An invasive species is an exotic, non-native species whose presence is likely to cause harm to human health, the economy, and/or the environment. In contrast, an exotic species^? is an alien, or non-native, species that is not naturally present in a habitat. All invasive species are exotic, but not all exotic are invasive. Invasive species are not the same as novel occurrences of species that shift into a region as they respond to climate change by following optimal environmental conditions.