My research is in the ecology and species composition of tropical and subtropical forests in both the Paleotropics and Neotropics. In the Brazilian Amazon, I have eight permanent study sites - embracing a total of over 22,000 trees which are regularly monitored - from the foothills of the Andes to the Atlantic, where my research is on the evolution and maintenance of tropical botanical diversity, the relationship between disturbance and diversity, tree demography, phytosociology, the ecology of flooded forest vs. terra firme forest, and allelopathy. In Belize I have 43 study sites, including one at Terra Nova, the world's first medicinal plant reserve, and one at El Pilar, a Late Classic ruined Maya city of forest-covered temples and pyramids, where my students and I are investigating the 1,200 year-old signature of the collapsed Maya Civilization on the species composition of the Maya forest. In collaboration with colleagues at Nanjing University (where I am an adjunct professor) and Hainan University, I have two study sites in the subtropical forests of Hainan Island, southern China, where we are investigating patterns of tree species distribution and the economic botany of the minority Li and Miao tribes.
Since I came to Grinnell in 1991, hundreds of Grinnell students have joined me on research or teaching expeditions to the tropics, and have learned tropical plant taxonomy using the 25,000 herbarium specimens of tropical trees kept in my laboratory at Grinnell.
My other passion is writing (See Grinnell's Community of Writers). The Ephemeral Islands; Islands in Space in Time; and A Land of Ghosts; and co-editor of Floristic Inventory of Tropical Countries. I specialize in literary nonfiction.