Mr. Paredes was the federal District Ranger for 245 miles of the Rio Grande that flows along the southern boundary of the Big Bend National Park. Together with his previous experience working as a river and trail guide in Texas, Mexico, Guatemala and elsewhere, he grew to be very knowledgeable about the Rio Grande, its flora, fauna, and the risks it faces from water pollution and diversions. Mr. Paredes also has been involved in private efforts to stop proposed low-grade coal mining in the Terlingua area, near his home.