When a foreign species is introduced to an ecosystem, it can upset a balance that has been in the works for a long time. Many native species have been driven near to extinction by these invaders taking over. Sometimes it takes a long time for people to realize that an alien species is having an effect on native wildlife and by then the species is so well established that getting rid of it is impossible.
There are hundreds of invasive species that have been introduced into the United States over time. These include fire ants, the Asian long-horned beetle, Africanized honeybees, ladybugs, gypsy moths, starlings, and many more. It is a costly and difficult problem to get rid of invasive species once they get into an ecosystem.
In 1884, at an ornamental plant exposition in New Orleans, American gardeners got their first glimpse of the beautiful purple flowers of the water hyacinth, a native plant of South America. A Florida gardener took a cutting back home and dropped it into his garden pond. Within weeks the water hyacinth had taken over the pond. To get rid of it, he pitched it into the St. Johns River. This began a century-long battle to get this aggressive plant back under control.
The water hyacinth grows at an amazing rate, spreading floating mats of vegetation so thick that it blocks light to the underwater environment, killing lakes and ponds. People tried to chop it up and then burn it, only to find that each small piece started a new plant! They brought in manatees to graze on the plants but they grew so fast up rivers and canals that within a few years they had spread to several southern states. Finally in the 1960s, people started spraying the water hyacinth with herbicides. Herbicide, a strong, toxic substance that poisons plants, did kill the water hyacinth, but it also meant that the poison got into rivers and lakes.
A Speedy Weed
Kudzu, an invasive vine from Japan, was imported because it grew fast and was a good ground cover that helped stop erosion. Soon it grew over whole forests blocking sunlight until all the trees died. It grew over barns, houses, fences, and power lines. Controlling it has not been easy. The most effective control found so far is grazing goats!
Some invasive species have a worse effect than others. Sailors brought dogs and pigs to the small, isolated island of Maurituis, off the coast of Africa, leading to the downfall of the flightless dodo, whose ground nests were plundered by these non-native predators. Weasels and cats brought to New Zealand also devastated the ground-nesting and flightless birds living there. Goats introduced to the Galapagos Islands have stripped vegetation clean. Many countries now have rules about bringing any plants or animals across their borders. They have learned some hard and expensive lessons from past introductions.