The Terminology of Biological Invasions

Getting Precise and Pro-active

Concept 1:

Why do we talk about where plants “are from”? 

When people move plant species from one region to another, they introduce the plant to a new environment. In most cases, introduced plants do not become problematic. But sometimes, they can establish and prolifically spread, becoming invasive. When plant populations become invasive, they interrupt ecological or economic processes in ways that cause harm, a phenomenon known as a biological invasion. Knowing where plants originate provides clues about how a plant might behave in a given environment. Origin carries no judgement about whether a plant is “good” or “bad”, it just describes a biological fact about a plant.

Concept 2:

What terms do we use to talk about plant origin? 

The terms native and non-native are used to describe whether a plant evolved in a given location and habitat type, or evolved somewhere else. A plant that has evolved in place is adapted to local environmental conditions and has developed a web of interactions with other plants, animals and microbes. This evolutionary history provides checks and balances on things like resource use and population spread. Plants that have not evolved in place can disrupt long-established interactions like pollination or evade checks and balances, thereby becoming over-abundant.

Concept 3: 

Why do we need to think differently about human-caused introductions versus other ways that plants move around?

First, people move plants long distances, overcoming dispersal barriers like oceans and mountains that plants would not typically overcome on their own. This movement drops novel species into systems where their ecological effects are hard to predict. In contrast, when plants expand their range edges slowly, without human help, they are likely to remain under the same checks and balances with which they evolved at the core of their range.

Second, the rate at which people move plants around creates a numbers game. Imagine throwing darts at a dart board. The more throws you take, the better your chances of hitting the bullseye. The same process works with introducing many different plant species over and over again – the chances increase that you’ll hit the bullseye (introduce an invader) as the number of introductions grows.