The coronavirus sometimes invades a population when a single infected person enters, spreading the disease, often unknowing–although not always. No matter how many precautions are taken by a community, a small number of members can put everyone else at risk. Although the third wave of the pandemic ended in the United States, dropping infection numbers to their lowest levels since the start of this catastrophe, the low numbers were not enough to end the disease.

The coronavirus itself is invasive, so it should be no surprise that invasive organisms can occur from a single instance, even a single individual. The emerald ash borer and spotted lanternfly arrived in the United States from small, localized infestations, likely on a piece of imported wood. In a few years, they spread to multiple states. The emerald ash borer is quickly working to make American ash trees–and their associated insects–extinct, though hopefully quick research by ecologists and biologists will slow it down enough for the natural ecosystem to recover. The spotted lanternfly feeds on several dozen plants, many commercially important natives and agricultural products, and in the absence of predators, it is voracious.

Insects, of course, are not the only rapid spreaders in an ecosystem, they just manage it well since they are mobile. However, many plants are self-fertilizing, meaning all they need is a single plant to spread. It might take awhile to build up critical mass, but when it does, the population explodes. Canada thistle (Cirsium arvense) is an example. Although it’s not known how many seeds were brought to the United States, they were all by accident, unlike common ornamentals or actual crops. Meanwhile it has spread across most of North America and is virtually impossible to control.

And the 200 million European starlings that currently inhabit North America? They originated as a few dozen released in New York in the late 1800s. Now they compete with native birds for food and habitat, forcing them out, replacing them, 200 million times over. Time and time again, we see the same story.

We could go on. As we saw in Preventing Pandemics in Nature, there is a host of problems with invasives, and a host of things needed to be done to prevent them. The point, however, is that in the months since that post, with hundreds of thousands dead, it is only more clear that it really takes all of us. Every member of a community matters in spreading or preventing a pandemic. Every member of a community matters in spreading invasives into the ecosystem.