Invasive species are an expensive problem in the United States. The most recent estimates show the devastation wrought by invasive species to crops, forests, wildlife, and homes costs the U.S. economy well over $100 billion annually.

According to the USDA’s National Invasive Species Information Center, an invasive species is an organism that is non-native to the ecosystem it currently resides in and causes — or is likely to cause — economic or environmental damage or negatively affect human health. An invasive species can be anything from an animal to a plant or a microbe.

To identify 30 of the most devastating invasive species, 24/7 Wall St. reviewed 113 invasive species from the USDA’s National Invasive Species Information Center. We selected the species that pose the most significant threats to wildlife, the environment, and the U.S. economy.

Click here to see 30 of the most devastating invasive species.

Invasive species are one of the leading causes for the decline and even extinction of some animal populations. For example, more than 400 of the 1,300 some species currently protected under the Endangered Species Act are imperiled because of displacement or predation by invasive species, or because of competition with it.

The rusty crayfish is a perfect example of a species that is displacing the native crayfish species in the Midwest. Rusty crayfish also pose a threat to other aquatic life in the area. They graze on and eliminate aquatic plants as well as eggs of native fish populations.

All invasive species take a toll on the U.S. economy, whether it’s by direct damage or through the necessary management or eradication of the pests. The microbe known as Exotic Newcastle Disease, a pathogen that kills poultry, costs the U.S. a whopping $236 million to eradicate between both major outbreaks in U.S. history.

One the biggest economic hits are caused by non-native insects and pathogens that attack agriculture and other plant wildlife. An estimated $40 billion is spent every year in the U.S. to repair the damage these invasive species inflict on crops and forests. And this number is projected to rise.

Unfortunately, humans are mostly to blame for introducing these foreign invaders to the nation’s ecosystem. Many of these invasive species come to the U.S. by means of imported goods, wood, or plants, among other means.

To identify the most devastating invasive species, 24/7 Wall St. reviewed the United States Department of Agriculture’s National Invasive Species Information Center. Invasive species are plants, animals, or other organisms such as microbes that are non-native to an ecosystem and cause economic or environmental damage or that are harmful to human health.