand Canyon, a Century of Change: Rephotography of the 1889-1890 Stanton Expedition."
"People have had a heavy effect on what appears to be a very isolated place," says Webb, of the USGS and the University of Arizona geosciences department. "As I was conducting my research, I was staggered when I discovered how much influence there has been."
Webb's research involved spending 100 days on the Colorado River directing a crew of about 14 researchers and river guides as they searched out the locations where historical photos had been shot. They took 1,300 photos altogether, including 445 that duplicate those first shot 100 years earlier by Robert Brewster Stanton, who ran the river to scout the best route for a water-level railroad.
The railroad was never built, of course, but Stanton's expedition - which shot photos at intervals of about two miles through the entire length of the canyon - left a priceless legacy, a detailed snapshot in time of one of the nation's largest remaining natural areas. In the process, Stanton unintentionally established the benchmark for a long-term monitoring program in the national park.
By comparing photos taken 100 years apart at approximately the same time of day from the same spots at about the same time of the year, Webb traced the lives of individual plants and changes in plant distribution. He documented changes in the rapids, studied the effects of grazing, and mapped debris flows - slurries of rock, mud, and water that start near the rim and sometimes flow all the way to the river, modifying both side canyons and rapids.
After collecting data on these phenomena (and many more) Webb has written an environmental history of Grand Canyon that is accessible to readers on several levels and is a must-read for anyone who has even a passing interest in the canyon and the many controversies surrounding it.
For starters, there are the photos. Webb has included a sampling of the Stanton photos side-by-side with modern views. Each set of photos includes extensive caption lines.
On another level is the text. Although this book documents the results of scientific research, all the discussions are understandable to the layman interested in Grand Canyon and the style is highly readable. For example, here's Webb talking about a debris flow in Diamond Creek in July, 1984: "Downstream in the constricted reach where the trucks were stalled, the other guides heard a roar that sounded like a bulldozer coming downstream, but it was moving too quickly for a bulldozer. They looked upstream to see a massive brown wave bearing down on them."
On yet another level, the book includes what must be one of the most extensive and readable reference sections ever assembled on Grand Canyon. It seems Webb has read nearly every important work written about the canyon since Lieutenant Joseph C. Ives inspected its lower reaches in 1857. There also are lists of plants, graphs, and other data in the appendices that will interest serious students of the canyon. Anyone who wants to know more about the Grand Canyon can find a wide array of sources in these notes.
Here are a few of the things Webb found as he rephotographed the canyon:
- Even dead things can last a long time in Grand Canyon. A juniper snag
that appeared in one of Stanton's photos was still there 100 years later.
More startling - carbon 14 dating revealed it died in A.D. 1400.
- Webb found 41 species of plants that had survived for at least 100 years.
In some areas, he was looking at the same individuals of mormon tea, creosote
bush, and other plants that Stanton saw. In other areas grazing by burros
and livestock has had major impacts.
- Sandbars have eroded, but erosion decreases with distance from the Glen
Canyon Dam. Reversing sandbar erosion was one of the reasons for the controlled
flood released into Grand Canyon this past spring.
- In almost all views, the number of cacti increased over the past
century.
In many cases the increase was very large, completely changing the vegetation
mix.
- The inner canyon below the old high-water mark has changed radically
since Glen Canyon dam was closed in 1963 and springtime flooding ended.
In some areas marshes have formed, in others tamarisk thickets have entirely
changed the habitat for wildlife.
- The delicate balance between tributaries and the river has shifted: The fans created by debris flows at the mouths of side canyons are getting larger and the rapids are getting narrower.
"There are parts of the canyon that are inaccessible to all but bighorn sheep and a few of the hardiest hikers," Webb says. "There are isolated pockets that are relatively unchanged. But you would be surprised that tamarisk (a non-native plant that was completely absent from Stanton's photos) is found in some amazingly remote places. And there is the overhead noise assault of aircraft."
But perhaps most amazing is that the Stanton photographs exist at all. In the book's final chapter, Webb says, "I remember standing in the National Archives holding one of Stanton's negatives and realizing that although Stanton and his crew are dead and their equipment is gone, those fragile rectangles of emulsion were there on his expedition. I was holding history in my hands. I also was holding a powerful tool that can change our perception of the natural world."
"Grand Canyon, a Century of Change" (290 pages in 10 1/2- by-8
1/4-inch format in the paperback edition) is available from the University
of Arizona Press for $60 cloth and $26.95 paperback. For a review copy,
contact Marjorie Sherrill at the University of Arizona Press
(520-621-3920).