Yosemite Valley This Week: A Moment of Spring Richness and an Uncertain Future

 

I admit it. I fear what lies ahead. That's not the usual opening statement in a photo-essay of Yosemite Valley at its best moments. But that's the problem. I was there last week, when the heaviest snowmelt should have been weeks in the future. And the valley was at its best, a lovely escape from the summer-like heat of the Great Valley downstream.

But the peak runoff is not weeks in the future. It is probably already past. This year's snowpack was an unmitigated disaster. The few storms that did come dropped a bit of snow, enough in some years to get by, but very warm and dry conditions during April dropped the snowpack to around 5-10% of normal, or what passes for normal in these uncertain times. The snowpack would usually keep the famous waterfalls busy until mid-June or even July, but many of them may be dry within a few short weeks. And then the fires will come. I don't know what lies ahead for this most beautiful of valleys, but a disastrous fire has to be considered as a possibility.

The natural condition of the floor of Yosemite Valley has always been controlled by wildfire. Lightning strikes have caused fires for thousands of years, leaving the valley floor as a patchwork of open meadows with a few mature oaks and ponderosa capable of surviving the occasional grass fires. When humans first discovered the valley thousands of years ago, they continued the practice of burning the valley floor every few years. They had their motives of course; the acorns of the fire-resistant Black Oaks provided much of their diet, and the hunting of game was easier when the prey was in an open meadow rather than a deep forest.

When the valley was "saved" by turning it first into a state park in 1864 and later into a national park in 1890, fire suppression became the governing philosophy. The park's original 745 acres of meadows were invaded by young saplings and the 65 acres of meadows today represents only 7% or so of their original extent. It didn't help that drainage outlet of one of the wetland areas was dynamited to keep down the mosquito population.

Much of the valley floor has become a thicket of young and unhealthy conifer trees, a fire hazard of the highest order. The park service has come around to accept the need for fires in the management of the valley, but their success has been spotty and controversial. Prescribed fires have been done in some areas of the park, but more than one has gotten out of control and damaged structures. And prescribed fires are done when soil and fuel conditions are on the wet side. That is not the case at Yosemite this year.

An alternate practice was begun around a decade ago, and it too has been controversial. Instead of burning, the park service has been allowing tree-cutting to be done in some areas to remove the unhealthy trees. The buzz of chainsaws does not seem compatible with the general notion of "preserving" natural lands, but it may be a necessary evil. It led to an unexpected change for me as we visited the park last week.

Everyone always seems to be in a hurry as they scurry through the park looking for parking spots. The traffic was a problem because the free park shuttles weren't running due to the pandemic. So to see the many features of the valley, one had to park and hike quite some distance, or else drive from parking lot to parking lot looking for a good view. I was letting traffic pass by pulling into roadsides that normally don't offer much in the ways of views. But this time was different.

A lot of trees had been cleared from a pullout that I knew had never had much of a view before. No one else was there, but as I got out I could see something was different. The rocks above were, well, unexpected. I've struggled at times to get an interesting angle on the Cathedral Spires (above), but they were easily visible. And as I turned, I realized the Three Brothers were also in the open (below). 

And as I turned yet again, I had a full-on view of El Capitan that showed the full expanse of the cliff from the "Nose" to Horsetail Falls. The sawn-down trees in the foreground were perhaps a sad mess (that will be cured in time by natural forces of decay), but the view of the cliffs was dramatic and quite unexpected. We sat in the pull-out and enjoyed a quiet lunch.

The Pacific Dogwoods were in full bloom. The trees are a somewhat nondescript part of the understory for much of the year, but during the spring the flowers are dramatic (and for the biologists among you, I know that the big white petals are actually modified leaves or bracts, and that the true flowers are in the "button" in the middle). 

