Discover 9 Invasive Species in Pennsylvania

Written by Niccoy Walker
Updated: June 1, 2023
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Invasive species are any living organisms that are non-native to an environment and whose presence causes negative impacts on the ecosystem. Many non-native plants and animals, such as tomatoes and cows, are beneficial to their introduced environments. But others can take root and cause imbalance or even chaos. Humans spread invasive species, either purposely or accidentally. Due to our vast global transportation network, species native to one region can easily find their way to another. In fact, every state has a list of invasive species, including Pennsylvania. Discover nine invasive species in Pennsylvania and learn about what makes them harmful.

Invasive Mammals in Pennsylvania

Pennsylvania has only one invasive mammal species.

1. Wild Boar

Wild Boar, Forest, Animals In The Wild, Large, Domestic Pig, Feral Hog

Wild boars have been spotted in Pennsylvania, with the potential to become a significant threat.


The wild boar is an emerging threat in Pennsylvania. This is due to the fact that feral swine were introduced to the United States in the 1500s as a food source for early settlers. But the livestock frequently escaped and began populating in the wild. This species causes $2.5 billion worth of agricultural damage each year in the country as they consume native plants and introduce invasive seeds. Wild boars can also be aggressive and spread deadly diseases. They live in Pennsylvania and have the potential to become a significant threat.

Invasive Birds in Pennsylvania

Here are two established invasive bird species in Pennsylvania:

2. European Starling

A European starling singing in the wild

These starlings are excellent mimics and can imitate other birds, machinery, and even human speech.

©Soru Epotok/

A group of literary lovers intentionally released European starlings into Central Park in 1980. This group of people, who wanted America to have all the birds in Shakespeare’s writings, tried a couple of times before these birds finally took hold. As a result, the European starling is one of the most prolific birds in the country. While they are beautiful and interesting birds, they are invasive. They damage crops and berry bushes. Additionally, they are notorious bullies that drive out native species from their environment. 

3. House Sparrow

house sparrow

Sparrows were imported to the continent in the 1850s for nostalgic purposes.

©Rob Christiaans/

House sparrows, despite their common presence, are not native to the United States. They were imported to the continent in the 1850s for nostalgic purposes. And many believed they would also control insect populations. But these birds are notorious for killing native birds, such as bluebirds and purple martins, and taking over their nests.

Invasive Fish and Other Aquatic Animals in Pennsylvania

There are five established invasive aquatic animals in Pennsylvania. Here are two of the most common:

4. Asiatic Clam

Freshwater Golden Clam - Asian Clam - Invasive Animals

Asian clams are widespread in Pennsylvania, where you will find them in most rivers, lakes, and streams. They can infest water treatment systems.

©Jay Ondreicka/

Asian clams spread through human transport and water currents, settling in sandy lake bottoms. They quickly infest water treatment systems, passing through filters and settling in pipes. They were likely introduced as a food source and can be used as live bait, spreading into freshwater sources. These clams reproduce quickly and negatively affect infrastructure and human activities. Asiatic clams are widespread in Pennsylvania, where you will find them in most rivers, lakes, and streams.

5. Common Carp

man holding giant common carp

Common carp release phosphorus, which increases the production of algae. They are damaging to the shallow lakes and wetlands of Pennsylvania.

©Fabien Monteil/

In an effort to cultivate carp in the mid-1800s, the common carp quickly reproduced and spread through many waterways. Like many invasive species, these fish reproduce easily and can live in many environments. While they may be fun to fish, they are damaging to shallow lakes and wetlands. They muddy the waters by rooting through plants. And they release phosphorus, which increases the production of algae.

Invasive Insects in Pennsylvania

There are eight established invasive insect species in Pennsylvania. Check out these two commonly found in the state:

6. Japanese Beetle

Japanese beetle on a green leaf.

Japanese beetles destroy the flowers and fruits of over 300 plants. They were brought here in 1916 by hitching a ride on Japanese plant roots.


During the 1916 World’s Fair, Japanese nursery stock was brought to the United States. The beetles hitched a ride on the plant’s roots and spread from there. While this species has natural predators in Japan, they lack anything to keep it in check in America, allowing it to spread easily and become highly destructive. They feed on grass roots, which damage pastures and lawns. Japanese beetles also destroy the flowers and fruits of over 300 plants.

7. Spongy Moth

Spongy moth - Lymantria dispar dispar

Spongy moths were accidentally released by an amateur entomologist conducting breeding experiments.

©Jay Ondreicka/

An amateur entomologist from 1869 was conducting breeding experiments with a spongy moth native to Europe. The moth escaped captivity and began reproducing. Today it is an invasive species across many areas of the United States. They invaded the hardwood forests of North America, where they lack natural predators. And they can thrive on hundreds of trees and plants. But they damage trees by consuming most of their leaves. And without leaves, trees can’t photosynthesize and eventually die. 

Invasive Plants in Pennsylvania

Pennsylvania has over 140 invasive plants within its borders. Some are more harmful than others. Here are two invasive plants that are particularly troublesome and difficult to contain:

8. Tree of Heaven

tree of heaven

The tree of heaven is native to China. It was brought here in the 1700s. But it quickly spread and displaced many native plant species.


Trees of Heaven were brought to America from China in the late 1700s. They were meant to be used in horticulture as shade trees, but they quickly spread and became a problem species. These plants have a rapid growth rate and are resistant to many diseases. Not only do they displace native plant species, but they can also damage sewer systems and foundations due to their root systems. And they are difficult to control because they easily reproduce.

9. Giant Hogweed

giant hogweed in field

Giant hogweed exhibits prolific seed production and grows in dense clumps. Their growth blocks the sun and erodes the soil, killing native species.


Giant hogweed is native to the Caucasus Mountains near Russia and the Middle East. Their origins in America are somewhat unknown. People who enjoyed the plant’s look may have introduced it to the country. It’s also possible that spice importation is responsible for introducing it to the U.S. The plant has prolific seed production, meaning they easily reproduce. And they can grow thick and dense, which kills other native plants by blocking sunlight. These plants can also erode the soil. Giant hogweed is a poisonous plant that causes health risks to humans. Contact with the plant’s sap can result in painful lesions similar to burns. 

Summary of Invasive Species in Pennsylvania: Complete List

The following organisms are established invasive species in the state of Pennsylvania:

Type of Invasive OrganismOrganisms
MammalWild boar
BirdEuropean starling, house sparrow, mute swan
Fish and Other aquatic animalsAsiatic clam, common carp, sea lamprey, Alewife, Allegheny crayfish
InsectJapanese beetle, spongey moth, emerald ash borer, Balsam woolly adelgid, brown marmorated stinkbug, elongate hemlock scale, pine sawfly, spotted-wing drosophila
Plant (highest priority)Tree of heaven, giant hogweed, mile-a-minute, purple loosestrife, Japanese knotweed, garlic mustard, palmer amaranth, porcelain berry, Japanese angelica tree, Japanese barberry, European barberry, Oriental bittersweet, poison hemlock, giant knotweed, hydrilla, Japanese stiltgrass, common reed, kudzu, European water chestnut
There are hundreds of established, emerging, and possibly invasive species in Pennsylvania.

The photo featured at the top of this post is © Martin Pelanek/

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About the Author

Niccoy is a professional writer for A-Z Animals and her primary focus is on birds, travel, and interesting facts of all kinds. Niccoy has been writing and researching about travel, nature, wildlife, and business for several years and holds a business degree from Florida State College. A resident of Florida, Niccoy enjoys hiking, cooking, reading, and spending time at the beach.

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