One of the most devastating events that can occur within an ecosystem is the introduction of a non-native species that has no natural predators. Without the natural boundaries of their native habitat, these species can overtake their new home in an extraordinarily short period of time.

The results can range from costly to catastrophic, and may require drastic measures to return the ecosystem to normal. Invasive species can endanger and even decimate resident species, and can be a major threat to the biodiversity of any habitat.

Eradicating a foreign species can be incredibly difficult, and oftentimes the best defense is prevention.

Check out some of the world’s worst invasive species, and find out what’s being done to stop them:

7. European Red Fox

Jim Stutzman/USFWS

Australia is experiencing one of the worst mammalian extinction events it has ever seen, and that’s due largely to an invasion of European red foxes. While they are critical to the balance of the food chain in their native habitat, they are a disaster in areas where they have no predators. They were originally brought to Australia for recreational hunting, these crafty critters have thrived and now inhabit much of the Australian mainland.

Conservationists have had some success saving Australian species by relocating them to islands of the mainland’s coast, where (hopefully) no red foxes will be introduced.

6. Kudzu

In the southern United States, one aggressive vine has all-but taken over. All seventeen Kudzu species originate in Asia, and they have been traditionally used as an herbal medicine. In the nineteenth century, it was introduced to the U.S. as an ornamental vine. In the years since, in its new sprawling habitat, it has become an eyesore.

In ideal conditions, the vine can grow up to one foot (30 cm) in all directions in one day, and can grow over sixty feet in one season. It can climb just about anything, and will repress or even overtake native plant life — meaning it’s everywhere, and it’s having a horrible effect on the environment.

Jan Carroll/USFWS

Kudzu is dense, and it grows fast. In order to stop it, you must remove it at the root — but act quickly, because before long it can cover whole habitats. However, one study found that it may be useful for producing biofuel — perhaps one day soon it will prove valuable… under closely controlled circumstances.

5. Asian carp

Jason Jenkins via The New York Invasive Species Clearinghouse

Although they are both typically called “Asian carp,” there are in fact two carp species, each native to Asia, that have taken over the Mississippi and Illinois river systems, and are attempting to make their way into the Great Lakes. They are filter-feeders, which means they are integral members of their natural habitat, but often out-eat the native species in their new ecosystems.

They were first introduced to the United States to complement the fresh-water fish market, but ended up overtaking many formerly biodiverse habitats. The U.S. government is currently taking action to prevent Asian carp species from spreading to the Great Lakes.

4. Red-Vented Bulbul

The red-vented bulbul, originally from Pakistan and southwest China, has spread through a number of Pacific islands, destroying crops and flowers, and aggressively chasing off native species. They are fairly small, but surprisingly noisy — and even more obnoxiously, they spread the seeds of invasive plants. They appear to have been introduced as captive birds, but somehow made their way into the wild.

KW Bridges via Global Invasive Species Database

Many affected countries have criminalized, or require a permit for, the import of these birds — in hopes that one day their population will be under control.

3. Asian Long-Horned Beetle

James Applaeby/USFWS

This distinct insect, called the Asian long-horned beetle, has a devastating impact on the ecosystems it infects. As larvae, these beetles can consume entire trees by eating them from the outside-in. They originate in China, Korea, and Japan — where there too the beetles are considered a pest — but as of at least 1996 have learned to thrive in the U.S., particularly in the northeast and California.

Beetle infestations can be minimized by isolating populations. One way you can help is to only use local firewood. Long-horned beetles are slow to spread, but can travel great distances by lurking in transported kindle wood.

2. Brown Tree Snake

The first brown tree snake was spotted in Guam in the 1950s, though speculation suggests that the species initially found its way to the island as a stowaway aboard a U.S. military vessel during World War II.

These sly snakes originate from Indonesia, New Guinea, and Australia — where they are important members of the ecosystem — but they have an excess of fauna to feast on in their new island home. The overwhelming population of these snakes has caused the disappearance of many of Guam’s indigenous species, including nearly all of its forest birds.

Gordon H. Rodda/USFWS

While there is infrastructure to prevent the spread of brown tree snakes to other ecosystems, at twelve- to fifteen-thousand snakes per square mile, they may be too widespread to eradicate without resorting to extreme solutions.

1. European Rabbit

Via Victorian Government

European rabbits, which amazingly are the common ancestor for all modern rabbits, are perhaps the most widespread invasive species on the planet. They were once confined to parts of Spain and France, but now live on every continent except Antarctica and Asia.

They also thrive in Australia, where they seem to exacerbate the red fox problem by providing them something to eat — although their numbers don’t appear to be dwindling in that region any time soon. The best defense against invading rabbits seems to be to minimize the damage they do — which, if you encounter enough of them, can be a lot.