African killer bees almost wiped out the European honeybee population in the U.S. Whether accidentally (killer bees) or deliberately (European bees), introducing species to a new area can have drastic consequences. This lesson explains why.
A Look at Introduced Species
Introduced species, also called alien species, are those that have been moved by humans to an environment where they didn’t occur naturally.
The term can refer to animals, plants, fungi, or microorganisms that are non-native to an area. Species introduction can be accidental or intentional.Many accidental introductions of species involve boats, which travel between continents. For example, the black rat, which is native to South Asia, has been hitching rides in ship cellars since the first century, spreading initially to Europe and subsequently throughout the rest of the world during the Age of Discovery. Species have also been accidentally introduced through water discharged by cruise ships and tankers, stuck to travelers’ clothes and shoes, or in imported wood and food.Sometimes species that don’t occur naturally in a habitat are deliberately introduced by humans for conservation efforts, population control of native species, or for boosting agriculture and fisheries. For example, although the U.
S. is today the largest producer of corn in the world, and corn is grown in every continent, corn didn’t used to exist anywhere but the Mexican mountains until Indians and explorers started taking it to other places. Sometimes species are introduced seemingly on a whim for human enjoyment, like the water hyacinth, which is originally from South America and has been used to beautify ponds in North America, Africa, Asia, Australia, and New Zealand.
Effects of Species Introduction
Species introduction can have drastic social, economic, and environmental effects.
Some of these are positive but more often they are negative, such as the disruption of the natural balance of ecosystems. However, let’s take a look at some of the positive and negative impacts.
One positive impact is increased food production.
Americans would have a much more limited menu if it weren’t for the introduction of livestock, such as cows, chickens, and pigs, and food products, such as tomatoes, potatoes, pears, and wheat from other parts of the world. Honeybees, too, were introduced from Europe and Africa.Other than increased food production for the area, species introduction can yield economic benefits from exports and employment opportunities. Chile, for example, is the second greatest producer of salmon in the world and salmon fisheries there employ tens of thousands. However, salmon didn’t exist there naturally; it was introduced from Europe, Norway, and Japan. Introduced trees may provide a habitat for many native species of birds, small mammals and invertebrates, and shelter for larger animals.
Among the negative impacts of species introduction are mixing of genes, which leads to diluting of native characteristics and habitat modification. The European rabbit was brought to Australia by a nostalgic Englishman who wanted to be reminded of home and make bunny stew occasionally. It led to huge environmental problems when the rabbit population got out of control due to overgrazing and consequent soil erosion.New species also compete with and prey on native species.
The Burmese python from Southeast Asia was introduced to the Everglades, and there are now 30,000 of them, threatening species of amphibians, reptiles, birds, and small mammals living in the wetlands.Pathogen introduction is also a big problem resulting from alien species. The Asian tiger mosquito, thought to have been introduced all over the world by the tire industry, has carried with it dangerous viruses, like the West Nile, and blight-infected potatoes from North America caused the infamous Great Irish Famine in which over a million people died of starvation.
Introduced species are those that have been moved by humans to an environment where they didn’t occur naturally. Species have been introduced accidentally through travel or by humans for conservation efforts, population control, or boosting of agriculture. Introducing a species can have both positive and negative impacts. The positive impacts include increased food production, economic impacts, and species habitat.
The negative impacts include mixing of genes, habitat modifications, competition with native species, and pathogen introduction.
|Key Words & Phrases||Explanations|
|Introduced species||alien species; those that have been moved by humans to an environment in which they didn’t occur naturally|
|Purposeful introduction||can sometimes lead to an increase in food production; it can have economic benefits|
|Accidental introduction||through water or travel; by humans for conservation efforts, population control, or the boosting of agriculture; can lead to the disruption of the natural balance of ecosystems|
|Positives||increased crop yields; the beautifying of areas|
|Negatives||destruction of native species; growth of insects that carry harmful pathogens|
A few benefits of successfully completing this lesson include your ability to:
- Verbalize the definition of introduced species
- Acknowledge the effects of introduced species
- Recognize the positive aspects of certain introduced species
- Discuss the more common negative affects of accidental species introduction