How to Stop Invasive Species

Preventing Invasive Species

Fly-fishers need to properly clean their equipment, including scrubbing their wading boots, to prevent the spread of invasives. George Ostertag/SuperStock/Getty

By guest contributor Deborah Seiler

Invasive species are widely considered one of the most destructive environmental issues of our time, dramatically altering native habitats. Once an invasive species has established itself in a new environment, removing it through control measures is often difficult or impossible without causing further environmental damage. As a result, preventing the spread of invasive species is of paramount importance.

By definition, invasive species are spread by human activity rather than natural dispersal. This rapid spread means that environments change too quickly for most native species to adapt to the new predator or competitor through evolutionary changes. It also means that the spread of new invasive species can easily be prevented – and the damage avoided – by following a few guidelines to remove attached plants and animals from personal gear before you travel.

Invasive Species Prevention: Freshwater

Freshwater habitats are relatively scarce: just 2.5 percent of the world’s water supply is fresh. These lakes, rivers, streams and wetlands provide habitat for important species as well as water for human consumption. Invasive species can decrease water quality and inhibit access in addition to harming native species. For example, invasive zebra mussels increase blooms of toxic blue-green algae, clog water intake pipes, and crowd out native mussel species.

Any person who travels between different bodies of water in a short period of time can be a vector for invasive species. This includes recreational anglers, boaters, aquatic researchers, construction crews and SCUBA divers, to name a few. The prevention steps below are effective to stop the spread of most aquatic invasive species. Additionally, the federal Lacey Act and many state laws prohibit the transport of invasive species, and may require people using waterbodies for recreation or industry to perform some of the specific steps listed below.

To stop the spread of invasive species, complete all these steps before you leave a water body. If you are using equipment that was not previously checked, complete these steps before entering a new waterbody as well.

Inspect and Remove any attached plants, animals and mud from your boats, waders, gear and other equipment that has been in the water. For boaters, this includes checking your boat propellers and trailers for attached weeds. For wading anglers, this includes inspecting and scrubbing the tread of your waders to remove mud and the small invasive species – such as New Zealand mudsnails – that are likely to cling to the bottom. Mud can also contain the seeds of invasive plants.

Drain water from bilges, livewells, coolers, boat motors and all equipment. This prevention step is important for two reasons. First, many states prohibit the transport of live fish, and may advise putting them on ice to stay fresh. Once your daily catch is out of water, it is not considered live and can be safely transported home. Second, some invasive species are too small to see. Two of the worst aquatic invasive species in the U.S., zebra and quagga mussels, are frequently spread in water on boats during their larval stage when they are too small to see.

Follow bait laws. Bait regulations vary by state, and it is best to purchase live bait from a licensed dealer where you plan to use it. Learn to recognize juvenile Asian carp – a disastrous invasive species in the Midwest – since it looks similar to some common bait minnow species.

Never dump bait, plants or pets. Many invasive species are spread when people inadvertently dump live bait – such as non-native minnows, worms or frogs – in or near the water, or release an exotic aquatic plant or pet from their aquarium. Unwanted bait should always be disposed of in the trash. Unwanted pets or plants can usually be returned to an aquarium supplier. Importantly, aquarium owners or gardeners should consult their state and federal lists of prohibited invasive species before purchasing a new plant or animal.

Dry equipment for five days. If you are unable to complete the steps above, completely drying your boat or equipment – especially at high temperatures – is an easy way to kill most attached invasive species. This step is especially important for gear that remains damp, such as wetsuits, in which some invasive species can survive.

Make a travel plan. If you know you will be visiting multiple waterbodies in less than 5 days, check ahead to learn which have aquatic invasive species. Plan your travel route to waterbodies with no or few invasive species first, and be sure to follow prevention steps carefully each time you exit the water.

Consult local experts for additional measures. In some sensitive locations, additional measures may be required to remove specific species that resist the measures above. If you plan to boat or fish in an unfamiliar waterbody, contact a local natural resource professional to check whether there are any species of concern or required prevention steps. Some examples of additional steps or requirements may include:

  • Decontamination wash – Several western states require that all boats entering or existing a water body undergo a high-temperature, high-pressure wash to kill attached invasive species. Boaters who skip this step face heavy fines.
  • Wader restrictions – Because invasive species are commonly moved in the tread of waters by trout anglers and researchers who visit multiple streams in a day, some states prohibit the use of felt-bottomed waders that harbor more invasive species. They may also advise vigorously scrubbing equipment for New Zealand mudsnails and other species that cling tightly to gear.
  • Chemical rinse – Occasionally, it may be best to use chemicals to disinfect your boat or gear if you are moving frequently between waterbodies. Consult local natural resource managers to learn which chemicals are effective for your state’s species of concern, and always follow the manufacturers label.

Invasive Species Prevention: Terrestrial Habitats

Terrestrial invasive species are those that harm land resources such as forests, agriculture, urban environments and protected areas like parks and refuges. Terrestrial invasive species come in many forms. Giant kudzu is a plant that quickly overgrows native vegetation (and whatever lays in its path). Rats and domestic cats are invasive species responsible for driving many island species of birds and reptiles to extinction.  Many of the worst terrestrial invasive species are the smallest – insects and fungi. Mountain pine beetle, an insect, has killed millions of acres of forest trees in the western North America, while Chestnut blight, a fungus that arrived to the United States in 1909, wiped out all mature chestnut trees in the eastern U.S in just 20 years. Today, several species of bats in the United States are threatened with extinction from white nose syndrome, also caused by a fungus.

What all these terrestrial invasive species have in common is introduction by humans. This also means that people today have the power to stop future environmental disasters by following a few key prevention steps.

Brush off boots, equipment, pets and clothing to remove plant seeds before you enter or leave a new area. If you have been in an area infested with invasives with your bike or OHV vehicle, brush or wash the vehicle. Additionally, many states and countries require that outdoor gear, such as tents, be inspected for seeds and non-native species before you cross the border, so be sure to brush off your gear before you pack for travel.

Don’t move firewood. Invasive insects like mountain pine beetle and emerald ash borer are destroying millions of acres of North American forests. To stop their spread, leave firewood at home when you camp and buy it within a 25-mile radius of your campsite. Burn all wood during your trip; don’t bring it back home.

Follow emergency guidelines. During invasive species disasters or habitat restoration, some areas may be closed to human traffic to protect the survival of native species. Always check for closures and special cleaning requirements. Currently, many caves are closed to public access to prevent the spread of white nose syndrome, which has killed nearly 6 million bats in North America and threatens the survival of several species.

Keep cats indoors. Domestic cats are an invasive species on most continents and islands. Highly-adapted predators, domestic cats have been responsible for at least 33 extinctions and are the leading cause of death for birds and small mammals in the United States, killing billions each year. One reason these numbers are so high is because, unlike native, wild predators, domestic cats are protected from disease and food shortages by their human owners, allowing them to live at higher densities than they would in nature.

Don’t dump pets or plants. Many invasive species are spread when people inadvertently plant or release an exotic plant or pet, such as the current epidemic of constrictor snakes in Florida. Unwanted pets should be turned over to shelters. Importantly, gardeners and exotic pet owners should consult their state and federal lists of prohibited invasive species before purchasing a new plant or animal. The large majority of non-native species are not invasive and will be legal to purchase.

Protect your property. Learn which invasive species are regulated in your state and keep watch over your property and neighborhood. You may be able to eradicate a new invasive or report it to land managers early on, before it becomes a problem. Although most non-native plants are not invasive, be sure to avoid prohibited species when gardening. Use native plants when possible, to support your local wildlife.