Peterson has four areas of expertise: forest ecology, range ecology, forest pathology, and mycology. He also has the unique designation of being the “world expert” on Southern Hemisphere conifer rusts.
When he goes out to compile inventories or just to look for plants, Peterson still finds novel, and sometimes entirely new, species. “Do you know where Lindrith is?” he asked. “It’s up north of Cuba. I recently found a new six-foot-high weed there. It’s native in Colorado. It isn’t invasive from afar; it just hadn’t been noticed in New Mexico.” He paused again. “Of course, I don’t yet have a good enough specimen to want to publish.” There is further work to be done.