The term "invasive species" is often heard in scientific fields, but what does it really mean for a plant or animal to be invasive? According to the USDA, an invasive species is a non-native whose introduction to an ecosystem causes economic or environmental harm. A species most frequently becomes invasive after humans transport it, either intentionally or unintentionally, to a new environment where it faces little to no grazing or predation threat and has an abundance of nourishment and space to grow. Without predators, diseases, or other constraints to limit its numbers, an invader can aggressively outcompete native species and become extremely difficult to eradicate. Because of this, some researchers believe invasive species may be the single biggest threat to endangered species.
