Tamarisk has a natural tendency to grow into very dense thickets, at times as many as 3000 plants per acre, which prevent the expansion of native vegetation (1). Native to Central Asia and the Mediterranean, this plant species has an “extensive root system well suited to the hot, arid climates and alkaline soils common in the western United States” (1). This specific species of plant mines into the watershed, monopolizing the water supply, and enabling tamarisk to thrive while native vegetation perishes.  Due to the depth of its far-reaching root system, tamarisks draw more salts from the groundwater than native vegetation which is then excreted through the leaves and deposited into the soil once they fall off the plant. This process causes an increase in soil salinity which in turn prevents the germination of many native plants, allowing tamarisk to take over. “Because tamarisk stands develop into dense thickets, sediment accumulates in their extensive root systems and promotes further tamarisk growth, “ (1, p.1).  From the rafts, we observed that tamarisk dominated the shoreline with no other flora competing for even the smallest space.  

In addition to out-competing other native plant species, the spread of tamarisk causes other problems as well.  The dense habitat of the plant limits recreational access to the river.  The dense growth also causes a fire hazard and allows fires to spread where once they weren’t such an influence on the ecosystem. Another impact is due to their accumulation of soil, tamarisks cause river and stream channels to gradual narrow and flooding increases (1, p.1).  Yet still another negative consequence is, “conversion to tamarisk typically coincides with reduction or complete loss of bird species strongly associated with cottonwood-willow habitats http://bulk.resource.org/gpo.gov/register/1995/1995_10708.pdf. If ecological reasons aren’t bad enough, “cottonwoods and willows are culturally valuable to tribes such as the Hopi and the Navajo.  Roots, branches, and logs are used in baskets, kachinas, and structures” (http://www.gcrg.org/bqr/13-3/aliens.html).  

As I stared at the river bank, I wondered what the area looked like 50 and 100 years ago, before the takeover of tamarisk?  Bret pointed out the huge flood plain in the upper part of the river that once existed before dams upstream started controlling the water flow. Bret showed us old river channels that were still lined by the native cottonwoods.  Camping under cottonwood trees in particular is ideal as the trees cast a cool shadow from the hot, high desert sun.

For all of the above reasons, the prevailing thinking has been to eradicate tamarisks and restore once native vegetation.  Mechanical, chemical, and biological eradication efforts have all been experimented with to prevent further spreading of tamarisks.  There have been attempts to reverse the damage that has already occurred and return river corridors in the West to their original state. Mechanical removal efforts are methods by which the shrub or tree is cut or mowed, however this is rarely effective as re-growth is high. Burning is not a viable option either as tamarisk can recover far quicker from fire damage than native vegetation can because it sprouts vigorously from the root crown. (2) The abundance of leaf litter from tamarisk raises the threat of wildfires which actually stimulates its growth, but destroys native vegetation such as cottonwoods and willows.

Chemical methods involve cutting the stump of a tamarisk two inches above the soil surface and treating it with an herbicide immediately. When the bark is dry, another herbicide can be applied near the base of the plant. In the fall months, herbicides may be sprayed on the foliage, however re-growth is common following these methods and re-treatment must be applied in order to kill the shrub (2).

Biological eradication methods involve the use living organisms in order to suppress the growth of the tamarisk species. Diorhabda elongata, or the “tamarisk leaf beetle,” has been tested since 1992 and approval of field testing was granted in 1999.  In 2001, beetles were released into the wild.  This biological control is still relatively “new” and the overall effect it will have on the suppression of tamarisk growth is still being observed and studied.  Beetles control tamarisk by feeding on the plants in massive hoards, completely defoliating the plant which prevents photosynthesize and storage of food in root systems. Repetition of this process over the course of years causes the roots to diminish in size to such a degree that they can no longer support the plant. Introduction of a foreign organism, like beetles, into an ecosystem has raised concerns.  Years of testing, prior to being released into the wild, has shown that the beetles prefer the species of tamarisk over other native flora (2).

