Yellowstone willows 2014 (IMAGE) Colorado State University Caption In 2001, CSU researchers established four intensive study areas in Yellowstone to test the effects of reduced browsing by fencing and increased water availability by creating simulated beaver dams. In this photo from 2014, the willows in the fenced area that also had increased water availability grew three times taller and much more densely than unfenced areas without groundwater access, shown in the foreground. Credit David J. Cooper Usage Restrictions None License Original content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.