Invasive Species

CORE DEFINITION

Invasive species are non-native species that successfully colonize new habitats and gain an asymmetric competitive advantage. Because these newly naturalized species have not yet reached equilibrium with the food web of the new habitat, they often lack predators higher up the food chain to limit their population, leading to overpopulation. This can damage the original ecosystem of the new environment, causing endangerment or even extinction of native species through predation, competition for food and territory, disease transmission, and disruption of vegetation. The negative impact of invasive species on habitat biodiversity can cause ecological, environmental, and/or economic losses. The term can also refer to certain native species that, when humans alter the food web, proliferate and cause damage - for example, on the northern coast of California, USA, where sea otters that preyed on purple sea urchins were heavily hunted and their numbers drastically reduced, allowing purple sea urchins to proliferate and severely damage local kelp forests. Since the 20th century, invasive species have become a serious economic, social, and environmental threat. The entry of organisms into long-established ecosystems is a natural phenomenon, but human-facilitated introductions have greatly expanded the speed, scale, and geographic range of invasions.