Utilizing remote sensing to supplement ground monitoring of Diorhabda elongata as a control agent for Tamarix ramosissima in Dinosaur National Monument

The plant Tamarix ramosissima has invaded significant riparian habitat along the Green River in Dinosaur National Monument. Commonly known as saltcedar or tamarisk, it was introduced from Eurasia to the Southwestern United States to prevent soil erosion along riverbanks. It has since come to affect water resources, recreation, wildlife, and ecosystem services. Various methods used to control Tamarisk's spread have had moderate success but have drained National Park Service's human and monetary resources. In June 2006, the saltcedar leaf beetle (Diorhabda elongata) was released as a biological control agent within the park to defoliate and ultimately eradicate the invasive species. This study examines the efficacy of using Landsat TM imagery to supplement ground monitoring of the beetle's spread and its effects on tamarisk in Dinosaur National Monument, and discusses the development of a GIS model to predict annual change in tamarisk cover and beetle populations. Through fieldwork we determined four areas of interest with favorable attributes for satellite detection. A change detection model was created by layering 2005-2008 data and quantifying mean NDVI. Results show that intra-year NDVI trends may be more effective for accurate detection than single-image year-to-year comparisons largely because intra-year environmental variability is significantly smaller. Additionally, our GIS model predicted significant growth of beetle population, implying that defoliation will become more apparent in future years. However, challenges to detecting this defoliation include the year-to-year variability of environmental factors, low spatial resolution of Landsat TM data, low visibility into parts of the Green River canyon, and the spectral mixing of tamarisk and native vegetation.