An adventive species is an organism that has arrived in a new geographic area, outside its historical range, primarily due to human activities, either accidentally or intentionally. The term often implies the species is not yet fully established, or its long-term status remains uncertain.
Understanding Adventive Species
An adventive species is any organism introduced to a new region by human actions. These non-native, or “alien,” species did not arrive through natural dispersal. Their presence is often temporary or localized, meaning they have not yet formed a self-sustaining population that can reproduce and persist independently.
While some may persist, their continued existence often relies on repeated introductions or they may simply die out. The term highlights their recent arrival, distinct from species that have naturally occurred in a region for extended periods.
Pathways of Introduction
Human activities are the primary drivers behind the introduction of adventive species to new environments. These pathways can be broadly categorized as either accidental or intentional. Accidental transport often occurs through global trade and travel.
One common accidental pathway is through shipping, where organisms can be carried in ballast water or by clinging to ship hulls (hull fouling). Air travel can also facilitate accidental introductions, with organisms hitchhiking in cargo or on aircraft. Contaminated agricultural products, such as seeds mixed with crop seeds or insects hidden within packaging, are other unintentional means of dispersal.
Intentional introductions, while deliberate, do not always aim for the species’ establishment in the wild. For example, ornamental plants might escape cultivation from gardens, or pets might be released into the wild. Organisms used for scientific research can also inadvertently escape their containment, leading to their presence in a new area.
Adventive Versus Related Terms
The classification of species in new environments can be complex. Distinguishing “adventive” from other terms like native, naturalized, and invasive species is important for clear understanding.
A native species is one that naturally occurs in a specific geographic area, having evolved there or arrived through natural dispersal over long periods without human involvement. These species form the baseline against which introduced species are compared.
A naturalized species, on the other hand, is a non-native species that has successfully established a self-sustaining population in a new environment. An adventive species can transition to a naturalized status if it successfully establishes a breeding population. For instance, sweet clover (Melilotus sp.), originally from Europe, has become naturalized in the Americas, reproducing without human intervention.
An invasive species represents a subset of naturalized species. It is a non-native species that not only establishes a self-sustaining population but also causes significant ecological harm, economic damage, or harm to human health in its new environment. While all invasive species are naturalized, not all naturalized species are invasive. For example, the kudzu plant, introduced to the southeastern United States, is considered invasive because it outcompetes and smothers native vegetation. Therefore, an adventive species is not classified as invasive unless it first becomes naturalized and subsequently demonstrates harmful impacts on the ecosystem.