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 sea life movement. Over time, the unique communities of fish and other marine life that form around these barriers begin to stabilize. With modern transportation technology and global markets, however, humans have removed many of these geographic barriers 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. Some invasive species are intentionally introduced into new territories as a new food supply or to control previously introduced species that have become pests.
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 invasives species contribute to the decline of native biodiversity by changing the natural community 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 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 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.
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, critical habitat for many native plants.