Rodolfo Dirzo, professor of biology at Stanford University, opened the Environmental Analysis and Action Symposium series on Wednesday, Feb. 20, when he presented “Tropical Biodiversity: An Endangered Natural Treasure.” Dirzo studies plant-animal interactions in an effort to better understand how the ecology and evolution of plants are affected by their biotic environment. His work is focused on tropical forest ecosystems, and he has written extensively on the topic, including a book, titled Tropical Forests: Biodiversity and Ecosystem Functioning. In addition, he has received numerous honors, including the Presidential Award in Ecology from the Secretary of Environment of Mexico.