Research by William Ripple and Robert Beschta is featured in the June 2010 issue of Oceanography.  The scientists’ study showed that cougars not only have direct effects on populations of animals such as deer and elk, but also indirectly affect entire ecosystems. Without cougars, deer dramatically increased, leading to loss of the riparian cottonwood trees deer love to nibble on. Lack of cottonwoods, which serve as riverbank anchors, resulted in extensive erosion. Biodiversity in Zion’s waterways plummeted.