We’ve all heard about the dangers of non-native plants: they outcompete natives; they carpet forest floors and smother roadsides; they cost us billions of dollars a year in control efforts. They’ve colonized huge swaths of the mid-Atlantic, where I live; I’ve written about them on this very blog. But is it possible that some introduced plants could prove beneficial in their new environments?
That’s certainly what Ariel Lugo thinks. Lugo, the director of the US Forest Service’s International Institute of Tropical Forestry, has long promoted a more catholic attitude toward plants of diverse origin. I recently visited him at the University of Puerto Rico’s Agriculture Experimentation Station in San Juan, where his office sits among groves of eucalyptus and bamboo—both of which humans introduced to the island. According to Lugo, the immigrant vegetation reflects the welcoming Puerto Rican spirit. “Here, we don’t persecute trees,” he says. “The federal government is the only one that persecutes trees.”
As far as Lugo is concerned, any species that can help his island recover from past environmental devastation—near complete deforestation, large-scale cultivation of sugarcane and other crops—is welcome. In 1992 he published a paper comparing the understories of pine and mahogany plantations with those in regrowing native forests. Lugo found that similar numbers of species were growing in both places, and that many of the understory plants in the plantations were native. Moreover, he found the older plantations were starting to give way to native overstory trees. “The study challenges the conventional dogma…and underscores the dangers of generalizing about all tropical tree plantations or all natural tropical forests,” he wrote. According to science writer Emma Marris, it took Lugo almost a decade to get his paper accepted.