Marine and Great Lakes Invasive Species
Many natural factors determine where species live in the ocean. Physical barriers such as land masses, currents, and large gaps in suitable habitat (like deep ocean basins that separate shallow reefs), limit movement of aquatic species. Over time, the unique communities of fish and other aquatic life that form around these barriers begin to stabilize. With modern transportation and global markets, however, humans have removed many of these geographic barriers, allowing the spread of non-native species and thus destabilized the ecosystems that had previously been isolated from outside influence.
Many invasive species are unintentionally introduced to new environments. Some escape from aquaculture, others hitch a ride on international shipping vessels, and still others are accidentally released from pet owners’ homes during natural disasters. For this reason, it is important for people to bring their pets with them when they evacuate or to ensure that pets are in an enclosure that will not allow them to escape, regardless of conditions. Some invasive species are intentionally introduced into new areas as a new food source, as a control for previously introduced species that have become pests, or by pet owners who don't want to keep their pet.
Whatever the cause, when invasive species arrive in their new environments, they harm natural and cultural resources in our parks by:
Outcompeting Native Species
Many invasive species contribute to the decline of native biodiversity by changing the natural community of the invaded ecosystem. Invasive species deplete the amount of available resources by outcompeting native species for these limited resources, and can reduce biodiversity of native species and create monocultures. This effect is particularly harmful when it occurs at or near the base of food webs. Invasive quagga mussels deplete plankton populations, a critical food source for a broad range of Great Lakes species, destroying the trophic balance throughout the Lakes.
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. Lionfish, which have invaded many of the southeastern ocean and coastal parks, have poisonous spines that can be hazardous to people snorkeling and SCUBA diving. Often the danger presented by invasive species is unexpected by park employees and visitors; improving awareness of these dangers is critical to reduce further harm.
Changing and 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.
Requiring Intensified Maintenance and Monitoring
Park staff 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 diverse management techniques which can be quite expensive.
Altering Natural Ecological Processes
Some invasive species physically alter the natural structure of park habitats and landscapes. Baby's breath is an invasive dune-dwelling plant in many coastal and Great Lakes parks that prevents the natural movement of sand dunes, which provide critical habitat for many native plants.