Not all scientists saccept that tamarisks need to be removed everywhere in the West. Biologists studying the endangered willow flycatchers discovered a significant amount of the remaining 400 pairs of birds now nest in tamarisks- indicating how long the plants have been around (3)  “The attraction is proximity to water, shade and a branching structure that apparently reminds the birds of the native willow trees they historically nested in.”  So, if enough beetles were released to eat, “… all of the tamarisk, the reasoning went, an important chunk of nesting habitat would disappear, pushing the bird closer to extinction.”  This argument is found in a fascinating article entitled, “Tackling tamarisk” a feature story- from the May 25, 1998 issue of High Country News by Paul Larmer.  Larmer interviewed an ecologist, Bob Ohmard, of Arizona State University,  who did “pioneering studies in the 1970s showing that tamarisk supports less animal life – from insects to birds and mammals – than native vegetation.  …Ohmart argues that tamarisk has merely taken advantage of our sick, static river systems, and that removal of it will leave next to no habitat for the willow flycatcher and other riparian-dependent species.  Dams and water diversions have permanently altered river corridors in the West, he says, rendering many inhospitable to native cottonwoods and willows.  ‘If you wipe out saltcedar, what will replace it? Not much,’ says Ohmart. ‘I’d rather see a monoculture of saltcedar than bare dirt. At least it holds in soil and provides a little habitat. We’re damn lucky tamarisk came along when it did.’  

Backing up Ohmart is Bertin Anderson, an ornithologist turned soil scientist based in Blythe, Calif.. “Removing tamarisk and replacing it with native vegetation isn’t going to happen on any major river in the Southwest,” says Anderson, who has spent the last 25 years restoring native vegetation to sites along the lower Colorado River for the Bureau of Reclamation, various Indian tribes and other clients.  Rivers and their banks have become saltier and drier since irrigated agriculture and dams came in more than 50 years ago, he says, and these conditions favor the hardier salt cedar over the cottonwoods and willows. Anderson says that dams have prevented the nurturing floods that wash salts out of the soil and moisten it to sustain native plants. “  Anderson says he analyzed a large portion of the Southwest’s rivers, looking at soil conditions, and found that 75 percent of the area is no longer suitable for natives.  ‘But a large percentage of the area is still suitable for tamarisk,’ he says. ‘In some places, the conditions are so bad that even tamarisk can’t survive.’  Ohmart’s and Anderson’s viewpoints have elicited visceral reactions from those involved with tamarisk control.  “I don’t want to damage the willow flycatcher, but it’s clear that the willow flycatcher has been hurt by saltcedar,” says DeLoach. “There are 50 other endangered riparian species that could benefit from biocontrol of saltcedar. The Fish and Wildlife Service needs to look at the benefits to the whole ecosystem, not just the willow flycatcher. You want to manage for flux.”  

It seemed like our PSU group was in such a rural, unpopulated area of Utah, and yet once we were told about the invasive tamarisks, the impact of humans became clearly visible. A quick glance to either shoreline along our three day trip down the river between Bluff and Mexican Hat on the San Juan provided first hand views of this overpowering plant species.  Only upon researching the topic did the controversial, complicated, conservation issues facing the West regarding this plant surface.  We gained a new appreciation for the longterm consequences of invasive species- a global issue of concern. 

Citations

1.)   http://www.tamariskcoalition.org/tamariskcoalition/index.html

2.)   http://www.discovermoab.com/tamarisk.htm

3)   https://www.hcn.org/issues/131/4174

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Golden eagle on the San Juan River

          Golden eagles are known to be monogamous and along with their mate they’ll maintain a territory of up to 60 square miles.  The golden eagle is the national bird of Mexico and is found along the whole western continent of North American from Alaska down to Mexico.  Some that live in the colder climates like Canada and Alaska migrate south in late fall but most maintain the same territory year round (http://en.wikipedia.org/wiki/Golden_Eagle#Heraldry). Golden eagles are more aggressive than bald eagles and will not allow bald eagles to coexist in the same area (correspondence with staff at the Sonoran Desert Museum, Tucson, AZ.)  As we moved past the eagle, its mate could be seen watching intently from the canyon wall. The high walls of the canyons provide the perfect place to make nests safe from predators.  The female lays an average of 2 eggs once a year that are white in color or occasionally white with small cinnamon color blotches. Both the male and the female help incubate the eggs for about 40 to 45 days until they hatch (http://dwrcdc.nr.utah.gov/rsgis2/Search/Display.asp?F lNm=aquichry).  This unexpected, close-up sighting of wildlife was one of the most memorable experiences of the trip. I will always remember the beauty of this majestic creature.

