Early people in this area found much of what they needed in the Rio Grande valley and moved throughout its grasslands and foothills in search of food and resources, while later settlements concentrated along the river and used its water for crops. For thousands of years, the Rio Grande flowed year-round as a meandering stream, but changes in the valley’s ecology began in the late 1800s and early 1900s when dams and canals manipulated river flows and the river was confined to a straightened channel. Although the benefits the river now provides to plants and animals have changed, its benefits to humans through crops, recreation, and water supply remain important. Today the Rio Grande, bordered by remnants of the lush cottonwood bosque, flows through the surrounding dry Chihuahuan desert, where a large diversity of mammals, amphibians, turtles, lizards, snakes, birds, fish, and insects find food and shelter.