Our journey through the valley was our first in nearly a year. It included a stop at one of the most congested spots, but as is always true, there was a reason for its popularity. The Tunnel View is close to the spot where European colonizers first viewed the valley in 1851. The party, a militia trying to chase down a group of Ahwahnechee people, was largely unimpressed with the valley. But their medic, Lafayette Bunnell, was deeply moved by the sight, and later interviewed Chief Tenaya and others to learn what he could of the valley. He is credited with the names of many of the features, including the name of the valley itself. Yosemite seems to have been a derivative of the Miwok name for Grizzly Bear. Their actual name for the valley was "Ah-wah-nee".

So a hot and dry summer season looms. I hope for the best.

Fire in the Sky: The Perspective That Comes When Time is Running Out

It was nothing more than the evening commute to school to give a final examination in my Earth Science course. It was a bit after 4 PM and the sun was settling into the horizon, and the spectacle of it all caused me to pull to the side of the road. I have a habit of taking my camera with me everywhere, so I was able to snap a few pictures of the seemingly striped orb. It was also a moment of reflection.

It was a beautiful sight, but it was tinged with great sadness. The color is coming from the homes and dreams of a lot of people in Southern California who are battling a devastating wildfire that has consumed nearly 250,000 acres (that's nearly 400 square miles). At least 700 homes have been lost already. The flames, driven by a severe Santa Ana Wind event, produced volcano-like plumes of smoke and ash that flowed out to sea and then up the coast of Central and Northern California. There is a ridge of high pressure out there, parked over an exceedingly warm Pacific Ocean that is diverting the normal late fall and early winter rainstorms far to the north. There has been no precipitation in our area for weeks, and none in the long-range forecast. The fires in SoCal come on the heels of the even more devastating fires that swept through the wine country a few weeks back, destroying thousands of homes, and killing several dozen people. The drought and the attendant wildfire intensity is seemingly back after a brief one year respite.

Source: www.latimes.com/local/lanow/la-me-fire-ledeall-20171213-story.html

It's hard to convince skeptics of climate change if they are not living in the path of the worst effects. But the effects are extending to more and more people as the decades slip by. There were warnings of mega-droughts and longer fire seasons in the west and southwest years ago. There were predictions of hurricanes amped up by warmer ocean water. There were the obvious forecasts of sea-level rise that are now having a visible impact in coastal cities like Miami, Florida and Venice, Italy. And the glaciers and icecaps are continuing to melt away as they were decades ago, and at an accelerating pace. Unprecedented record-setting heatwaves are becoming distressingly commonplace. The evidence of global climate change is becoming ever more apparent to people around the world, and to their leaders as well, all of whom are signatories to the Paris Climate Accords. Every country, that is, except one. The United States of America.

Many people, probably most, don't consider science when they stand in the voting booth and make their choices. A distressing number of people end up never standing in the booth for one reason or another, but too often because of voter suppression activity. The rest are thinking about the "issues" like standing for national anthems (or kneeling), or building walls, or any one of dozens of temporary controversies (look up Willie Horton ads some day). Perhaps most think about misogyny, racism, taxes, or the economy. These things are important, of course, because these are issues of life, and quality of life. But few think about science, the environment, and the long term effects of what we are doing with the choices that we make. In the long run, these are some of the most important things that impact our lives. But our political representatives can only think in time frames of two, four, and six years, the length of their terms in office. We need to hold their feet to the fire (figuratively) to make choices that benefit us all long after their terms have ended.

Perhaps the most important game in town right now is education. It is only through education that people can make the right choices that will secure their future and the future of their children and their grandchildren. An educated populace is not going to be hoodwinked and cheated by charlatans and con-men running for public office. And education never stops in high school or college. It is a life-long skill, especially now when the entire breadth and depth of human knowledge can be accessed by the phone in your pocket. Take advantage of it.

