Invasive species
Introduced species that cause ecological or economic harm.
Invasive species are introduced organisms that harm their new environment, causing ecological, environmental, or economic damage. Since the 20th century, they have become serious economic, social, and environmental threats worldwide. Human-facilitated introductions, beginning with early migrations and accelerating through the Age of Discovery and international trade, have greatly increased the rate, scale, and geographic range of invasion.
- field
- Invasion ecology / invasion biology
- known_for
- Adversely affecting habitats and bioregions; subset of established non-native species that threaten native species and biodiversity
- notable_plant_examples
- Kudzu vine, water hyacinth, common ragweed, yellow starthistle
- notable_animal_examples
- European rabbits, domestic cats, red swamp crayfish
Lore & Background
The term 'invasive species' is poorly defined and often subjective. It may include plants, animals, fungi, and microbes; some broaden it to include native species that have colonized human habitats. Some sources name Homo sapiens as an invasive species, but broad appreciation of human learning capacity and behavioral plasticity may argue against any fixed categorization. The definition of 'native' can also be controversial, as with the reintroduction of horses to North America by Spanish conquistadors, sparking debate over whether feral horses were native or exotic to the continent of their evolutionary ancestors. The field lacks standard terminology, leading to proposals such as Colautti and MacIsaac's nomenclature system based on biogeography rather than taxa, which evaluates individual populations based on their success in that environment. Causes include high propagule pressure from repeated human movement, such as ship traffic or vehicles along highways. Ecosystem-based mechanisms involve resource availability, edge effects from disturbance, and the role of species diversity—debated at different spatial scales. Island ecosystems may be more prone to invasion due to fewer strong competitors and predators, as seen with the brown tree snake on Guam. Intensively managed fenced areas are also more prone to invasion due to disturbance and dispersal pathways.
Reader's Guide
Invasive species represent a significant and growing concern in ecology and environmental management. Their study, primarily within invasion ecology, has been shaped by Charles Elton's foundational work but remained sparse until the 1990s. This ambiguity complicates policy and management. The causes of invasion are multifaceted, involving human-mediated dispersal, propagule pressure, and ecosystem dynamics such as resource availability and disturbance. Island ecosystems and intensively managed fenced areas are particularly vulnerable. Notable examples include kudzu vine, water hyacinth, European rabbits, and domestic cats. The legacy of invasive species research highlights the need for standardized language and a nuanced understanding of ecological impacts, as debates continue over definitions and the relationship between biodiversity and invasibility. Their economic, social, and environmental threats underscore the importance of continued study and management.
Did You Know?
- The term 'invasive species' is poorly defined and often very subjective.
- Some sources name Homo sapiens as an invasive species, but broad appreciation of human learning capacity may argue against any fixed categorization.
- Island ecosystems may be more prone to invasion because their species face few strong competitors and predators.
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