Bullying is not just a problem in school yards; it’s also a problem in nature! Invasive species are plants and animals that are brought to a new habitat and bully the native species to the point where many can’t survive. They are usually hardier, more demanding and reproduce much faster. Since they are new to a habitat, they don’t have any natural predators. That means there aren’t any species to stop them from taking over an area.
In this top ten, we take a look at ten invasive species from the Global Species Database’s 100 most invasive species.
Asian carp refers to several carp species native to Asia including grass carp, silver carp, bighead carp, black carp, common carp and others.
Native To: Eastern Russia and China
Introduced To: North America and Europe
How did they get there? Asian carp were brought over as food, part of the pet trade and for sport fishing.
Why are they a problem? Asian carp are large, have big appetites and reproduce quickly. They take food and habitat away from native fish and have been known to prey on the eggs of other fish species. When carp eat, they stir up sediments and organisms from the lake and river beds changing a clear lake into murky one and changing the type of species that can survive there.
Zebra Mussel (Dreissena polymorpha)
Native To: Black, Caspian, Aral and Azov seas
Introduced To: Russia, Europe and North America
How did they get there? Zebra mussels were brought over in ballast water (water carried by ships to help them stay balanced while at sea). They also attach to the outsides of boats or get carried around by floating vegetation.
Why are they a problem? Zebra mussels are one of the most aggressive freshwater invaders because their population numbers grow so quickly. Massive populations of zebra mussels filtering water can severely impact native plankton, which reduces food for fish. These plankton-eating fish then have to find a new source of food or move to a new lake in order to survive. Unfortunately, that isn’t an option for many species. Zebra mussels also leave very little for native mussels to filter, causing them to starve as well.
Cane Toad (Rhinella marina)
Native To: Northern South America, Central America and Mexico
Introduced To: Many countries with warm climates, like Australia
How did they get there? Cane toads were brought over as a way to control crop pests.
Why are they a problem? Cane toads have an amazing defense mechanism; they produce toxic ooze. While predators in their native habitat are immune to this toxic ooze, predators in other areas are not. Many animals that attempt to eat a cane toad die instead. With nothing around to keep their numbers in check, populations of cane toads in non-native habitats have exploded and they are taking their toll on native animal and plant species.
European Starling (Sturnus vulgaris)
Native To: Europe, Asia and Northern Africa
Introduced To: North America, Southern Africa, Australia and New Zealand
How did they get there? European starlings were brought over as a way to control pests, as pets and by a group of people trying to introduce all the birds mentioned in the works of Shakespeare into North America.
Why are they a problem? European starlings form huge flocks, many times with more than 3,000 birds. When a flock this size feeds on fruit and grains, it can cause serious damage to a farm. These birds are also aggressive, fighting with native species over food and territory. They will even take over other birds’ nests, leaving native birds without a place to lay their eggs or raise their young.
The European/Common Rabbit (Oryctolagus cuniculus)
Native To: Southern Europe and North Africa.
Introduced To: All continents except Antarctica and Asia
How did they get there? Rabbits were brought over as a source of food and as a way to remind people of the country they came from during colonial times.
Why are they a problem? Rabbits reproduce very quickly. In one year, one female can have between 18-30 babies! Their population numbers grow so large and they eat so much that they have pushed native plant species to the brink in certain areas. They also compete for food and shelter with native animals, causing a decline in the number of native species in the area. They have caused soil erosion from burrowing and overgrazing, leading many species who depend on that environment to suffer.
Kudzu (Pueraria montana var. lobata)
Native To: Eastern Asia and some Pacific Islands
Introduced To: North America and Europe
How did they get there? Kudzu has been sold as a plant for gardens and for eating.
Why are they a problem? Kudzu is an aggressive vine, capable of growing up to 26 cm (a little less than 1 ft.) a day. Since it expands so quickly, it smothers other plants, stopping them from having access to sunlight. Kudzu can even kill mature trees. This prevents native plants from growing and changes the ecosystem structure. What’s even worse is that once kudzu starts growing, it is extremely difficult to get rid of.
Asian long-horned beetle (Anoplophora glabripennis)
Native To: China, Japan, Korea
Introduced To: North America and Europe
How did they get there? Asian longhorn beetles were brought over in shipments of wooden packaging materials and trees
Why are they a problem? Asian longhorn beetles aren’t picky about where they lay their eggs; almost any deciduous tree will work. As larvae, they eat the soft sappy bark, which makes it hard for nutrients to reach other parts of the tree. As they grow, the larvae burrow into the middle of the tree leaving large tunnels as they move, making the tree physically weaker. As adults, Asian longhorn beetles emerge from the tree, breaking through the bark leaving large holes. Many trees don’t survive once they are infested with Asian longhorn beetles.
Small Indian mongoose (Herpestes auropunctatus)
Native To: Southeast Asia
Introduced To: Asia, Central America, South America
How did they get there? Small Indian mongooses were brought over for pest control for rats and snakes.
Why are they a problem? Small Indian mongooses are aggressive predators. They are blamed for the decline of bar-winged rail (extinct), Jamaica petrel (critically endangered and possibly extinct), hawksbill turtles (critically endangered), pink pigeon (endangered), Amami rabbit (endangered) and many other birds, reptiles and mammals. Mongooses also carry rabies and other human diseases.
Northern Pacific seastar (Asterias amurensis)
Native To: Waters around China, Japan, Korea
Introduced To: Australia
How did they get there? Northern Pacific seastars were brought over in ballast water (water carried by ships to help them stay balanced while at sea). They can also be attached to boats and fishing equipment or be transported along with live fish.
Why are they a problem? Northern Pacific seastars are aggressive eaters. They will eat almost anything they can find. To make matters worse, Northern Pacific seastars reproduce very quickly. In one area where they were introduced, their population reached an estimated 12 million seastars in just two years. They have been blamed for the decline of the critically endangered spotted handfish.
Water hyacinth (Eichhornia crassipes)
Native To: The Amazon basin and waterways of Western Brazil, South America
Introduced To: Africa, Asia, North America, Australia and New Zealand
How did they get there? Water hyacinth was brought over as a decorative plant, for animal food, as part of the aquarium trade, by getting stuck on boats and through the spreading of seeds
Why are they a problem? Water hyacinth is a fast growing water plant. They are known as one of the world’s worst weed, found in more than 50 countries. In the right conditions, a small patch of water hyacinth can double in size in just 6 days! These plants are thick and dense, clogging up rivers and making in nearly impossible for animal life to move through them. They block sunlight and oxygen from getting to other plants below the water, causing the ecosystem to change dramatically.
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