When Species Invade

The idea that the introduction of a single species can so devastatingly impact an ecosystem is as frightening as it is fascinating. These species are able to disrupt the local florae and faunae of a region over years, causing the local wildlife to either adapt to their presence... or die out. In the case of the emerald ash borer, the fate of numerous ash trees in Michigan and even London, apparently, is the unfortunate “die out” option.

Other species, over time, have been introduced into foreign regions, and their effects are far-reaching. One example of such a species is one variety of the fire ant. Solenopsis invicta, known also as red imported fire ant, is native to South America, though its tenure in that part of the world was apparently not permanent. At a seaport in Alabama, Cargo ships from Brazil in the 1930s unloaded goods that had apparently been infested with the species, allowing them to spread. Though this was the first example of the species introduced elsewhere, it is not the only one. The red invasive fire ant has also been found in Australia, Taiwan, Philippines, China–all from similar methods.

The effects of the ant have been far-reaching, and their negative impact on the environment are much to be despised. They are quite the household pests, damaging flower and vegetable gardens. They also damage agricultural assets, including animals and livestock, which result in an annual five billion dollars spent on treating this damage. They prey on pollinators, which ultimately harms the species these insect pollinate.

The northern snakehead is another example of such an invasive species, native to China, Korea, and Russia. This fish species, known also as Channa argus, is a valued species of food fish for its high retail value. Thus, it’s been theorized that its introduction to the United States was not an accident at all, but rather a deliberate attempt to generate an additional source of revenue. However, it can do quite the opposite. The northern snakehead is an adept predator, feeding on other species of fish. It has been known to significantly harm the populations of other species of fish, posing an economical threat to fisheries. The northern snakehead has also indirectly caused environmental harm. When the species was discovered in Crofton, Illinois, locals used a pesticide known as Rotenone to eliminate the fish. Not only did this kill numerous other fish, but other forms of wildlife drinking from the lake were also harmed by the pesticide as well.

One final species that has been introduced to a region only to do it harm is the cotton thistle. This species, though innocuous at first glance, has posed an agricultural threat to North America and Australia. It was introduced to Europe, North America, and Africa as a simple ornamental plant, though its rapid growth and spread was unprecedented and created a lasting issue. This dense weed’s presence can make foraging for agricultural animals difficult, and can also ruin whole crops. Wild animals like deer and elk, too, can have their food sources eliminated when this species grows thick and dense in particular regions.