Can a native species become a biodiversity threat? While we typically think that only introduced species can become invasive, there are numerous cases where a native species, when reacting to a novel condition, can become problematic for ecosystems and the other species in its environment. The example in this video is hay-scented fern (Dennstaedtia punctilobula), which — often combined with the effects of deer overpopulations (another native but now-problematic species) — can prevent forests fro