May 29, 2023

Invasive species are wreaking havoc on our ecosystems: Here’s how

Remember that fish you decided to release when it got too big for its tank? What about that cute tropical plant you have in your yard? Or those seeds you picked off your shoes when you got home from a hike? These are some examples how invasive species can move around and cause mayhem to a distant ecosystems.

Invasive species—that’s any species of alien and non-native plant or animal unnaturally introduced into a habitat—are one one of the biggest drivers of biodiversity loss around the world. 

Mammals, amphibians, insects, and plants all have the capability of becoming invasive if they manage to spread in their new environment, wreaking havoc on the local ecosystem and native species that live there. Invasive species are a big problem, so what are some factors contributing to the spread of alien species and what can we do about it?

Understanding invasive species

According to the National Invasive Species Information Center, a species is considered invasive when it is “non-native (or alien) to the ecosystem under consideration, and whose introduction causes or is likely to cause economic or environmental harm or harm to human health.”

Invasive species establish themselves in an ecosystem and rapidly multiply, outcompeting the native wildlife for resources and becoming dominant in the area. The effect of this invasion is obviously having a big effect on global biodiversity.

In the past, mother nature’s vast oceans, acres of land, and mountain ranges presented formidable barriers for all but the strongest species. Ecosystems evolved in relative isolation over millions of years. It wasn’t until the first human migration that we saw the unintentional introduction of alien species. As we explored the globe, our plants and animals came with us—but the magnitude and frequency of those early introductions were nothing compared to today. 

A black and white image of a ship

Invasive species not only disrupt natural ecological processes, but lead to biodiversity loss and even the extinction of other species. They can also cause substantial economic losses which directly impact us. Industries such as agriculture, fishing, and forestry are all affected by the spread of alien species and disease.

What are some examples of invasive species?

Invasive species are absolutely everywhere—many of which you may have heard of, or even seen, and not known are  invasive! So what are some other examples of invasive species?


Known for their poisonous spikes and striped scales, Lionfish are an incredibly invasive species to the southern coastline of the United States. In the last decade, their population has skyrocketed, and the current theory is that the first Lionfish in the area were fish tank escapees, as they’re a popular addition to tropical aquariums. While they might look pretty cool, these guys are incredibly disruptive to Florida’s coastline.

Adult lionfish are predominantly small fish-eaters and have no real predators outside their native environment (the South Pacific and Indian Ocean). The result is that a single Lionfish parked in a reef can deter native fish from the region by up to 79%. As their population booms, the more stress is put on reefs that are already struggling due to climate change and overfishing. 

Bark beetles

In Germany’s Harz forest, bark beetles have taken over. Over the decades the region's diverse forest has been replaced by fast-growing spruce trees, creating a monoculture that is less able to withstand the devastating effects of climate change.

Spruce trees are usually able to fend off the beetle through the secretion of resin, but lack of water caused by years of drought have meant the spruce forests are unable to maintain their natural defenses. This has led to the bark beetle killing off more than 20,000 hectares of forest in the Harz region alone since 2018. 

Wild boar

Wild boar are a menace to forests all over the United States. You might remember that hilarious 2019 viral Twitter moment, where one user expressed fears over “30-50 feral hogs” invading his yard—well that might not be too far off from the truth. 

Wild boar (also known as feral swine) devour crops and destroy native vegetation. They were originally introduced to the US in the 1500s as a source of food by  early European settlers. But they escaped their enclosures and livestock wasn’t managed very well, so they spread in the wild. Their presence is damaging to agriculture, forest ecosystems, and human health and safety. 

Wild sugarcane

Usually found growing in the tropics of India, Asia and New Guinea, wild sugarcane has become a serious invader of cultivated land throughout Central America, which often results in land abandonment—when an area is intentionally left. Wild sugarcane was originally introduced for use in sugarcane breeding programs, but its spread has reduced the productivity of a number of crop species including wheat and tea. This is because the wild sugarcane needs less water and lower nutrient requirements to grow so it can easily displace other plant species. Wild sugarcane monocultures also encourage the spread of pests and diseases, which can be spread to other crops and native plants.

