Tammies Targeted in Drought Mitigation Efforts

Tamarisk, that bane of southwestern rivers, is being targeted by river managers, volunteers and a nonprofit group in an effort to recoup the loss of precious river flows, particularly in the current drought. The tamarisk tree, native to the Middle East, was introduced early last century to stabilize bank erosion, but quickly naturalized, crowding out native species and sucking as much as 500,000 acre-feet a year of scarce desert water by some estimates.

Prior to the construction of Glen Canyon Dam, tamarisk growth was limited to higher elevation terraces and tributaries in Grand Canyon National Park (GCNP), but stable flow regimes in most years encouraged their spread. The high flow of 1983, over 100,000 cfs, killed one third of the tamarisks below the 60,000 cfs water mark. In 1996 the short-duration “spike flows” of 45,000 cfs and lower failed to remove any tamarisks. Flows in 2000, with short, low peaks below 33,000 cfs, followed by steady flows, caused an increase in the already widespread germination of tamarisks.

Tamarisk control was initiated in Grand Canyon National Park in 1998. To date, 134,808 trees have been removed from 4,496 acres in 63 tributaries of the river. An average of 12% of the removed trees required follow up treatment in order to fully eradicate. Volunteers donated 8,000 volunteer hours valued at $137,500.

Tamarisk removal is particularly critical in GCNP, as this World Heritage Site contains 1737 different plant species and has more floral diversity than, and the most plant species of, any national park. 42% of Arizona’s native flora is represented in the park.

Colorado’s Horsethief Canyon and Dinosaur National Monument are among the sites selected for the release of the tamarisk’s only known predator, the salt cedar leaf beetle. The beetle is currently chewing away at 3 sites and could be released in Dinosaur National Monument soon, after completion of a required Environmental Assessment. There will be pre- and post-monitoring at each site for five years with data being collected every two weeks. Because the beetle cannot reproduce in areas with fewer than 14 ½ hours of sunlight per day, release is confined to areas above 38 degrees north. Once a tree has been defoliated by the beetles, the leafless tree is then manually eradicated.

The San Miguel River, a tributary of the Dolores River in the Upper Colorado River Basin, remains one of the few naturally functioning riparian ecosystems in the Western United States. The Tamarisk Eradication Project is preserving and protecting the biological health of the riparian areas throughout the San Miguel River Watershed by removing non-native invasive trees in order to establish the San Miguel as the only naturally functioning—and free of non-native trees—river in the Upper Colorado River Basin by 2006.

Nancy Seamons, Environmental Coordinator for River Runners for Wilderness, attended the Tamarisk Symposium in Grand Junction, Colorado, co-hosted by The Tamarisk Coalition and the Colorado State University (CSU) Cooperative Extension biennially. This year’s symposium, held on October 12 -14, 2005, was well attended by nearly 250 national and international researchers, on-the-ground program managers, environmental representatives and federal/state/local agencies. Participants heard presentations and discussed topics including current research, control projects, restoration, mapping and funding, legislation and planning, economics and biological control.

Throughout the summer of 2005, the Tamarisk Coalition mapped tamarisk and Russian olive (another non-native tree wreaking havoc) along the riparian corridors of the Arkansas and Colorado Rivers and their tributaries. Accessing the rivers by roads and the river channel itself, field technicians are “ground truthing,” or verifying the presence and characteristics of tamarisk and Russian olive stands in comparison to satellite and aerial photos.

The Tamarisk Coalition is a 501(c)3 non-profit whose mission is to provide education, technical assistance, and coordinating support for the restoration of riparian lands and is working with Congress to provide $80 million over five years for tamarisk control and revegetation for large scale projects, critical research, long term management and funding options. To learn more about tamarisk and invasive plants, visit the Tamarisk Coalition web site at www.tamariskcoalition.org.