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Tackling Tamarisk on the Purgatoire to Improve the Watershed by Ryan Boggs, The Nature Conservancy John Heideman, Tamarisk Coalition Shelly Van Landingham, Colorado State Forest Service SERVK:E The lower Purgatoire River watershed spans more than 200 miles, including the river and tributary feeder streams. The main stem of the Purgatoire flows east from the 14,069 -foot Culebra peak high in the Sangre de Cristo mountains to Trinidad, Colorado, and then northeast to Las Animas, Colorado, where it converges with the Arkansas River. This watershed is home to one of the most intact native fisheries in the Central Shortgrass Prairie east of the Rocky Mountains. The river's tributaries have also created lush side canyons that sustain several rare plant species. And a diverse prairie mosaic of shale outcroppings, pin on juniper woodlands, and extensive prairie uplands with native grasses and shrubs is found above the canyons. Due to the decades -long invasion of aggressive, non - native woody plants including tamarisk, Russian olive, and Siberian elm, the Purgatoire's globally rare riparian plant communities are being threatened. These plant pests, particularly tamarisk, also increase the fire risk to communities and watersheds because the plants ignite easily and when they burn, they cause fire to spread rapidly and create intense heat. In addition, they compromise healthy riparian forests, and negatively impact livestock production and the economic sustainability of communities that rely on a strong agricultural base. Tamarisk is not unique to the Purga- toire. This invasive species, which was imported from the Middle East in the early 1900s for erosion control and its ornamental qualities, has choked rivers throughout the southwestern United States. It has also transformed many of Colorado's Eastern Plains riparian areas from healthy, viable habitat with diverse plant communities that support 90 percent of the area's wildlife into crowded monocultural forests with little biodiversity. 12 Tamarisk, which is also known as salt cedar, has a voracious appetite for water. Every year, tamarisk in the Arkansas River drainage in Colorado uses enough water to supply all of Pueblo's domestic water for that year. It also degrades ecosystems in other ways. For example, it increases the salinity of the surface soil, which renders it unsuitable for use by other plants; it widens flood plains, clogging stream channels and increasing sediment deposits; and it diminishes human enjoyment of and interaction with the river and sur- rounding environment. The unique distribution of tamarisk in the Purgatoire River Watershed, which ranges from light infestations above the Trinidad Reservoir to heavier, denser stands downriver, makes the area ideal for large -scale con- trol. And improving the Purgatoire Watershed through large -scale control is exactly what the Tackling Tama- risk on the Purgatoire Project —or TTP —is all about. TTP is a collaborative effort between public agencies, non -profit organizations, and private landowners who work, live, and play in the Purgatoire River Water- shed. They have been working together during the