Non-Native Species

Park Ranger Japanese Knotweed
Park Ranger is attacked by Japanese Knotweed

NPS photo/D. Panek

The two great destroyers of biodiversity are,
first habitat destruction and,
second, invasion by exotic species.

–E.O. Wilson, Harvard ecologist

The spread of invasive species is a major factor contributing to ecosystem change and instability, ultimately leading to biodiversity reduction. Preventing non-native invasive species establishment has a much better success rate than trying to eliminate a species once it is established. At Apostle Islands, both aquatic and terrestrial species continually threaten the park. From microscopic organisms to large trees, the potential is always there for non-native species to invade and overtake fragile ecosystems that make the lakeshore a popular destination for hikers, boaters, and sightseers alike.


Invasive Species

Invasive species are exotic species which cause harm to the economy, environment, or human health.

Invasive species:

  • Cause more harm than good to the invaded ecosystem

  • Have high growth and reproduction rates

  • Are free from limiting predators, competitors, parasites or diseases in the invaded ecosystem

  • Easily disperse/move from place to place

Kayaker cleaning his boat of invasives
Kayaker cleaning his boat of invasives.

NPS photo/N. Howk

What Can Be Done?

Many of these species come to the lakeshore via boats, on clothing or gear, and even on firewood. For example, it is possible to transport zebra mussels from water body to water body through just a few drops of water containing larval forms. Whether kayaking, sailing, hiking, camping, fishing, or enjoying a picnic, paying attention can help keep invasive species out.

Remember the following:

  • Burn only dead and down firewood from the islands. Non-local firewood can be infested with spongy moths or emerald ash borer.

  • Clean, drain, and dry watercraft of all sizes.

  • Dispose of all fishing bait properly, not in the lake.

  • Clean all camping, boating, hiking, and other equipment prior to coming to the park.

  • Brush your boots and remove seeds to the garbage (not compost). Spotted knapweed, garlic mustard, and other seeds will stick to hiking boots and clothing.

  • Remove seeds (like purple loosestrife) and burs from pets’ fur, and pay attention to tire treads picking up buckthorn berries.

  • Get involved in conservation efforts and educate yourself and others about invasive species.

  • Landscape with native species and avoid transplanting non-native plants from other areas.

  • Do not dispose of aquarium plants or animals in lakes, rivers, or drains.

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    Last updated: February 2, 2023

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