Species introduced to new environments pose significant challenges to waterways worldwide. These organisms can alter natural habitats, impacting environmental stability and human interests.
Defining Aquatic Non-Native Species
Aquatic non-native species are organisms introduced, intentionally or unintentionally, to an aquatic ecosystem where they do not naturally occur. While many cause minimal issues, those that spread aggressively and harm native wildlife or habitats are typically classified as invasive. They differ from native organisms, which evolved in their specific ecosystem over time.
Human activities often introduce these species into new waterways. Common pathways include ballast water discharge from ships, accidental releases from aquaculture or the pet trade, and recreational activities. Boating and fishing, for example, can inadvertently transport non-native species on equipment, boat hulls, or trailers between different bodies of water.
Threats to Aquatic Ecosystems and Wildlife
Non-native species pose substantial threats to aquatic ecosystem stability and biodiversity. They outcompete native organisms for resources like food and habitat, leading to population declines. For instance, New Zealand mudsnails can dominate streambeds, depriving native invertebrates and their fish predators. This competition can disrupt existing food webs.
Non-native species can physically alter aquatic habitats, making them unsuitable for native flora and fauna. Some invasive plants, like water primrose, form dense mats that block sunlight, reducing oxygen levels and displacing native vegetation. Certain species, such as the Chinese mitten crab, burrow into riverbanks, causing erosion and destabilizing riparian areas. These alterations lead to a loss of natural habitat structure, necessary for many specialized native species.
Non-native species may introduce diseases or parasites to which native populations lack natural immunity. This can result in widespread illness and mortality among native fish and wildlife, contributing to population declines. The combined effects of competition, habitat modification, and disease introduction can significantly reduce aquatic biodiversity, sometimes leading to native species extinction. These impacts are considered a major driver of biodiversity loss globally, sometimes even surpassing pollution or climate change.
Economic and Human Activity Impacts
Non-native aquatic species impose substantial financial burdens and negatively affect human activities. Control and eradication efforts for established invasive populations are often costly. For example, controlling Floating Pennywort in Britain can cost £250,000 to £300,000 annually. The economic impact of invasive species in the United States alone is estimated at $120 billion annually.
Infrastructure can suffer significant damage from certain non-native species. Zebra mussels, for instance, attach to and clog water pipes, power plant intakes, and other submerged structures, requiring millions in annual maintenance and repairs. Their presence can disrupt water treatment plants and affect lock gates, leading to costly operational inefficiencies. These species can also damage boat engines and steering equipment.
Commercial fisheries often experience losses due to competition and predation by non-native species on native fish stocks. Invasive fish can reduce game fish populations, impacting fishing. Recreational activities like boating, swimming, and fishing can also be severely affected. Dense growths of invasive aquatic plants can make waterways impassable, and impacts on fish populations can diminish fishing experiences, reducing tourism and property values.
Steps to Prevent Their Spread
Preventing the spread of non-native species in waterways is an effective strategy to protect aquatic environments. Individuals can contribute by adopting simple habits during water-based activities. A widely promoted practice for boaters and anglers is “Clean, Drain, Dry.” This involves thoroughly cleaning boats, trailers, and fishing gear to remove any visible plants, animals, or mud before leaving a water body.
After cleaning, drain all water from the boat’s bilge, livewells, and engine. Allow all equipment to completely dry before moving to another waterway to eliminate any remaining non-native organisms. Proper disposal of unwanted aquarium pets or plants is also crucial, ensuring they are never released into natural waterways or storm drains. Avoid moving water, live bait, or organisms between different bodies of water to prevent unintentional introductions.