The sun doesn't seem to move all that fast when it is high in the sky and hours are left in the day. But when the end of the day is near, and one has the perspective of the horizon, the darkness comes quickly. We are being given that "gift" (or warning, if you wish) of perspective concerning climate change. We've been given the predictions and projections from twenty and thirty years ago, with results that are sometimes off by a bit, but almost invariably worse than expected. I don't know when it is too late; it is different for different groups of people and different biomes and ecosystems. But we have been warned.

In any case, that's what I thought about while the sun sank below the horizon and the darkness set in.

Can't See the Forest for the Creek; Or is it the Other Way Around? California's Mega-droughts

The eastern Sierra Nevada is home to one of the strangest forests I know of. It's not the species of tree that is odd; they are mostly Ponderosa, a pretty but unremarkable tree which can also be found on the adjacent slopes. What's strange is that these trees are dead. Not the "recent forest fire" kind of dead. It's that they have been dead for the nearly a thousand years. Oh, and they are still standing, and are located in the middle of a good sized river.

The West Walker River drains a rather large region in the vicinity of Leavitt Meadows and Sonora Pass. Several forks come together near the junction of Highways 108 and 395, and the river plunges into a narrow gorge before spreading out into the Antelope Valley near Topaz Lake on the Nevada border. The trees, and there are several dozen, are found at the head of the gorge near the campground at Chris Flat. Studies have found that these trees sprouted, grew to maturity, and died within a relatively limited period of time between about 800 and 1350 C.E. (common era, equivalent to A.D.).

The weird part is that the trees pretty much filled the entire canyon bottom. They don't do well immersed in water, which seems to suggest that there was almost no room for a river channel when these trees were growing. This implies that the river was much smaller and therefore there were two crippling droughts that lasted on the order of 200 years  and 140 years respectively. Once the droughts ended, the river filled the channel with sediment again, perhaps supplemented by outwash gravels from the Matthes glaciation (the Little Ice Age).

These ghostly forests exist in other parts of the Sierra Nevada. Tenaya Lake, Lake Tahoe, and Fallen Leaf Lake all have submerged forests that grew to maturity during these periods when the lakes didn't have enough water to flow through their outlets. Oral histories of California's Native Americans also hint at terrible droughts.

In human time frames, droughts are a fact of life here in California. We had extended droughts from 1928-1934, 1960-61, 1976-77, 1988-92, and most notably, from 2011-2016.  Our population has grown so large that each drought becomes more problematic, and we muddle through on the strength of a few extraordinary precipitation years like 2017 that fill reservoirs for a time. What would we do if another century-long drought were to come? And what role will anthropogenic global warming play? I might not be here to find out, but my grandchildren might have a real struggle.

A Picture Tells the Story. We're in Big Trouble Out West.

Source: http://drought.unl.edu/MonitoringTools/NASAGRACEDataAssimilation.aspx

It's a terrifying picture. We have been through 12 of the driest months ever recorded in California, and there is no relief in sight. One can tell we are in trouble when the only part of state not suffering a crippling drought is Death Valley and the Mojave Desert. The rain totals thus far in the Central Valley are at Death Valley levels.

A persistent high pressure belt has been diverting the winter storms north. They are then barreling through the central and eastern United States, causing moronic senators and representatives to bellow about how global warming/climate change is somehow an elaborate hoax designed to hurt their benefactors in the fossil-fuel energy business. If a snowstorm disproves a century of careful research by thousands of climatologists, what are we to make of the worst drought ever in California, and horrific heat waves in Australia and Argentina? It's been in the middle to high sixties here at home these last few weeks. If that makes my friends who are shivering back east a bit resentful, just consider what it's going to be like out here in a few months. Yosemite and my precious Sierra Nevada have already suffered through the worst wildfire ever, and more of the same is in store.

These kinds of climate changes that we are experiencing have been predicted and are happening now. It's not always easy to see the changes on a day to day basis, and sometimes the changes might seem positive. For one, we have not had a single Tule Fog day this entire winter. I hate the foggy sieges that used to last for weeks on end, but if it would mean rain and snow for us in California, I would welcome them today.

