Native, Endemic, and Invasive Species

A native species occurs naturally in an area, an endemic species is found only in one specific region and nowhere else, and an invasive species is a non-native species that spreads and causes harm. In brief: the kangaroo is native to Australia, the Hawaiian honeycreepers are endemic to Hawaii, and the cane toad, introduced to Australia in 1935, is an invasive species there. A species can be native in one place and invasive in another.

These terms matter because moving species around the world is one of the main causes of biodiversity loss. This guide defines each term, explains how species become invasive, compares the categories, works through a classification example and corrects common mistakes.

What is a native species?

A native species, or indigenous species, lives in an area as a result of natural processes, without being introduced by people. It has evolved with other species in the ecosystem, and its predators, parasites and food sources are part of the same community.

“Native” always refers to a place. The red fox is native in Europe and North America, but it is not native in Australia. Scientists often use a reference date to decide what is native, since species arrive and disappear naturally over long periods of time.

What is an endemic species?

An endemic species is native to a particular area and found nowhere else in the world. The area can be small, like one island or lake, or large, like a continent. All endemic species are native where they occur, but not all native species are endemic.

• Lemurs are endemic to Madagascar (together with nearby small islands).
• Galápagos giant tortoises are endemic to the Galápagos Islands.
• Baikal seals live only in Lake Baikal in Russia.
• Kiwi birds are endemic to New Zealand.

Endemic species are especially vulnerable. They often have small populations and a limited range, so one event, such as a new predator or habitat loss, can drive them to extinction. Islands have many endemic species because isolation allows species to evolve separately.

What is an invasive species?

An invasive species is a species introduced outside its natural range that spreads and causes ecological, economic or health damage. Not every non-native species is invasive. Wheat, potatoes and honeybees are non-native in many places but do not spread harmfully into wild areas. The terms “non-native”, “alien” and “introduced” describe origin only, and “invasive” describes impact.

Well-known invasive species include the cane toad in Australia, the zebra mussel in North American lakes, the Burmese python in Florida, kudzu vine in the southeastern United States, and the European rabbit in Australia.

How do species become invasive?

Most invasions are caused by humans, either deliberately or by accident. Species are transported by ships, aircraft and trade.

• Deliberate introduction: for farming, hunting, pets, gardens or pest control. Cane toads were released to control beetles that damaged sugar cane.
• Accidental transport: in ballast water of ships, in soil on plants, or in packing materials. Zebra mussels reached the Great Lakes this way.
• Release of pets and aquarium animals: Burmese pythons in Florida are thought to have established from released pets.

A newcomer is more likely to succeed when it has no natural enemies in the new place, reproduces quickly, tolerates a range of conditions and the ecosystem has already been disturbed. Invaders can outcompete natives, eat them, spread disease, change the habitat or hybridize with native species. Island species are particularly at risk, because they often have no defenses against new predators.

Native, endemic and invasive species compared

Worked example: classifying species on an island

A survey of an imaginary oceanic island lists the following species. Classify each one using the questions “Did it arrive naturally?”, “Is it found elsewhere?” and “Is it spreading and causing harm?”

1. Island finch: It arrived naturally long ago, evolved into a distinct species and is found only on this island. It is endemic and therefore also native.
2. Seabird that nests on cliffs: It arrived naturally and also breeds on other islands. It is native but not endemic.
3. Goats released by sailors: They were introduced by people. They eat island plants and cause erosion. They are invasive.
4. Vegetable crops in gardens: They were introduced by people but do not spread into wild areas. They are non-native but not invasive.
5. Rats from ships: They were introduced by accident, eat the eggs of ground-nesting birds and spread widely. They are invasive.

The classification depends on place and impact and not on the species name. The rat is native in parts of Asia, but invasive on this island.

What does history show?

Humans have moved species for thousands of years, but the pace increased with European exploration and global trade after the fifteenth century. Charles Elton’s 1958 book The Ecology of Invasions by Animals and Plants helped to establish invasion biology as a field of study.

Many endemic island birds have gone extinct after the arrival of rats, cats and other mammals. The flightless dodo of Mauritius is a famous example, although its extinction in the seventeenth century probably had several causes, including hunting and introduced animals.

How are invasive species managed?

Prevention is cheaper than removal. Governments inspect cargo, regulate ballast water and restrict the import of risky species. Once a species has established, options include early detection and rapid removal, trapping or hunting, herbicides, and in some cases biological control with a natural enemy from the original range.

Biological control carries risk. The cane toad itself was introduced as a control agent and became a pest. Programs today require extensive testing before release. Some island projects have successfully removed rats and goats, which allowed native plants and birds to recover.

Which mistakes are common?

Mistake 1: Using native and endemic as synonyms

Endemic is a stricter term. A native species may live in many countries, but an endemic species lives in only one defined area.

Mistake 2: Calling every introduced species invasive

Only those that spread and cause harm are invasive. Many introduced crops and garden plants do not.

Mistake 3: Assuming a species is invasive everywhere

Status depends on location. Kudzu is native in Asia, where it is controlled by natural enemies, and invasive in the southeastern United States.

Mistake 4: Believing that invaders always win because they are stronger

Often the main reason is that they have escaped their natural predators and diseases, or that native species lack defenses against them.