In recent years, concerns about the spread of so-called “invasive species” have so troubled some environmental observers that Congress passed the National Invasive Species Act and the executive branch adopted a management plan to control them. But according to an article by Ron Bailey of the Reason Institute, this battle against non-native species is driven more by culture than any real science. Citing several prominent sources, Bailey notes that biological invasion is a natural process that doesn’t weaken eco-systems, but simply transforms them into different ones. And while certain invasive species like tree snakes can harm native birds, fewer than 6 percent of endangered species are menaced by non-native immigrants.