Sugarcane against a blue background

Domestic cats

We love our pets, but unfortunately they can be a huge problem for our wildlife. For an estimated 10,000 years humans have domesticated cats (and many other animals) for companionship, but the problem is that our love of our furry friends has turned them into an incredibly damaging invasive species. 

Cats in particular are predators—even domesticated, well-fed felines. One report estimated that free-ranging domestic cats kill 1.3-4.0 billion birds and 6.3-22.3 billion mammals every year. Domestic cats have also been implicated in the global extinction of at least 63 species; 40 birds, 21 mammals, two reptiles; and currently endanger a further 367 species which are at risk of extinction.

European starling

European starlings are first recorded to have been released in New York’s central park in 1890—and almost 140 years later, these tiny birds are a huge problem for several reasons. Today they inhabit most of the world’s continents, spreading disease to both livestock and humans, which has been directly linked to healthcare costs of up to $800 million. Starlings also compete aggressively against other bird species for nesting sites and are a nuisance for farmers.

What causes invasive species to spread?

So what has caused all these plants and animals to end up in brand new locations? What has driven the spread of alien species? Well you have probably guessed it by now—it’s us, or at least, we are the biggest contributor. 

Both the intentional and unintentional spread of plants, animals and organisms around the world through human migration has helped invasive species move from one side of the planet to another. In fact, careless “accidents” now account for the majority of successful invasions.  

Houses built up along a river system

Other human activity such as infrastructure development has forced species out of their homes, or made them adapt to brand new ones, and agricultural practices regularly introduce non-native plants and animals for cultivation and livestock.

Another big driver of alien species is climate change (which is also thanks to us). As temperatures rise, certain species are forced to expand their grazing, habitats and routines to find food and shelter. This puts them into direct competition for resources, where they need to outcompete the native species in order to survive.

Over the course of human history, no period of time has seen quite so much damage to global biodiversity than over the last century—and invasive species are a huge driver of this loss.

Read more: Why we are focussing on the biodiversity crisis

What can we do to prevent invasive species?

While ecosystems can recover and build up protection against invasive species, they need time, and in many cases, a helping hand. Humans caused this problem, so it’s up to us to give mother nature a boost!

Integrated Pest Management

One way conservationists are making a difference is by adopting an Integrated Pest Management (IPM) approach. IPM focuses on long-term solutions to reduce the use of pesticides and also managing pest damage by using the most economical means. The goal is to prioritize ecological balance and minimize reliance on pesticides, promoting sustainability. 

Some countries—famously Australia and New Zealand—have very strict border controls when it comes to transporting animals and plants from abroad. Increasing or introducing biosecurity measures prevent the accidental spread of invasive species through contaminated cargo, packaging materials, or travelers' belongings.

Habitat Restoration

Habitat restoration goes a long way in protecting ecosystems from invasive species. Many countries around the world have pledged ambitious restoration goals to help restore and protect the world’s ecosystems. The United Nations has even declared that the 2021–2030 period will be the decade of ecosystem restoration, with the goal of empowering a global movement, investing in research and finance restoration on the ground. 

A diver inspecting some coral

Planet Wild

If these promises are kept, it is good news for the planet in the long-run, but in the meantime it’s also vital to support the conservationists, activists, ecologists and nature lovers’ who are actively tackling biodiversity loss as we speak—such as the work done by Planet Wild and our inspiring mission partners!

Planet Wild is a community of passionate individuals dedicated to tackling the biodiversity crisis—and we need people like you that deeply care about nature to help our planet bounce back. Invasive species are causing a huge amount of damage to global biodiversity, but with your help  we can come together to help become part of the solution. No nonsense, no empty promises, just direct action to fight one of the biggest issues affecting our planet right now.

About Planet Wild

Planet Wild is committed to rewilding the planet through monthly missions that work directly with grassroots organizations dedicated to fighting the biodiversity crisis. When you become a Planet Wild member, your contribution will directly fund innovative and exciting projects all over the world, so you can make a difference from home. Learn more about what we do here.

A bison wearing sunglasses

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