Based on data from 10 long-term forest monitoring plots, including seven from the Smithsonian’s ForestGEO network, a team led by Jacob Usinowicz during his doctoral dissertation at the University of Wisconsin-Madison, provides the first evidence that the ‘storage effect’ enables tree species to coexist and is stronger in the tropics. The team’s results, published in the Sept. 20 edition of the journal Nature, address a question that has long challenged biologists: Why are there so many more species in the tropics?