S Sriharan, J Everitt, and C Yang
“Global warming is projected to have immense effects on freshwater and wetland ecosystems. Wetlands and aquatic ecosystems are quite vulnerable to climate change. Exotic invasive weeds are a serious problem in the Rio Grande River system of Texas. The Rio Grande is one of the longest river systems in the United States. The river extends 3,040 km from its source in the San Juan Mountains of Colorado to the mouth at the Gulf of Mexico on the United States- Mexico border in extreme south Texas. The Rio Grande River system of Texas has serious problems due to exotic invasive weeds such as waterhyacinth [Eichhornia crassipes (Mort.) Solms.], [Hydrilla verticillata (L. F.), Royle], saltcedar (Tamarix chinensis Lour.), giant reed (Arundo donax L.), Eurasian watermilfoil (Myriophyllum spicatum L.), and wild taro [Colocasia esculenta (L) Schott]. These invasive plant species have displaced much of the original native vegetation. Water shortages in the Rio Grande have been exacerbated by the invasion and spread of the above-mentioned weeds. Remote sensing techniques offer potentially timely, cost-effective means of obtaining reliable data for these areas.
“The scientists at the USDA ARS Laboratory in Weslaco, Texas, in cooperation with the senior author at Virginia State University, have been conducting research on the utilization of aerial photography and videography integrated with global positioning system (GPS) and geographic information system (GIS) technologies for detecting and mapping exotic invasive weeds in the Rio Grande system from the mouth of the river the near Boca Chica in extreme south Texas to El Paso in west Texas.This paper describes the results of several aerial remote sensing studies conducted from 2002 to 2006 on the Rio Grande River from its mouth near Brownsville in south Texas to El Paso in west Texas. Aerial photography and videography were used to detect plant species. Aerial imagery was obtained under sunny conditions with photographic and videographic systems mounted vertically in either a Cessna 206 or Cessna 404 Titan aircraft. Video imagery was integrated with GPS and GIS technologies to develop distribution maps denoting infested locations of the invasive weeds. Our findings indicated that approximately 1,285 river-km of the Rio Grande was plagued by infestations of waterhyacinth, hydrilla, saltcedar, giant reed, Eurasian watermilfoil, and wild taro. The aquatic species, waterhyacinth and hydrilla infested approximately 225 river-km in the extreme southern portion of the Lower Rio Grande Valley of Texas. The wetland species saltcedar infested approximately 460 river-km from Lajitatas to near El Paso in west Texas. Giant reed infested approximately 600 river-km along the Rio Grande from near Laredo in south Texas to near Presidio in west Texas. Eurasian watermilfoil occurred along a 66 river-km area from below Amistad Reservoir near Del Rio to north of Eagle pass in southwest Texas. The joint use of these technologies provides valuable information on the distribution of invasive weeds in the Rio Grande system along the Texas-Mexico border. It is anticipated that these technologies can be used for a variety of natural resource management of ecosystems, wetlands, coasts, and deltas.”