Remote sensing has been an important tool in evaluating ecosystem health and invasive species monitoring, mapping and management. In the early 1800s, several species of Tamarix were introduced to the United States. Three of these, all commonly referred to as saltcedar have become “one of the most threatening invasive species in the United States over the next ten years” (Wang L. et al., 2012, p.3). The saltcedar have dominated the basin in the southwestern US and northern Mexico’s semiarid climate, due to its hardy nature and ability to tolerate the dry conditions.
Due to the importance of accurately identifying, mapping, and inventorying this invasive plant, researchers have turned to several different remote sensing capabilities to determine which offered the best capabilities to take on this task. In a study by Wang L. et al., the researchers chose QuickBird, AISA and Landsat TM to determine which would offer better multiresolution and multiresource remote sensing imagery.
The study site was located near Candelaria, TX, along the Rio Grande river, among the many canyons and valleys of this semiarid region. The flora is mostly composed of saltcedar with some willow mixed in. Researchers then began composing data from all three image producing methods. Once researchers had their data, they were able to complete a comprehensive study of the imagery and determine which would better work for reconnaissance of the invasive species.
QuickBird remote sensing has been used for detecting invasive species in the past but had been reported to have limitations with detecting small strands of scattered trees. Airborne Imaging Spectroradiometer for Applications (ASIA) is known for its ability to provide data at a very fine resolution, (between 1-4 meters), but can be quite costly. Landsat TM is reported to be ideal due to its wide coverage and low cost. Researchers concluded that out of the three, ASIA outperformed QuickBird in saltcedar identification and achieved high scores in accuracy. Landsat TM showed similar accuracy to AISA methods, but was significantly better with computing efficiency.
The ability to use remote sensing in reconnaissance of threatening invasive species will allow for better potential for mapping, monitoring and managing a serious problem in the United States. This study outlines the classification accuracy between each method, allowing for better quality reconnaissance.
Le Wang, José L. Silván-Cárdenas, Jun Yang & Amy E. Frazier (2012): Invasive Saltcedar (Tamarisk spp.) Distribution Mapping Using Multiresolution Remote Sensing Imagery, The Professional Geographer, DOI:10.1080/00330124.2012.679440