The old gray tamarisk ain’t what it used to be

by Bill Boyle

The next time you drive through the Moab Valley, take a look around. You may notice that the entire valley is full of gray and dying tamarisk trees.

Tamarisk, also known as salt cedar, has invaded water courses throughout the western United States. Nowhere has the impact been greater than in southeast Utah.

A native of central Asia, tamarisk was introduced in the 1800s to control stream bed erosion. They thrived too well, crowding out the native species along stream beds. The result is stream beds throughout the West that are crowded with thick tamarisk and little else.

While early photographs show a nearly treeless plain in the San Juan River Valley near Bluff, tamarisk and the Navajo Dam above Farmington, NM changed the San Juan River.

The San Juan River corridor is now crowded with nearly impenetrable thickets of tamarisk. The presence of the dam means that the wild San Juan, which caused so much challenge for the early Anglo settlers of the area, is little more than a controlled ditch downstream.

The impact of tamarisk overgrowth was evident to the SWAT teams who were searching for fugitives in the San Juan River bottoms in 1998. The tamarisk thickets were so thick that the search was miserable and dangerous.

Concerned biologists wondered what controlled the tamarisk in their native lands. They investigated closely and found an obscure beetle in central Asia, the tamarisk leaf beetle, that loves to eat tamarisk and only tamarisk.

The beetle was introduced in Delta, Utah under a carefully controlled quarantine in 2004. The results were good and they were introduced to the Moab Valley in the past year.

The impact has been immediate and dramatic. Stands of tamarisk along the Colorado River and up every tributary large and small have been attacked in masse by hordes of the beetles. They strip the vegetation off the tamarisk early in the growing season. As a result, experts estimate that it will take several years before the tamarisk are killed.

No one knows what will happen then. The trees will be dead and dry along the streambeds. Their tangled root systems, which are so effective in stopping stream bed erosion, are likely to stay in the stream beds even longer.

Natural vegetation will eventually finds its place again along the stream beds.

It just may be a matter of time before the beetles make their way to the San Juan River corridor. The impact will be as great or greater along portions of the San Juan as it has been on the Colorado.