9 Facts Everybody Ought to Know About Invasive Species [2023]

Published on

September 18, 2023

Written by

Sally Esposito

Photo credit

Sally Esposito

What are invasive species and how do they impact island wildlife and ecosystems?

How much do you know about the science of invasive species on islands? If you’re like most people, you’ve probably heard some stories about how animals or plants that are not native to an island can cause problems for the local ecosystem. But do you know why they’re so disruptive, and what we can do to stop their worst effects? Test your knowledge with these nine key facts, backed up by decades of scientific evidence!

Island Conservation Invasive Species Laysan Albatross Eggs Nest
Many seabirds lay their eggs in the open, such as this Laysan Albatross, leaving them extremely vulnerable to the impacts of invasive species.
Photography: Olivier Langrand / Island Conservation

Test your knowledge. How many invasive species facts do you already know? 

1. According to the National Invasive Species Center, an invasive species has the following two characteristics:
  • Non-native (or alien) to the ecosystem under consideration, and
  • Causes (or is likely to cause) harm to human health, the economy, or the environment

Differentiating between invasive species and non-native species is important–and confusion between the terms has caused problems in the past!

2. Where have the majority of all recorded extinctions occurred?

On islands–with invasive species as the primary causes!

3. Invasive mammals threaten island biodiversity, threatening native species via:

predation, competition for resources, and habitat destruction. Scientists studied these threats on Gough Island in 2004.

 

4. Estimated to occur on 80% of the world’s archipelagos, which kind of mammal is considered to be among the world’s 100 worst invasive alien animals?

Rodents. Rats and mice, in particular, are extremely pervasive, with the house mouse boasting a range more extensive than any mammal besides humans!

5. Can invasive rodents spread diseases to humans?

Yes! Humans are at risk of rat bite fever, salmonella poisoning, monkeypox, and a variety of other diseases.

6. Do humans spread invasive species to islands?

Yes, both intentionally and unintentionally. For example, rats are prolific stowaways on ships, and other species like mongoose and goats are introduced on purpose.

7. How fast do invasive rodents reproduce?

Really fast–in some cases reproducing more than five times a year! A 2017 study found that a single pair of rats could theoretically produce half a billion descendants in just three years. Once introduced, they can swiftly take over the native habitats they invade.

8. The most cost-effective tool to prevent extinctions, restore ecosystems, and protect native species is:

Removing invasive species. It’s unequivocal–and re-introducing native plants and animals, a process called rewilding, is most successful when the invasive species have been removed!

9. From how many islands have invasive rodents been successfully removed?

More than 600! The success rates of these projects is huge, and they have a long history–more than 2,000 eradication projects on over 1,200 islands stretching back to the late 1800s!

A problem with a solution

Every year, we learn more and more about the threats invasive species pose to island ecosystems. A recent report from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, in fact, shows that the human costs might be higher than we estimated, stopping island communities from pursuing sustainable development and climate resilience.

While many of these invasive species facts might seem bleak, others point to restoration and rewilding as effective methods to combat their worst effects. At Island Conservation, we are full of success stories about what happens when we take action to stop invasive species and restore healthy ecosystems. Join us to restore islands for people and nature!

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