If we are moving towards a mega-drought, geologic history gives us a clue about what to expect. Two century-long droughts have already taken place in the last 1,200 years. I've discussed the effects previously in this post:  http://geotripper.blogspot.com/2010/05/fridays-fun-fotos-fluvial-forest.html

These dead trees in the middle of the Walker River in the eastern Sierra Nevada were growing to maturity while the river was largely nonexistent during one of California's horrific megadroughts.

Friday's Fun Fotos: the Fluvial Forest Discussed

I posted some pictures of a "fluvial forest" this morning (fluvial=river) asking for an explanation about how these trees came to exposed in the river channel, and in short order got three excellent answers. I've provided a larger format picture above to give some perspective on the setting (click on the image to see the bigger picture). This is the West Walker River, a few miles downstream from the junction of Highway 395 and Highway 108 from Sonora Pass in California's Sierra Nevada.

It's rather striking and strange to see so many trunks of mature trees sitting in the active channel, as Jeffrey pine really can't tolerate soaking for more than a few weeks a year. They otherwise do quite well on the shady slopes to the right in the picture above (and not so well on the dry slopes to the left). I have to admit that this was my thesis area, but I didn't really give the trees much thought 25 years ago, yet they reveal an interesting story.

Anne had a great idea, saying that mining wastes could have caused the filling of the channel, smothering the trees. This would be a great explanation, and such a thing indeed happened in the Sierra Nevada during the hydraulic mining era of the Gold Rush (I posted a picture of a tree trunk formed this way some time back). The problem is that no mines of any consequence were present in the area.

Rob provides a glacial explanation, in which glacial outwash buries a forest, and then a surging glacier planes off the trunks. This is an appealing explanation because this part of the canyon was very close to the terminus of the Tioga and Tahoe glaciers. Glaciers would explain it, except the age of the trees are wrong. One set of the trees in this fluvial forest grew between AD 900 and 1100, while another set grew between AD 1210 and 1350. Smaller glacial episodes in the last two thousand years never approached the area.

Lockwood comes the closest to explaining what happened here, suggesting that a debris flow filled part of the canyon, killing and burying the trees, and then the river exhumed the forest. But there is an interesting twist: the valley is really narrow here (look at the top photo; there is barely enough room for the river and the highway, and when the river floods, there is no room for the highway at all. It disappears and has to be rebuilt, most recently in 1997). The trees, and there are dozens of them, were pretty much filling the entire canyon bottom. There was almost no room for a river channel when these trees were growing. This suggests that the river was much smaller in the two time periods the trees represent. In other words there were two crippling droughts that lasted 200 and 140 years respectively. Once the droughts ended, the river filled the channel with sediment again, and debris flows, as Lockwood suggests, undoubtedly had a role. Outwash from the Matthes glaciation may have been a factor as well.

There is confirming evidence for such mega-droughts in other areas of the Sierra Nevada. Tenaya Lake, Lake Tahoe, and Fallen Leaf Lake all have submerged forests that grew to maturity during these periods when the lakes didn't have enough water to breach their outlets. Oral histories of California's Native Americans also hint at terrible droughts.

In human time frames, droughts are a fact of life here in California. We had extended droughts from 1928-1934, 1960-61, 1976-77, and 1988-92. We may or may not be ending a three year drought this year as well. Our population has grown so large that each drought becomes more problematic, and we muddle through on the strength of a few extraordinary precipitation years that fill reservoirs for a time. What would we do if another century-long drought were to come? And what role will anthropogenic global warming play? I, for one, wouldn't particularly care, because I will be dead, but my grandchildren might have a real struggle.

Stine, S., 1994. Extreme and persistent drought in California and Patagonia during mediaeval time. Nature 369:546-549. I can't find a copy of Stine's paper on the web, but Stine's findings are discussed briefly here (page 15-16), and here (page 296)