I finally made it to the southernmost end of Florida and the greater Everglades ecoregion – I spent a week in and around Everglades National Park and Big Cypress National Preserve, adventuring by foot, boat, and bicycle and getting wet, muddy, and mosquito-bitten in the process! It was different from what I had expected, and I discovered some fascinating facts to pass on! Fresh water flowing slowly but steadily towards the ocean, over surface bedrock, has created five distinct ecosystems within those 4,000 square miles. The next few posts will go into more depth on what I learned and experienced, and provide some recommendations for exploring this area in even greater depth! Enjoy!
Arizona and the Sonoran Desert
Joshua Tree, CA – Tucson, AZ
Mile 5949 – 6493
October 15 – October 17, 2010
Immediately upon leaving Joshua Tree National Park, the desert around me took on a starker appearance. I saw almost none of the “megaflora” characteristic of the Mojave Desert in the park – no Joshua Trees, no mesquite, none of the larger cacti. In fact, the desert that had seemed so full of life in the park now looked like the vast wasteland I had always imagined it to be. For the most part, this continued to be the case as I headed straight east into Arizona, soon crossing back into the Sonoran Desert.
The towns I passed through on my way, few and far between, looked equally bleak. I think that it was the lack of water, combined with generally mild temperatures, that made the buildings and their landscaping somehow less “civilized”-looking than what I am used to. There was, of course, dust everywhere, buildings didn’t need to have the sturdy roofs and walls that northern snow and cold require, and there wasn’t the water to spare for elaborate gardens, let alone lawns (though some homes, apparently to show off their good wells, had palm trees planted in the yard). That said, there isn’t much of an economy in the area, aside from ranching and whatever is needed to serve the immediate needs of those ranchers, fifty miles or more from the nearest town of 1,000. I’m not sure what keeps people out there – though, to be honest, I’m still not completely sure why people tried to settle there in the first place, unless it was the strangely beautiful, otherworldly appearance of the desert.
The charismatic cactus of the Sonoran Desert is the saguaro, which can grow up to 50 feet tall. Sometimes called the giant saguaro, they are the largest cactus species in the United States. Like the Joshua Trees, large populations of saguaros look like forests, with the other cacti, shrubs, and even small trees serving as the “underbrush.” I, however, saw only a few saguaros scattered here and there along the hundreds of miles I traveled through eastern California and western Arizona. This was particularly true in central Arizona, south and west of Phoenix, where ranching and (what passed for) cropland were clearly widespread. Just outside of Tucson, though, lies Saguaro National Park, set aside to preserve some of the great “saguaro forests” and the rest of the ecological community of the Sonoran Desert.
Why are these giants of the desert – the saguaro and the Joshua tree – nearly invisible outside of the preserves named for them? I’m not completely sure, but it seems pretty clear that humans are responsible, at some level. The saguaros in Saguaro N.P. are actually at the edge of their range – in a terrain too steep and cold to support agriculture as reliably as the flats (and in Arizona, that’s really saying something). Joshua Tree N.P. is in one little corner of the Mojave Desert, yet even in the adjacent town named for that giant agave, there were few Joshua trees around. Both plants, but especially the saguaro, have had human uses for as long as people have inhabited the desert. The Tohono O’odham, and the ancient Hohokam before them, ate and preserved the juicy fruits and used the woody stems for building. It seems likely that early Europeans in the area would have done the same, as a substitute for non-existent trees. In addition, grazing animals compact the soil and trample young seedlings.
While some use of these plants is part of the balance of life and death in the desert, they are a very delicate species and cannot withstand the heavier impacts resulting from white settlement. According to the national park brochure, a saguaro may grow only ¼ inch tall in its first year, reaching a foot after 15 years, and up to seven feet in 50 years. It does not begin to flower and produce fruit until around 30 years old. When one of these cacti it cut down, then, it may take well over a hundred years to replace it, and damaging the surrounding soil and vegetation ecology, or
removing all of the remaining fruits and seeds, will clearly have a devastating effect on the population.
Enough depressing talk, though – there are places where the desert ecology is well-preserved and maintained, and they are awesome. I didn’t have enough time to really explore Saguaro National Park, nor did I get to the Sonoran Desert Museum in its west unit, which I have heard from several sources is wonderful. I did get to drive the loop road in the east unit, though, and get out for a couple short walks. It would be great to get back and see more sometime – two thirds of the park is designated wilderness, and in the Rincon Mountains on
the eastern side, one can hike up to scrub oak and even Ponderosa pine forests. Tucson itself, which lies between the two parks, is a beautiful desert city, with towering cacti in front yards and mountains surrounding the town. My own (great-) aunt’s garden, in the foothills north of downtown, was as beautiful as the National Parks, if slightly less wild.
Roadside Geology (and some Ecology) of Oregon
One thing that struck me, driving back and forth through western Oregon, was how young the landscape was. The Cascades are still volcanically active (witness Mt. St. Helen’s), and the geologically-recent eruptions throughout that range mean that the soil and vegetation are still relatively simple. In the last post, I showed you the Belknap Crater, near McKinley Pass, and its surrounding lava flows.
That volcano erupted over 4,000 years ago, and very little has colonized the area since then. Bright green lichen has gained a toe-hold on much of the rock, but pioneer grass and pines are a long time in following, and only a portion of the area has enough vegetative history to have developed a thin layer of soil.
This same story repeats itself throughout the state, as the overlapping volcanic and glacial histories define the landscape and its ecology. Glaciers of the last Ice Age defined the wide valley of western Oregon between the coastal mountains and the Cascade range, and the eastern second set of mountains,
however, and the eastern portion of the state is considered High Desert, barren and sparsely populated, despite the glacial deposits found there. In between, the Cascades rise,formed by millennia of volcanic eruptions. Despite having more rainfall than the eastern desert, disturbance by rock-fall, erosion, unchecked winds, and of course molten lava create a harsh life there for trees and groundcover.
In addition to affecting the vegetation, volcanic activity changed the terrain. Driving through the state, one can still see evidence
of these eruptions as though they had just ended. In geological terms, I guess they really have! Where rivers have carved
through softer layers, the hardened lava almost looks like it is still moving: separate layers of distinct lava flows can be seen in places like the Upper Rogue River’s gorge. Along the banks of this Wild and Scenic River there is also a very clear example of the lava tube formation. In this case, lava flows continuously out from a volcano (sometimes for periods of several months), and eventually the upper crust of the flow hardens after prolonged air contact. The continuing eruption, however, keeps the flow moving between that hardened crust and the bedrock below. Once the volume of lava has decreased, and the flow finally stops altogether, the crust
remains, but the tube through which the molten lava has been flowing is empty. These tubes can (apparently) be miles long. Most times the crust eventually collapses, leaving deep holes at the surface, or shallow caves when encountered from the side. In some cases, water, always looking for the easiest way to the sea, breaks through softer rock into these tubes. This is the case on the Upper Rogue, where the river, diverted by the eruptions, worked its way through both collapsed and entire lava tubes to create the gorge seen today.
I certainly am not a geologist (if you couldn’t tell from the preceding paragraphs), and the volcanic landscape still seems eerily barren to me, but I learned to identify what I was viewing with a basic understanding, and witness these patterns repeated as I went along. Crater Lake (initially formed by an eruption 7,000 or so years ago) may be one of the more famous locations
for viewing the aftermath of volcanic activity, and I spent a day hiking and driving around its rim. Check out the next post for the stunning detail of that trip!