Invasive Species MARINE AND gREAT lAKE National Parks

An invasive species is any species that is introduced or non-indigenous to an ecosystem, and whose presence causes or is likely to cause economic or environmental harm or harm to human health (Executive Order 13112, 1999). Invasive species are increasingly changing the natural landscapes of our ocean, coastal and Great Lakes National Park Units.

Ocean, coastal and Great Lakes parks are working to identify invasive species within their boundaries, understand how these species are impacting park resources, and determine what park managers can do to prevent these species from further damaging natural and cultural resources.

Invasive species harm natural and cultural resources in our parks by:

1. Outcompeting native species

Many invasive species contribute to the decline of native biodiversity by changing the natural trophic structure of the invaded ecosystem. By outcompeting native species for limited resources, invasive species deplete the available resources for all consumers. This effect is particularly harmful when it occurs at or near the base of food webs. Invasive quagga mussels (Dreissena rostriformis bugensis) deplete plankton populations, a critical food source for a broad range of Great Lakes species, destroying the trophic balance throughout the lakes.

2. Threatening the safety of park employees and visitors

Several invasive species have biological characteristics that pose a danger to the safety of park employees and visitors. Often the danger presented by invasive species is unexpected by park employees and visitors and improving awareness of these dangers is critical to reduce further harm. For example, the Lionfish (Pterois volitans), which have invaded many of the southeastern ocean and coastal parks, disrupt food webs in parks by consuming native fish and invertebrates. They also have venomous spines that can cause painful stings to swimmers, snorkelers, divers or anglers. The National Park Service adopted a Service-wide Lionfish Response Plan in 2012 to mitigate impacts to marine resources and communicate risks to visitors and employees in parks.

3. Changing or degrading the experience of park visitors

Visitors travel to National Parks to experience and observe the natural scenery and biodiversity, and to experience the nation's natural and cultural heritage. Reduction of native animal and plant populations, extensive habitat alteration by invasive species, and efforts to maintain habitat integrity by eradicating invasive species may detract from visitors' appreciation and experience of National Parks.

4. Requiring intensified maintenance and monitoring

Park staffs must increase monitoring of park habitats and plant and animal communities for evidence of disturbance and invasion. This puts pressure on limited budgets and park employees to maintain the unique natural beauty of each park. Physical removal and control of invasive species are intensive activities that require long-term and diverse management techniques.

5. Altering natural ecological processes

Some invasive species physically alter the natural structure of park habitats and landscapes. Baby's breath (Gypsophila paniculata) is an invasive dune-dwelling plant in many coastal and Great Lakes parks that prevents the natural movement of sand dunes, critical habitat for many native plants.

This website and database will help park staff learn more about the invasive species in National Parks to increase critical awareness. As more information is collected, the database will grow.

The National Park Service compiled this database using reports of invasive species in National Parks from U.S. Geological Survey (USGS), NPSpecies, Government Performance Results Act (GPRA) reports, NPS Coastal Watershed Assessments (CWA), and The Nature Conservancy.

The threat to marine ecosystems does not depend on the number of invaded species present, but the level of impact those species have on its ecosystem. The quantified threat-scoring index was developed by The Nature Conservancy and incorporated into the National Park Service database in order to assess the level of impact from invasive species and determine which parks are at the highest risk. Each invasive species found in The Nature Conservancy's database was assigned a score from 1-4 (where data allowed) based upon the following categories: 4 - Disrupts entire ecosystem processes with wider abiotic influences; 3 - Disrupts multiple species, some wider ecosystem function, and/or keystone species or threatened species; 2 - Disrupts single species with little or no wider ecosystem impact; 1 - Little or no disruption; 0 - not ranked according to categories (Great Lakes); and (dash) unknown or not enough information to determine score.

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