Chelsi on Ladder in Mancos CanyonLadders in Ute Mountain Ute Tribal Park

Ladders in Ute Mountain Ute Tribal Park

          The San Juan River wasn’t the only place we saw evidence of this animal in the Southwest.  The golden eagle is represented in artifacts from different cultures on the Colorado Plateau, specifically, the Native American tribes.  Golden eagle feathers are still used in some traditional ceremonies, and significant places are appropriately named for the birds. On our last day of our journey through the four corners region, we visited the Ute Mountain Tribal Park, on the back side of Mesa Verde.  Marshall, our Ute guide, not much older than ourselves, was incredibly knowledgeable about so many aspects of the area-history, culture, and flora and fauna. The last cliff dwelling we visited in Mancos Canyon was accessed by climbing down four wooden ladders, hiking along a ledge for approximately a mile, then up a fifth long ladder, not suitable for those fearing heights, and finally we had to duck under an overhang for approximately 15 feet to reach a well preserved ruin in an alcove sitting half way up the canyon wall.

View of Eagle's Perch Ruin

View from Eagle's Perch Ruin

This remarkable site, more easily reached by eagles than humans, was aptly named Eagle’s Nest.  From our first day to our last, the eagle, in one way or another, welcomed us to the Southwest, and for me became symbolic of our trip.

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Ammonite Fossil Next To Quarter For Scale

Rafting down the upper section of the San Juan River from Sand Island to Mexican Hat, in southeastern Utah, there is a fossil stop near the entrance of Lime Creek, after the river emerges from the canyon. While much of the San Juan River passes through colorful layers of sandstone, the fossils of note are in a dark gray limestone.  Here is definite evidence that what is now desert was once covered by marine water.  The ancient Paradox Sea inundated a large area in the region and teemed with the marine life whose remains are before us.

I’m not the only one with “paleo-passion” (a term possibly coined by writer Donovan Webster in his article, “The Dino Wars: Who Owns American’s Fossils”, Smithsonian Magazine, April 2009, p. 48-57), but as an earth science educator, I feel protective of even one small trace of a fossil- what’s called a “fossil mold”, an impression made in the substrate. This is the only ammonite fossil I’ve seen in its actual place of formation and so to me it is noteworthy.  A thoughtless individual could damage the find, chiseling the mold out of the surrounding matrix, although I can’t imagine the tools or techniques that would be required to do so. It’s possible the true fossil form- the actual body of the animal making the mold- was removed by an eariler collector.  In discussing our itinerary on the river, I make sure our guide, Brett LeCompte, working for the Four Corners Outdoor School, stops at the fossil site.

We read and hear so much on our geo-cultural travel study trip to the Colorado Plateau about policies and practices regarding how to respectfully visit Ancestral Puebloan ruins, that I am curious about laws protecting fossils.  With a little research, I learn that currently fossils can be taken from private lands with permission of the owner for private collections or auction.  Some fossil materials, like petrified wood, in limited quantities, may be taken from public lands without permits.  However, additional legislation- the Paleontological Resources Protection Act- has been drafted mandating, “only trained, federally certified professionals be allowed to extract fossils from public lands,” (Webster, p. 56). The intent of the bill is to substanially increase penalties for illegal fossil excavation.

I wonder how much concern there is for ammonities which can be found for sell in fossil stores and on the web.  Webster logged onto Ebay and found an ammonite specimen, expecting to go for $3000. Excavating specimens from their resting place eliminates the educational and scientific context, and for me the special significance and value of the fossil.

Ammonite structure

This particular fossil, resulting from ages of compression and cementation, is an invertebrate specimen, a highly developed marine mollusk belonging to the extinct family of ammonites of the cephalopod class. Similar to the shells of snails, cephalapods shells are divided into chambers. Modern members of cephalopods, like the squid and octopus have only two gills, while members of the ammonoid and nautiloid families have four gills. (I can’t imagine gills being distinguishable in a fossil.)

These living animals first appeared during the Silurian Period, approximately 400 million years ago and were abundant and widespread in oceans during the Jurassic and Cretaceous geologic periods. Ammonites are important index fossils, because they can be used to provide a relative date for the rock layer in which they are found as species evolved over time.

The shells of ammonites had hollow chambers separated by walls called septa. A tube called the siphuncle, connected the body with the chambers allowing the animal to use water or air to change its buoyancy in order to rise or drop in the ocean.  Only the last and largest chamber was occupied by the living animal.  Ammonites vary greatly in size, the largest early forms could be 15 feet. Shell shapes varied as well; some can be snail like and others are uncoiled.

Ammonites fed on plankton and lived exclusively in marine environments and so their presence indicate the location of prehistoric seas.  Now, the arid West means little vegetation covers the rocks, making fossils like ammonites easier to find. The limestone and other sedimentary layers of rock deposited in ancient environments are now being exposed, revealing what this corner of the world was once like. For me, this fossil stop is as rich a window into the past as any of the human related historical sites we visit.

Rowing through the Paradox Formation

Travelling along this river by boat, takes you back in time, not only to the time of Ancestral Puebloans, but to a period where the environment was very different.  In relation, our modern concerns about how climate change might impact a particular region, seem so anthropomorphically insignificant.

A nice animated image show several perspectives of an ammonite can be found at:  http://www.paleodirect.com/ammonites.htm, accessed on 3-27-09.

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The first species we came across was in a domesticated setting, but does still roam free in some parts of the West. The American Buffalo once played an enormous role in the lives of the native people of the West. These tribes followed and lived by the herds that provided them with everything they needed to live on. Once the white man came out West and discovered these majestic animals, things drastically changed. Buffalo hunting became one of the main industries of the plains, often with kills of 250 animals a day. Millions of buffalo once roamed the western plains, but by the late 1800s only about 300 were left in the wild (http://www.fws.gov/species/species_accounts/bio_buff.html). In 1894, buffalo hunting was made illegal and conservation efforts over the years have brought the number of buffalo up to about 200,000 (http://www.fws.gov/species/species_accounts/bio_buff.html). However, these gentle giants will never again have total free roam over the land that once was theirs.

Driving through Colorado, on our way to the base camp in Utah, we came across another of the West’s best known animals on the side of the road. The Big Horn Sheep can be found all over the West, although its range changes seasonally. This animal is best known for the attribute that gave them their name; their big curled horns. The males use these horns when competing for territory or for females, in head butting contests that can last up to 20 hours! (http://www.nhptv.org/Natureworks/bighornsheep.htm). They are also well known for their climbing and jumping abilities, which help them to live in areas that are unsuitable for most other species and to evade predators.

Once on the San Juan River, we encountered many other animals, both wild and domesticated. I say domesticated, but as the horses and the cattle we encountered basically have free range of the land, I would almost classify them as wild. They were all along the river banks and we encountered many when we were on our hikes as well. The wildlife we encountered was varied. There were several species of birds that we saw on our first day on the river. The first were a few Blue Herons, some Cliff Swallows, and we thought we saw a Willow Flycatcher. The Southwestern Willow Flycatcher is an endangered species due to habitat destruction and large flood control dams (http://audubon2.org/webapp/watchlist/viewSpecies.jsp?id=217). Due to its status, it is great if we actually did see one. We also believe we saw a Bald Eagle soaring above us on the second day of the river trip. It may have been a Golden Eagle, but whichever it may have been was definitely a sight to see. As for other animals, there were many lizards running about the warm rocks along the sides of the river. I do not know the species, but they were tiny. There were also many chipmunks running in and out of holes as we passed them. We came upon a funny site when I pointed out what I thought to be a large nest, and it turned out to be a large porcupine. As we realized what it was, we saw another one in a neighboring tree, both of which appeared to be sunning themselves. All along the river bank were beaver homes as well. It was interesting to see them because when I think of a beaver, I think of a dam on a pond. This is not the case with these beavers. They burrow into the sides of the river beds and make their homes here. Sometimes there were sticks around the entrances, but for the most part there were just concealed holes. Our guide pointed out that the lack of dams is most likely due to the fact that the river is not constant in speed and depth. We did not actually see any beavers, but between their homes and all the chewed logs, there were signs of them everywhere.

One of the animals I encountered that sticks out foremost in my mind was a hare. I say this not because the hare was overly amazing or anything, but because it almost gave me a heart attack. I knew hares were abundant in the area, but had not seen one until I was going to bed and it was dark out and I almost stepped on one as I was walking to my tent. It took off in such a flash that I wasn’t sure what it was at first. I figured it out once my heart came back down to earth. There were also coyotes in the area. We could hear them at night, but did not actually see any. I’m sure there were many more intriguing animals along the river that we just did not run into, but I was thoroughly satisfied with the amount we were able to see.

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